Headspace sampling with in situ carbodiimide-mediated derivatization for the determination of ibuprofen in water samples

A method using headspace generation and in situ derivatization with water soluble EDC (1-3-(dimethylamino)propyl]-3-ethylcarbodiimide) and TFEA (2,2,2-trifluoroethylamine) has been optimized for the determination of ibuprofen (2-(p-isobutylphenyl)propionic acid), one of the most common non-steroid anti-inflammatory drug (NSAIDs) residues in surface and wastewater samples. Derivatization was carried out in the vial of the headspace sampler (HS) in only 15 min, after which instrumental measurements were made with gas chromatography-mass spectrometry (GC-MS). As the injection system, a programmed temperature vaporizer (PTV) in the solvent-vent injection mode is proposed in order to increase the sensitivity of the measurements. The effects of the variables affecting HS generation, the derivatization reaction, and the instrumental PTV conditions were studied. A limit of quantification as low as 32 ng/L was achieved, and repeatability values were below 10%. Accuracy of the method was evaluated using spiked ultrapure water at three concentration levels, obtaining apparent recoveries between 96% and 104%. The proposed method was applied to the quantification of ibuprofen in sea water and urban wastewater samples.