The application of tandem mass spectrometry to the analysis and identification of analgesics and non-steroidal anti-inflammatory drugs such as paracetamol, ibuprofen and indomethacin following thin-layer chromatography (TLC) is described. TLC was combined successfully with mass spectrometry and with tandem mass spectrometry using silica gel and diol-bonded silica gel high performance TLC plates. The diol-bonded phase was found to be superior for use with biological samples and enabled the identification of paracetamol, ibuprofen and salicylhippuric acid (the major metabolite of acetylsalicylic acid) in human urine extracts following normal therapeutic doses.
Thin-layer chromatography (TLC) remains a popular method for qualitative analysis, and for the screening of samples such as urine for drugs.' However, when compounds of interest are detected by this type of screening, confirmation of the identity of the compound(s) of interest is then usually undertaken using another method such as gas chromatography mass spectrometry (GUMS). Very often this requires that the sample be subjected to extraction and subsequent derivatization before the analyte is in a suitable form for chromatography. However, if the aim of the analysis is confirmation of identity, then the use of mass spectrometric techniques directly on the material present in the TLC spot/band represents a practical alternative to GC/ MS etc. In previous studies we have demonstrated the application of TLC/MS, and more recently TLC/tandem mass spectrometry (MS/MS) to a variety of compound types. This has included the use of TLC/MS and TLC/MS/ MS for the identification of natural products? drugs and metabolite^^'^ and industrial chemicals5 in a variety of matrices and from various TLC stationary phases (reviewed in Refs 6, 7). Here we present the results of studies using TLC/MS and TLC/MS/MS on non-steroidal anti-inflammatory drugs, analgesics and metabolites, both as pure substances and when present in urine extracts.