ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRIC DETERMINATION OF ULTRA-TRACE AMOUNTS OF TIN BY IN-SITU PRECONCENTRATION IN A GRAPHITE TUBE USING FLOW-INJECTION HYDRIDE GENERATION WITH ONLINE ION-EXCHANGE SEPARATION

A method was developed for the ultra-trace determination of tin by in situ preconcentration in a graphite tube using a flow injection hydrid e generation technique with on-line ion-exchange separation. The sampl e was prepared in 2M hydrochloric acid before being passed through an incorporated micro-column packed with a strongly basic anion-exchanger D-201. The tin was retained as its chlorostannate complex and subsequ ently eluted by de-ionized water into the hydride generation system. T he hydride and hydrogen gases evolved were separated from the liquid p hase in a gas-liquid separator and transferred into a palladium-coated graphite tube pre-heated to 300 degrees C to collect the analyte, whi ch was later atomized at 2300 degrees C. With the reported system, tin was determined at a sampling frequency of 30/hr with a detection limi t (3 sigma) of 0.01 mu g/l. using 10.7 ml sample. The precision was 1. 5% RSD at the 0.5 mu g/l. level. The proposed method was applied to th e determination of tin in tap water, hair, serum samples and geologica l reference samples.