MODIFICATION OF ANALYTICAL FORMS IN INDIRECT ATOMICABSORPTION DETERMINATION OF PHOSPHORUS

Abstract

The new analytical forms for indirect atomic absorption determination of phosphorus – the 11-molybdoironphosphate heteropolycomplex and ion associate of copper(ІІ) phenantrolinate- molybdophosphate – were theoretical substantiated and tested which provide the lower detection limit, acceleration and simplifi cation of the technique. Optimal conditions of the formation and separation (extraction and fl otation) of the proposed complex compounds were studied. The indirect atomic absorption method of phosphorus determination point is to bind of phosphate ions to a stable complex compounds with a marker element and then to determine marker element concentration using atomic absorption method determination and to calculate the analyte concentration using the concentration of the marker element. Optimal conditions for ion associate fl otation were established for the analytical form of the ion associate of copper(II) phenanthrolinate complex with molybdophosphate anion: the solution acidity is in pH range from 2.5 to 3.5, the concentration ratio of ammonium molybdate and copper phenantrolinate(II) is 80:1. It has been found that the proposed analytical form provides better selectivity while phosphorus determination. The 500-fold excess of Na+, K+, Ca2+, Mg2 +, W(VI), S2O3 2–,NO3 –, Cd2 + does not infl uence. As for analytical form based on the triple metal-substituted phosphorus heteropolyanion using iron(III) as metal-indicator the extraction separation was used. The extractants and solvents of various types (alcohols, esters, ketones) were investigated. It was found that the best extractants are butan-2-one and cyclohexanone. The most suitable solvent for direct fl ame atomic absorption iron determination in the extract is butan-2-one. The iron analytical signal in the butan-2-one medium is 1.4 times more in comparison with the aqueous solution increases while it is 1.3 times less in cyclohexanone. The indirect fl ame atomic absorption phosphorus determination technique in water was developed, which differs from the known before by improved reproducibility, speed, selectivity. The detection limit is 0.005 mg/l, the relative standard deviation does not exceed 0.06, the analysis duration is 35 minutes.

Keywords

• phosphorus
• indirect determination
• atomic absorption spectrometry