Flow-injection extraction spectrophotometric determination of bismuth as tetraiodobismuthate(III) with the tetramethylenebis(triphenylphosphonium) cation

Bismuth can be determined spectrophotometrically at 495 nm after its extraction as tetramethylenebis(triphenylphosphonium) tetraiodobismuthate(III) into dichloromethane. The carrier stream is 2 M sulphuric acid and the reagent stream contains 2% (w/v) potassium iodine and 0.4% (w/v) tetramethylenebis(triphenylphosphonium) bromide. The injection rate is 20 h^-1. The calibration graph is linear up to 20 μ ml^-1 bismuth and the detection limit is 0.24 μ ml^-1 bismuth, based on injection volumes of 250μl. The system has been applied to determination of bismuth in pharmaceutical samples.