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The Leadville Mill <br />2.2.1 PH <br />Environmental Sampling Procedures <br />Water Sample Collection <br />Page 2 -2 <br />The pH scale is from 0.0 standard units (su) to 14.Osu, with 7.Osu being neutral. <br />Because pH is a negative logarithm of the hydrogen ion activity, a change of one su <br />equals an order of magnitude change in concentration. Combination electrodes may <br />be used in field determination of pH due to the convenience of a single electrode <br />system. The combination electrode contains both the glass and the reference <br />electrode in a single housing. This electrode is generally not affected by color, <br />turbidity, colloidal matter, high salinity, oxidants, or reductants. Factors that cause <br />interference in pH measurements include the following: <br />• Temperature - Temperature compensation must be applied if the sample <br />temperature is not within 2 °C of the calibration buffer temperature. If the pH <br />meter is not equipped with automatic temperature compensation (ATC), the <br />calibration is conducted by manual adjustment of the electrode response <br />(temperature offset) as described in the manufacturer's instructions. <br />Temperature of the solution at the time of pH measurement must be <br />reported together with the pH value. <br />• Sodium Content - Errors in pH measurement will occur for samples of high <br />sodium content and pH above 10. This error can be eliminated by using a low <br />sodium error electrode. <br />• Oily & Organic Samples - The following method is not suitable for oily or <br />organic samples, because the electrode response can be impaired by coatings <br />from these materials. Electrodes can be easily cleaned as described in the <br />manufacturer's instructions. <br />PROCEDURE FOR PH MEASUREMENT <br />Follow instructions in the owner's manual supplied by the manufacturer to stabilize <br />system and to operate the pH meter. Use the owner's manual to select <br />recommended solutions to maintain electrodes in good condition during long -term <br />or short-term storage. If required, keep electrodes wet by returning them to storage <br />solutions when not in use. <br />• Equipment Calibration <br />1. Equipment must be calibrated prior to use each time the instrument is <br />turned on. The pH meter and the electrode must be calibrated <br />Apr#2013 <br />