Zoulis N E, Nikolelis D P, Efstathiou C E
Laboratory of Analytical Chemistry, University of Athens, Greece.
Analyst. 1990 Mar;115(3):291-5. doi: 10.1039/an9901500291.
The pre-concentration of indole and other indolic compounds of biochemical and pharmaceutical interest at a carbon paste electrode (Nujol/graphite) has been studied. All the compounds examined can be determined, by direct voltammetric measurements in their solutions, in the concentration range 1-8 microM. Indole, methylated indoles, harmaline and serotonin were accumulated at the electrode by a combined adsorption/extraction process. By applying the medium-exchange procedure, the accumulated compounds can be determined in the same concentration range, after a 60-s pre-concentration period, enhancing, therefore, the selectivity of the voltammetric determination. A procedure for the indirect determination of L-tryptophan in serum has been developed, which is based on these findings. L-Tryptophan was cleaved to indole by tryptophanase, and indole was subsequently determined voltammetrically after a 2-min pre-concentration period at the carbon paste electrode. From 0.3 to 1.2 micrograms of L-tryptophan in a total of 75 microliters of serum sample (20-80 microM) can be determined with an average error of ca. 0.03 microgram, whereas the recovery of added L-tryptophan in serum samples is in the range 105-115%.
已对碳糊电极（凡士林/石墨）上吲哚及其他具有生化和药学意义的吲哚类化合物的预富集进行了研究。通过对所研究化合物溶液进行直接伏安测量，可测定浓度范围为1 - 8 microM的所有化合物。吲哚、甲基化吲哚、哈尔明碱和血清素通过吸附/萃取联合过程在电极上富集。采用介质交换程序，在60秒预富集期后，可在相同浓度范围内测定富集的化合物，从而提高了伏安测定的选择性。基于这些发现，已开发出一种间接测定血清中L - 色氨酸的方法。L - 色氨酸经色氨酸酶裂解为吲哚，随后在碳糊电极上进行2分钟预富集后，通过伏安法测定吲哚。在总共75微升血清样品（20 - 80 microM）中，0.3至1.2微克的L - 色氨酸可被测定，平均误差约为0.03微克，而血清样品中添加的L - 色氨酸回收率在105 - 115%范围内。
