Determination of ultra-micro amounts of sulfur in igneous rocks by spectrofluorimetry using 2(o-hydroxyphenyl) benzoxazole derivatization and tin(II)-strong phosphoric acid-assisted reduction

A new and very sensitive method was developed for the determination of ultr a-micro amounts of sulfur in igneous rock samples. The sulfur compounds in an igneous rock sample are reduced and released in the form of hydrogen sul fide by heating with a tin(II)-strong phosphoric acid (SPA) reagent. The li berated hydrogen sulfide is carried by a flow of nitrogen into a copper(II) absorbing solution to obtain a precipitate of copper(II) sulfide. The rema ining copper(II) ion forms a chelate with 2-(o-hydroxyphenyl)benzoxazole (H PB) and quenches the fluorescence of HPB. The amount of sulfide is determin ed by measuring the HPB fluorescence intensity. The optimum reaction condit ions were stoichiometrically investigated. By the present method using 0.1- 0.2 g of rock sample, ultramicro amounts of sulfur (0.1-12.8 mu g) could be quantitatively separated, collected, and determined with a relative standa rd deviation of 1.37% for a sample containing 5.7 mu g of sulfur (95% confi dence level). (C) 2000 Elsevier Science B.V. All rights reserved.