Selective isolation of pesticides and cannabinoids using polymeric ionic liquid-based sorbent coatings in solid-phase microextraction coupled to high-performance liquid chromatography

Multivariate optimization for extraction of 2-methylimidazole and 4-methylimidazole from açaí-based food products using polymeric ionic liquid-based sorbent coatings in solid-phase microextraction coupled to gas chromatography-mass spectrometry

In this study, polymeric ionic liquids featuring different functional moieties were applied as sorbent coatings in direct-immersion solid-phase microextraction (DI-SPME) for the extraction of 2-methylimidazole (2-MI) and 4-methylimidazole (4-MI) from açaí-based food products followed by gas chromatography-mass spectrometry (GC-MS) analysis. The analytical method was optimized using a sequential experimental design. Variables used in GC-MS such as desorption time, as well as for SPME-DI, including extraction time, extraction temperature, incubation time of extraction, amount of NaCl in the extract, and stirring rate, were optimized. The fitness-for-purpose of the method was verified by the linearity of matrix-matched calibration curves (R2 ≥ 0.9921), adequate recoveries (81.7-89.7 %), and precision (relative standard deviations ≤11.2 %). The method was applied to twenty-five samples of açaí-based food products. 4-MI was found in four samples whereas 2-MI was not detected above the limit of detection. The method was found to be suitable for quality control analysis.

Polymeric ionic liquid sorbent coatings in thin film microextraction: Insight into sorbent selectivity for pesticides and cannabinoids

Polymeric ionic liquid (PIL) sorbent coatings consisting of polymerizable cations and anions were employed as sorbent coatings in thin film microextraction (TFME) for the extraction of pesticides and cannabinoids. The blades consisted of a thin film of PIL sorbents chemically bonded to vinyltrimethoxysilane-functionalized nitinol sheets. The imidazolium- or ammonium-based PIL sorbents contained aromatic benzyl moieties as well as polar hydroxyl groups or aliphatic functional groups within the chemical structure of the IL monomer. The chemical structure of the IL crosslinkers of the PILs were kept constant across each sorbent, except for the anion, which consisted of either bis[(trifluoromethyl)sulfonyl]imide ([NTf2-]), p-styrenesulfonate ([SS-]), or 3-sulfopropyl acrylate ([SPA-]). Temperature, salt content, and methanol content were optimized as extraction conditions to maximize pesticide-cannabinoid selectivity using Doehlert design of experiments (DOE). Effects of these three factors on selectivity and extraction efficiency are discussed. The optimal extraction conditions consisting of sample temperature (31°C), sodium chloride (30% w/v), and methanol content (0.25% v/v) are compared to initial sorbent screening conditions at a sample temperature of 40°C, 15% (w/v) sodium chloride, and 2.5% (v/v) methanol content. PIL sorbent swelling behavior at different salt and methanol content conditions and its effect on extraction efficiency are hypothesized. Selectivity factors for the sorbents indicated that aromatic moieties within the IL monomer may enhance pesticide-cannabinoid selectivity under optimized conditions, but the extraction efficiency of pesticides that are known to coelute with cannabinoids in the chromatographic separation may be enhanced by employing sorbent coatings with [SPA-] anions.

Understanding the influence of polymeric ionic liquid sorbent coating substituents on cannabinoid and pesticide affinity in solid-phase microextraction

To understand factors that drive pesticide-cannabinoid selectivity in solid-phase microextraction (SPME), eight new polymeric ionic liquid (PIL) sorbent coatings were designed and compared to four previously reported PIL sorbent coatings for the extraction of pesticides. The four PIL sorbent coatings consisted of either vinylimidazolium or vinylbenzylimidazolium ILs with long alkyl chain substituents (i.e., -C8H17 or -C12H25) and bis[(trifluoromethyl)sulfonyl]imide ([NTf2-]) anions, from which the eight new PIL sorbent coatings were adapted. Modifications to the chemical structure of IL monomers and crosslinkers included incorporation of polymerizable p-styrenesulfonate or 3-sulfopropyl acrylate anions, the addition of aromatic moieties, and/or the addition of polar functional groups (i.e., -OH or -O- groups). A total of ten commonly regulated pesticides and six cannabinoids were examined in this study. The effect of salt on the solubility of pesticides and cannabinoids in aqueous solutions was assessed by determining their extraction efficiencies in the presence of varied methanol content. Differences in their solubilities appear to play a dominant role in enhancing pesticide-cannabinoid selectivity. The selectivity, represented as the ratio of pesticide total peak areas to cannabinoid total peak areas, also exhibited a moderate correlation to the affinity of the sorbent coatings towards both the pesticides and the cannabinoids. A positive correlation was observed for the pesticides and a negative correlation was observed for the cannabinoids, suggesting that selectivity was driven by more than the presence of salt in the samples. The sorbent coatings' affinity towards each class of analytes were examined to determine specific interactions that might influence selectivity. The two main structural modifications increasing pesticide-cannabinoid selectivity included the absence of aromatic moieties and the addition of hydrogen bond donor functional groups. Extractions of simple aromatic molecules as probes were performed under similar extraction conditions as the cannabinoids and confirmed the influence of hydrogen bonding interactions on sorbent coating affinity.