Evaluation of single-point calibration in flow potentiometric stripping analysis.

The use of a single-point calibration in flow potentiometric stripping analysis has been evaluated. For a number of sample matrices, the results obtained by calibration methods agree with those obtained by using standard addition. The most serious source of systematic error is inhibition in the deposition step, caused by organic surfactants and chelating agents in the sample matrix. Consequently, the use of the calibration method should be restricted to samples which have been totally mineralized. It is shown that most sources of systematic error in the calibration method will result in underestimation of the analyte concentration.