Determination of trace levels of manganese in various biological and environmental samples by atomic absorption spectrometry after solid-liquid extraction and preconcentration with the ion pair formed by the nitroso-S anion and the tetradecyldimethylbenzylammonium cation.

Manganese is quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-S) and tetradecyldimethylbenzylammonium (TDBA) chloride on microcrystalline naphthalene in the pH range 9.5-10.6 from large volumes of aqueous solutions of various samples. After filtration, the solid mass consisting of the manganese complex and naphthalene is dissolved in 5 mL dimethylformamide and the metal is determined by flame atomic absorption spectrometry. Alternatively, the manganese complex can be quantitatively adsorbed on TDBA-naphthalene adsorbent packed in a column and determined similarly. About 0.2 microg manganese can be concentrated in a column from 400 mL aqueous sample with a concentration as low as 0.5 ng/mL. Eight replicate determinations of manganese at 0.8 microg/mL gave a mean absorbance of 0.156 for the final solution with a relative standard deviation of 1.4%. The sensitivity for 1% absorption was 23 ng/mL. The interference of a large number of anions and cations was studied, and the optimized conditions developed were used for trace determinations of manganese in various alloys, and in biological and environmental samples.