Method for correcting for acid and salt matrix interferences in ICP-AES

Abstract

The methods currently employed for correcting mineral acid and salt matrix interferences in the analysis of aqueous samples by inductively coupled plasma atomic emission spectrometry (ICP-AES) involve additional steps in the sample preparation or analysis procedures, lengthening them appreciably. A new method has been developed to compensate for the effects of varying acid and salt concentrations on the efficiency of sample introduction into the plasma that does not involve the use of internal references, precise matrix matching, or standard additions. The method uses the intensity of a hydrogen emission line at 486.133 nm (H-beta). The H-beta intensity is proportional to sample introduction rate and to the hydrogen content of the sample solution. The hydrogen content of the sample solution is dependent on the acid/salt type and concentration. Interference calibration curves are prepared for a specific acid/salt matrix relating observed H-beta intensities and apparent concentrations for each of the elements (and wavelengths) in the analytical program. These calibration curves are used to perform the interference corrections for samples having that acid/salt matrix. The H-beta measurements are precise and the interference calibration curves reproducible over periods of at least several months. Application of this method is illustrated by analyses of NBS oyster tissue and Al alloy prepared in nitric acid matrix. Solutions of these materials containing 2–55 % ( v v ) concentrated HNO 3 were analysed accurately using a set of ICP-AES calibration standards containing 1 % ( v v ) HNO 3.