SPECTROPHOTOMETRIC DETERMINATION OF TRACE AMOUNTS OF TUNGSTEN IN GEOLOGICAL SAMPLES AFTER PRECONCENTRATION ON AMBERLITE XAD-1180

A method for the preconcentration of trace amounts of tungsten as its thiocyanate complex, using a column filled with Amberlite XAD-1180 res in, is proposed. After elution with a small volume of acetone, the ana lyte was determined spectrophotometrically with potassium thiocyanate and stannous chloride. The influence of several ions, as interferents, is discussed. The proposed method was applied to the determination of tungsten in geological samples with good analytical results, such as recoveries of 95% or above, relative standard deviations of 6% or belo w (n = 10) and a detection limit of 12 mu g l(-1).