Application of photoacoustic spectrometry to flow-injection analysis

Photoacoustic spectrometry (PAS) based on pulsed laser excitation has been coupled to flow-injection analysis (FIA) to detect nitrite, nitrate, iron, ammonia, and phosphate ions in water with the aim to verify its potentiality with respect to conventional FIA systems. Excitation has been performed by means of a Nd:YAG laser with a 2nd harmonic generation and a dye laser; a conventional flow-injection cell has been used as photoacoustic cell. Standard solutions and real samples such as ground water, river water, fog and waste water have been analyzed. A good agreement has been obtained between the results of the proposed technique and those of traditional laboratory techniques. The best analytical configuration, in terms of loop length and integration time, has been also defined. The performance as limit of detection (LOD) was comparable for both techniques. The main points to be developed in order to improve the analytical response of PAS-FIA are reported.