Simultaneous determination of hemoglobin and cysteine based on Brdička catalytic currents

The effect of the concentration of ammonia on the catalytic currents of bovine and human hemoglobin, cysteine, cystine and glutathione was studied, and the concentration of 3.5 mol l-1 was found optimal for analytical purposes. Mixtures of hemoglobin and cysteine exhibited catalytic wave positions suitable for their simultaneous quantitation. In a buffer containing 3.5 M ammonia, the catalytic current of hemoglobin is virtually independent of the concentration of cysteine, and at a constant concentration of hemoglobin, the catalytic current of cysteine increases linearly with its concentration over the range studied. Statistical evaluation gave evidence that hemoglobin and cysteine can be determined simultaneously in the above buffer. When accounting for some interfering effects with respect to the catalytic currents of glutathione and cysteine, complexation phenomena and properties of the hemoglobin surface layer must be taken into consideration.