Improved sensitivity by use of gas chromatography—positive chemical ionization triple quadrupole mass spectrometry for the analysis of drug related substances

• NH3 has better ionization characteristics than CH4 for GC-PICI-MS/MS purposes.
• Combining chemical ionization and GC–MS/MS improves the detection capabilities.
• A PICI-GC–MS/MS screening method was developed and evaluated.

In 2013, the World Anti-Doping Agency (WADA) drastically lowered the minimum required performance levels (MRPLs) of most doping substances, demanding a substantial increase in sensitivity of the existing methods. For a number of compounds, conventional electron impact ionization gas chromatography tandem mass spectrometry (GC-EI-MS/MS) is often no longer sufficient to reach these MRPLs and new strategies are required.In this study, the capabilities of positive ion chemical ionization (PICI) GC–MS/MS are investigated for a wide range of drug related compounds of various classes by injection of silylated reference standards. Ammonia as PICI reagent gas had superior characteristics for GC–MS/MS purposes than methane. Compared to GC-EI-MS/MS, PICI (with ammonia as reagent gas) provided more selective ion transitions and consequently, increased sensitivity by an average factor of 50. The maximum increase (by factor of 500–1000) was observed in the analysis of stimulants, namely chlorprenaline, furfenorex and phentermine. In total, improved sensitivity was obtained for 113 out of 120 compounds.A new GC-PICI-MS/MS method has been developed and evaluated for the detection of a wide variety of exogenous doping substances and the quantification of endogenous steroids in urine in compliance with the required MRPLs established by WADA in 2013. The method consists of a hydrolysis and extraction step, followed by derivatization and subsequent 1 μL pulsed splitless injection on GC-PICI-MS/MS (16 min run). The increased sensitivity allows the set up of a balanced screening method that meets the requirements for both quantitative and qualitative compounds: sufficient capacity and resolution in combination with high sensitivity and short analysis time. This resulted in calibration curves with a wide linear range (e.g., 48–9600 ng/mL for androsterone and etiochanolone; all r2 > 0.99) without compromising the requirements for the qualitative compounds.