Column preconcentration of trace manganese with the ion pair of 2-nitroso-1-naphthol-4-sulfonic acid tetradecyldimethylbenzyl-ammonium chloride supported on naphthalene and determination by derivative spectrophotometry

A column preconcentration method has been developed for the determination o f trace amounts of manganese by preconcentration on 2-nitroso-1-naphthol-4- sulfonic acid (nitroso-S)-tetradecyldimethylbenzylammonium (TDBA) naphthale ne as an adsorbent using a simple funnel tipped glass tube. Manganese react s with nitroso-S to form a water soluble brown colored chelate anion. The c helate anion forms a water insoluble Mn-Nitroso-S-TDBA ion pair on naphthal ene packed in a column in the pH range 9.6-10.5 at a flow rate of 1-2 ml/mi n. The solid mass consisting of manganese complex and naphthalene is dissol ved in 5 nil of dimethylformamide (DMF) and the metal determined by second derivative spectrophotometry. The calibration curve is linear in the concen tration range 0.2535.0 mug of Mn in 5 ml of the final DMF solution. Eight r eplicate determinations of 25 mug of standard manganese solution give a mea n peak height of 4.0 with a correlation coefficient of 0.9995 and relative standard deviation of 1.1%. The sensitivity was calculated to be 0.502(d(2) A/d lambda (2))/ mug ml(-1) from the slope of the calibration curve. The de tection limit was 0.020 mug ml(-1) for manganese at the minimum instrumenta l settings (signal to noise ratio = 2). Various parameters effecting the me thod such as the effect of pH, volume of aqueous phase and interference of a number of metal ions on the determination of manganese have been evaluate d to optimize the conditions for its determination in standard alloys and b iological samples.