Chloride Interferences in Graphite Furnace Atomic Absorption Spectrometry

Abstract

The premature loss of analyte as a volatile halide Is shown to be an Important Interference In some situations. When this char step Interference Is avoided, an Interference In the atomization step can arise when large amounts of halide are present during that step. This atomization interference results from the binding of the analyte as a vapor phase metal halide, thereby preventing some portion of the analyte from absorbing atomic radiation. This vapor phase Interference can be circumvented in several ways. The most convenient Is the use of high concentrations of HNO3 or H2SO4 which drives off more of the chloride as HCI during the dry and char steps. As much CaCI2 In solution as 1 mg reduced the Mn signal In the presence of HNO3 and Mg(NO3)2 by only 15%. Analogous experience was found with Tl. We believe the experience Is quite general. The halide which Interferes In the vapor phase Is retained from the char step by adsorption or Intercalation on the graphite tube. Thus we can expect still further Improvements In the handling of large amounts of halide matrix when glassy carbon or solid pyrolytic tubes become available. © 1984, American Chemical Society. All rights reserved.