Sensitive and very selective determination of titanium by adsorptive-catalytic stripping voltammetry with methylthymol blue, xylenol orange and calcein

Titanium(IV) forms the complexes with methylthymol blue (MTB), xylenol orange and calcein in the weakly acidic solutions (pH 2.4-3.8). These complexes can be used for a highly selective and sensitive determination of titanium by adsorptive-catalytic stripping voltammetry (AdCtSV) with increase of the reduction peak current, thanks to the presence of chlorate ions. The detection limits (3 sigma of the blank value) obtained under the optimal experimental conditions are 1.10 nM for MTB, 0.41 nM for xylenol orange and 0.12 nM for calcein after 30, 30 and 60 s of the accumulation time, respectively. The peak current is proportional to the concentration of titanium(IV) in the range of 8.7-93 nM for MTB, 8.7-690 nM for xylenol orange and 1.7-160 nM for calcein. Elements such as iron, aluminium or molybdenum do not interfere with the determination of titanium. Described reagents were applied to the determination of titanium in crystalline quartz and silica glass samples with good results. Electrothermal atomic absorption spectrometry (ET-AAS) was used as a reference method to the AdCtSV measurements. (C) 2001 Elsevier Science B.V. All rights reserved.