Spectrophotometric determination of fluoride in drinking water using aluminium complexes of triphenylmethane dyes

A sensitive spectrophotometric determination of fluoride in drinking water has been developed using aluminium complexes of triphenylmethane dyes (chrome azurol B and malachite green) as spectrophotometric reagents. The method allowed a reliable determination of fluoride in the range of 0.5-4.0 mg.l(-1) for chrome azurol B and 0.0-2.0 mg.l(-1) for malachite green. The molar absorptivity for the complexes of chrome azurol B at 582 nm and malachite green at 622 nm is 1.44 x 10(4) and 2.56 x 10(4) l.mol(-1).cm(-1), respectively. The sensitivity, detection limit, quantitation limit, and percentage recovery for 1.5 mg.l(-1) fluoride for the method using chrome azurol B were found to be 0.125 +/- 0.003 mu g.ml(-1), 0.2 mg.l(-1), 0.5 mg.l(-1), and 97.1 +/- 4.2, respectively, and for malachite green were 0.143 +/- 0.002 mu g.ml(-1), 0.1 mg.l(-1), 0.3 mg.l(-1), and 97.9 +/- 4.1, respectively.