Abstract

A method for indirect extraction-spectrophotometric determination of phosphorus using the formation of 12-tungstophosphate (12-TPC) heteropoly complex has been developed. The conditions for the formation and extraction separation of the 12-TPC with butyl acetate were studied. 12-TPC is formed and extracted over a wide pH range — from 0.05 to 0.4 M (as H+)—at a tungstate concentration of 2 mM. After separation, tungsten in the composition of 12-TPC is determined by the absorption of its complex with phenylfluorone. The apparent molar absorption coefficient significantly exceeds the known methods and equals to 3.3×10⁵ mol–1 L cm⁻¹ at 515 nm. Calibration range for phosphorus is from 3 to 30 µg L⁻¹ with LOD of 1.0 µg L⁻¹ and correlation coefficient of 0.9998. The method is simple to implement, rapid, highly sensitive and has good reproducibility. The possibility of eliminating the interfering influence of a number of elements that may be present together with phosphorus in alloyed steels, namely chromium, nickel, vanadium, molybdenum, and tungsten, has been studied. A method for analyzing steel and other alloys containing these elements has been developed and verified by analyzing standard samples.

Keywords: spectrophotometry, phosphorus determination, analysis of steels, extraction

Article language: En