Analytical applications of furnace atomic non-thermal excitation spectrometry (FANES) and molecular non-thermal excitation spectrometry (MONES). Part 4. Determination of trace amounts of phosphorus by FANES

Abstract

A method of determining phosphorus by furnace atomic non-thermal excitation spectrometry (FANES) has been developed. The phosphorus is introduced into the FANES source as a solution of sodium dihydrogen phosphate. The measurements are carried out at 213.5/213.6 and 253.3/253.5 nm, the transition at 213.5/213.6 nm being the more sensitive one. The thermal and chemical conditions were optimised, the best chemical modifier being La³⁺ ions as they stabilise phosphate ions as LaPO₄. Using the optimum amount of lanthanum (2 µg) the pre-treatment temperatures could be increased considerably (300 to 800 °C at normal pressure and 350 to 400 °C at low pressure). The best detection limit obtained is 90 pg of phosphorus, which is an improvement by a factor of 60 in comparison with the best values obtained with commercially available electrothermal atomisation atomic absorption spectrometric (ETAAS) instruments. Examples for real analyses with associated matrix interferences are given.