Flow injection on-line separation and preconcentration for electrothermal atomic absorption spectrometry. Part 1. Determination of ultratrace amounts of cadmium, copper, lead and nickel in water samples

Abstract

Combining a micro-scale flow injection preconcentration system on-line with electrothermal atomic absorption spectrometry results in a powerful integrated system. The most outstanding advantages are improved detection limits achieved by preconcentration and matrix separation, and low contamination because of the totally closed system. The discontinuous process of preconcentration is suitably accommodated in the measuring cycle of a graphite furnace, even enhancing the cycle time for complex matrices, because the lengthy programmes that are needed in order to separate the analyte from excess of matrix compounds are avoided. The integrated system permits fully automated operation, avoiding time-consuming manual work and enhancing the reproducibility and precision. Results obtained for the determination of ultratrace amounts of some elements in sea-water demonstrate the high sensitivity, good accuracy and precision of this technique. Using a time based technique equivalent to only 3 ml of sample, the sensitivity of the graphite furnace technique was enhanced about 20-fold compared with a 40 µl injection volume. Detection limits achieved were 0.8, 6.5, 17 and 36 ng l^–1(3σ) for Cd, Pb, Cu and Ni, respectively.