Quantitative Determination of Derivatized Drugs

In some cases, the quantitative determination of an abused drug may be needed, for example, if this is prescribed by Section 24a of the German traffic law. 

Cannabis is by far the most commonly used illicit drug. Most people who abuse hard drugs such as heroin also abuse cannabis. Tetrahydrocannabinol (acid and A -metabolite) is regulated in the German traffic law (see Table 7-1), and amphetamine, opiates (morphine) and cocaine (as benzoylecgonine metabolite) are also mentioned. 

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Another example of the quantitative determination of a drug is provided by LSD. Because of the very high retention index (3595) of the LSD-TMS derivative, chromatography is not easy. Well-deactivated silylated inserts are recommended. The extracts from a human specimen should be free of matrix (reextraction). For the derivatization, the extremely dry residue is taken up in BSTFA/TMCS (Fluka 15238) and derivatized for 20 min at 70°C. Instead of pure BSTFA/TMSC, a 30-50% solution in a dry solvent such as acetic acid, diethyl ether or dioxan can be used. 

Capillary gas chromatography of morphine and codeine was described by Christophersen and Rasmussen in connection with their studies on flash heater derivatization of drugs for gas chromatographic analysis. Derivatization was found necessary for relative polar compounds such as morphine and codeine because of the often undesirable adsorption observed with glass capillary columns. Trimethylsilylation was performed with N,0-bis-(trimethylsilyl)acetamide and ethylmorphine was used as an internal standard for the quantitative determinations on a 20 m by 0.35 mm I.D. glass capillary, wall coated with SE-30. Calibration graphs for concentrations of 1-10 yg/ml in ethylacetate were constructed. The data obtained from the reproducibility test showed that at 5.0 pg/ml the relative standard deviation was 1.5 % for codeine and 4.3 % for morphine. 

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