Progress on Keto Groups Derivatization of Steroid Hormones in Gas Chromatography-Mass Spectrometry Analysis

New approach to derivatisation for oestradiol esters detection in animal blood plasma using negative chemical ionisation GC-MS

In 1996, the EU prohibited the use of substances with anabolic action for food-producing animals (EU Directive 96/22/EC). In cases of illegal use of steroid hormones, these substances are usually applied to the animals in the form of esters. The reliable determination of intact steroid esters in animal tissues or body fluids is an unequivocal proof of illegal treatment of animals with EU prohibited anabolic substances. Previously our laboratory developed a sensitive method for determination of oestradiol benzoate and other steroid esters in blood plasma using LC-MS/MS, validated according to Commission Decision 2002/657/EC. This study describes a GC-MS method which has been developed for five oestradiol esters in blood plasma. The sample preparation procedure consisted of protein precipitation, phospholipids removal and cleaning on an alumina column. Oestradiol esters were derivatised with 2, 3, 4, 5, 6-pentafluorobenzoyl chloride (PFBCl) and pyridine in dichloromethane. The measurement of oestradiol esters was carried out by GC-MS/NCI with Cool On-Column injection. Methane was used as a negative chemical ionisation reagent gas. The method for determination of oestradiol esters in blood plasma has been validated according to Commission Decision 2002/657/EC. Decision limits for all analytes were observed below 0.05 ng mL^-1. The method is robust for bovine and porcine plasma analyses and can be applied both for screening and confirmatory determination in routine residue monitoring.

Sample Multiplexing: Increased Throughput for Quantification of Total Testosterone in Serum by Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND

For high-volume assays, optimizing throughput reduces test cost and turn-around time. One approach for liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays is sample multiplexing, wherein the analyte of interest is derivatized in different specimens with reagents of different molecular weight (differential mass tagging). Specimens can then be combined and simultaneously analyzed within a single injection to improve throughput. Here we developed and validated a quantitative, sample-multiplexed LC-MS/MS assay for serum total testosterone (TT) based on this approach.

METHODS

For the sample-multiplexed assay, calibrators, controls, and patient specimens were first extracted separately. After mass tagging with either methoxyamine or hydroxylamine, they were combined and injected into the LC-MS/MS system. To evaluate assay performance, we determined limit of quantification (LOQ), linearity, recovery, and imprecision. A method-comparison study was also performed, comparing the new assay with the standard LC-MS/MS assay in 1574 patient specimens.

RESULTS

The method was linear from 2.5 to 2000 ng/dL, with accuracies from 93% to 104% for both derivatives. An LOQ of 1.0 ng/dL was achieved. Intra-assay and total CVs across 4 quality control concentrations were less than 10%. The assay demonstrated good agreement (Deming regression, 1.03x + 6.07) with the standard LC-MS/MS assay for the patient specimens tested (TT, 3 to 4862 ng/dL).

CONCLUSION

Sample multiplexing by differential mass tagging of TT increases LC-MS/MS throughput 2-fold without compromising analytical accuracy and sensitivity.

Reference intervals for the urinary steroid metabolome: The impact of sex, age, day and night time on human adult steroidogenesis

OBJECTIVE

Urinary steroid metabolomics by GC-MS is an established method in both clinical and research settings to describe steroidogenic disorders. However, population-based reference intervals for adults do not exist.

METHODS

We measured daytime and night time urinary excretion of 40 steroid metabolites by GC-MS in 1128 adult participants of European ancestry, aged 18 to 90 years, within a large population-based, multicentric, cross-sectional study. Age and sex-related patterns in adjacent daytime and night time urine collections over 24 hours were modelled for each steroid metabolite by multivariable linear mixed regression. We compared our results with those obtained through a systematic literature review on reference intervals of urinary steroid excretion.

RESULTS

Flexible models were created for all urinary steroid metabolites thereby estimating sex- and age-related changes of the urinary steroid metabolome. Most urinary steroid metabolites showed an age-dependence with the exception of 6β-OH-cortisol, 18-OH-cortisol, and β-cortol. Reference intervals for all metabolites excreted during 24 hours were derived from the 2.5th and 97.5th percentile of modelled reference curves. The excretion rate per period of metabolites predominantly derived from the adrenals was mainly higher during the day than at night and the correlation between day and night time metabolite excretion was highly positive for most androgens and moderately positive for glucocorticoids.

CONCLUSIONS

This study gives unprecedented new insights into sex- and age-specificity of the human adult steroid metabolome and provides further information on the day/night variation of urinary steroid hormone excretion. The population-based reference ranges for 40 GC-MS-measured metabolites will facilitate the interpretation of steroid profiles in clinical practice.

Current status and recent advantages in derivatization procedures in human doping control

Derivatization is one of the most important steps during sample preparation in doping control analysis. Its main purpose is the enhancement of chromatographic separation and mass spectrometric detection of analytes in the full range of laboratory doping control activities. Its application is shown to broaden the detectable range of compounds, even in LC–MS analysis, where derivatization is not a prerequisite. The impact of derivatization initiates from the stage of the metabolic studies of doping agents up to the discovery of doping markers, by inclusion of the screening and confirmation procedures of prohibited substances in athlete's urine samples. Derivatization renders an unlimited number of opportunities to advanced analyte detection.

Occurrence, fate and removal of synthetic oral contraceptives (SOCs) in the natural environment: a review

Synthetic oral contraceptives (SOCs) are a group of compounds with progestagenic and/or androgenic activities, with some also possessing estrogenic activities. Recent research has documented that some of these emerging contaminants have adverse effects on aquatic organisms at very low concentrations. To facilitate the evaluation of their latent risks, published works on their occurrence and fate in the environment are reviewed. Androgenic/progestagenic relative potencies or relative binding affinity of these SOCs as well as their physicochemical properties and toxicity are summarized. Appropriate analytical methods are outlined for various environmental sample types, including methods of sample preparation and limit of detection/quantification (LOD/LOQ). Finally results on their occurrence and fate in wastewater treatment plants (WWTPs) and other environments are critically examined.