Determination of 1-arylpiperazines, a new class of designer drugs, in serum

The 1-arylpiperazines, including benzylpiperazine, 1,3-chlorophenylpiperazine, 1,4-methylphenylpiperazine, and 1,3-trifluoromethylphenylpiperazine, are a relatively new class of designer drugs that have come to be of interest. The research presented here outlines both a LC/MS based method and a GC/MS based method to detect this class of drugs in serum. In these analyses, the highest accuracy is obtained with the use of internal standards. Although isotopically labeled compounds make the best internal standards, these compounds are not currently available. As a result, structural analogs were examined to determine which would be useful as internal standards, and 1,4-chlorophenylpiperazine and 1,3-methylphenylpiperazine were selected as the GC/MS and LC/MS internal standards, respectively. The compounds were isolated from serum using solid phase extraction, and samples analyzed using GC/MS were derivatized using heptafluorobutyric acid anhydride with ethyl acetate, while samples analyzed by LC/MS required no derivatization. Both methods were validated by testing serum samples spiked to three levels: 0.3 mug/mL, 1 mug/mL, and 5 mug/mL. While both methods worked, statistical analysis proves that the LC/MS based method is the better of the two for quantitation, and the GC/MS method is best for identification.