Flameless atomic absorption spectrometry of manganese

Flameless atomic absorption spectrometry of manganese has been investigated. The burner assembly of a conventional atomic absorption spectrometer was replaed by an atomization chamber. A tantalum heating element was supported between two electrodes in an enclosed pyrex chamber with optical-quality silica windows. A sample solution containing manganese was atomized by heating electrically on the tantalum heating element in a stream of argon. The optimum conditions, effect of manganese compounds, interference and application were described for the determination of manganese. The following optimum conditions were used: lamp current 8 mA, slit width 150 μ, inert gas argon and flow rate of argon 2 l/min. The manganese line used was 2795 Å. The sensitivity (the amount of manganese at 1% absorption) of the method was 1.1×10-11 g. A relationship between the absorption and the heating element temperature was examined. The highest absorption signal was obtained when the heating element temperature level was minimal (1600°C). A certain drop in the peak height was observed at the higher heating element temperature levels, which can be attributed to the sluggish response of the detection amplification and recorder systems used for measuring transient signals. The manganese absorption was affected by the types of manganese compounds. Manganese phosphate caused higher manganese absorption compared with manganese chloride and bromide, irrespective to heating element temperature. It is assumed that a part of manganese chloride evaporates before atomization. Manganese nitrate, perchlorate, sulfate and potassium permanganate gave lower manganese absorption compared with manganese chloride and bromide at low heating element temperatures, but at the high temperature (2400°C) no difference in the manganese absorption was observed except the case of potassium permanganate. It is assumed that the formation of the stable oxides is responsible for the low manganese absorption. The foreign compound interferences observed with manganese chloride were markedly different from those with manganese sulfate. Calcium chloride, strontium chloride, nickel chloride, cobalt chloride and aluminum chloride caused some depressing effect on the manganese absorption by a manganese chloride solution, whereas these foreign compounds gave an enhancing effect on the manganese absorption by a manganes sulfate solution. No interference from iron on the manganese absorption was observed when 0.5 μg/ml sol