On-line preconcentration and analysis of zinc in water by flow injection-knotted reactor:: Application to geological and environmental exploration

A preconcentration on-line system composed of flow injection (FI) and a knotted reactor (KR), associated with inductively coupled plasma atomic emission spectrometry (ICP-AES) has been used to determine Zn concentrations in river water. The zinc was retained as Zn-2(5-bromo-2-pyridilazo)5-diethylaminofenol precipitated complex on the knotted reactor (KR). The limit of detection (0.09 mu g L-1 of Zn) of this method makes it particularly suitable for hydrochemical exploration in geological and environmental projects. This application has been validated in the volcanogenic gold (copper, zinc, lead) deposit of La Carolina in the province of San Luis, Argentina. The Carolina Stream and the Grande River have been sampled for water downstream this deposit. The regional background in river water is 2 mu g L-1. Six times this concentration has been observed at more than 6.5 km from the source, La Carolina mine.