Silver chemical vapor generation for atomic absorption spectrometry: minimization of transport losses, interferences and application to water analysis

Abstract

A study of a transport process and interferences in the method of Ag chemical vapor generation (CVG) with AAS detection was performed. A modified externally heated quartz multiatomizer with a heated inlet arm was designed to minimize transport losses. Both transport efficiency and spatial distribution of a residual analyte in an apparatus were studied by means of 111Ag radioactive indicator. Compared to our previous study the apparatus design was significantly modified: removal of a spray chamber and heating of an inlet arm to 300 °C allowed us to reduce transport losses from 65% to 4% and thus to improve overall CVG efficiency up to 32.5%. Lower (ambient) or higher (700 °C) temperature was inferior to 300 °C due to either losses of Ag with aerosol droplets by deposition or trapping of decomposed Ag particles on a quartz surface, respectively. The interfering effect of hydride forming elements (As, Se) and some transition metals (Cu, Co, Ni, Au) was examined. No serious negative interference was observed up to 10 μg ml−1 level, with the exception of Au causing 18% signal depression already at 0.5 μg ml−1 level. Transmission electron microscopy and energy dispersive X-ray spectroscopy indicated mixed Ag and Au particles and formation of cross-linked structures was revealed. The upward calibration curvature was observed which was treated using power curve regression. The limit of detection under optimized conditions was 1.0 ng ml−1 and the method was also successfully tested using two proficiency testing samples of drinking water.