研究了玻碳汞膜电极在次黄嘌呤溶液中的电化学行为及在此溶液中对抗坏血酸的电催化性能.结果表明:底液中加入一定量的次黄嘌呤能很好地抑制汞在较高的电位下溶出,并且汞膜电极在此溶液中有较好的稳定性,从而扩大了汞膜电极可用电位范围,为在较高电位下应用汞膜电极测定抗坏血酸提供了条件.在pH 1.81缓冲溶液中,抗坏血酸在汞膜电极上于0.25 V处出现灵敏的不可逆氧化峰(以银-氯化银电极作参比电极),峰电流在5×10-5~2.4×10-3mol·L-1范围内与浓度呈线性关系;检出限分别为8×10-6mol·L-1.该方法用于维生素C片剂中抗坏血酸含量的测定,分析结果的相对标准偏差(n=7)为1.3%,回收率在101.2%~104.5%之间.

Electrochemical behavior of mercury-filmed glassy carbon electrode (GCE) in base solution containing hypoxanthine and the electrocatalytic oxidation of ascorbic acid by hypoxanthine at the Hg-filmed GCE were studied.It was found that addition of a definite amount of hypoxanthine to the base solution was profitable in respect for inhibition of stripping of mercury from the electrode at high potentials,improving the stability and extending applicable potential range of the Hg-filmed GCE.It was also found that in a base solution of pH 1.81,a sensitive irreversible oxidative wave relative to ascorbic acid was observed at its peak potential of 0.25 V (vs.Ag-AgCl electrode).Linear relationship between peak current (Ip) and concentration of ascorbic acid was obtained in the range of 5×10-5-2.4×10-3mol·L-1,with detection limit of 8×10-6mol·L-1.The proposed method has been used in the analysis of vitamin C tablets giving values of RSD (n=7) of 1.3% and of recovery in the range of 101.2%-104.5%.