Thermal lens spectrophotometry of phosphorus using a near-infrared semiconductor laser

Abstract

A thermal lens spectrophotometer consisting of a near-infrared semiconductor laser was constructed. The theoretical sensitivity of the present spectrophotometer using a 10-mW laser was 61 times better than the conventional spectrophotometer for the sample in chloroform. When the sample of phosphorus was measured directly in the aqueous phase based on a heteropoly blue method, the detection limit was 2.2 ppb and 0.7 ppb for single and dual beam methods, respectively. When the sample was measured after solvent extraction into 2-butanol, the detection limits were improved to 0.2 ppb for both the methods, which corresponds to an absorbance of 2 x 10/sup -4/. The achieved detection limits were about an order of magnitude better than absorption spectrometry using a conventional 1-cm sample cell. The minimum detectability was mainly limited by blank absorption occurring from the solvent. The determination was also carried out after ion-pair solvent extraction with Zephiramine into chloroform. The solvent blank was much lower for chloroform, but the detection limit remained identical with the previous results. The minimum detectability was limited by reagent blank in this case. 24 references, 3 figures, 1 table.