New Calibration Model: Combining Integrated Calibration Method and H-point Standard Addition Method to Detect and Avoid Interference Effects

Abstract

A new calibration methodology based on the combination of integrated calibration method (ICM) and the H-point standard addition method (HPSAM) is presented. It allows the diagnosis and correction of errors caused in an analytical system by different kinds of interference effects. Six calibration solutions consisting of mixtures of sample, diluent, and one standard are prepared in accordance with the ICM principle to integrate the external calibration method with the standard addition method and thereby to detect and eliminate proportional interferences. Absorbance increments chosen according to the HPSAM principle are proposed to correct the errors caused by additive interferences. A set of as many as six apparent estimations of analyte concentration in a single calibration procedure is calculated for validating accuracy. As a consequence, doing calibration by the ICM-HPSAM method, it is possible to obtain the final analytical results with considerably improved accuracy. The determination of calcium in several different water samples (containing amounts between 4.9 and 127 mg L⁻¹) with Arsenazo III has been chosen as an example because it is biased if the errors are not diagnosed and corrected. The results are characterized by small (not higher than 8%) relative error (RE), and good precision (RSD values smaller than 6%).