Determination of phosphorus by graphite furnace atomic absorption spectrometry. Part 2. Comparison of different modifiers

Abstract

Various modifiers were investigated with respect to the highest applicable pyrolysis temperature and best characteristic mass for phosphorus and also their influence on the tube lifetime and the reproducibility of integrated absorbance values. Palladium alone or with the addition of calcium was found to be the best modifier for the determination of phosphorus by graphite furnace atomic absorption spectrometry. The maximum applicable pyrolysis temperature is 1400 °C. The best sensitivity is obtained for atomisation from a pyrolytic graphite platform in a pyrolytic graphite-coated tube. The characteristic mass is around 5.5 ng (0.0044 A s)^–1 with Zeeman-effect background correction. Lanthanum, yttrium and nickel modifiers permit essentially the same pyrolysis temperature and give comparable sensitivity but not short- and long-term stability of integrated absorbance signals. Lanthanum exhibits in addition a pronounced memory effect and attacks graphite when used at high concentration. Mechanisms involved in the various reactions are discussed and experiments with a dual-cavity platform were carried out to distinguish between possible mechanisms.