PRECONCENTRATION WITH A SOLVENT-SOLUBLE M EMBRANE-FILTER AND A SPECTROPHOTOMETRIC DETERMINATION OF TRACE THIURAM IN WATER

A simple and rapid preconcentration and spectrophotometric method was proposed for the determination of trace thiuram in water using a solve nt-soluble membrane filter. Less than 80 mu g of thiuram in 500 cm(3) of a sample solution acidified with sulfuric acid was converted into a light-yellow complex in the presence of a large excess of copper (II) and ascorbic acid at pH 6. The complex was retained rapidly and quant itatively on a cellulose nitrate membrane filter by filtration under s uction. The filter was quickly dried with a hair dryer and dissolved i n 3 cm(3) of 2-methoxyethanol which contained a small volume of concen trated sulfuric acid. The solution was heated with a hot-water bath fo r about 30 s. The color of the complex became deep-yellow showing an a bsorption maximum at 390 nm. The absorbance of the solution was measur ed at the absorption maximum against a reagent blank. Beer's relations hip was obeyed over the concentration range from 50 to 160 mu g dm(-3) of thiuram. The detection limit was 1 mu g dm(-3) for three times the standard deviation of the blank basis. High concentrations of Ca2+, M g2+, Na+, K+, Al3+, Cl-, SO42- and NO3-, and sub-mg dm(-3) levels of F e3+ did not interfere with the determination. The recoveries of thiura m added to river water and ground water were satisfactory.