Top Tips for Conducting DMR-QA Analyses documents/ERA_Top_Tips... · DMR-QA 33 Opens Monday, March 25. Closes Midnight, Monday, July 8. PT providers send graded reports by July 29

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Top Tips for Conducting

DMR-QA Analyses


Moderator: Rick Persichitte

Senior Account Representative

ERA – A Waters Company

Presenter: Tom Widera

Product Line Manager - Inorganics

ERA – A Waters Company


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Agenda

Quick tips to help you get through DMR-QA 33

Analysis tips

— pH

— Total Residual Chlorine (TRC)

— Total Suspended Solids (TSS)

— Demand (BOD and CBOD)

— Ammonia

Questions


Tom Widera

Product Line Manager - Inorganics

ERA - A Waters Company


Quick Tips to Help You Get Through DMR-QA 33

Opens Monday, March 25.

Closes Midnight, Monday, July 8.

PT providers send graded reports by July 29.

Permittees send report to DMR-QA coordinator by August 26.

Corrective Action reports due by October 7.

If running WP, report results by close of WP study.

WP must close between January 1 and July 8.

Run analyses as soon as possible.

Allow time for things to go wrong.

Run CRM Samples. Establish a routine quality control process

with the use of CRMs.


pH

1. Electrode checking and maintenance

2. Calibrate Your meter every day

3. Use fresh buffers

4. Temperature compensation

5. Run samples at room temperature


Tips for Running pH

The pH electrode needs routine maintenance to operate

properly. The electrode reading should stabilize within 30

seconds. Any longer than that is an indicator that the

electrode needs maintenance.

Film builds up on the outside of the electrode and needs to be

cleaned at least monthly to allow proper contact with the

sample. Allow the electrode to sit in hot soapy water or 1%

HNO3 for at least one hour. Rinse thoroughly with DI water.

For non gel electrodes, the inside of the electrode should also

be maintained monthly. The filling solution evaporates over

time. Constantly refilling the solution causes saturation of the

solution within the electrode. Monthly, empty the filling

solution, fill and rinse the electrode twice with DI water, rinse

once with filling solution then fill with fresh filling solution.


Tips for Running pH

Proper operation of the electrode can be monitored by reading

mV readings of the buffers. Place the electrode in the pH 4

buffer and take reading. Place electrode in pH 7 buffer and

take a reading. The difference in those reading should be 171

mV ± 9 mV.

pH meters are fairly stable. However, they may drift upwards

of 0.05 s.u. over a week. The limits are only ±0.2 s.u. This

drift could cause a failure. Calibrate your meter every day you

run samples to increase accuracy.

Fresh buffers should be used every day. Never reuse a buffer

solution. The pH 10.0 buffer readily adsorbs CO2 which will

change the pH. It is unstable. It is recommended to use the

pH 10.0 buffer for only 3 months after opening.


Tips for Running pH

Automatic temperature compensation (ATC) is critical. Small

changes in temperature can cause big differences in pH.

The meter is designed to compensate pH for any temperature

changes.

The ATC can compensate for any temperature change.

However, it is recommended to run buffers and samples no

more than 5o apart. Cold samples will cause the filling solution

to change temperature. As the temperature changes in the

electrode, the pH readings will drift. It is recommended to

place buffers and samples on the bench the night before you

run the test.


TRC

1. Use organic and chlorine free deionized water

2. Do not use plastics

3. Run TRC samples immediately after diluting

4. Recalibrate your meter annually

5. Proper meter zeroing


Tips for Running TRC

Ensure that the water used to dilute the sample is both organic and chlorine free. Organic contaminants may produce a false free chlorine reading. Water coming into your lab has been treated with chlorine. Ensure that no chlorine exists in the DI water by running a blank DI sample.

Plastics contain micropores. These micropores are excellent places for the chlorine molecule to deposit itself causing low results. Do not allow the sample to come into contact with plastics. Avoid plastic flasks and do not use disposable pipet tips.

Chlorine is unstable. It is light sensitive and degrades quickly when exposed to air. This is the reason why chlorine is considered a 15 minute test when reporting for DMRs. Chlorine will begin to degrade immediately. ERA has done research to determine if the sample is run within 2 hours of diluting, then no appreciable degradation is noticed.


Tips for Running TRC

HACH meters are very popular for TRC and are effective in

running the test. Most HACH meters are internally calibrated,

so calibrating each time you run is not necessary. However,

the calibration will drift over time causing erroneous readings.

It is recommended, and sometimes required, to have the

meters re-calibrated by a certified technician annually.

Most HACH methods require zeroing the instrument prior to

running the samples. Zero the meter correctly. Take a portion

of the sample to be run and place in the meter without DPD in

it. Zero the instrument to remove any interferences. Then add

DPD to the sample to color.

Allow adequate time for the DPD to react with the chlorine in

the sample.


TSS

1. Use enough sample

2. Rinse apparatus thoroughly

3. Dry thoroughly

4. Minimize environmental controls

5. Run filter blank


Tips for Running TSS

When using gravimetric tests, ensure that you can accurately

and appropriately read the amount of residue left in the pan.

Use no less than a 4 place balance.

Environmental controls play a big role in the accuracy of TSS

measurements. The more mass of residue that is on the

balance, the less these environmental controls come into play.

TSS powder will stick to everything. Make sure you rinse all

glassware that comes into contact with TSS thoroughly with DI

water. Mix the sample extremely well as the TSS is heavier

than water and will tend to sink. Rinse the graduated cylinder

and vacuum filtration apparatus at least three times with DI

water to ensure no TSS residue sticks.

Moisture is an issue with TSS. Run a blank filter to determine

that you are not gaining or losing moisture in the test.


Tips for Running TSS

Ensure that the sample is completely dry. Dry the sample

using your normal procedure. Once dry weight is measured,

place the sample back in the oven for at least 30 minutes and

reweigh to ensure that a constant weight is achieved.

Use a desiccator to ensure that you are not introducing

moisture when cooling.

Cool sample long enough. Ceramic crucibles take longer to

cool than aluminum pans. Although the crucibles may feel cool

to the touch, if not completely cooled readings will be affected.

Also, crucibles will cool at different rates. As a general rule

allow the crucibles to cool for at least an hour. Cool the

samples for equal amounts of time for each drying event.


BOD/CBOD

1. Adjust ph to proper level (6.5-7.5)

2. Setup method properly

3. Use adequate sample sizes

4. Run GGA

5. Use only aliquots meeting method criteria


Tips for Running BOD/CBOD

It is critical that the test be run with samples between pH 6.5-

7.5. If the sample is too acidic or basic, it will distress the

microorganisms, causing falsely low oxygen depletion. ERA

research has shown that a 0.2N NaOH solution is effective for

pH adjusting. It will take about 3-5 mL to adjust the pH of the

ERA Demand sample.

Method conditions are critical for proper oxygen depletion.

— Initial DO should be between 7-9 mg/L.

— Incubation should be exactly 5 days at a temperature of 20±1oC.

— DO difference should be at least 2.0 mg/L

— There should be at least 1.0 mg/L residual DO.

— Do not allow any air to enter the sample during incubation.

Run seed control. Control should be 0.6-1.0 mg/L

Blank correct before reporting results.


Tips for Running BOD/CBOD

Use enough seed to facilitate oxygen depletion.

Poly seeds and raw influent seed have different strengths.

Spike each bottle individually with seed. Do not spike the

diluted sample with seed.

Run a Glucose/Glutamic Acid (GGA) check as per the method.

This will determine if your method is in control.

When determining which aliquots to use in the test, make sure

you have enough sample to meet the 2.0 mg/L depletion and

do not use too much sample so you are left with less than 1.0

mg/L residual.

Only use aliquots that meet the method criteria when

determining which aliquots to report.


Ammonia by ISE

1. Change membrane often

2. Slope electrode

3. Calibrate meter appropriately

4. Adjust ph appropriately

5. Maintain constant temperature


Tips for Running Ammonia by ISE

The ammonia electrode uses a membrane that measures partial pressures on both sides of the membrane. The membrane needs to be changed weekly as it will begin to clog over time, thus reducing its ability to measure the partial pressure.

Ensure that the electrode is functioning properly by performing a slope of the electrode. This is done by spiking two aliquots of ammonia with a 10 fold change in concentration (such as 10 and 100 ppm). The difference in mV reading should be 54-60 for the electrode to be considered working properly.

Ensure that the meter is calibrated appropriately and each time an analysis is done. Observe the calibration range for your analysis. The smaller the dynamic range the more accurate the analysis will be. For example the values of ammonia will be 0.65 to 19 mg/L. Calibrating from 1-100 in this case may cause inaccuracies in the analysis.


Ammonia testing is actually meauring the ammonium ion which is volatile at a pH > 11. To avoid low reading ensure the pH is adjusted > 11. The blue ISA solution is good to use as it stays blue at a pH > 11 but turns clear at a pH< 11. Using NaOH is also OK, as long as you pH check your sample.

Since the sample is being stirred causes heat to be created by the stir plate, place a material on the stir plate which will avoid heat transfer to the sample. A 1o change in temperature can change your values by a much a 5%.

Remember to report your results as NH3-N not NH3-NH3.

If you are using a High Performance electrode, ensure to read the manual carefully. This electrode is very sensitive and drifts easily. Do not rinse the electrode with DI water. Dunk the electrode in a container of DI water and dab dry with a Kimwipe.

Tips for Running Ammonia by ISE


QUESTIONS


Contact ERA

800.372.0122

303.431.8454

6:00 am – 6:00 pm Mon-Thu (MT)

6:00 am – 5:00 pm Fri (MT)

[email protected]

www.eraqc.com

www.facebook.com/eraqc

www.youtube.com/eraqc

Documents

Top Tips for Conducting DMR-QA Analyses documents/ERA_Top_Tips... · DMR-QA 33 Opens Monday, March 25. Closes Midnight, Monday, July 8. PT providers send graded reports by July 29