pH by Multi-meter

Caduceon Environmental Laboratories Page: 1 of 8 pH Revision Date: 20 April 2017 Method A-pH-01 Revision #: 1.7 Management Review: SG Quality Review: SB

pH by Multi-meter 1.0 Scope and Application 1.1 This method is applicable to the determination of pH in water samples with a range of approximately

1.0-14.0 pH units. 1.2 The relative detection difference is 0.02 pH units. Results are reported at a corrected temperature of

25oC. 2.0 Principles and Theory 2.1 Principles

2.1.1 The measurement of pH is the determination of hydrogen ion activity in an aqueous solution. The glass pH electrode responds to the hydrogen ion concentration (activity) by developing an electrical potential at the glass/liquid interface. At a constant temperature, this potential varies linearly with the pH of the solution being measured.

2.2 Theory

2.2.1 pH is defined as –log [H+]; it is the intensity of acidity. At 25ºC, pH 7.0 is neutral (i.e., the activities of the hydrogen ions (H+) and hydroxyl ions (OH-) are equal), each corresponding to an approximate activity of 10-7 moles/L. The neutral point is temperature dependent, varying from pH 7.5 at 0ºC to pH 6.5 at 60ºC.

2.2.2 The glass pH electrode system includes a temperature probe, and in many modern pH meters or

‘multi-meters’, the pH of the sample is temperature corrected to 25ºC. 2.3 Interferences

2.3.1 Sodium error in strongly alkaline solutions is low, even at pH values as high as 11. This interference can be further reduced by the use of a “low sodium error” electrode.

2.3.2 Sample to sample cross-contamination can occur if proper rinsing of the pH probe is not

performed between determinations. Special care should be taken following dirty samples, and those with high or low pH values.

3.0 Safety 3.1 Follow all applicable safety rules from the Caduceon Safety Manual. 3.2 Consult MSDS before handling chemicals. 4.0 Sample Requirements 4.1 Sample Collection

4.1.1 Collect water samples, unpreserved, in clean plastic bottles and store at 4 ± 3oC. The minimum volume required is 100mL.

4.1.2 Care must be taken when collecting samples to ensure that unwanted material is not included

in the sample. If a sample is received with material that may not be appropriate for inclusion in the analysis, the Client/Submitter must be contacted for further instructions.

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4.2 Sample Holding Times

4.2.1 Water samples should be analysed as soon as possible after collection but can be stored for up to 4 days (section 10.1.2) at 4 ± 3oC. Warm to room temperature before analysis.

5.0 Equipment 5.1 Labware

5.1.1 Sample Bottles, 80mL Specimen Containers, Plastic 5.1.2 Sample Bottles, 500mL Plastic 5.1.3 Magnetic Stirrer and Stir Bars 5.1.4 Beakers, 100 or 150mL

5.2 Equipment

5.2.1 pH meter Accumet Model AB200 pH/Conductivity Meter 5.2.2 pH probe stand 5.2.3 pH probe Accumet Combination pH Electrode NOTE: may contain built-in ATC probe 5.2.4 Temperature probe (if necessary) Accumet ATC probe (see CP-023)

6.0 Reagents

Document ordering, receiving and storage of Reagents, Supplies and Standards, using the appropriate forms, as directed in SOP-25 Receiving of Chemicals, Products and Essential Parts, and other applicable procedures.

6.1 Reagents

6.1.1 Reagent Water (DI) prepared as per CP-024 6.2 Calibration Standards

6.2.1 Calibration, pH 4.0 Certified Buffer Solution, Purchased from Fisher Scientific, ensure to order new solution before expiry date. Transfer about 40mL to a 80mL sample bottle and label as pH4, with the date and analyst initials. Obtain new aliquot of solution on a monthly basis or as needed. Store at room temperature.

6.2.2 Calibration, pH 7.0 Certified Buffer Solution, Purchased from Fisher Scientific, ensure to

order new solution before expiry date. Transfer about 40mL to an 80mL sample bottle and label as pH7, with the date and analyst initials. Obtain new aliquot of solution on a monthly basis or as needed. Store at room temperature.

6.2.3 Calibration, pH 10.0 Certified Buffer Solution, Purchased from Fisher Scientific, ensure to

order new solution before expiry date. Transfer about 40mL to an 80mL sample bottle and label as pH10, with the date and analyst initials. Obtain new aliquot of solution on a monthly basis or as needed. Store at room temperature.

6.3 Quality Control Samples

6.3.1 QCpH-06, pH 6.00 Certified Buffer Solution, Purchased from Fisher Scientific, ensure to order new solution before expiry date. Transfer about 40mL to an 80mL specimen container. Label as QCpH06, with the date and analyst initials. Obtain new aliquot of solution on a monthly basis or as needed. Store at room temperature.

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7.4 Documentation

7.4.1 Document all Calibration, QC and sample information on Form ALK-1 Alkalinity Worksheet. 7.4.2 Document all QC failures in the Non Conformity log.

7.4.3 Document all equipment maintenance, comments and any changes in Multi-meter log book.

7.4.4 The analyst must enter QC data into the QC data file after each batch of analysis.

7.4.4.1 The QC data files are found on the Caduceon server at the following location:

\\192.168.6.14\Quality_Documents_and_Records\QA_QC\QC_Logs\Richmond_Hill.

7.4.4.2 Open these files and enter the data (Dates, Expected and Found Concentrations for QCpH-06, QCpH-09 and Duplicate results) in the appropriate fields.

7.4.4.3 The Excel program will calculate the % recoveries for the QC Samples and the %

difference for the Duplicate samples.

7.4.4.4 The QA Officer will maintain the Excel program files. Control Charting and trend analysis are performed using CP-031.

8.0 Calculations and Reporting 8.1 There are no calculations for pH analysis. 8.2 Refer to Caduceon CP-012 LIMS Training for details of the recording of results in the Laboratory

Information Management System (LIMS).

8.2.1 The temperature-corrected pH results are entered into the Instrument Run module of the LIMS Job Book.

9.0 Method Validation and Performance (data from Jan 2013 to June 2015) 9.1 Water

9.1.1 Method Validation Data

Data Points Calculation

Precision, % 65 3.57

Recovery, % 65 98.5

Accuracy, % Error 65 1.5

Based on Ultracheck QC

9.1.2 Quality Control Standards

Sample ID # of Data

Points Expected (pH units)

Mean (pH

units)

Average Bias

(pH units)

Standard Deviation

UCL (pH units)

LCL (pH units)

QCpH6 457 6.00 6.01 0.01 0.028 6.09 5.92

QCpH9 468 9.00 8.95 -0.05 0.075 9.17 8.73

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ExtQC 65 100% 98.5 1.5 1.82% 104% 93%

9.1.3 Duplicate Analyses

Analytical Range # of Data Points Acceptable Limits-RPD %

All 184 0.75

9.1.4 Method Uncertainty

9.1.4.1 The expanded uncertainty is determined as per CP-026. The data accumulated in the QC log is used to calculate the expanded uncertainty.

Typical Concentration

(pH units) Combined Uncertainty

(pH units) Expanded Uncertainty *

(pH units)

6.0 0.022 0.042

9.0 0.019 0.043

* Expanded uncertainty is reported at 95% confidence interval (coverage factor k=2)

9.1.5 Method Performance

9.1.5.1 The Method Performance is monitored by the results of PT sample analysis. Each round’s reported results and consensus values are entered in the Method QC log. The % Recovery is calculated on a minimum of 8 sample results. The maximum allowable deviation of a PT result is based on 3sd.

Mean % Recovery 99.8

Standard Deviation (sd) 1.1

3sd (99% Confidence Level) 3.3

# of Data Points 64

9.2 Based on the method validation data supplied above, this method has been deemed as fit for its

intended use (as stated in Section 1 of this document). 9.3 Unless otherwise indicated, all tables found in section 9 of this method contain original validation data

and are present to support the statements made in section 9.2. All analysts must refer to the relevant QAQC logs for the current limits when verifying data is acceptable for reporting.

10.0 References 10.1 Analytical Methods

10.1.1 Standard Methods for the Examination of Water and Wastewater, Method 4500-H+, Current revision.

10.1.2 Protocol for the Sampling of Industrial/Municipal Wastewater, MOE, Current revision. 10.2 Caduceon Standard Operating Procedures

10.2.1 Caduceon CP-022, Thermometer Calibration & Verification 10.2.2 Caduceon CP-024 Preparation of Lab Grade Water 10.2.3 Caduceon CP-031 Control Charting 10.2.4 Caduceon SOP-25 Receiving of Chemicals, Essential Parts and Equipment

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10.2.5 Caduceon CP-026 Determination of Uncertainty in Measurement 10.2.6 Caduceon CP-012 LIMS Training 10.2.7 Caduceon CP-032 Non Conformities 10.2.8 Caduceon Safety Manual

10.3 Instrument Manuals

10.3.1 Accumet Operations Manual 10.3.2 Accumet Combination pH Electrodes Instruction Sheet

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Log of Revisions

Date Rev Description Author

30-Jun-2010 1.3 Section 5.1- Updated Labware list. Section 7.1- Added more requirements to meter calibration procedure. Section 7.3- Added sample aliquot step anduse of ATC probe. Section 9- Updated the method validation data. Updated Analyst worksheet form id throughout the document. Updated all SOP references

CW/DEP

14-Sep-2010 1.4 Section 7.1.2 – Added slope acceptance criteria Section 7.1.3 – Added the specific steps to analyze the QC samples Section 7.2 – Updated to Richmond Hill

CW

14-Jul-2014 1.5 Removed use of Ext QC Standard Section 7.1.5 – Revised wording Section 7.2.3 – Updated Run Structure Section 7.2.4 – Added new section item Section 10.1- Updated references Multi-year sign off added

SG

02-Jul-2015 1.6 Section 4.2.1 – Updated holding times to reflect current practice Updated section 5.2 to include new equipment Section 6.2.2 – Corrected expiry date Section 7.4.4.1- Update to include new location of QC logs Updated section 9 to include current validation data

CB/SKB

20-Apr-2017 1.7 Section 9.3 update to explain data is original validation data SKB

Document Review This document was last reviewed and authorized by: Laboratory Branch Manager Date This document was last reviewed and authorized by: Laboratory Branch Manager Date This document was last reviewed and authorized by: Laboratory Branch Manager Date This document was last reviewed and authorized by: Laboratory Branch Manager Date

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