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Clinical Chemistry 43: 1801-1803, 1997;
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(Clinical Chemistry. 1997;43:1801-1803.)
© 1997 American Association for Clinical Chemistry, Inc.

Oak Ridge Poster Sessions

Specific Determination of Urinary Free Cortisol by Solid-Phase Microparticle Extraction Capillary Electrophoresis with Fused Silica Capillaries

Lokinendi V. Rao, John R. Petersen, Michael G. Bissell, Anthony O. Okorodudu and Amin A. Mohammada

a author for correspondence: fax (409) 772-9231, e-mail aamohamm@utmb.edu

Measurement of 24-h urinary free cortisol (UFC) provides the most sensitive and specific diagnostic information for adrenal malfunctions, especially for Cushing syndrome (1)(2). The existing methodologies include immunoassays (3)(4)(5) and HPLC, with and without solid-phase extraction and derivatization (6)(7). Immunoassays for UFC are precise but overestimate the concentration because of antibodies' cross-reactivity with various metabolites and with synthetic corticoids having a chemical configuration similar to that of cortisol (8). HPLCs, on the other hand, although very specific, require large volumes of mobile phase, as well as sample pretreatment. Capillary electrophoresis (CE) overcomes many of these problems through the use of an open-tubular format, thus avoiding interaction of analytes with the solid-phase resin. Earlier, we reported the feasibility of rapid UFC detection in solid-phase extraction CE with a neutral capillary (9). Using a neutral capillary, we could demonstrate a detection limit of 552 nmol/L for UFC in human urine.

However, neutral capillaries have several disadvantages: Not only are they expensive, they also are unstable and lack a uniform capillary coating. This makes the neutral capillary unattractive for the development of a routine clinical laboratory assay. In the present study, we developed a solid-phase microparticle extraction (SPME) coupled micellar electrokinetic capillary chromatography (MEKC) with . . . [Full Text of this Article]


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Copyright © 1997 by the American Association for Clinical Chemistry.