On-line coupling of SEC and RP–LC for the determination of structurally related enkephalins in cerebrospinal fluid

• Published in: Journal of pharmaceutical and biomedical analysis 2002-11, Vol.30 (4), p.1393-1401
• Main Authors: Stroink, Thom, Wiese, Gerard, Teeuwsen, Jan, Lingeman, Henk, Waterval, Joop C.M, Bult, Auke, de Jong, Gerhardus J, Underberg, Willy J.M
• Format: Article
• Language: English
• Subjects: Aminoacids, peptides. Hormones. Neuropeptides; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Cerebro-spinal fluid; Chromatography, Gel - instrumentation; Chromatography, Gel - methods; Chromatography, High Pressure Liquid - instrumentation; Chromatography, High Pressure Liquid - methods; Enkephalins; Enkephalins - cerebrospinal fluid; Enkephalins - chemistry; Fundamental and applied biological sciences. Psychology; Humans; Multidimensional separations; On-line coupling; Proteins; Reproducibility of Results; Reversed phase liquid chromatography; Size exclusion chromatography; Structure-Activity Relationship
• ISSN: 0731-7085; 1873-264X
• DOI: 10.1016/S0731-7085(02)00434-X

On-line coupled analytical techniques can be advantageous in the assay of smaller peptides in complex biological matrices such as plasma, cerebro-spinal fluid (CSF) and tissues. The present study shows the feasibility of the recently reported on-line coupled size exclusion chromatography (SEC) and reversed phase liquid chromatography (RP–LC) separation system for the quantitation of structural related peptides in biological matrices, as demonstrated for a number of enkephalins in CSF. The degradation of the peptides, caused by endogenous peptidases in the matrix, could sufficiently be inhibited with imipramine HCL to allow an assay with satisfactory linearity and intraday (0.70–4.9%) precision. The sensitivity of the method, with a concentration limit of quantitation (LOQ) of 2 μg/ml is comparable with other kinds of assays for peptides and sufficient for the quantitation of peptide drugs with higher therapeutic ranges in biological matrices. However, for the assay of low concentrations of peptides, such as endogenous components of a biological matrix, the sensitivity may need improvement. The LOQ cannot be improved by increasing the sample amount, because of interference of other endogenous components of the CSF. This indicates that a larger selectivity is desired. The LOQ may be improved by using more sensitive and selective detection methods such as mass spectrometry or fluorescence after post-column derivatization. Miniaturization of the system, combined with on-line trapping may also contribute to a better sensitivity.