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The microwave-assisted digestion of dietary supplements using diluted nitric acid under oxygen pressure for subsequent indirect determination of phosphorus and sulfur by ion chromatography (IC) was proposed. Different concentrations of nitric acid (from 1 to 14.4 mol L−1) and oxygen pressures (from 5 to 20 bar) were evaluated. Dissolved organic carbon and residual acidity were used to choose the most suitable digestion condition. Using the proposed method, it was possible to digest up to 1350 mg of dietary supplements using only 5 mol L−1 HNO 3 under 5 bar of oxygen pressure. Comparing to conventional digestion procedure it was possible to digest up to 60% higher sample mass using HNO 3 around 30% more diluted. Recoveries ranging from 96 to 102% were obtained when recovery tests using a standard solution or a mixture with certificate reference material were carried out. The concentration of P and S indirectly determined by IC agreed with the results obtained by conventional microwave-assisted digestion using concentrated HNO 3 and subsequent determination by inductively coupled plasma optical emission spectrometry. [ABSTRACT FROM AUTHOR]

A single analysis of hair for determining halogens (chlorine, bromine, fluorine, and iodine) and sulfur by ion chromatography with suppressed conductivity and mass spectrometry detection (IC-MS) was proposed. Inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry (ICP-MS) were also used to compare the results. For this purpose, 300 mg of human hair were digested by microwave-induced combustion (MIC) using 20 bar of oxygen pressure. The analytes were absorbed in 100 mmol L−1 NH4OH. Trueness of the proposed method was evaluated by analysis of a CRM of human hair; by recovery tests, using standard solution at two levels (50% and 100%), and by comparison of results with those obtained by ICP OES (Cl and S) and ICP-MS (Br and I). Suitable recoveries (ranging from 92 to 105%) were obtained, and the results from CRM analysis did not differ significantly from those described in the certificate. Moreover, results obtained by IC-MS did not present significant differences (p > 0.05) from those obtained by ICP OES and by ICP-MS. Precision was evaluated in terms of repeatability and intermediate precision, and the relative standard deviations were always lower than 8%. The proposed method presented good accuracy and it is a reliable strategy for human hair analysis. Final digests obtained using the MIC method were fully compatible with all proposed determination techniques. Compared to others reported in the literature, the proposed method presents several advantages, especially given that it is possible to determine halogens and sulfur in a single analysis. [ABSTRACT FROM AUTHOR]