Titanium dioxide nanoparticle based solid phase extraction of trace Alizarin Violet, followed by its specrophotometric determination

Nanometer-sized titanium dioxide (nano-TiO2) is shown to be a viable material for the preconcentration of Alizarin Violet (AV, a common dye and biological stain). In the preconcentration step, a 5-ring cyclic ester is formed between the ortho-dihydroxy groups of AV and two hydroxy groups of the titanic acid on the surface of the nano-TiO2. Under optimized conditions, the adsorption capacity of nano-TiO2 is similar to 20 mu g.mg(-1), the adsorption efficiency is 98 %. The adsorbed AV can be eluted with 5 mL of 5 mol.L-1 5-sulfosalicylic acid with an elution efficiency of more than 91.8 %. The preconcentration factor is 50 in case of 250 mL samples. Spectrophotometric determination of AV in the eluate gives a linear calibration plot in the range between 18.8 mu g.L-1 and 10 mg.L-1 and a detection limit (3 s; for n=11) of 18.8 mu g.L-1. The method is simple and fast. It was successfully applied to the analysis of AV in spiked natural waters, and recoveries were found to range between 94.2 and 97.3 %.