Tris(pentafluoroethyl)trifluorophosphate-basd ionic liquids as advantageous solid-phase micro-extraction coatings for the extraction of organophosphate esters in environmental waters

• Ionic liquid [HMIM][FAP] was used as a SPME coating for the first time.
• High hydrophobicity and thermostability make [HMIM][FAP] an excellent SPME coating.
• [HMIM][FAP]-based SPME fiber exhibits superior stability and durability.
• This SPME fiber shows good extraction efficiencies and enrichment factors for OPEs.

Ionic liquids (ILs) containing the tris(pentafluoroethyl)trifluorophosphate [FAP] anion and various cations have great potential in sample preparation because of their excellent hydrophobicity, thermostability and low hydrolysity. In the present study, a [FAP]-based IL, 1-hexyl-3-methylimidazolium tris (pentafluoroethyl) trifluoro phosphate ([HMIM][FAP]), was used as coatings of solid-phase microextraction (SPME) for extracting organophosphate esters (OPEs) from environmental water samples. This SPME fiber was fabricated by coating a stainless steel wire substrate with [HMIM][FAP] via a simple direct dip-coating approach, and the extraction was conducted by the direct immersion solid phase microextraction. Coupling to gas chromatography mass spectrometry (GC–MS), the developed SPME method exhibited excellent selectivity and sensitivity towards the extraction of 11 OPEs from aqueous samples. Satisfactory linearity (R2 ≥ 0.99) of the calibration curves was obtained over the range of 0.05–50.0 ng mL−1 with the limits of detection (LODs, S/N = 3) and limits of quantification (LOQs, S/N = 10) ranged from 0.13–7.40 ng L−1 and 0.50–24.0 ng L−1, respectively. The proposed SPME method showed excellent extraction efficiency to OPEs with enrichment factors in the range of 168–2603, and acceptable reproducibility with relative standard deviations (RSDs) ≤15% for single fiber (n = 7) and ≤16% for fiber-to-fiber (n = 3 × 3) at a concentration level of 0.5 ng mL−1, respectively. The prepared IL-based fiber was successfully applied to determine eleven common used OPEs in tap water, influent and effluent of sewage treatment plant, with results are comparable to those determined by the reference (UPLC–MS/MS), and spiked recoveries in the range of 84.0–108%, 82.1–123% and 82.8–100%, respectively.