STANDARD OPERATING PROCEDURES SOP: 2077 PAGE: 1 of 11 REV: 0.0 DATE: 11/21/00

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1 PAGE: 1 of 11 CONTENTS 1.0 SCOPE AND APPLICATION 2.0 METHOD SUMMARY 3.0 SAMPLE PRESERVATION, CONTAINERS, HANDLING AND STORAGE 4.0 INTERFERENCES AND POTENTIAL PROBLEMS 5.0 EQUIPMENT/APPARATUS 6.0 REAGENTS 7.0 PROCEDURE 8.0 CALCULATIONS 9.0 QUALITY ASSURANCE/QUALITY CONTROL 10.0 DATA VALIDATION 11.0 HEALTH AND SAFETY 12.0 REFERENCES 13.0 APPENDIX A - Digi-Sense Digital ph/mv/orp Operator s Manual REPLACES: SOP #2077, Revision 0.0; 12/19/96. U.S. EPA Contract EP-W

2 PAGE: 2 of SCOPE AND APPLICATION This standard operating procedure (SOP) describes the measurement of ph in aqueous media using a COLE-Palmer Digi-Sense digital ph/mv/orp meter. These are standard (i.e. typically applicable) operating procedures which may be varied or changed as required, dependent upon site conditions, equipment limitations, or limitations imposed by the procedure. In all instances, the ultimate procedures employed should be documented and associated with the final report. Mention of trade names or commercial products does not constitute U.S. Environmental Protection Agency (U.S. EPA) endorsement or recommendation for use. 2.0 METHOD SUMMARY The electromotive force (EMF) produced in the glass electrode system varies linearly with ph. This linear relationship is described by plotting the measured EMF against the ph of different buffers. Sample ph is determined by extrapolation (1). 3.0 SAMPLE PRESERVATION, CONTAINERS, HANDLING and STORAGE No preservation is necessary. Samples should be stored in glass or polyethylene bottles, maintained at 4 o C and analyzed immediately. Analyses are typically performed at room temperature. All samples and calibration buffers should be allowed to equilibrate to ambient temperature prior to analysis. The amount of the sample to be collected and the proper sample container type (i.e., glass, plastic), chemical preservation, and storage requirements are dependent on the matrix being sampled and the parameter(s) of interest, and are discussed in ERT/SERAS SOP #2003, Sample Storage, Preservation and Handling for water matrices. 4.0 INTERFERENCES AND POTENTIAL PROBLEMS The combination electrode is relatively free from interference from color, turbidity, colloidal matter, oxidants, reductants, and high salinity, except for a sodium error at ph >10 (1). Measurements of ph are affected by temperature in two ways: mechanical effects that are caused by changes in the properties of the electrodes, and chemical effects caused by equilibrium changes. Standard ph buffers have a specific ph at indicated temperatures. 5.0 EQUIPMENT/APPARATUS The following are standard materials and equipment required for testing: ph meter, Model No

3 PAGE: 3 of REAGENTS Combination ph electrode Magnetic stir plate Magnetic stir bars Thermometer 9V battery At least two standard known ph buffers are needed to calibrate the meter. The three most common are ph 4.00, 7.00, and buffers. The buffers selected should bracket the ph of the samples. A saturated aqueous potassium chloride (KCl) solution is used for filling the combination electrode. If separate glass and reference electrodes are used, the reference electrode is filled with saturated aqueous KCl. Deionized or distilled water should be used for rinsing the probe between samples. 7.0 PROCEDURE 7.1 ph Calibration Procedure 1. Press ON/OFF key to turn meter on. 2. Connect the ph probe to the meter. 3. Immerse the probe in buffer Press the ph/mv key to select ph. 5. Adjust temp EC control to the temperature of buffer Note: Both buffers should be at the same temperature. 6. Adjust the standardize control to read 7.00 ph on the display. 7. Rinse the ph probe with deionized or distilled water and blot dry. 8. Immerse the probe in the second buffer (4.00 or 10.00) 9. Adjust the temp EC control to the temperature of the second buffer. 10. Allow the reading to stabilize, and then adjust the SLOPE control to the value of the second buffer. 11. Rinse probe with deionized or distilled water. Calibration is now complete. The ph meter should be calibrated at the beginning of every eight-hour operating period, and the calibration must be checked at least once during every subsequent eight-hour period.

4 PAGE: 4 of Operation 1. Push the ON/OFF key to turn the meter on. 2. Push the ph/mv key until the annunciators indicate the desired mode. For millivolt or ORP (oxidation-reduction potential) measurement: Press the ph/mv key until the display shows millivolts. Verify the probe connection, then rinse the probe with distilled water and blot dry. Immerse the probe in the sample to be measured. Allow the displayed reading to stabilize, then take the reading. 7.3 Temperature Compensation Temperature compensation can be set manually by the temperature o C adjustment over a range of 0 o to 100 o C. 7.4 Sample Measurement 1. Measure the temperature of the sample to be measured 2. Rinse the probes with distilled or deionized water. Blot dry. With the meter on, place the electrode in the sample solution to be measured, which is being magnetically stirred. 3. If the meter is calibrated using ph 4.00 and ph 7.00 buffers and the sample reading is >7.00, the meter will be recalibrated using ph 7.00 and buffers. Adjust the temp EC control the match the sample solution temperature. The sample ph will be displayed. Record the reading once the meter has stabilized. For millivolt or ORP measurement: Press the ph/mv key until the display show millivolts. Verify the probe connection, then rinse the probe with distilled water and blot dry. Immerse the probe in the sample to be measured. Allow the display reading to stabilize, then take the reading. 7.5 Battery Replacement The ph meter uses a 9 volt battery with a life of 2000 hours. If the low battery indicator is on, stop operation and replace the internal battery with a new 9 volt battery. 7.6 Cleaning the Probe The glass bulb is the sensitive part of the probe, it should always be kept clean. Rinse the probe with deionized or distilled water after use. Before storage, rinse the probe with tap or distilled water, shake dry and place the probe in the protective cap, which should be filled with a KCl solution or equivalent probe storage solution.

5 PAGE: 5 of CALCULATIONS If KCl or equivalent storage solution is not available, use a 4.00 ph buffer, 7.00 ph buffer, or tap water. Distilled water should never be used. The value displayed is read directly as ph. The temperature of the samples and calibration buffers should be identical to assure accuracy. Record sample temperature with ph value. 9.0 QUALITY ASSURANCE/QUALITY CONTROL All data must be documented on field data sheets or within site or laboratory notebooks. All instrumentation must be operated in accordance with the manufacturer s instructions. Equipment check-out procedures and calibration activities must be performed. (See section 7.1). Duplicate samples should be processed with the frequency of one in twenty samples. Duplicate samples will be used to determine precision DATA VALIDATION By careful use of a laboratory ph meter with good electrodes, a precision of ±0.02 ph unit and accuracy of ± 0.05 ph unit can be achieved. However ±0.1 ph unit represents the limit of accuracy under normal conditions, especially for measurement of water and poorly buffered solutions (1) HEALTH AND SAFETY General laboratory safety practices should be followed. Waste samples should be handled with care due to the uncertainty of the properties and contents involved. Refer to the specific material safety data sheet (MSDS) for the hazardous properties of any chemical or reagent utilized in this analysis. All excess samples, used samples, and waste material generated during analysis must be disposed in accordance with ERT/SERAS SOP #1501, Hazardous Waste Management. When working with potentially hazardous materials, follow U.S. EPA, OSHA, and Lockheed Martin health and safety procedures. More specifically, refer to ERT/SERAS SOP #3013, Laboratory Safety Program REFERENCES (1) American Public Health Association (APHA) Standard Methods for the Examination of Water and Wastewater, 18th Edition. Baltimore, Maryland: Port City Press. (2) Cole-Parmer Instrument Co. Digi-Sense Digital ph/mv/orp Meter Operator s Manual, A , Edition 2692.

6 PAGE: 6 of APPENDIX A - Digi-Sense Digital ph/mv/orp Operator s Manual

7 PAGE: 7 of 11 APPENDIX A Digi-Sense Digital ph/mv/orp Meter Operator s Manual SOP #2077 November 2000

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