Interactive calibration by a recursive generalized standard addition method

Abstract

The generalized standard addition method (GSAM) has recently been introduced for calibration to avoid matrix effects and many interferences. In GSAM, all additions and measurements precede the calculations of the K matrix (sensitivities of all analytes at all sensors_ and the analyte concentration. A recursive version of GSAM is presented here. Some new powerful properties are added to the method: (1) on-line checking of the validity of the linear model during the data acquisition stage, (2) simultaneous evaluation of the value and precision of the elements of the K matrix during the additions, and (3) access to an on-line interactive calibration, terminating the addition when the precision is within the desired limits or a deficiency in the model has been detected. The method is demonstrated for spectrophotometric measurements of copper and nickel in the presence of EDTA.