| Abstract
| - An extremely sensitive adsorptive wave of BSA at about−1.73 V (vs SCE) has been obtained in the solutioncontaining 8 × 10-7 mol/L CoCl2, 0.2 mol/L guanidinehydrochloride, and 0.2 mol/L NaOH by using single-sweep polarography. The interaction of BSA with guanidine in an alkaline solution results in its Co(II) complexwith a positive excess charge. Thus, the complex isstrongly adsorbed by the DME as a result of staticelectrical attraction. The adsorption efficiently accumulates the electrochemical active complex of Co(II)−BSAonto the DME. In the following potential scan, the complexproduces a sensitive adsorptive reduction peak, which canbe used to determine low-level BSA. In the absence ofguanidine, the complex of Co(II)−BSA with a negativeexcess charge is repulsed by the DME. The reductioncurrent is very small. The peak current depends on bothBSA and Co(II) ion concentrations. HSA is similar to BSAin polarographic behavior. At the optimal conditions, thepeak height is linearly proportional to the BSA or HSAconcentration in the range of 0.005−20 mg/L (correlationcoefficient 0.999). The detection limit for BSA or HSA is0.002 mg/L. Lysozyme, common amino acids, and metalions have no interference with the protein determination.The new method could be useful in protein studies.
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