Evaluation of alternate lines of Fe for sequential multi-element determination of Cu, Fe, Mn and Zn in soil extracts by high-resolution continuum source flame atomic absorption spectrometry.

The usefulness of the secondary line at 252.744nm and the approach of side pixel registration were evaluated for the development of a method for sequential multi-element determination of Cu, Fe, Mn and Zn in soil extracts by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). The influence of side pixel registration on the sensitivity and linearity was investigated by measuring at wings (248.325, 248.323, 248.321, 248.329, and 248.332nm) of the main line for Fe at 248.327nm. For the secondary line at 252.744nm or side pixel registration at 248.325nm, main lines for Cu (324.754nm), Mn (279.482nm) and Zn (213.875nm), sample flow-rate of 5.0mLmin(-1) and calibration by matrix matching, analytical curves in the 0.2-1.0mgL(-1) Cu, 1.0-20.0mgL(-1) Fe, 0.2-2.0mgL(-1) Mn, 0.1-1.0mgL(-1) Zn ranges were obtained with linear correlations better than 0.998. The proposed method was applied to seven soil samples and two soil reference materials (IAC 277; IAC 280). Results were in agreement at a 95% confidence level (paired t-test) with reference values. Recoveries of analytes added to soil extracts containing 0.15 and 0.30mgL(-1) Cu, 7.0 and 14mgL(-1) Fe, 0.60 and 1.20mgL(-1) Mn, 0.07 and 0.15mgL(-1) Zn, varied within the 94-99, 92-98, 93-101, and 93-103% intervals, respectively. The relative standard deviations (n=12) were 2.7% (Cu), 1.4% (Fe - 252.744nm), 5.7% (Fe - 248.325nm), 3.2% (Mn) and 2.8% (Zn) for an extract containing 0.35mgL(-1) Cu, 14mgL(-1) Fe, 1.1mgL(-1) Mn and 0.12mgL(-1) Zn. Detection limits were 5.4microgL(-1) Cu, 55microgL(-1) Fe (252.744nm), 147microgL(-1) Fe (248.325nm), 3.0microgL(-1) Mn and 4.2microgL(-1) Zn.