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R9 Laboratory SOP 560
TOTAL ALKALINITY, TITRIMETRIC METHOD
Summary
This method describes the standard and sample analysis of waters for total alkalinity by titration. This method is applicable to drinking, ground, surface, and saline waters that can be characterized as carbonate systems. It is suitable for all concentration ranges of alkalinity. This method is based on Standard Method 2320, Alkalinity.
Total alkalinity in drinking, surface, saline, and ground water samples is a function of the carbonate, bicarbonate, and hydroxyl ion concentrations. A representative sample aliquot is titrated with standardized sulfuric acid to an electrometrically determined end-point of pH 4.5.
For low alkalinity samples, the titration is continued to reach a second end-point 0.3 pH-units below the initial end-point. Based upon the volume of acid used, the alkalinity in the sample is calculated and reported in units of mg/L CaCO3.
For total alkalinity measurements, the sample must not be filtered, diluted, concentrated, or altered prior to titration. If the sample is altered, then the results must be qualified accordingly. For example, if the sample is filtered, the results might be considered as "dissolved" alkalinity. The measurement process is not affected by sample pre-treatment.