Measurement of aluminium in dialysis fluid and water by a spectrophotometric procedure

A method is described for the spectrophotometric assay of aluminium in dialysis fluid and water using the ternary complex formed between aluminium, Chrome Azurol S and cetylpyridinium chloride. Absorbance is measured at 640 nm. The molar absorptivity of the complex is estimated to be 1.25 ± 0.03 × 105 l mol–1 cm–1. The method is linear over the range 25–250 µg l–1 and the detection limit is approximately 5 µg l–1. Interference from copper and iron is masked by the addition of ascorbic acid and 2,2′-bipyridyl. Phosphate does not interfere; fluoride shows a tolerable interference and oxalate and citrate show major interference.