Analytical Sciences

Determination of the Degradation Compounds Formed by the Oxidation of Thiophosphinic Acids and Phosphine Sulfides with Nitric Acid

Begoña MENOYO, María P. ELIZALDE,  and Ana ALMELA

Dpto. Química Analitica, Universidad del País Vasco, Apdo. 644, 48080 Bilbao, Spain

The degradation process that takes place at room temperature when bis(2,4,4-trimethylpentyl)monothiophosphinic acid (R₂P(S)OH), bis(2,4,4-trimethylpentyl)dithiophosphinic acid (R₂P(S)SH) and tris(2,4,4-trimethylpentyl)phosphine sulfide (R₃PS) are in contact with 5 M HNO₃ has been studied by FT-Infrared, FT-Raman spectroscopy and by gas chromatography with mass spectrometry detection (GC-MS). An exposure period of ten days of the rough reagents to 5 M HNO₃ causes complete oxidation of the compounds. This process mainly leads to the formation of nitrogen dioxide, elemental sulfur and the oxo-analogues of the reagents. For dilute solutions of the reagents it was observed that after 15 min of contact with phase-shaking, R₂P(S)OH and R₃PS are completely oxidized to yield R₂P(O)OH and R₃PO, respectively, whereas for R₂P(S)SH, the oxidation process is less severe, because the dithioacid is still present in the oxidized mixture, the oxidation products being R₂P(S)OH and R₂P(O)OH.

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