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Clayton Group Services Paget Standard Operating Procedures SOP -9 - Field Measurement of pH, Conductivity, and Temperature 2. Sample measurements - Place the electrodes in the water sample and read the pH off the meter. Measurements should be taken as soon as possible after sampling and with a minimum disturbance to the sample. Record the measurements in the field logbook. 3. Maintenance - The electrodes should be stored in their protective caps with a drop or two of distilled water or in a Parafilm-covered beaker of tap water. Inspect weekly - The reference electrode should be at least half -full of the filling solution. When the meter is to be stored for a week or longer, the filler hole should be plugged. Check the glass electrodes for cracks. Check the batteries before each usage and carry an extra battery and screwdriver into the field. Temperature Typically, temperature simply is measured by placing the electrode from the pH, conductivity, temperature meter into the water and reading the temperature off the meter. However, if more precision is required, two National Bureau of Standards (NBS)- calibrated thermometers are used as follows: • Check the thermometers for cracks or caps in the mercury. • Pour at least 200 mL of sample taking care not to touch the sides of the sample container with the thermometer. • After allowing the thermometer to equilibrate, record the temperature to the nearest 1 degree Celsius (°C). • Quarterly, check the thermometer against an NBS-calibrated thermometer. Readings should be within 0.5°C of the calibration thermometer. Conductivity If a pH, conductivity, temperature meter is used, conductivity is measured by placing a water sample into the water receptacle on the meter, setting the conductivity scale to the desired range, and reading the conductivity directly off the meter. Following measurements on the water, all equipment should be cleaned thoroughly. All activities and measurement results need to be documented in the filed log book and field log sheets. S:\Ermr\Proj\SOPS\SOP-9.doc