Polymeric ionic liquid open tubular capillary column for on-line in-tube SPME coupled with UHPLC-MS/MS to determine endocannabinoids in plasma samples

Highlights: • Polymeric ionic liquid monomers (PIL) and PIL cross-linker was synthesized. • Selective PIL-based wall-coated open tubular capillary columns were synthesized. • PIL-based wall-coated open tubular capillary was used as a sorbent phase. • PIL capillary was used in on-line in-tube SPME/UHPLC-MS/MS method. • The method was applied to determine endocannabinoids in plasma samples. -- Abstract: This manuscript describes the development of wall-coated open tubular capillary column with polymeric ionic liquids (PILs) for on-line in-tube solid phase microextraction coupled with ultra high-performance liquid chromatography tandem mass spectrometry (in-tube SPME/UHPLC-MS/MS) to determine anandamide (AEA) and 2-arachidonoyl glycerol (2 A G) in plasma samples. Selective PILs were synthetized from the [VC₆IM][Cl], [VC₁₆IM][Br], and [(VIM)₂C₁₀]2 [Br] - ionic liquids - by in-situ thermal-initiated polymerization in a fused silica capillary column for in-tube SPME. The synthesis procedure was optimized, and the capillary columns were characterized using spectroscopic and chromatography techniques. The chemically bonded and cross-linked PIL-based sorbent phase (thickness coating: 1.7 μm) presented high chemical and mechanical stability. Among the sorbents evaluated, the PIL-based capillary, [VC₁₆IM][Br]/[(VIM)₂C₁₀]2 [Br] presented the best performance with a sorption capacity of 37,311 ng cm⁻³ and 48,307 ng cm⁻³ for AEA and 2 A G, respectively. This capillary was reused more than ninety times without significant changes in extraction efficiency. The in-tube SPME-UHPLC-MS/MS method presented a linear range from 0.1 ng mL⁻¹ to 100 ng mL⁻¹ for AEA, and from 0.05 ng mL⁻¹ to 100 ng mL⁻¹ for 2 A G, with coefficients of determination higher than 0.99, p-value for Lack-of-fit test higher than 0.05 (α of 0.05), precision with coefficient of variation (CV) values ranging from 1.6 to 14.0% and accuracy with relative standard deviation (RSD) values from −19.6% to 13.2%. This method was successfully applied to determine AEA and 2 A G in plasma patients with Parkinson's disease. The concentrations in these plasma samples ranged from 0.14 to 0.46 ng mL⁻¹ for AEA and from <0.05 ng mL⁻¹ to 0.51 ng mL⁻¹ for 2-AG.