Use of hydrogen as a carrier gas for the analysis of steroids with anabolic activity by gas chromatography-mass spectrometry.

Due to the impact in the media and the requirements of sensitivity and robustness, the detection of the misuse of forbidden substances in sports is a really challenging area for analytical chemistry, where any study focused on enhancing the performance of the analytical methods will be of great interest. The aim of the present study was to evaluate the usefulness of using hydrogen instead of helium as a carrier gas for the analysis of anabolic steroids by gas chromatography-mass spectrometry with electron ionization. There are several drawbacks related with the use of helium as a carrier gas: it is expensive, is a non-renewable resource, and has limited availability in many parts of the world. In contrast, hydrogen is readily available using a hydrogen generator or high-pressure bottled gas, and allows a faster analysis without loss of efficiency; nevertheless it should not be forgotten that due to its explosiveness hydrogen must be handled with caution. Throughout the study the impact of the change of the carrier gas will be evaluated in terms of: performance of the chromatographic system, saving of time and money, impact on the high vacuum in the analyzer, changes in the fragmentation behaviour of the analytes, and finally consequences for the limits of detection achieved with the method.

Automated sample preparation and gas chromatographic-mass spectrometric analysis of urinary androgenic anabolic steroids.

This paper presents an automated method for extracting anabolic agents from urine samples for their GC-MS analysis by selected-ion monitoring. The sample preparation was carried out in a Hewlett-Packard 7686 SPE PrepStation system. Each 0.6-ml aliquot was hydrolyzed, extracted, dried and trimethylsilyl (TMS) derivatized in a 2-ml vial without any hands-on labor. When sample preparation was finished 2 microl of the extract was injected into the gas chromatograph by split (1:10) mode. Due to the small amount of free space in the 2-ml vials for handling the sample, parameters like time of hydrolysis, type of shaking, number of extractions and some TMS derivatization parameters had to be adjusted to achieve the best recovery for all of the compounds in the screening. Manual and automated sample preparation schemes were compared in terms of linearity, precision, accuracy, limit of detection and recovery data. When large concentrations were analyzed using the automated method no carry-over effect was observed.

Análisis de anfetamina en orina por medio de microextracción en fase sólida / Analysis of amphetamine in urine by headspace solid phase microextraction

En este trabajo se presenta un método automatizado de extracción y análisis por GC (gas chromatography)-MS (mass spectrometry) para la detección de anfetamina en muestras de orina. El sistema esta constituido por un muestreador automatico, un cromatografo de gases y un espectrometro de masas de trampa de iones. El muestrador esta equipado con una aguja en cuyo interior hay una pequeña fibra retráctil de polidimetil siloxano, que puesta en contacto con la muestra, líquido o gas, absorbe selectivamente los analitos. La técnica es conocida como microextracción en fase sólida, SPME (Solid Phase MicroExtraction). En el estudio se hace un análisis detallado de todos los parámetros que afectan al rendimiento de las fibras, esto es; volumen de muestra, tipo de fibra, temperatura de absorción, tiempo de absorción, pH y fuerza ionica del medio. En la preparación de la muestra, tras ajustar manualmente el pH (pH 12) e incrementar la fuerza ionica de la muestra, 200 ml de orina son dispensados en un vial encapsulado de 2 ml. Tras solocar el vial en el carrusel termostatizado, Tª absorción 60°C, la fibra es introducida en el vial. Pasados 10 minutos de absorción, la fibra se retrae en la aguja y se inserta en el portal de inyección del cromatografo de gases, donde debido a alta temperatura, Ta desorbción 200°C, el analito desorbe de modo inmediato. El límite de detección es de 0.25 mg/l, el coeficiente de correlación lineal es de 0.9916 y la desviación estándar relativa menor del 5 por ciento. La concentración mínima de anfetamina que en la muestra pudo ser confirmada mediante un espectro de masas con índice de correlación mayor del 90 por ciento con su correspondiente espectro de librería, fue de 0.5 mg/l(AU)