Kinetic control of peak shapes in atomic absorption arsenic determinations by arsine generation

The rate processes that control the absorbance vs. time profiles that are obtained in the atomic absorption determination of arsenic(III) by the sodium borohydride reduction to arsine have been identified. The individual rate constants for each of these rate processes have been calculated from the theoretical curves that give a best fit with the experimental peaks. The peak shapes are determined to a great extent by the rate of hydrogen gas evolution and by the rate of removal of dissolved arsine. Several suggestions have been made for improving the sensitivity of the determination of arsenic(III). The kinetic factors that control the peak shapes can be employed to optimize any configuration of a hydride generator that is used in atomic absorption spectrophotometry