Stability studies of testosterone and epitestosterone glucuronides in urine
ABSTRACT The stability of testosterone glucuronide (TG), epitestosterone glucuronide (EG) and the T/E ratio in urine has been studied. Samples were analyzed by gas chromatography coupled to mass spectrometry (GC/MS). Urine samples were submitted to a solid-liquid cleanup followed by extraction of unconjugated testosterone (T) and epitestosterone (E) with tert-butyl methyl ether (free fraction). The remaining aqueous phase was hydrolyzed with beta-glucuronidase and extracted at alkaline pH with n-pentane. Analytes were analyzed by GC/MS as their enol-trimethylsilyl (TMS) derivatives. The urine for stability testing was obtained from an excretion study after the administration of T to healthy volunteers. The homogeneity of the sample was verified before starting the stability study. The stability of TG and EG was evaluated at different storage conditions. For long-term stability testing, analyte concentration in urine stored at 4 degrees C and -20 degrees C was determined at different time intervals for 22 months. For short-term stability testing, analyte concentration was evaluated in urine stored at 37 degrees C for 3 and 7 days. The effect of repeated freezing (at -20 degrees C) and thawing (at room temperature) was studied for up to three cycles. Data obtained in this work demonstrated the stability of TG, EG and the T/E ratio in sterilized urine samples stored at 4 and -20 degrees C for 22 months and after going through repeated freeze/thaw cycles. Decreases in concentration were observed after 7 days of storage at 37 degrees C due to the partial cleavage of the glucuronide conjugates; however, the T/E ratio was not affected. These results show the feasibility of preparing reference materials containing TG and EG to be used for quality control purposes.
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ABSTRACT: In elite sports, indirect testing of testosterone abuse is mainly based on the testosterone over epitestosterone (T/E) ratio. Since this marker is characterized by a small ratio of intra- to inter-individual variation, it is surprising that current anti-doping strategy uses a screening test based on a population-based limit. From a database of more than 15,000 steroid profiles obtained from routine controls, the collection of steroids profiles of 11 elite athletes followed during 2 years, and a longitudinal study involving 17 amateur athletes, 8 of which were orally administrated testosterone undecanoate pills, we selected 12 case studies to represent the possible scenarios to which the anti-doping laboratories are confronted. Various detection strategies at the disposal of the laboratories are employed and discussed, including isotope ratio mass spectrometry (IRMS) analysis and a Bayesian interpretation of the T/E-time profile. The weak sensitivity versus specificity relation of a population-based limit for the T/E ratio is outlined. As a result, we propose a Bayesian screening test whose T/E threshold progressively evolves from a population basis to a subject basis as the number of individual test results increases. We found that this screening test heightens drastically the capacity to detect testosterone abuse, at no additional financial and administrative expenses for anti-doping authorities.Forensic science international 02/2008; 174(2-3):166-72. DOI:10.1016/j.forsciint.2007.04.001 · 2.12 Impact Factor
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ABSTRACT: A simple method using liquid chromatography-linear ion trap mass spectrometry for simultaneous determination of testosterone glucuronide (TG), testosterone sulfate (TS), epitestosterone glucuronide (EG) and epitestosterone sulfate (ES) in urine samples was developed. For validation purposes, a urine containing no detectable amount of TG, TS and EG was selected and fortified with steroid conjugate standards. Quantification was performed using deuterated testosterone conjugates to correct for ion suppression/enhancement during ESI. Assay validation was performed in terms of lower limit of detection (1-3ng/mL), recovery (89-101%), intraday precision (2.0-6.8%), interday precision (3.4-9.6%) and accuracy (101-103%). Application of the method to short-term stability testing of urine samples at temperature ranging from 4 to 37 degrees C during a time-storage of a week lead to the conclusion that addition of sodium azide (10mg/mL) is required for preservation of the analytes.Journal of Chromatography B 12/2006; 844(1):168-74. DOI:10.1016/j.jchromb.2006.07.010 · 2.69 Impact Factor
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ABSTRACT: For a correct interpretation of analytical results in doping control, knowledge on the stability of prohibited substances in the urinary matrix is a prerequisite. So far, limited data is available on the stability of prohibited substances in unaltered urine because most of the studies investigating the stability of drugs have used stabilized, sterilized, or filtered urine. In this work, the long-term stability of ephedrine, methylephedrine, cathine, 19-norandrosterone glucuronide, and a wide range of diuretics was determined over a period of 9 months at -20 degrees C, 4 degrees C, 22 degrees C, and 37 degrees C. Short-term stability, including the influence of 6 freeze-thaw cycles and 15 h storage at 60 degrees C, was also investigated. Often, a tolerance limit of 15%, similar to what is commonly used in the evaluation of precision data during method validation, is used to evaluate stability. This paper describes an alternative approach, using measurement uncertainty data to evaluate long-term stability with a probability of 95%, and proposes a simple alternative for investigating the stability for non-threshold substances. The results indicate that all the investigated substances are stable (alpha=0.05) when stored at -20 degrees C and 4 degrees C, but that at higher temperatures significant degradation effects can occur. The study also shows that degradation can be dependent on the urinary matrix and that the results from stability studies using stabilized, filtered, or sterilized urine can underestimate degradation effects.Journal of analytical toxicology 11/2007; 31(9):543-8. DOI:10.1093/jat/31.9.543 · 2.63 Impact Factor