TRAINING MANUAL February 2007, Edition 1

Catalog Number DOC296.53.00740

QuikChem IC+ for Omnion 3.0

TRAINING MANUAL

February 2007, Edition 1

© HACH Company, 2007. All rights reserved.

Visit us at www.lachatinstruments.com

http://www.hach.com

Table of Contents

Section 1 Introduction ....................................................................................................................... 5Section 2 Ion chromatography theory ........................................................................................... 7

2.1 Separation techniques ................................................................................................................. 72.2 QuikChem ion chromatography (IC) system................................................................................ 72.3 Chromatogram water dip ............................................................................................................. 92.4 Suppression of background conductance.................................................................................... 9

2.4.1 Suppressor reactions .......................................................................................................... 92.4.2 Suppressor regeneration .................................................................................................. 10

Section 3 Equipment overview ...................................................................................................... 113.1 Autosampler............................................................................................................................... 113.2 PDS200 and DRD Dilutors......................................................................................................... 13

3.2.1 PDS200 dilutor configurations .......................................................................................... 143.2.1.1 Sample is aspirated without the dilutor .................................................................... 143.2.1.2 Sample is aspirated by the dilutor. ........................................................................... 153.2.1.3 Diluent is aspirated by the dilutor ............................................................................. 153.2.1.4 Sample and diluent are delivered to an empty dilution tube .................................... 163.2.1.5 Diluted sample is aspirated and travels to the manifold........................................... 16

3.3 Peristaltic pump RP-100 ............................................................................................................ 173.4 Eluent pump............................................................................................................................... 183.5 System unit ................................................................................................................................ 183.6 IC injection valves ...................................................................................................................... 193.7 Conductivity detector ................................................................................................................. 203.8 Valve operation .......................................................................................................................... 203.9 Manifold ..................................................................................................................................... 233.10 IC column................................................................................................................................. 23

Section 4 Equipment specifications............................................................................................. 254.1 Conductivity module................................................................................................................... 254.2 Eluent pump............................................................................................................................... 254.3 PEEK tubing dimensions ........................................................................................................... 254.4 Peristaltic pump flow rate........................................................................................................... 26

Section 5 System startup ................................................................................................................ 275.1 Startup procedure ...................................................................................................................... 275.2 Startup reminders ...................................................................................................................... 27

Section 6 Omnion 3.0 software for IC .......................................................................................... 296.1 Configure the IC channel ........................................................................................................... 29

6.1.1 Set control bits for QC8500............................................................................................... 296.2 Simultaneous FIA and IC operation ........................................................................................... 30

6.2.1 Starting FIA and IC runs ................................................................................................... 306.2.2 FIA contamination of IC components................................................................................ 30

6.3 Creating templates..................................................................................................................... 316.4 Set timing ................................................................................................................................... 31

6.4.1 Run time as minutes ......................................................................................................... 316.4.2 Short time to valve ............................................................................................................ 326.4.3 Retention time................................................................................................................... 33

6.5 Analyte settings.......................................................................................................................... 336.5.1 Set method to IC ............................................................................................................... 336.5.2 Add analytes ..................................................................................................................... 336.5.3 Analyte properties ............................................................................................................. 34

6.5.3.1 Calibration by height ................................................................................................ 346.5.3.2 Minimum peak width ................................................................................................ 346.5.3.3 Area integration type ................................................................................................ 34

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Table of Contents

6.5.3.4 Threshold..................................................................................................................356.6 Integration tools..........................................................................................................................35

6.6.1 Using manual integration...................................................................................................356.6.1.1 Adjusting the baseline window .................................................................................366.6.1.2 Adjusting the integration window ..............................................................................38

6.6.2 Removing manual integration............................................................................................406.7 Changing the threshold ..............................................................................................................416.8 Clearing the threshold ................................................................................................................426.9 Locating samples .......................................................................................................................436.10 Custom reports.........................................................................................................................436.11 Spiking samples .......................................................................................................................44

6.11.1 Theory .............................................................................................................................446.11.2 Spike procedure ..............................................................................................................45

6.12 Omnion 3.0 practice project .....................................................................................................46Section 7 Maintenance .....................................................................................................................47

7.1 Preventative maintenance..........................................................................................................477.2 Maintenance guide .....................................................................................................................477.3 Maintenance schedule example.................................................................................................487.4 Inspecting the guard disc ...........................................................................................................487.5 Manifold removal ........................................................................................................................497.6 System shutdown .......................................................................................................................49

Section 8 Troubleshooting exercises ...........................................................................................518.1 Chromatography errors ..............................................................................................................518.2 Troubleshooting scenarios .........................................................................................................528.3 QuikChem IC Quiz .....................................................................................................................60

Section 9 Frequently asked questions.........................................................................................63Section 10 Support information.....................................................................................................67Appendix A Glossary .......................................................................................................................69

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Section 1 Introduction

Welcome to the ever-growing group of Lachat instrument users! In addition to providing high quality hardware and software, you will find that Lachat Instruments is dedicated to strong after-sales service and support.

About Lachat InstrumentsThe mission of Lachat Instruments is to design, sell and support advanced instrumentation for performing automated chemical analysis. The instruments are used for a variety of purposes including the testing of drinking and wastewater for pollutants, analyzing nutrients in agricultural samples and determining various constituents in pharmaceuticals and biologicals.

Lachat Instruments provides several sample preparation products such as block and in-line digestors and distillation units for cyanides, phenolics, sulfides, ammonia and surfactants.

Lachat Instruments offers inter-connectivity of different instruments through its unique CoWorker platform. CoWorker enables multiple analytical instruments to operate simultaneously and independently on the same instrument platform. All instruments share the use of several peripherals including the dilutor, sampler, sampling pump, electronics unit and data station. CoWorker is a highly efficient concept to ensure maximum utility for capital equipment purchases.

Lachat flow injection analyzers and ion chromatographs can be upgraded by the customer in the field. This upgrade capability allows for less sophisticated configurations to be upgraded as budgets allow and technical requirements demand.

Company HistoryLachat Chemicals, Inc., was founded by Lawrence Lachat in 1961 with the plan of selling research-grade chemicals. The business was sold to H.O. Ranger in 1974. In 1976 an Instrument Division was established to produce high technology analytical instruments.

In December 2000, Lachat Instruments was acquired by the Environmental Water Quality Division of Danaher Corporation, a publicly traded company with revenues approaching $3.5 billion.

The acquisition by Danaher places Lachat Instruments, a Hach Company brand, with many superior environmental companies such as Hach Company, Radiometer Analytical and Dr. Lange. Lachat automated laboratory analyzers are a perfect complement to the capabilities of the other Danaher water quality companies. The acquisition of Lachat Instruments by Danaher enables strong partnerships for the development of new products.

Thank you once again for selecting Lachat Instruments to serve your ion analysis needs. We look forward to a long and mutually satisfying relationship.

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http://www.hach.com

Section 2 Ion chromatography theory

2.1 Separation techniquesChromatography is a general term applied to a wide variety of separation techniques based upon the sample partitioning between a moving phase, which can be gas or liquid, and a stationary phase, which may be either liquid or a solid.

The discovery of chromatography is generally credited to the Russian botanist Mikhail Tswett who in 1903 described his work on separation of pigments in green leaves using a chalk column. The term chromatography, from the Greek words chroma (color) and graphein (write), was used by Tswett to describe colored zones that moved down the column.

In the early years, chromatography techniques were generally in the form of liquid-solid chromatography (LSC). Thin-layer chromatography (TLC) was developed in 1938 by Izmaillov and Schraiber, and later refined by Stahl, in 1958. In 1941, Martin and Synge revolutionized liquid chromatography and set the stage for the development of gas chromatography and paper chromatography.

2.2 QuikChem ion chromatography (IC) systemThe Lachat Ion Chromatography System is classified within the Ion-Exchange chromatography techniques (Figure 1).

In the QuikChem Ion Chromatography System, sample is injected into an eluent solution stream by a six-port valve. The sample is swept by the eluent liquid into the IC manifold, which consists of one or two IC columns. The separation occurs in the columns where there is a stationary phase that retains the ions by ion exchange or other mechanism.

The retention time in the column depends upon the charge and size of the ion. All of the ions of one species will come out of the column at approximately the same time. The conductivity of the ions is measured at the detector. The signal is then processed by a computer.

Figure 1 Chromatography Techniques

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Ion chromatography theory

The conductivity measured by the detector generates a peak-like response due to the distribution of the ions passing through the flow cell (Figure 2).

To calibrate the system, a set of standards of known concentrations (calibration standards) are run. The area of each peak (response) can be plotted against the known concentrations. A regression analysis can be performed to find the best mathematical model that fits the data points. The line that best fits among the calibration data points is known as a calibration curve. The calibration curve can be represented graphically (Figure 3) and/or as an equation.

The concentration of an unknown sample can be determined by running it under the same conditions used for the calibration standards. The peak area (response) of the sample can be plugged

Figure 2 Chromatogram peak response

Figure 3 Calibration graph

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into the calibration curve equation to determine the sample concentration (see Figure 4).

2.3 Chromatogram water dipA water dip will occur in IC for anions when the ionic strength of the sample is different than the ionic strength of the eluent. The anions in the sample displace the anions from the eluent (carbonate and bicarbonate) that are adsorbed onto the column packing material. These displaced carbonate and bicarbonate anions, after passing through the suppressor column, will appear on the chromatogram as a peak.

If the ionic strength of the sample is less than that of the eluent, there is a negative water dip. If the ionic strength of the sample is greater than that of the eluent, there is a positive water dip. If the ionic strength of the sample is the same as that of the eluent, there is no water dip.

2.4 Suppression of background conductanceThe QuikChem suppressor column contains a cation exchange resin that suppresses conductivity from the eluent. If not suppressed, the eluent can mask the signal from the analyte.

2.4.1 Suppressor reactions

QuikChem Method 10-510-00-1-A (USEPA 300, part A)The eluent (mixture of sodium carbonate and sodium bicarbonate) possesses conductivity that can mask the signal from the analyte ions. This problem is overcome by suppressing the eluent conductivity. This process occurs in the suppressor cartridge which contains a cation exchange resin.

The stationary phase (resin) of the suppressor cartridge contains a high concentration of hydrogen ions. These hydrogen ions are exchanged for the eluent sodium ions as described in equations (1) and (2). The resulting eluent species is carbonic acid, which has very low conductivity. These suppression reactions lower the noise and improve the detection limits.

Figure 4 Calibration graph—determining sample concentration

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On the other hand, the analyte counter cations are converted to hydrogen ions which have greater conductivity than the original salt structure (equation (3)). The suppressor cartridge is regenerated after each sample run.

Eluent reactions

(1)

(2)

where:R = functional group present in the suppressor cartridge

Analyte reaction (fluoride)

(3)

where:R = functional group present in the suppressor cartridge

The signal to noise ratio is enhanced. The equivalent conductance for H+ is about seven times greater than that of Na+.

2.4.2 Suppressor regenerationIn the Lachat approach (US Patent No. 5,567,307), the suppressor cartridge is regenerated using a ten-port valve while the sample is being loaded using a six-port valve. When the six-port valve injects the sample, the suppressor cartridge is fully regenerated and ready to perform chemical suppression for the injected sample.

R–H+ Na+ HCO3-

+ + R–Na+ H2CO3+→

2(R–H)+ 2Na+ 2CO3-2

+ + 2(R–Na)+ H2CO3+→

R–H+ Na+ F-+ + R–Na+ H+ F-

+ +→

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Section 3 Equipment overview

3.1 AutosamplerThe current models of autosamplers available for use with the QuikChem 8000/8500 analyzers include the ASX-400 series (Figure 5) and ASX-500 series XYZ samplers (Figure 6).

Figure 5 ASX-400 autosampler

Figure 6 ASX-500 autosampler

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Equipment overview

General information

• Controlled by the computer

• Automatic arm to sample and dilute standards and samples

• Manual sampling is available

Cables and electronics

• Power cord

• Communication cable (default: COM1)

• Power switch

• Fuses or reset button

Components

• Wash reservoir

• Sample tray

• Sample and standard racks

• Empty tube rack for dilutions

Operation

• Power on and power off

• Probe alignment

• Sample positions

• Standard positions

Maintenance

• Cleaning

• Alignment

• Spills

Troubleshooting

• Time-outs

• Errors

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Equipment overview

3.2 PDS200 and DRD Dilutors

General information

• Dilutor works in conjunction with the solenoid valve

• PDS200: solenoid valve mounted on dilutor (Figure 7)

• DRD (dual resolution dilutor): solenoid valve attached to sampler

• Dilution range: 1.6 to 4000-fold. Recommended up to 1000-fold.


• Power cord

• Communication cable (pins 1, 2 and 3)

• Fuses

Components

• Dilutor valve

• Solenoid valve

• Pistons

• Tubing, connectors and ferrules

• Inlet filter

Operation

• Diluent solutions

• Degassing

• Storage

• Tubing connections

• Priming

Maintenance

• Replace the flares annually

• Prime after use, especially if diluent is not deionized water

Figure 7 PDS200 dilutor

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Equipment overview

Troubleshooting

• Leaks

• Seal replacement

• Air bubbles

• Blockages

• Accuracy

3.2.1 PDS200 dilutor configurations

3.2.1.1 Sample is aspirated without the dilutor

Figure 8 No dilution

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Equipment overview

3.2.1.2 Sample is aspirated by the dilutor.

3.2.1.3 Diluent is aspirated by the dilutor

Figure 9 Sample aspirated by the dilutor

Figure 10 Diluent is aspirated by the dilutor

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Equipment overview

3.2.1.4 Sample and diluent are delivered to an empty dilution tube

3.2.1.5 Diluted sample is aspirated and travels to the manifold

Figure 11 Sample and diluent are delivered to empty dilution tube

Figure 12 Diluted sample is aspirated and travels to the manifold

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Equipment overview

3.3 Peristaltic pump RP-100

General information

• Sample

• Wash water

• Air

• Pump regenerant

• Pump speed: 35 or as specified in the method


• Power cord

• Communication cable

• Fuses

Components

• Cartridges

• Tension lever

• Power switch

• Minimum and maximum buttons

• Normal and manual buttons

Operation

• Securing the pump tubing

• Adjusting the tension

• Selecting pump tubing

• Flow rate—see section 4.4 on page 26

Maintenance

• Cleaning

• Cartridge maintenance

• Pump tubing maintenance and replacement

Troubleshooting

• Pump test

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Equipment overview

3.4 Eluent pump

General information

• Pump eluent through the system

• Specifications—see section 4.2 on page 25.


• Power cord

• Communication cable

• Fuses

Components

• Pump head

• Lubricating lines

• Prime/purge valve

• Power switch

• Pump controls

• In-line filter

• Dampening device

Operation

• Priming

• Storage

• Control panel

Maintenance

• Cleaning procedure

Troubleshooting

• Pump control test

3.5 System unitThe system unit consists of:

• Main chassis

• Computer

• One or more channels

• Printer

An IC channel consists of:

• Six-port IC injection valve

• Conductivity detector

• Ten-port IC injection valve

• IC manifold (columns)

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Equipment overview

3.6 IC injection valvesAn IC injection valve is detailed in Figure 13.

General information

• Six-port valve injects sample into the IC manifold

• Ten-port valve regenerates the suppressor cartridge

Components

• Stator

• Rotor

• Motor

• Sensors

• Bracket

• Sector wheel. The notch with a hole next to it indicates the load state. The notch with no hole indicates the inject state.

Maintenance

• Flush with deionized water

• Clean ports

• Clean spills

Troubleshooting

• Blockages

Figure 13 IC Injection valve

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Equipment overview

3.7 Conductivity detector

General information

• Signal measurement

• Controlled temperature flowcell


• Detector cable

• Detector distribution panel

• IC SPM cable

Components

• Flow cell

• Temperature control switch

• Detector bracket

Operation

• Zero, background, gain factor, fast response, inverse polarity

Maintenance

• Flow cell maintenance

Specifications

• See section 4.1 on page 25.

3.8 Valve operationFigure 14 on page 21 details the flow of sample and reagents through the QC8500 system during the inject state. Figure 15 on page 22 details the flow of sample and reagents through the QC8500 system during the load state. For most applications, both valves rotate simultaneously when changing from the inject to load state or when changing from the load to inject state.

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Equipment overview

Figure 14 Inject state, flow through 6-port and 10-port valves

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Equipment overview

Figure 15 Load state, flow through 6-port and 10-port valves

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Equipment overview

3.9 ManifoldManifolds vary with the instrument configuration. A general manifold diagram for QuikChem method # 10-510-00-1-A is detailed in Figure 16.

• Manifold parts description

• Nuts and ferrules

• Columns, frits and guard disc

• PEEK tubing

• Manifold installation (refer to the Hardware Installation Manual)

3.10 IC columnColumn length is the length of the black-color column body. Ideally it should be measured with column end fittings (tan color) taken out. For practical purposes, determine the length by adding 2.5 cm to the black-color column body that can be seen without removing the column end fitting.

Guard discMost anion analytical columns have a guard disc (Figure 17) positioned at the entrance of the column to prevent any particulate material from entering and disrupting the column bed. The guard disc is placed on top of a frit (Figure 17) and can be identified by the tan PEEK outer ring and white center. The frit has a narrower outer ring, which is commonly green PEEK. The frit can also be identified by the tan, granular appearance of the center material.

Figure 16 General manifold diagram1

1 Instrument specific. Consult the Lachat method for the diagram specific to your equipment.

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Equipment overview

Replace the guard disc when high column backpressure is observed, or if the disc shows significant staining. Column maintenance does not include frit replacement, as removal of the frit may damage the column bed.

Figure 17 IC column—guard disc and frit

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Section 4 Equipment specifications

4.1 Conductivity module

4.2 Eluent pump

4.3 PEEK tubing dimensions

Conductivity module

Sensitivity 10,000, 1000, or 100 µS/cm (gain: 0.1, 1, 10)

Full scale 10 V

Background zero range 5000 µS/cm

Background zero precision 0.025% full scale

Response time standard: 0.75 s; fast response: 0.03 s

Digital resolution 1, 0.1, 0.01 nS/cm

Bulkhead fluidic fitting PEEK

Flow cell cavity CTFE KEL-F Teflon, 0.25 µL volume

Flow cell constant 30 cm-1

Flow cell electrodes Passivated high-grade type 316 stainless steel

Flow cell fittings PEEK

Heater Teflon tubing on aluminum mandrel

Eluent pump

Flow rate 0.10–9.99 mL/minute

Pressure 0–6000 psi

Accuracy 2%

Precision 0.2% RSD

Voltage 0 to 10 V full scale

Color I.D. (inches) O.D. (inches) Lachat Part. No.

Yellow 0.007 0.0625 28052

Tan 0.010 0.0625 28031

Green 0.030 0.0625 28032

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Equipment specifications

4.4 Peristaltic pump flow rateTable 1 details flow rates for the peristaltic pump when different tubing sizes are used.

All tubes above the bold line in Table 1 use the white collar adapter and the 0.030 inch transmission tubing (Cat. No. 50021). All tubes below the bold line use the black collar adapter and the 0.060 inch transmission tubing (Cat. No. 50029).

The measured flow rates are precise to ±10% of the value given in Table 1. The white or gray notch on the colored pump tube collar indicates the flow-regulated pump tubing (Figure 18).

Table 1 Peristaltic pump flow rates for various tubing sizes

Tygon No. Duraprene No. Color Diameter, inner (mm) Measured flow rate1(mL/min)

53403 54403 Orange-Blue 0.254 0.16

53404 54404 Orange-Green 0.381 0.23

53405 54405 Orange-Yellow 0.508 0.49

53406 54406 Orange-White 0.635 0.76

53407 54407 Black-Black 0.762 0.94

53408 54408 Orange-Orange 0.889 1.28

53409 54409 White-White 1.016 1.45

53410 54410 Red-Red 1.143 1.75

53411 54411 Gray-Gray 1.295 2.47

53412 54412 Yellow-Yellow 1.422 2.95

53419 54419 Yellow-Blue 1.524 3.07

53413 54413 Blue-Blue 1.651 3.44

53414 54414 Green-Green 1.854 4.23

1 Pump tube colors used most often were flow rate tested using Duraprene pump tubing at a pump speed of 35.

Figure 18 Pump tube collar

Notch

Collar

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Section 5 System startup

5.1 Startup procedureAfter the instrument is powered on, follow the steps listed below:

• Install the manifold on the channel to be used for the analysis.

• Complete all injection valve fluidic connections.

• Complete all conductivity module connections.

• Set all pump tubes on the peristaltic pump. Refer to the QuikChem method for requirements. The sample line pump tube may vary among methods.

• Run deionized water through all the lines to make sure there are no leaks. If no leaks are found, put the reagents in-line.

• Prime the eluent pump with eluent solution. Purge the manifold lines to prevent air from going into the columns and the conductivity module.

• If the system uses a dilutor, place the diluent line in the diluent solution. Also be sure to place some empty test tubes in the empty tubes rack.

• Pour the calibration standards into test tubes. Pour some samples into test tubes.

• Start the analysis by editing the template with standards and some samples.

5.2 Startup remindersBe sure the following tasks have been completed when starting IC:

• Are the columns that are specified in the QuikChem® method being used?

• Is the correct sample loop connected to ports 1 and 4 of the 6-port valve?

• Are all tubing lengths correct?

• Are the columns positioned in the correct direction (see arrows)?

• Is the eluent less than 12 hours old?

• Has the eluent been filtered and degassed?

• Is the methanol lubricating solution flowing?

• Are all of the modules turned on during system startup?

• Is the probe installed and aligned properly?

• If using a dilutor, have test tubes been placed in the empty tube rack?

• Is a fresh container of diluent being used for the dilutor?

• Are there enough standards in the standard vials?

• Are all the waste lines connected? Do they drip into the waste container or drain?

• Is the waste container empty?

• Has the software been started before pumping reagents?

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System startup

• Was the eluent pump primed?

• Was the purge valve closed after the eluent was primed?

• Has the sample(s) been filtered as indicated in the method?

• Has the correct polarity been set on the conductivity module?

• Has the system been checked for leaks?

• Are the reagent lines in the correct reagent containers?

• Have the reagents (including eluent) been prepared as described in the QuikChem* method?

• Are the correct standards in the standard vials?

• Has the correct template been opened or edited for the method being run?

• Is sample without air being injected into the columns?

• Has the timing been set properly in the Run Properties window.

• Is the probe hitting the sample racks?

• Has the configuration, rack type and probe installation been checked?

• Is the printer loaded with paper?

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Section 6 Omnion 3.0 software for IC

The Omnion 3.0 software that is used for ion chromatography (IC) is also used for flow injection analysis (FIA). The software features covered in this section are specific to ion chromatography. For general topics regarding software not covered in this manual, please refer to the Omnion 3.0 Software User Manual (Cat. No. 02134).

6.1 Configure the IC channelTo configure an IC channel for a system that has both FIA and IC, treat the IC channel as a separate instrument. Although the IC channel is physically connected to the FIA channel(s), the channels must be treated as separate instruments in order to run FIA and IC at the same time. In most cases the IC and FIA channels will share the same sampler.

Figure 19 details the configuration of an IC channel when the channel is the third physical channel on the Lachat instrument. It is not necessary to configure a heater for the IC channel.

6.1.1 Set control bits for QC8500When using the QC8500 instrument, use the Invert Outputs option.

1. Click INVERT OUTPUTS (Figure 19). This button will then be labeled NORMAL SETUP (Figure 20).

2. Select the appropriate channel number for Inverted Control Bits in the QC8500—System Unit A section. For example, if the IC channel is physically connected to Channel 3 (Figure 19) select box number 3 in the Inverted Control Bits field (Figure 20).

Figure 19 IC configuration in Omnion 3.0

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Omnion 3.0 software for IC

6.2 Simultaneous FIA and IC operation

6.2.1 Starting FIA and IC runsWhen FIA and IC are set up as separate instruments, a run can be started with each instrument. To start a run for each instrument:

1. Open a template (section 6.3) for each instrument. For example Run 1 and Run 2.

2. Start each run.

For an eleven-minute anion run, the sampler will switch between the two instruments. After injecting an anion sample for IC, the sampler will inject as many FIA samples as it can until it needs another IC sample.

6.2.2 FIA contamination of IC componentsWhen running FIA and IC together, there must be one sample line that runs through all valves. If the FIA samples are not particularly clean, the IC valve and channel may become clogged or contaminated.

The IC valve will clog more easily then the FIA valves. Additionally, particulates or organic compounds from the FIA samples can enter the IC injection valve and then enter the IC column. If the FIA samples are not filtered through 0.45 micron filters, it may not be desirable to run the IC and FIA channels together.

Figure 20 IC configuration in Omnion 3.0—inverted control bits

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6.3 Creating templatesWhen using Omnion 3.0 software, templates can be created for each method, or combination of methods, that are used. Templates allow information that does not change from run to run to be re-used. This information includes various timing parameters, calibration standard concentrations and DQM (Data Quality Management) samples and/or sets.

Templates are convenient because the user does not have to re-enter the same information each day. Instead the user edits the run worksheet before running samples. Omnion 3.0 includes some preprogrammed methods that can be used as starting templates.

When running FIA and IC together, the IC channel should be configured as Instrument 2. The templates for IC must have the correct instrument reference in the Run tab of the Run Properties window (Figure 21).

6.4 Set timingIn the Timing tab of the Run Properties window the run time, time to valve, and retention time are set differently for IC than for FIA.

6.4.1 Run time as minutesIC methods require longer run times than FIA for the analytes to separate. Use minutes instead of seconds.

1. Select the Timing tab in the Run Properties window. Select RUN in the navigation tree.

2. Check the three boxes Use Minutes, Channel in Minutes and Analyte in Minutes (Figure 22).

Figure 21 IC run template

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6.4.2 Short time to valveTime to Valve is not used the same in IC as in FIA. With FIA, a dye is run to determine when the sample reaches the valve. With IC, the sample valve and ten-port valve must change state very quickly. This is because the ten-port valve is responsible for regeneration of the suppressor. By using a short time to valve, both valves are put into the load state soon after the sampler draws the sample.

Select the appropriate channel in the RUN tree and enter the value (specified in the method) in the Time to Valve field (Figure 23).

Figure 22 Timing—setting run time as minutes

Figure 23 Timing—time to valve and retention time

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6.4.3 Retention timeIn IC each peak is identified by its retention time. Instead of using inject to peak start to locate and identify the peaks, the peak maximum is used. The amount of time from injection of the sample to the highest point of its peak is the retention time. Select the appropriate channel in the RUN tree and select Use Retention Time (Figure 23).

6.5 Analyte settingsUse the Analytes tab in the Run Properties window to select IC as the method, add analytes, and change analyte properties.

6.5.1 Set method to ICSelect the appropriate channel in the ANALYTES tree. Select IC for the method (Figure 24).

6.5.2 Add analytesIon chromatography typically has multiple analytes per channel. The ADD ANALYTE button is active only when a channel is selected (Figure 24). Add as many analytes as necessary, depending on the method being used.

Figure 24 Run Properties window—set method to IC

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6.5.3 Analyte propertiesWhen a specific analyte is selected in the ANALYTES tree, four additional fields that are specific to IC will be displayed (Figure 25). These fields are Calibration By Height, Minimum Peak Width, Area Integration Type and Threshold.

6.5.3.1 Calibration by heightIf Calibration by Height is selected, the peak height rather than peak area will be used in the calibration. The default (unchecked) selection is peak area. Peak area is recommended because it integrates noise across an entire peak, giving more precise concentrations and lower method detection limits.

6.5.3.2 Minimum peak widthMinimum Peak Width (in minutes or seconds) defines a minimum peak width for IC peaks. Any peak that is narrower than the input value will not be defined as a peak and will not be integrated.

6.5.3.3 Area integration typeTwo options exist for Area Integration Type—Valley to Valley and Horizontal Baseline.

When Valley to Valley is selected, which is the default for each analyte, the integration will occur from the baseline to the valley between two peaks (Figure 26).

When Horizontal Baseline is selected, the integration will occur along the baseline. This option is useful when there are two peaks very near each other without baseline separation (Figure 26).

Figure 25 Run Properties window—change analyte properties

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6.5.3.4 ThresholdThe threshold is used to set a level below which the area of the peaks will not be integrated.

A section of the baseline is selected that the software uses to calculate the maximum second derivative or how fast the peak rises. A peak with a smaller second derivative than the selected section of the baseline will not be integrated. Setting the threshold level is discussed in more detail in section 6.7 on page 41.

6.6 Integration toolsIntegrating peaks for ion chromatography involves adjusting the peak expectation windows just as for FIA. Additional tools may be needed to correctly integrate the peaks, especially when separation is not complete and there is no resolution back to baseline between two adjacent analytes. The additional tools include manual integration, minimum peak width, area integration types and threshold.

6.6.1 Using manual integrationManual integration is used to adjust the integration for a single peak. Use manual integration to change the integration for a specific injection without affecting other chromatograms in the run.

There are two adjustments for manual integration. One is adjustment of the baseline window and the other is adjustment of the integration window. In some cases only one adjustment may be needed. In other cases it will be necessary to adjust both the baseline window and integration window. The following procedures are used for making these adjustments.

Figure 26 Integration—Valley to Valley vs. Horizontal Baseline

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6.6.1.1 Adjusting the baseline window1. Right-click on the peak to be adjusted. A menu will be

displayed (Figure 27).

2. Select Adjust Baseline Window for Manual Detection. An integration box will be displayed (Figure 28).

Figure 27 Manual baseline adjustment—menu

Figure 28 Manual baseline adjustment—integration box

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3. Click on the integration box. Use the 2-way or 4-way arrow to move the box to set the baseline. The baseline will run from where the box intersects the data trace on the left to where the box intersects the data trace on the right (Figure 29).

4. Right-click on the peak and select Run Manual Integration (Figure 30). The baseline will adjust to the new setting (Figure 31).

Figure 29 Manual baseline adjustment—set integration box

Figure 30 Manual baseline adjustment—Run Manual Integration

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.

6.6.1.2 Adjusting the integration windowThe integration window can be manually adjusted so that the integration will start and stop at selected times.

1. Right-click on the peak to be adjusted. A menu will be displayed (Figure 32).

Figure 31 Manual baseline adjustment—adjusted baseline

Figure 32 Manual integration adjustment—menu

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2. Select Adjust Integration Window for Manual Detection. An integration box will be displayed (Figure 33).

3. Click on the integration box. Use the 2-way or 4-way arrow to move the box to set where the integration will start and stop. The area above the baseline will be integrated from where the box intersects the data trace on the left to where the box intersects the data trace on the right.

4. Right-click on the peak and select Run Manual Integration. The integration window will adjust to the new setting (Figure 34). Note how the baseline continues on after the peak. This extension of the baseline represents an example of when the baseline window should be adjusted in addition to the integration window.

Figure 33 Manual integration adjustment—integration box

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6.6.2 Removing manual integration1. To remove the manual baseline or integration adjustment,

right-click on the peak that was adjusted to display the menu.

2. Select Clear Manually Adjusted Peak to remove the manual integration from the selected peak.

3. To clear all manually adjusted peaks select Clear All Manually Adjusted Peaks.

Figure 34 Manual integration adjustment—adjusted peak and extended baseline

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6.7 Changing the thresholdAll thresholds are set to 0 by default. To change the threshold, complete the following steps:

1. Right-click in the data window to display the menu (Figure 35). Select Enable Threshold Mode>select the analyte.

2. Drag across a portion of the baseline to select it. This portion of the baseline will be used for setting the threshold (Figure 36).

Figure 35 Threshold mode—select analyte

Figure 36 Threshold mode—select baseline for threshold

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3. Right-click and select Rerun Peak Detection or Rerun Peak Detection Ignoring Calibration Standards.

The threshold value will change in the Analytes tab of the Run Properties window (Figure 37).

4. Adjust the threshold value in the Run Properties window until the desired noise level is achieved. If areas are determined for sections that contain only noise, increase the threshold value. If areas are not determined for peaks that are being integrated, decrease the threshold value.

To apply the changes, switch to the Channel Display window, right-click and select Rerun Peak Detection.

6.8 Clearing the thresholdTo clear the threshold, right-click in the Channel Display window and select Clear Threshold.

The threshold can also be cleared in the Run Properties window>Analytes tab by setting the threshold value to 0. Then right-click in the Channel Display window and select Rerun Peak Detection.

Figure 37 Threshold value field

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6.9 Locating samplesThe Locate Sample feature is useful for locating a specific sample or for scrolling through each chromatogram. This feature is primarily for IC but can also be used for long FIA runs.

1. Right-click in the data window to display the menu.

2. Select Locate Sample. The Locate Sample window will be displayed (Figure 38).

6.10 Custom reportsA custom report for IC is generated and used in the same manner as for FIA. The one significant difference is in regards to the channel data display charts.

To include all sample peaks in a custom report:

1. Open the Custom Report Format window>Charts tab.

2. In the Channel Data Displays section, select Show All Peaks in Selected Sample (Figure 39).

The report will include a chart (chromatogram) for each sample.

Figure 38 Locate Sample window

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6.11 Spiking samples

6.11.1 TheoryThere are two important factors to keep in mind when spiking samples:

• Spikes test for matrix effects, not interferences.

• The spike volume should be small to minimize dilution of the matrix.

The following three rules should be followed when spiking samples:

• Rule 1: The spike should approximately double the concentration of the analyte in the sample.

• Rule 2: If the sample is near the MDL, spike at 5x the MDL.

• Rule 3: If the sample is in the top 40% of the working range, either choose a sample with a lower concentration or dilute the original sample. If diluted, the diluted sample must be run and spiked.

Figure 39 Custom Report settings for IC

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Example:A sample containing nitrate and nitrite has a nitrogen concentration of 3.0 mg N/L. The working test range is 0.1–10 mg N/L. Following Rule 1, the spike should increase the nitrogen concentration by 3.0 mg N/L.

It is good lab practice to use a specially prepared spike solution that is separate from the stock standard. Many labs also require that this solution come from a different container or lot of the raw material.

6.11.2 Spike procedure1. Determine the volume that the spike will be added to.

Example: sample cups hold 10 mL. Digestion tubes are diluted to 20 mL.

2. Determine the pipet volume to use. 5, 10 and 20 µL pipettes are common and reproducible. Larger pipettes dilute the matrix and smaller volumes are difficult to use with high precision.

Example: select a 10 µL pipet.

3. Determine the concentration of the spike solution using the following equation:

where:Spike solution conc. = initial concentration of the spike solutionVolume of spiked sample = total volume after spike addedVolume of spike solution = volume of spike that was added to sampleSpike level = final concentration of spike solution in the sample

Example:A spike is to be added to a sample so that the analyte concentration increases by 3.0 mg/L. The total sample volume after spiking will be 10 mL. A 10 µL pipet will be used. What should the concentration of the spike solution be?

Total volume 10 mL = 10,000 µL

The concentration of the spike solution should be 3000 mg/L.

4. Run the spiked sample and calculate the percent recovery. A range of 80–120% is generally considered good and 70–130% acceptable. The equation for this determination is:

Example:

The measured concentration of the original (non-spiked) sample is 3.09 mg N/L. The measured concentration of the spiked sample is 5.72 mg N/L. What is the percent recovery of the sample spike?

spike solution conc. volume of spiked samplevolume of spike solution------------------------------------------------------------------ spike level×=

spike solution conc. 10,000 µL10 µL

-------------------------- 3 mg/L× 3000 mg/L= =

% recovery spiked sample conc. unspiked sample conc.–spike level

------------------------------------------------------------------------------------------------------------------------- 100×=

% recovery 5.72 mg/L N 3.09 mg/L N–3.0 mg/L N

----------------------------------------------------------------------- 100× 87.7%= =

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6.12 Omnion 3.0 practice projectTime frame:

The Lachat trainer will indicate which tasks below should be performed.

1. Edit a template.

• Include at least 3 calibration standards.

2. Calibrate the system without running samples.

• Adjust parameters in the Analyte tab of the Run Properties window if necessary.

• Optimize analyte timing: adjust retention times

• Rerun peak detection

• Print calibration report

3. Run samples

4. Create a custom report format

• Save the custom report format

• Print the custom report

5. Export results to Microsoft® Excel® spreadsheet software.

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Section 7 Maintenance

7.1 Preventative maintenancePreventive maintenance is extremely important to keep the Lachat ion chromatography system operating at its maximum potential and to ensure long-term operation.

Keep all modules clean and dry at all times. Start a weekly maintenance schedule (section 7.3) to record dates for regular maintenance tasks.

Refer to the System User Manual for complete maintenance instructions for the following components:

• Dilutor

• Autosampler

• Peristaltic pump

• Eluent pump

• Injection valves

• Conductivity module

• Columns

• System unit

• Computer

• Printer

7.2 Maintenance guideThe general maintenance guide shown in Table 2 can be used for quick reference.

Table 2 Maintenance guide

Component Task Daily Weekly Monthly 6 months

Autodilutor Clean surfaces x

Autosampler Clean surfaces x

Clean and apply silicone to x-axis, y-axis and probe holder x

Peristaltic pump Spray silicone on cloth and rub onto oilers x

Replace pump tubes x

Clean pump tube adapters x

Eluent pump Clean surfaces x

Valves Clean ports x

Columns Clean x

Replace guard disc x

Conductivity detector Clean and dry all surfaces x

System unit Clean x

Computer Clean hard drive x

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Maintenance

7.3 Maintenance schedule exampleThe maintenance schedule example shown in Table 3 can be used to maintain system components on a regular schedule.

7.4 Inspecting the guard discThe Guard-Disc® prevents particulates from entering the high efficiency column bed. The adsorptive disc material is encapsulated in a solid polymer matrix bed. The disc and the adsorptive material can be examined to determine if replacement is necessary.

1. Identify the head of the anions column, as indicated by the wrench flat on the column body. Do not open the bottom end of the column!

2. Using two properly sized wrenches, unscrew the column cap at the head of the column. The column should be held upright.

3. Remove the Guard-Disc from the column head and inspect it from both sides. Replace the Guard-Disc if it shows color stains on both sides or if the column has high back pressure.

4. Carefully place a Guard-Disc into the small well on top of the pressed-in frit at the column head. Screw the column cap back in place. Do not overtighten! Use just enough torque to prevent leaks.

Table 3 Maintenance schedule example

Component Task Name Date

Autodilutor Clean surfaces

Autosampler Clean surfaces

Clean and apply silicone to x-axis, y-axis and probe holder

Peristaltic pump Spray silicone on cloth and rub onto oilers

Replace pump tubes

Clean pump tube adapters

Eluent pump Clean surfaces

Valves Clean ports

Columns Clean

Replace guard disc

Conductivity detector Clean and dry all surfaces

System unit Clean

Computer Clean hard drive

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Maintenance

7.5 Manifold removal• Flush the manifold according to the procedure in section 7.4.

• Detach all columns from the PEEK tubing. Cap the columns at both ends.

Note: Store columns in a refrigerator if the system will be idle for more than two days. The tubing may be left installed for the next operation.

• Remove the PEEK and transmission tubing, sample loop and regenerant loop from the valves.

• Remove the manifold from the Sample Processing Module (channel).

• Carefully wrap the transmission lines around the manifold and store it in the manifold box provided. Store the PEEK tubing, sample loop and regenerant loop as well.

7.6 System shutdown• Shut off the eluent pump. Allow pressure to drop to zero.

• Place the inlet filter line to deionized water.

• Prime the eluent pump with the deionized water.

• Purge manifold lines to avoid any air going into the columns or the conductivity module.

• Run the eluent pump for about 10 minutes to flush the eluent out of the system.

• If the system will not be used for a couple of days, cap all of the columns, eluent pump and conductivity module.

Note: if the eluent pump will not be used for more than a month, prime the pump with isopropanol. The alcohol in the pump will prevent the growth of any bacteria. DO NOT pump alcohol through the columns.

• Place the peristaltic pump lines in deionized water. Flush lines with water for about 10 minutes.

• Place the peristaltic pump (transmission) lines in an empty beaker. Flush out the deionized water for about 5 minutes.

• Turn off the peristaltic pump and release the pump tube cartridges by pressing the tube cartridge holders on the side of the pump.

• Switch OFF the master power strip after properly closing all files in the computer.

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Section 8 Troubleshooting exercises

8.1 Chromatography errorsThe following errors may occur due to problems with hardware, software, chemistry or fluidics (Figure 40).

• No peaks

• Integration problems

• Low correlation coefficient

• Retention time drift

• Air spikes

• Split peaks

• Odd-shaped peaks

• Baseline drift upwards

Figure 40 Troubleshooting tree

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Troubleshooting exercises

8.2 Troubleshooting scenariosDetermine the problem and solution for the following chromatograms.

Problem:

Solution:

Figure 41 Chromatogram A

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Problem:

Solution:

Figure 42 Chromatogram B

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Problem:

Solution:

Figure 43 Chromatogram C

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Problem:

Solution:

Figure 44 Chromatogram D

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Problem:

Solution:

Figure 45 Chromatogram E

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Problem:

Solution:

Figure 46 Chromatogram F

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Problem:

Solution:

Figure 47 Chromatogram G

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Problem:

Solution:

Figure 48 Chromatogram H

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8.3 QuikChem IC QuizCircle the correct answer for the following questions:

1. Air in the eluent pump during operation may:

a. Enhance sample results

b. Affect retention times

c. Damage the dampener

d. Cause an explosion

e. Decrease the back pressure

2. If no peaks are generated when running a method:

a. Check the system configuration

b. Check connections

c. Check the method parameters

d. Check fluidic connections, reagents and standards

e. All of the above

3. A what backpressure will an analytical column disconnect?

a. < 50 psi

b. 50–500 psi

c. 500–1000 psi

d. > 1000 psi

e. Columns may be disconnected at any time

4. Retention time is defined as:

a. Time where the maximum point of a peak is located

b. Time where two peaks meet

c. Time it takes for an ion to go through the column

d. The capacity of a column to retain ions

e. Time the first peak appears on the screen

5. Indicate which statement below is true:

a. A calibration must be run before any samples can be run

b. Retention times never change for a specific method

c. Columns should be stored dry to avoid damage

d. If the suppressor cartridge is not regenerated, the baseline will drift upward

e. Samples should never be filtered

6. Which of the following will result in high back pressure:

a. Guard disc on profiling column needs to be changed

b. Clog or crimp in peek tubing

c. Six port or ten port valve clogged or misaligned

d. Running unfiltered samples and/or eluent

e. All of the above

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7. The cause of a positive water dip is:

a. Sample was not filtered

b. Suppressor cartridge is not working

c. Conductivity module is not working properly

d. The ionic strength of the injected sample is greater than that of the eluent

e. The eluent is too strong

8. Indicate which statement below is true:

a. Air present at the detector gives a tall positive spike

b. Separation of analytes can be improved by preparing stronger eluent

c. Our cycle period need only be long enough that the last analyte we are interested in resolves to baseline.

d. Pumping filtered DI water can help clean columns

e. All of the above

9. Poor separation of ions may be the result of:

a. Eluent too strong

b. Age or Condition of columns

c. Pump flow rate set too high

d. One or more analytes out of range of the method

e. All of the above

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Section 9 Frequently asked questions

1. What sample preparation is necessary before injecting a sample into an IC?

The samples must be filtered through a 0.45 µm nylon filter. This is essential to prevent clogging the ports on the injection valve and the connecting tubing. Use a commercially available filter that connects to a syringe.

The sample pH must be between 2 and 12. Samples outside of this range should be adjusted. Use a commercially available cartridge that connects to a syringe to adjust the pH. Push the sample through an appropriate cartridge to adjust the pH.

Oily and greasy samples must be passed through a C18-type cartridge that will selectively remove oil and grease.

If the sample contains a high concentration of an ion that will interfere with the analysis, remove the ion using an ion-selective cartridge. For example if a sample contains 2000 ppm chloride in a sample that is to be analyzed for nitrite, use a silver-saturated cartridge to selectively remove chloride, bromide, and iodide from the sample.

Dilution can also be used to minimize interferences. Dilution can be performed either manually or pre-programmed through the software if using a Lachat XYZ sampler/auto-dilutor.

2. When determining whether an IC method can be used for analyzing samples, why is it important to know what other ions are present in the sample?

Non-target ions that are present in the sample can interfere with the test. For example, a nitrite analysis on a sample containing a high concentration of chloride is not possible. In the QuikChem method 10-510-00-1-A, the nitrite peak elutes adjacent to the chloride peak. A high concentration of chloride (500 mg/L) will completely mask the nitrite peak.

3. How long do the columns last? How much do the columns and other consumables cost?

The maximum column life will be attained by following good practices such as filtering the eluent through a 0.2 µm filter, filtering the samples through a 0.45 µm filter and routine maintenance. The frequency with which the columns are used will also affect the column life. A good guard column and guard disc in the analytical column also extends the life of the analytical column.

With proper care and relatively clean samples, the analytical columns and suppressor cartridge should last for approximately one thousand injections. A symptom of an aging column is seen when the peaks start eluting faster than under normal conditions. When this symptom is noticed, the columns can still be used by lowering the eluent strength or by reducing the flow rate. A symptom of an aging suppressor is seen when the baseline does not stay suppressed through the end of the run.

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Frequently asked questions

4. Can the columns be cleaned?

Filtering of eluent and samples will increase the column life. Despite all of the care taken, the columns do get contaminated. Typical symptoms include increasing back pressure, peaks eluting too fast, split peaks and diminished detector response for one or many peaks.

The guard column should be cleaned first because it is smaller and will clean faster than the relatively longer analytical column. If the symptoms do not occur when a new sample is injected, it is not necessary to clean the analytical column. The guard column should be replaced periodically as part of preventive maintenance.

The guard and analytical columns can become contaminated by metals such as iron, copper and lead. Columns can also become contaminated by particulates, surfactants and other organics. The metal contamination can be eliminated by pumping sodium EDTA through the columns.

5. Is it possible to manually inject samples?

Yes. The sample can be introduced to the valve using the peristaltic pump rather than a syringe. The valve toggles to load and inject using an electronic actuator. The system can be upgraded at a later time to an XYZ autosampler.

6. Does Lachat have methods for disinfection by-products?

Yes, QuikChem IC method 10-540-00-1-B provides mg/L quantification for the following species:

• Chlorite

• Bromate

• Bromide

• Chlorate

Chlorate and chlorite may be present in drinking waters that are disinfected by chlorine. Bromate may be present in drinking waters that are disinfected by ozone.

7. Does Lachat have methods for organic acids?

Yes, QuikChem IC method 21-550-00-1-A separates oxalic, maleic, malic, citric, tartaric, succinic, formic, acetic, fumatic, and adipic acids in approximately 18 minutes. The method is based on ion-exclusion separation of these acids, followed by suppressed conductivity detection.

8. Does Lachat have ion-exclusion columns?

Yes, the organic acids method is based on an ion-exclusion column.

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Frequently asked questions

9. Can the water-dip and fluoride peak become separated?

Yes, the water-dip and fluoride peak are fully resolved due to the unique column technology and suppression device with minimal dead volume.

10. How should the columns be stored?

Pump deionized (DI) water through the columns at the end of each day. The anion columns should be stored in DI water if not used for more than a day. The cation columns should be stored in eluent if not used for more than three days. To store, disconnect the tubing and fitting on the columns and connect the end plugs on the columns. Always store the columns with the end plugs to prevent them from drying out.

Important Note: Store columns in a refrigerator to avoid bacterial growth. Bacterial growth can contaminate samples and cause high backpressure.

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Section 10 Support information

Technical support departmentThe Technical Support Department is open Monday through Friday from 6:30 a.m. to 5 p.m. MST. Our technical support chemists are available during these hours to answer your questions. You may also contact technical support via e-mail.

Repairs and returnsAny item(s) shipped to Lachat Instruments must be accompanied by a job number or return number. This requirement applies to loaners, repairs, column repacks, returns (credits and exchanges), etc. Obtain the job or return number from the Lachat Technical Support Department before shipping any item(s) to Lachat Instruments.

Send all loaners, returned merchandise, and repairs to:

Lachat Instruments—Hach CompanyJob number or return number5600 Lindbergh Drive, North dockLoveland, CO 80538

Service contracts & loaner policyU.S. customers: Upon expiration of the limited warranty, Lachat offers a variety of service contracts. There is also a loaner program available to US customers.

International customers: Your local Lachat distributor will explain the services available in your country.

Advanced training and equipment qualification visitsAre you a new Lachat user? Get trained by our staff of professional trainers! Our trainers are technical support chemists with extensive knowledge in chemistry, software and hardware. The Lachat training provides you with the tools necessary to get the instrument up and running right away. Our expertise is passed on to you so that you don't have to spend many hours trying to figure out how to run the instrument.

Advanced training sessions and on-site equipment qualification (EQ) visits are also available. Please contact our Technical Support Department to learn more about these services.

Software upgradesContact our Technical Support Department to inquire about the latest software release and pricing. Some version upgrades may be free of charge.

Install the software upgrade following the instructions on the CD and the computer screen. Read the Release News included with the software to learn about what is new in the software upgrade.

• Telephone: • 800-247-7613 or 970-669-3050

• FAX: • 970-962-6732

• E-mail: • [email protected]

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Support information

Lachat methods library and USEPA approved methodsThe Lachat library consists of more than 350 methods. You may request a Methods List from a Lachat Representative or visit www.lachatinstruments.com. If you have purchased a manifold for a certain analyte, you may obtain other complete methods for the same analyte. As a Lachat customer, you may request a QuikChem method for a manifold that you do not own. However, this method will not include the manifold diagram.

The methods approved by the United States Environmental Protection Agency (USEPA) are compiled on a page in the Methods List. You can identify USEPA approved methods by the # sign next to the QuikChem method number, e.g. 10-107-04-1-A#.

Lachat onlineOur home page is located at www.lachatinstruments.com. The Lachat Sales Department may be contacted via e-mail:

[email protected]

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Appendix A Glossary

The following terms are commonly used in ion chromatography.

Analytical column—The column where the major separation of ions occurs. The column used in IC method 10-510-00-1-A has dimensions of 7.5 x 100 mm.

Eluent or mobile phase—The reagent that is constantly pumped through the injection valve, columns and detector by the high-pressure pump. Composition: e.g. a mixture of sodium bicarbonate and sodium carbonate used in the QuikChem anion method 10-510-00-1-A, or methanesulfonic acid used for the cation method 10-520-00-1-C & D.

Guard column—The guard column precedes the analytical column and is packed with a stationary phase similar to that of the analytical column. The guard column prevents particulate matter (e.g. large size (>0.2 µm) particles or humic fractions present in soil extracts) from passing through the analytical column. It is shorter in length and therefore easier and less expensive to replace than the analytical column. The guard column used in the IC method 10-510-00-1-A has the dimensions of 4.6 x 50 mm.

Ion chromatography (IC)—The method of separating ions by passing a liquid sample through a column. The ions are measured by a suitable detector.

Non-suppressed IC (NSIC) or single column IC (SCIC)—The eluent stream in NSIC is fed directly to the detector. The technique is based mainly on an article published in 1979. Some of the features include: (a) eluents of low conductance, e.g. p-hydroxybenzoic acid or phthalic acid, (b) columns of low-exchange capacity, and (c) poor detection limits.

PEEK tubing and fittings—PEEK (poly-ether-ether-ketone) tubing is commonly used in IC and has excellent resistance to organic and inorganic liquids.

Sample loop—Tubing that defines the volume of sample to be injected into the manifold for separation. The sample loop is usually connected to ports 1 and 4 of the injection valve. The most common sample loops have volumes of 50 µL, 100 µL or 200 µL.

Stationary phase—Columns are packed with solid material known as the stationary phase. The ions in the sample have varying affinities for the stationary phase and become separated as the sample moves through the stationary phase. Commonly used materials for the stationary phase include polystyrene divinyl benzene (PSDVB), silica, alumina and other polymers and copolymers.

Suppressor column—The suppressor column contains a cation exchange resin that suppresses conductivity from the eluent. If not suppressed, the eluent can mask the signal from the analyte.

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Glossary

Suppressed IC (SIC), dual-column IC (DCIC) or chemically suppressed IC (CSIC)—The background conductance of the eluent stream is chemically suppressed before being fed to the detector. The technique is based on an article published in 1975.

For example when CSIC is used for anions, stronger eluents are used, e.g. carbonate and bicarbonate. The eluent provides a combination of divalent and monovalent species. The ratio of carbonate to bicarbonate can be altered to obtain separation between mono-, di-, and tri-valent anionic species. Compared with non-suppressed IC, the columns have relatively high exchange capacity.

Water dip—Observed in the CSIC analysis of anions. The water dip occurs as follows:

1. The carbonate and bicarbonate anions of the eluent are adsorbed onto the exchange sites of the column.

2. The injected sample or standard displaces these eluent anions from the column.

3. The displaced eluent anions traverse through the suppressor column or other suppressor device.

4. The chemical suppression results in the formation of carbonic acid and manifests as a water-dip in the chromatogram.

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Documents

TRAINING MANUAL February 2007, Edition 1