Role of counteranions in polymeric ionic liquid-based solid-phase microextraction coatings for the selective extraction of polar compounds.

A polymeric ionic liquid (PIL) poly(1-vinyl-3-hexylimidazolium chloride) (poly(ViHIm(+)Cl⁻)) was designed as a coating material for solid phase microextraction (SPME) to extract polar compounds including volatile fatty acids (VFAs) and alcohols. The extracted analytes were analyzed by using gas chromatography (GC) coupled with flame ionization detection (FID). Extraction parameters of the HS-SPME-GC-FID method, such as ionic strength, extraction temperature, pH and extraction time were optimized. Calibration studies were carried out under the optimized conditions to further evaluate the performance of the PIL-based SPME coating. For comparison purposes, the PIL poly(1-vinyl-3-hexylimidazolium bis[(trifluoromethyl)sulfonyl]imide) (poly(ViHIm(+)NTf2⁻)) was also used as the SPME coating to extract the same analytes. The results showed that the poly(ViHIm(+)Cl⁻) PIL coating had higher selectivity towards more polar analytes due to the presence of the Cl⁻ anion which provides higher hydrogen bond basicity than the NTf2⁻ anion. The limits of detection (LODs) determined by the designed poly(ViHIm(+)Cl⁻) PIL coating ranged from 0.02µgL⁻¹ for octanoic acid and decanoic acid and 7.5µgL⁻¹ for 2-nitrophenol, with precision values (as relative standard deviation) lower than 14%. The observed performance of the poly(ViHIm(+)Cl⁻) PIL coating was comparable to previously reported work in which commercial or novel materials were used as SPME coatings. The selectivity of the developed PIL coatings was also evaluated using heptane as the matrix solvent. This work demonstrates that the selectivity of PIL-based SPME coatings can be simply tuned by incorporating different counteranions to the sorbent coating.

Sorbent coatings for solid-phase microextraction based on mixtures of polymeric ionic liquids.

Four polymeric ionic liquids based on two different cations, poly(1-vinyl-3-hexylimidazolium) and poly(1-vinyl-3-hexadecylimidazolium), combined with two different anions, bis[(trifluoromethyl)sulfonyl]imide (NTf 2-) and chloride (Cl(-)), were combined in various weight percentages and used as sorbent coatings for solid-phase microextraction gas chromatography (SPME-GC). The selectivity of the fiber coatings for 12 test analytes was examined. The extraction efficiency of n-alcohols increased with an increase in the weight percentage of chloride ion in the sorbent coating. The ability to tune the interactions between the coating material and the analytes was exploited and resulted in distinct changes in the limits of detection for hydrogen-bonding analytes with varying chloride ion content in the sorbent coating.

Utilization of a benzyl functionalized polymeric ionic liquid for the sensitive determination of polycyclic aromatic hydrocarbons; parabens and alkylphenols in waters using solid-phase microextraction coupled to gas chromatography-flame ionization detection.

The functionalized polymeric ionic liquid poly(1-(4-vinylbenzyl)-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide (poly(VBHDIm(+)NTf(2)(-))) has been used as successful coating in solid-phase microextraction (SPME) to determine a group of fourteen endocrine disrupting chemicals (ECDs), including polycyclic aromatic hydrocarbons (PAHs), alkylphenols, and parabens, in several water samples. The performance of the PIL fiber in direct immersion mode SPME followed by gas chromatography (GC) with flame-ionization detection (FID) is characterized with average relative recoveries higher than 96.1% from deionized waters and higher than 76.7% from drinking bottled waters, with precision values (RSD) lower than 13% for deionized waters and lower than 14% for drinking bottled waters (spiked level of 1 ng mL(-1)), when using an extraction time of 60 min with 20 mL of aqueous sample. Detection limits varied between 9 ng L(-1) and 7 ng mL(-1). A group of real water samples, including drinking waters, well waters, and swimming pool waters, have been analyzed under the optimized conditions. A comparison has also been carried out with the commercial SPME coatings: polydimethylsyloxane (PDMS) 30 µm, and polyacrylate (PA) 85 µm. The functionalized PIL fiber (∼12 µm) demonstrated to be superior to both commercial fibers for the overall group of analytes studied, in spite of its lower coating thickness. A normalized sensitivity parameter is proposed as a qualitative tool to compare among fiber materials, being higher for the poly(VBHDIm(+)NTf(2)(-)) coating. Furthermore, the partition coefficients of the studied analytes to the coating materials have been determined. A quantitative comparison among the partition coefficients also demonstrates the superior extraction capability of the functionalized PIL sorbent coating.

Tuning the selectivity of polymeric ionic liquid sorbent coatings for the extraction of polycyclic aromatic hydrocarbons using solid-phase microextraction.

A new generation polymeric ionic liquid (PIL), poly(1-4-vinylbenzyl)-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide (poly(VBHDIm(+) NTf(2)(-))), was synthesized and is shown to exhibit impressive selectivity towards the extraction of 12 polycyclic aromatic hydrocarbons (PAHs) from aqueous samples when used as a sorbent coating in direct-immersion solid-phase microextraction (SPME) coupled to gas chromatography (GC). The PIL was imparted with aromatic character to enhance π-π interactions between the analytes and the sorbent coating. For comparison purposes, a PIL with similar structure but lacking the π-π interaction capability, poly(1-vinyl-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide) (poly(HDIm(+) NTf(2)(-))), as well as a commercial polydimethylsiloxane (PDMS) sorbent coating were evaluated and exhibited much lower extraction efficiencies. Extraction parameters, including stir rate and extraction time, were studied and optimized. The detection limits of poly(VBHDIm(+) NTf(2)(-)), poly(HDIm(+) NTf(2)(-)), and PDMS coatings varied between 0.003-0.07 µg L(-1), 0.02-0.6 µg L(-1), and 0.1-6 µg L(-1), respectively. The partition coefficients (logK(fs)) of eight PAHs to the three studied fiber coatings were estimated using a static SPME approach. This study represents the first report of analyte partition coefficients to any PIL-based material.

Exploiting the versatility of ionic liquids in separation science: determination of low-volatility aliphatic hydrocarbons and fatty acid methyl esters using headspace solid-phase microextraction coupled to gas chromatography.

The determination of high-molecular weight aliphatic hydrocarbons and fatty acid methyl esters possessing high boiling points and low vapor pressures was performed using a headspace solid-phase microextraction gas chromatography (HS-SPME-GC) method comprised entirely of ionic liquids (ILs). The method utilizes three independently structurally engineered ILs in which the imparted physical and chemical properties make them compatible with the requirements of each component of the method. Component one is composed of a thermally stable IL solvent used to increase the equilibrium concentration of analytes in the HS, component two is a SPME sorbent coating based on a polymeric ionic liquid (PIL) for the selective HS extraction of analytes, and component three is an IL-based low-bleed GC stationary phase that performs the selective separation of the analytes. The method demonstrates the versatility of ILs within separation science in addition to determining these analytes, for the first time, using HS extraction at elevated temperatures with detection limits ranging from 0.3 to 0.6 mg kg(-1), relative recoveries from 69.9% to 106%, and precision (relative standard deviation for the overall method) from 6.9% to 16%.

Polymeric ionic liquids as selective coatings for the extraction of esters using solid-phase microextraction.

A new class of stationary phase coatings for solid-phase microextraction (SPME) based on polymeric ionic liquids (PILs) is presented. PIL-based SPME coatings exhibit exceptional film stability, high thermal stability, reproducible extraction efficiencies, and long lifetimes. A series of three homologous polymeric imidazolium-based ionic liquid coatings were synthesized by free radical reaction. The fiber coatings were used to extract esters and fatty acid methyl esters from aqueous solution followed by gas chromatographic separation and flame ionization detection. To examine the effect of the matrix on the coatings, extractions were carried out in a synthetic wine solution followed by recovery experiments in two real wine samples. When carrying out the extractions in aqueous solution, the detection limits for most analytes ranged from 2.5 to 50microgL(-1) whereas lower detection limits were obtained for larger fatty acid methyl esters. Recovery experiments carried out in red and white wines ranged from 70.2% to 115.1% using the PIL fibers compared to 61.9% to 102.9% using a commercial polydimethylsiloxane fiber of similar film thickness. The structural tuning capability of these new coating materials makes them widely amendable to performing task-specific microextractions.