The electrochemical behavior of alpha-ketoglutarate at the hanging mercury drop electrode in acidic aqueous solution and its practical application in environmental and biological samples

摘要

The voltammetric behavior of alpha-ketoglutarate (alpha-KG) at the hanging mercury drop electrode (HMDE) has been investigated in acetate buffer solution. Under the optimum experimental conditions (pH 4.5, 0.2 M NaAc-HAc buffer solution), a sensitive reductive wave of alpha-KG was obtained by linear scan voltammetry (LSV) and the peak potential was -1.18 V (vs. SCE), which was an irreversible adsorption wave. The kinetic parameters of the electrode process were alpha = 0.3 and k(s) = 0.72 1/s. There was a linear relationship between peak current i(p,alpha-KG) and alpha-KG concentration in the range of 2 x 10(-6) - 8 x 10(-4) M alpha-KG. The detection limit was 8 x 10(-7) M and the relative standard deviation was 2.0% (Calpha-KG = 8 x 10(-4) M, n = 10). Applications of the reductive wave of alpha-KG for practical analysis were addressed as follows: (1) It can be used for the quantitative analysis of cc-KG in biological samples and the results agree well with those obtained from the established ultraviolet spectrophotometric method. (2) Utilizing the complexing effect between alpha-KG and aluminum, a linear relationship holds between the decrease of peak current of alpha-KG Deltai(p) and the added Al concentration C-AlIII in the range of 5.0 x 10(-6)-2.5 x 10(-4) M. The detection limit was 2.2 x 10(-6) M and the relative standard deviation was 3.1% (C-AlIII = 4 x 10(-5) M, n = 10). It was successfully applied to the detection of aluminum in water and synthetic biological samples with satisfactory results, which were consistent with those of ICP-AES. (3) It was also applied to study the effect of Al-III on the glutamate dehydrogenase (GDH) activity in the catalytically reaction of alpha-KG + NH4+ + NADH reversible arrow L-glutamate + NAD(+) + H2O by differential pulse polarography (DPP) technique. By monitoring DPP reductive currents of NAD+ and cc-KG, an elementary important result was found that At could greatly affect the activity of GDH. This study could be attributed to intrinsic understanding of the aluminum's toxicity in enzyme reaction processes.