Acetic acid improves the sensitivity of theophylline analysis by gas chromatography–mass spectrometry

In the analysis of theophylline by gas chromatography–mass spectrometry (GC–MS), we found that the addition of acetic acid to the solvent (ethyl acetate) decreased the adsorption of theophylline to the glass wool packed into the inlet liner. The addition of acetic acid to ethyl acetate improved the sensitivity for theophylline (optimum concentration of 3%). This simple and sensitive method without derivatization can be applied to the quantification of theophylline in serum samples in clinical and toxicological practice.