The Electrochemical Behavior of α‐Ketoglutarate at the Hanging Mercury Drop Electrode in Acidic Aqueous Solution and Its Practical Application in Environmental and Biological Samples

The voltammetric behavior of α-ketoglutarate (α-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 α-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 α=0.3 and ks=0.72 1/s. There was a linear relationship between peak current ip, α-KG and α-KG concentration in the range of 2×10−6–8×10−4 M α-KG. The detection limit was 8×10−7 M and the relative standard deviation was 2.0% (Cα-KG=8×10−4 M, n=10). Applications of the reductive wave of α-KG for practical analysis were addressed as follows: (1) It can be used for the quantitative analysis of α-KG in biological samples and the results agree well with those obtained from the established ultraviolet spectrophotometric method. (2) Utilizing the complexing effect between α-KG and aluminum, a linear relationship holds between the decrease of peak current of α-KG Δip and the added Al concentration C in the range of 5.0×10−6–2.5×10−4 M. The detection limit was 2.2×10−6 M and the relative standard deviation was 3.1% (C=4×10−5 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 AlIII on the glutamate dehydrogenase (GDH) activity in the catalytically reaction of α-KG+NH+NADH⇌L-glutamate+NAD++H2O by differential pulse polarography (DPP) technique. By monitoring DPP reductive currents of NAD+ and α-KG, an elementary important result was found that Al could greatly affect the activity of GDH. This study could be attributed to intrinsic understanding of the aluminum's toxicity in enzyme reaction processes.