Qualitative analysis barbiturates

Barbiturates in either the free acid or salt forms are readily soluble in methanol and thus this is the solvent of choice for extraction in qualitative analysis. A known mass of the dose form is dissolved in a volume of methanol to provide the drug component at a working concentration of between 1 and 20 mgml The extract should be filtered or centrifuged prior to analysis in order to remove any unwanted particulate materials. For quantitative analysis, ethyl acetate can be used as the extraction solvent - if the drug is in the free acid form - with the extract treated in the same way as described above. If the original material is in the salt form, then the drug can be converted to the free acid form and extracted if required. 

In some cases, the forensic scientist will be required to quantify barbiturates and benzodiazepines in drug samples. Due to the problems associated with sample derivatization, quantification of barbiturates can best be achieved by using HPLC. Benzodiazepines are thermally labile compounds and thus HPLC is again the method of choice for qualitative analysis. 

A number of methods have been reported recently for the gas chromatographic separation of nonderivatized "free" barbiturates. The method (35) below is applicable to the qualitative and quantitative analysis of barbiturates, glutethimide and Dilantin from serum. It is a simple, rapid but accurate procedure using only 3 cm of serum. Dilantin could be separated on the same column as the barbiturates after it had been converted to its methylated derivative. 

Benzodiazepines may conveniently be extracted into methanol for both qualitative and quantitative analyses. The dose form should be triturated in methanol and as with barbiturates any solid material removed by centrifugation or filtration prior to analysis of the drug in solution. 

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