Trace-level detection of sulfonamide antibiotics using quaternary ammonium polymeric ionic liquid-based effervescence-enhanced dispersive solid-phase extraction followed by LC-DAD analysis in environmental waters

Abstract

Conventional ionic liquids possess several disadvantages, such as high viscosity, difficult sampling/retrieval, and great loss in aqueous solution, limiting their wide applications in the pretreatment field. To solve these drawbacks, we synthesized a quaternary ammonium polymeric ionic liquid (PIL) and pressed it into an effervescent tablet for developing an effervescence-enhanced dispersive solid-phase extraction method (QAP-EDSE). The pressed effervescent tablet was composed of PIL as an extractant, tartaric acid as an acidic source, NaHCO₃ as an alkaline source, and water-soluble starch as a filler, respectively. Under the CO₂-driven dispersion, the QAP-EDSE method integrated rapid enrichment, extraction, and dispersion into one synchronous step. Employing the one-factor-at-a-time approach, several important variables were optimized as follows: 200 mg of P[VBTHEA]Cl as sorbent, 400 μL of acetone as elution solvent, 5 min of elution, solution pH 9.0, and 1 : 1.25 molar ratio of alkaline to acidic sources. Combining LC-DAD analysis, this proposed approach offered the limits of detection as low as 0.11-0.31 μg L^-1 and satisfactory recoveries of 81.40-102.62% for five sulfonamides (SAs) in environmental waters. The lower relative standard deviations (1.9-6.7%) evidenced the higher intraday and interday experimental precision by this method. Overall, the newly developed method is environmentally benign, time-saving, and easy to operate with low detection limit and high recovery and thus shows excellent prospects in the trace-level detection of SAs in environmental waters.

Fig. 1. The schematic procedures for the synthesis of P[VBTHEA]Cl (a), preparation of effervescent tablets and QAP-EDSE operations (b).

Fig. 2. SEM images of P[VBTHEA]Cl at 1000 (a), 2500 (b), 5000 (c), and 10 000 (s) × magnification.

Fig. 3. EDS mapping (a), FT-IR spectra (b), ¹³C NMR spectra, and TGA curve (d) of P[VBTHEA]Cl.

Fig. 4. BET specific surface area (a), zeta potential (b), transition of SMD from the molecular state to the ionic state under varying solution pH (c), and chromatographic profiles of five SAs standards in ultrapure water (d).

Fig. 5. Optimization of the important variables for the QAP-EDSE method. (a) Amount of P[VBTHEA]Cl, (b) type of elution solvent, (c) volume of eluent, (d) solution time, (e) Solution pH, and (f) recyclability of P[VBTHEA]Cl.

Fig. 6. Typical chromatograms of SAs in real-world water samples by the QAP-EDSE/LC-DAD method.