中文摘要：

以化学氧化法制备了膨胀石墨，再以石蜡作为粘合剂制备了膨胀石墨电极，该电极兼备电化学传感器和富集待测物分子，缩短传质过程时间的特点。优化了测定条件，在此基础上建立了一种直接测定色氨酸的电分析方法。结果表明：在0．02-0．12mmol／L范围内，电极响应与色氨酸浓度呈良好的线性关系，检出限为2．0×10-mol／L，RSD为2．4％。该电极具有良好的选择性，除酪氨酸外，浓度高达5．0mmol／L（色氨酸浓度的100倍）的其它8种氨基酸在电极上均没有可测的响应。用该电极测定了医用氨基酸注射液中色氨酸的含量，结果与标称值相符。对色氨酸在膨胀石墨电极表面的富集原因和反应机理进行了初步探讨。

英文摘要：

Expanded graphite was prepared by chemical oxidation, and then expanded graphite electrode was fabricated using paraffin as adhesive. The electrode has characteristics of electrochemical sensing , enriching the molecules of analyte and shortening the time used in mass transfer. Various experimental parameters were optimized to analyze tryptophan by employing differential pulse stripping voltammetry. The results of experiment demonstrate that the relationship between the electrode response and the concentration of tryptophan is linear in the range of 2.0 × 10^-5 - 1.2 × 10^-4 mol/L, the detection limit is 2.0 × 10^-7 mol/L, and the RSD is 2.4%. The electrode has good selectivity, other eight amino acids of which the concentrations were about 100 times higher than those of tryptophan have no response on the electrode except tyrosine. The content of tryptophan in medical amino acid injection was determined using the electrode with satisfactory results. The reaction mechanism of tryptophan on expanded graphite electrode surface was also discussed.