Trace metals analysis using continuum source simultaneous multielement graphite furnace atomic absorption spectroscopy

Abstract

A novel instrument for simultaneous multielement graphite furnace atomic absorption is described. This instrument employs a continuum light source and an echelle-charge injection device array detector system to achieve both simultaneous analysis of multiple wavelengths and true simultaneous background correction. The charge injection device detector also allows continuous wavelength coverage from 400-190 nm. Multichannel GFAAS analysis improves not only analytical speed but enables the use of elements resistant to matrix effects to assist in the identification of matrix effects in other elements and confirmation of calibration accuracy. The research project described discusses not only basic instrument design but also practical application of the new design to current analytical problems. Analysis of Ag, Pb, Tl, Cr, and Mn in drinking water, and red table wine allowed not only evaluation and investigation of instrumental problems but also allowed investigation of the various chemical problems associated with simultaneous multielement determinations in general. Multielement analysis involves the use of compromise furnace conditions, and matrix effects can further complicate multielement determinations. The use of chemical modifiers such as a mixed Pd(NO₃)₂ and Mg(NO₃)₂ modifier provide a partial solution to some of the problems associated with multielement determinations. For the two applications, the analytes were split into two groups. One group analyzed Ag, Pb, and Tl and the other analyzed Cr and Mn. The modifier system was applied to the Ag, Pb, and Tl analysis. For drinking water, analytical results were obtained with errors and RSD's less than 10%. The modifier system was not effective when water solutions contained high levels of Na and Ca. For red wines, the modifier system was effective for Ag, Pb and Tl. However, maximum pretreatment temperatures were approximately 100-200°C lower than that of high purity water. No detectable levels of Ag or Tl were found in any of the wine samples analyzed. Trace levels of approximately 20 ppb Pb and Cr were detected in several red wines. Levels of Mn approached 1 ppm. Matrix effects were found to suppress the Pb signal and enhance the Tl signal. Sample recoveries for both elements typically ranged from 80-120%.