Determination of sulfamethoxazol by oscillopolarographic kinetic method

The time difference (y) between the reaction of sulfamethoxazol with Br2 and the reaction blank solution with Br2 is directly proportional to the nascent concentration of sulfamethoxazol (C), a little surfeit of Br2 can make a slot on oscillogram of trace platinum-platinum electrodes. The slot can be used to indicate end point. In this paper, a new method for the determination of sulfamethoxazol is developed on the basis of the combination oscillography and kinetic analysis. This method is sensitive, simple, fast and no interference from solution color and precipitation. Apparatus: Ls-1A A.C oscillographic titrator (Made in Shandong 7th Factory of Telecommunication, China). Sample determination method: Take 5 mL test solution containing 80-100 μ g/ml of sulfamethoxazol in the beaker of 100 mL, add the following reagents: 10 mL 0.50 mol/L KBr, 20 mL 0.10 mol/L HCl, Put the electrodes in the solution. Use ice-water cool the solution, temperature dropped to 273k, then starting electromagnetic stirrer, add 2.5 mL 0.10 moL/L KBrO3 (273k) in the solution, start the time counter until there is the slot made on the oscillogram. At the same time begin the blank experiment. 1. Electrode pair: We choose the trace platinum electrode as the indicator electrode and the platinum electrode as the reference electrode; 2. Temperature: Use ice-water cool, the temperature of the reacting substances to 273k. 3. Concentration of the reacting substances: Concentration of the reacting substances should be allowed to change between the following concentration limits: 0.032-0.067mol/L HCl, 0.080-0.13 mol/L KBr, 0.0027-0.0067 mol/L KBrO3. 4. The calibration equation: y(s)=-0.2968+2.045C(μ g/ml) the linear range is 13-108 μ g/ml, r=0.9998.the lowest detection limit is 1.5 μ g/ml. 5. Analysis of sample: The method was applied to determine sulfamethoxazol contents in tablet sulfamethoxazol. In 9 determinations, the relative standard deviation is 0.3%, the average concentration of sulfamethoxazol is 78.85%. There is no significant difference between the result of this method and that of pharmacopoeia method (1) So this is a reasonable and practical method.