Determination of selenium in clinical plasma samples related to atopic dermatitis study by chronopotentiometric stripping method.

Galvanostatic stripping chronopotentiometry (GSC) was developed and applied for the determination of selenium in human plasma. In this work GSC based on composite carbon electrode coated by a gold layer was optimized concerning various electrochemical parameters (coating procedure, electrolysis potential, electrolysis time, dissolution current). Along with this, the sample preparation was optimized with respect to mineralization conditions (type and concentration of decomposition agent, temperature, time). The human plasma samples mineralized in an autoclave under the optimized conditions (160 degrees C, 100 min, 22 mol/l HNO3) were appropriately diluted by background electrolyte solution (0.100 mol/l H2SO4 + 0.001 mol/l HCl) and directly analyzed by the optimized GSC method. The proposed method was characterized by excellent performance parameters, the limit of detection was 0.2 ng/ml, accuracy <5%, reproducibility <4%. The proposed method was applied for the investigation of the relationship between atopic dermatitis and selenium concentration in human plasma. Here, patients suffering from atopic dermatitis were monitored during their treatment with a pharmaceutical preparation containing inorganic selenium (Zinkosel). After six months therapy increased levels of selenium in plasma were detected in 76% of the patients with an improvement of the clinical state in 65% of the patients.