In-tip solid-phase microextraction: a method for determination of sulphonamide residues in environmental water samples

This study involved the development of an in-pipette tip solid-phase microextraction (SPME) method using activated charcoal as an adsorbent. Simultaneous determination of three sulphonamide antibiotic residues in environmental water was performed using this method, coupled with high-performance liquid chromatography-photodiode array (HPLC-PDA) detection. Seven extraction parameters were optimised by one-variable-at-a-time (OVAT) and response surface (RSM) methods. Optimum extraction efficiency was achieved when 10 mL of sample solution at a natural pH (pH 5-6) was loaded through a 1 mL pipette tip packed with 10 mg of adsorbent, washed with 1 mL of hexane and eluted with 500 mu L of 1% ammonium in methanol solution. Under the optimised experimental condition, this method manifested good linearity (5-500 mu g L-1) at the coefficient of determination, R-2 of 0.9992 to 0.9993, high sensitivity (limit of detection, LOD: 0.38-1.14 mu g L-1; limit of quantification, LOQ: 1.14-3.35 mu g L-1), and satisfactory recoveries (82.8-108.7%) with acceptable reproducibility (RSD < 4.6%). Real sample analysis of five environmental water samples sourced from Universiti Malaya, Kuala Lumpur and Malacca showed that the samples contained either none or traces of the target sulphonamides (SAs) with their concentration lower than the LOQs. In contrast to other methods, the comparison outcomes depicted that this in-tip SPME method was beneficial in terms of its simple, reusable, cost-saving setup together with a significant reduction in chemical consumption.