Determination of fluoride and oxalate using the indicator reaction of Zr(IV) with methylthymol blue adsorbed on silica gel.
Solid-phase spectrophotometric and visual test-methods of fluoride and oxalate determination are proposed. The methods are based on the competitive reactions of ZrOCl2 with methylthymol blue immobilized on silica gel and fluoride or oxalate in solution. Absorbance of the solid-phase reagent at 590 nm decreases with the growth of fluoride and oxalate contents in solution. The developed methods demonstrate high selectivity. The interference of Bi(III) and SO4(2-), PO4(3-) is eliminated by the addition of 0.01 mol L(-1) solution of ascorbic acid and 0.01 mol L(-1) of BaCl2, respectively. To eliminate the fluoride interference with oxalate determination 1x10(-3) mol L(-1) solution of Ca(NO3)2 at pH 1.5 was added. The anions of the organic acids were destructed prior to F- determination by ultrasonic exposition (44 kHz, intensity of < or = 10 W cm(-2) for 3 min). The proposed methods were applied to the analysis of mineral water, toothpaste and biological fluids.
Analytical Chemistry Department, Taras Shevchenko Kyiv University, Volodymyrska Street 64, Kyiv 01033, Ukraine. zaporozh@bigmir.net
Olga A
OA
Zaporozhets
Lyudmila Ye
LY
Tsyukalo
D000327:Adsorption; D001979:Bromthymol Blue / Q000031:analogs & derivatives / Q000737:chemistry; D005459:Fluorides / Q000032:analysis*; D007202:Indicators and Reagents / Q000737:chemistry; D008900:Mineral Waters / Q000032:analysis; D010070:Oxalates / Q000032:analysis* / Q000652:urine; D012463:Saliva / Q000737:chemistry; D058428:Silica Gel; D012822:Silicon Dioxide / Q000737:chemistry; D014100:Toothpastes / Q000032:analysis; D015040:Zirconium / Q000737:chemistry
D007202:Indicators and Reagents; D008900:Mineral Waters; D010070:Oxalates; D014100:Toothpastes; C002074:methylthymol blue; D058428:Silica Gel; D012822:Silicon Dioxide; D015040:Zirconium; D005459:Fluorides; D001979:Bromthymol Blue