Evaporation preconcentration of trace elements in rainwater for inductively coupled plasma emission spectrometry

Abstract

An evaporation preconcentration of rainwater sample was studied for the analysis of trace elements by inductively coupled plasma emission spectrometry (ICP-AES). The evaporation preconcentration procedure is favorable for multi-elements analysis by ICP-AES because most of the elements, except for mercury and other volatile ones, can be enriched simultaneously. A conventional type of rotary evaporator was reformed setting a newly designed sample vessel made of teflon inside the glass bottle which can be separated into two parts, and compared to the former type of evaporator having a vessel made of hard glass. From the experiments using twice distilled water it was found that small amount of B, Na, Mg, Si, and Ca dissolved out from the surface of the glass vessel giving some positive error. From the teflon vessel, however, no contamination of elements was detected. When removing the cotent from the vessel into a measuring cylinder, adhesion of tiny amount of concentrated sample water occurred on the surface of the vessel to cause an error in the calculation of the enrichment factor. It was found that the volume of the adhered solution on the surface of a glass flask was nearly constant (0.5 ml) independently of the volume of the solution under this conditions, and using this value the correction of the result was possible. Such an adhesion, on the other hand, was not observed for the case of teflon vessel within the accuracy of our experiments. In conculusion, although the improved rotary evaporator with a teflon vessel is not more time-saving than a conventional glass evaporator, it is more advantageous in the following items; (1) No dissolution of element from the surface of the cocentration vessel; (2) High efficiency in preconcentration of rain samples (1000 ml to 1 ml); (3) No backward flow of condensed water on the glass part of the evaporator into the teflon vessel. © 1985, The Japan Society for Analytical Chemistry. All rights reserved.