A new silylating reagent – dimethyl(3,3,3-trifluoropropyl)silyldiethylamine – for the derivatisation of non-steroidal anti-inflammatory drugs prior to gas chromatography–mass spectrometry analysis

• DIMETRIS – a new silylating reagent for the derivatisation of NSAIDs.
• Derivatising properties of DIMETRIS compared with those of BSTFA and TMSD.
• Possibility of using MS and ECD detectors for the GC determination of new derivatives.
• Study of the influence of complex matrices on derivatisation and GC–MS analysis.
• A new SPE-GC–MS method for determining NSAIDs based on derivatisation with DIMETRIS.

This paper discusses a new silylating reagent – dimethyl(3,3,3-trifluoropropyl)silyldiethylamine (DIMETRIS) – for the derivatisation of non-steroidal anti-inflammatory drugs (NSAIDs) prior to GC–MS analysis. DIMETRIS reacts with seven target compounds (diclofenac, ibuprofen, ketoprofen, naproxen, flurbiprofen and paracetamol, as well as salicylic acid, a degradation product of acetylsalicylic acid) at 30 °C for 30 min, producing mono-O-dimethyltrifluoropropylsilyl (mono-O-DMTFPS) derivatives. The mass spectra of these new derivatives are given and fully interpreted. The usefulness of mono-O-DMTFPS derivatives for the qualitative and quantitative analysis of NSAIDs using GC–MS is compared with that of trimethylsilyl and methyl analogues. Methyl derivatives are found to be less appropriate for this purpose because they yield the lowest detector responses during GC–MS measurements. Both silyl derivatives are more suitable for determining such NSAIDs, although the matrix effect with mono-O-DMTFPS derivatives is smaller. Finally, SPE-GC–MS(SIM) based on the derivatisation of NSAIDs by DIMETRIS is evaluated, validated and applied to the determination of these drugs in sea water (Baltic Sea) and wastewater samples collected in Poland. This work confirms that DIMETRIS is suitable for the trace analysis of NSAIDs in real samples and provides an interesting alternative to silylating and methylating reagents.