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Analytical capillary electrophoresis of oxalate, histidine-containing dipeptides, melatonin and tryptophan metabolites, and taxol in the presence of cephalomannine and baccatin III

Olga Albert McPhail, University of Massachusetts Amherst


The high efficiency of capillary electrophoresis (CE) coupled with universality of direct UV absorbance detection allowed the quantification of the following matrices: (1) oxalate in numerous biological systems such as: human albumin, urine, parental nutrition solutions (intralipid infusion, multi-vitamin infusion), fifteen premature baby formulas produced by the two leading baby food companies, commercial skim and 1% fat milk emulsions; (2) histidine-containing antioxidants, carnosine and anserine, in pork and chicken muscle tissue extracts; (3) melatonin in the presence of the products of tryptophan metabolism and (4) taxol in the presence of such interferents as cephalomannine and baccatine III. The importance of accurate oxalate quantification in various biological systems is directly connected to the formation of kidney and, possibly, gall bladder stones in premature babies and adults, since oxalate is a direct precursor in the formation of calcium oxalate, the final product of metabolism of oxalic acid. The method developed allowed quantification of underivatized samples with a 6 ppb detection limit for oxalate using direct photometric detection. The naturally occurring histidine-containing dipeptides, carnosine and anserine, are directly responsible for the following properties of muscle tissues of pork, chicken, fish, etc.: freshness, color, texture, and flavor. The present methods of antioxidant quantification based on HPLC with fluorescence detection lack sensitivity, specificity and reproducibility. A reliable CE method using direct UV absorbance detection was developed for fast, accurate, reproducible, sensitive and selective quantification of the analytes at ppm levels in the muscle extracts and at ppb levels in aqueous standards without derivatization of the muscle extracts. Much attention has been focused lately on the healing properties of the naturally occurring hormone melatonin. The analyte is currently quantified by HPLC with fluorescence and/or electrochemical detection, which, unfortunately, lacks specificity and sensitivity for melatonin in the presence of tryptophan and its products of metabolism. An attempt was made to develop a specific, sensitive, fast and simple method of analyte quantification without any kind of sample derivatization, solid phase and/or liquid phase extraction, and/or preconcentration. This allowed the separation and quantification of melatonin in the presence of major HPLC interferents such as tryptophan, hydroxytryptophan, and seratonin. Taxol, a highly functionalized taxane diterpene amide, has recently emerged as an effective chemotherapeutic agent for treatment of ovarian tumors, breast carcinomas and malignant melanoma. Micellar electrokinetic chromatography was successfully applied to separate several taxanes in about 11 minutes using minute amounts of sample and minimal amounts of buffer to decrease the solvent waste. (Abstract shortened by UMI.)

Subject Area

Analytical chemistry|Biomedical research|Food science

Recommended Citation

McPhail, Olga Albert, "Analytical capillary electrophoresis of oxalate, histidine-containing dipeptides, melatonin and tryptophan metabolites, and taxol in the presence of cephalomannine and baccatin III" (1997). Doctoral Dissertations Available from Proquest. AAI9737563.