instrumental techniques applied to mineralogy and geochemistry

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98 Clemente Recio such as blood and urine to regulatory levels requires the high selectivity and sensitivity offered by GC/MS and LC/MS/MS. Gas Chromatography-Isotope Ratio Mass Spectrometry (GC-IRMS), on the other hand, is proving a powerful tool for the detection of drug abuse in both humans and animals, potentially applicable to the analysis of any organic metabolites. IRMS is now widely accepted as the only technique that can unambiguously distinguish between endogenously produced and synthetic, selfadministered performance enhancing drugs. The measurement of deuterium isotopes provides additional evidence for sourcing drug metabolites. This technique has been accepted by the IOC Medical Commission (1997) as a viable technique for distinguishing between exogenous and endogenous steroid metabolites. The World Anti-Doping Agency (WADA, 2004) requests that any T/E ratio above 4 be confirmed by means of stable C isotope analysis. Testosterone There is an increasing need in sport for new methodologies in proving testosterone misuse. Up to recently, Study V GC-MS was employed day 1 V 2 V 3 V 4 V 5 to determine the 1 0.26 1.28 4.69 0.10 0.12 excreted Testosterone / 2 0.33 1.48 5.26 0.11 0.11 Epitestosterone ratio 3 0.65 8.77 29.30 0.26 0.70 4 1.95 24.20 36.90 1.77 6.69 from urine. A value of 5 2.81 45.80 41.80 2.01 5.91 greater than 4:1 was 6 2.79 33.20 61.80 1.96 3.71 7 3.03 15.40 54.90 1.91 4.24 considered as 8 4.13 36.40 57.70 1.48 5.95 confirmation of drug 9 5.30 30.30 39.70 1.51 5.78 administration (WADA, 11 3.20 26.50 33.00 0.58 3.69 13 0.77 2.63 3.42 0.68 3.41 2004). This ratio was 15 0.22 0.99 4.37 0.19 2.27 accepted because the 17 0.26 2.02 4.80 0.13 0.21 distribution of world population fell below this figure. However, there are minorities whose ratio can be naturally higher (Table 3; see Sottas et al., 2008). Also, this ratio can be manipulated downwards by simultaneous administration of epitestosterone. The GC-MS test is therefore fallible, potentially giving both false positives and false negatives (Sottas et al.,
Alike as two water drops: distinguishing one source of the same substance from another 99 2008). There are methods for overcoming this; the administration of a drug called ketoconazole to an athlete with a naturally high T/E ratio results in a decrease of such ratio, but in athletes who have received exogenous testosterone it causes the ratio to increase. This test could be used to determine innocence or guilt after a positive T/E test, but it involves administering a drug to detect a drug. Additionally, the athlete needs to be supervised for up to 8 hours for the drug to take affect, therefore being invasive and inconvenient for both the sampling officer and the athlete. 100 10 V 1 V 2 V 3 V 4 1 V 5 Regulatory Limit 0,1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Day of test FIGURE 6. Evolution of the 13 C values of Table 3. All but one volunteer test positive. The use of Stable Isotope Ratio Mass Spectrometry, however, has shown that synthetic testosterone (derived from plants) has a lower 13 C than the endogenous hormone (for example, Shackleton et al., 1997). The quantity of urine collectable from an athlete in events is minimum (50-100ml), and this has to be split to perform several analyses. Targeting the metabolites of testosterone, especially the androstanediols, which are naturally abundant and are at a higher concentration than testosterone, would make it easier to detect and monitor isotopically. The technique, therefore, uses a multistep, but
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SEMINARIOS DE LA SOCIEDAD ESPAÑOLA
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FOREWORD On the occasion of the Spa
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INDEX Electron back-scattered diffr
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8 Elisabetta Mariani et al Introduc
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10 Elisabetta Mariani et al success
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14 Elisabetta Mariani et al FIGURE
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16 Elisabetta Mariani et al FIGURE
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18 Elisabetta Mariani et al In-situ
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TEM in Geology. Basics and applicat
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X-ray Absorption Spectroscopy in Mi
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X-ray Absorption Spectroscopy in Mi
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