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अमूर्त

Stability of 7-ketocholesterol, 19-hydroxycholesterol, and cholestane-3β,5α,6β-triol during storage: Derivatization issues.

T P Busch, H B Gross and A J King

Cholesterol oxide products (COPs) may be present as contaminants in standards or evolve during storage of standard solutions or during analysis. If evolved during storage or analysis, they are considered artifacts. It is paramount that standard oxides, often needed for routine analyses, remain stable under varying conditions of storage and analysis. An investigation was undertaken to determine if solutions of 7-ketocholesterol (7-keto), 19-hydroxycholesterol (19-OH) and cholestane-3β,5α,6β-triol (triol) remained stable over 0, 1, 3, 5 and 7 d when stored at 23 ± 2°C, 4°C, and -20°C. Chromatographic results, expressed as LS means, allowed for adjustment of the impact of injection number, a confounding variable. LS means for tms ethers of 7-keto and 19-OH significantly increased by day. Temperatures for storage times of 7-keto were significantly different with LS means increasing as temperature increased. For the triol tms ether, LS means significantly increased at 23 ± 2°C and 4°C when compared to -20°C; but no discernible trend was observed. Overall, as injection number increased, more derivatized compounds and less underivatized compounds were detected. Injection number was significant for 7-keto tms, underivatized 7-keto, combined 7-keto, 19-OH tms, the related 19-OH peak, and the triol tms ether. For triol, significance for the interaction of day and liner, but not liner, was indicated. Injection number, liner, or day when the liner was changed did not significantly affect the triol related peak.