A sensitive method for determination of phosphorous by continuum source graphite furnace atomic absorption spectrometry after a novel ionic liquid assisted cloud point extraction

Abstract

Wall and platform atomisation have been investigated for the determination of phosphorus using palladium modifier in continuum source graphite furnace atomic absorption spectrometry (CS-GFAAS). Wall is found to have a better sensitivity compared to platform. This could be due to increase in population of non resonance line used in determination of phosphorus, since wall is heated directly. However, wall has inherent matrix interference problems, hence a matrix separation and pre-concentration procedure using ionic liquid assisted cloud point extraction is described. The method is based on the formation of hydrophobic ion-associate between anionic phosphomolybdate and 1-butyl-3-methylimidazolium chloride in the presence of H₂SO₄. The non-ionic Triton X-114 micelles have been used for pre-concentration of this ion-associate from a bulk aqueous phase into a small surfactant-rich phase. The main parameters affecting the extraction process are optimized. The characteristic mass of 0.4 ng is achieved after cloud point extraction. Under the optimized conditions, the pre-concentration factor is 50. The limit of detection is 0.06 μg g⁻¹, for solid samples and 0.6 ng mL⁻¹ for water. The recoveries are in the range of 95–98% with 2–4% relative standard deviation. The accuracy of the procedure is validated by analyzing NIST 8435 whole milk powder, 1549 non-fat milk powder, 1548 total diet and 1568a rice flour, and BCR 063R skim milk powder certified reference materials.