No abstract

In this work, a durable and easy to handle thin film microextraction (TFME) device is reported. The membrane is comprised of poly(divinylbenzene) (DVB) resin particles suspended in a high-density polydimethylsiloxane (PDMS) glue, which is spread onto a carbon fiber mesh. The currently presented membrane was shown to exhibit a substantially lesser amount of siloxane bleed during thermal desorption, while providing a statistically similar extraction efficiency toward a broad spectrum of analytes varying in polarity when compared to an unsupported DVB/PDMS membrane of similar shape and size which was prepared with previously published methods. With the use of hand-portable GC-TMS instrumentation, membranes cut with dimensions 40 mm long by 4.85 mm wide and 40 ± 5 μm thick (per side) were shown to extract 21.2, 19.8, 18.5, 18,4, 26.8, and 23.7 times the amount of 2,4 dichlorophenol, 2,4,6 trichlorophenol, phorate D10, fonofos, chloropyrifos, and parathion, respectively, within 15 min from a 10 ppb aqueous solution as compared to a 65 μm DVB/PDMS solid phase microextraction (SPME) fiber. A portable high volume desorption module prototype was also evaluated and shown to be appropriate for the desorption of analytes with a volatility equal to or lesser than benzene when employed in conjunction with TFME membranes. Indeed, the coupling of these TFME devices to hand-portable gas chromatography toroidial ion trap mass spectrometry (GC-TMS) instrumentation was shown to push detection limits for these pesticides down to the hundreds of ppt levels, nearing that which can be achieved with benchtop instrumentation. Where these membranes can also be coupled to benchtop instrumentation it is reasonable to assume that detection limits could be pushed down even further. As a final proof of the concept, the first ever, entirely on-site TFME-GC-TMS analysis was performed at a construction impacted lake. Results had indicated the presence of contaminants such as toluene, ethylbenzene, xylene, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, and tris(1-chloro-2-propyl)phosphate, which stood out from other naturally occurring compounds detected.

The primary goal of the present study is the inter-laboratory evaluation of a thin film microextraction (TFME) technique to be used as an alternative approach to liquid-liquid extraction (LLE). Polydimethylsiloxane/divinylbenzene (PDMS/DVB) and PDMS/DVB-carbon mesh supported membranes were used for the extraction of 23 targeted pesticides, while a thermal desorption unit (TDU) was employed to transfer these analytes to a GC/MS instrument for separation and detection. After optimization of the most critical parameters, both membranes were capable of achieving limits of detection (LOD) in the low ng L range while demonstrating excellent robustness, withstanding up to 100 extractions/desorption cycles. Furthermore, limits of quantification (LOQ) between 0.025 and 0.50 μg L were achieved for the 23 compounds selected from several classes of pesticides with a wide range of polarities. A wide linear range of 0.025-10.0 μg L with strong correlation to response (R > 0.99) was attained for most of the studied analytes. Both membranes showed good accuracy and repeatability at three levels of concentration. Moreover, the method was also validated through blind split analyses of 18 surface water samples, collected within 3 months, using TFME at the University of Waterloo and LLE at Maxxam Analytics (Mississauga, ON) which is an accredited commercial analytical laboratory. Good agreement between the two methods was achieved with accuracy values ranging from 70 to 130%, for the majority of analytes in the samples collected. At the concentration levels investigated, 90% of the analytes were quantifiable by TFME, whereas only 53% of the compounds were reportable using the LLE method particularly at concentrations lower than 1 μg L. The comparison of TFME and LLE from several analytical aspects demonstrated that the novel TFME method gave similar accuracy to LLE, while providing additional advantages including higher sensitivity, lower sample volume, thus reduced waste production, and faster analytical throughput. Given the sensitivity, simplicity, low cost, accuracy, greenness and relatively fast procedure of TFME, it shows great potential for adoption in analytical laboratories as an alternative to LLE.

A novel hydrophilic−lipophilic balanced (HLB) thin film solidphase microextraction (TF-SPME) device is proposed for polarity-balanced determinations of volatile organic compounds. The proposed HLB particles used in the preparation of these membranes were prepared using a precipitation polymerization technique and determined to have a specific surface area of 335 m 2 /g with an average pore diameter of 13 Å. Membranes prepared from these particles were found to extract 1.8, 2.2, 1.9, 1.7, 2.0, and 1.3 times more benzene, 2-pentanone, 1-nitropropane, pyridine, 1-pentanol, and octane, respectively, than the established divinylbenzene/polydimethylsiloxane (DVB/PDMS)-based membranes. Furthermore, membranes prepared from these lab-made particles were shown to extract significantly (p = 0.00047) larger amounts of these analytes than membranes prepared from comparative commercial HLB particles. The intermembrane extraction efficiency between 3 membranes was determined to be reproducible at 95% confidence for 4 different coating chemistries tested, including the DVB/PDMS membranes, and those prepared with 3 different HLB compositions. Furthermore, method reliability was established by confirming that, once extracted, modified McReynolds standards were stable on the HLB/PDMS membranes stored in thermal desorption tubes on an autosampler rack for at least 120 h, for 5 of the 6 standards, but only for 24 h for pyridine at a 95% level of confidence. Finally, using a TF-SPME enabled, portable GC/MS instrument, an entirely on-site proof of concept application was performed for the determination and quantitation of chlorination byproducts in a private hot tub, successfully identifying chloroform, bromodichloromethane, dichloroacetonitrile, chlorobenzene, benzonitrile, and benzyl chloride, while further quantifying chloroform and dichloroacetonitrile at levels of 270 and 79 ppb with %RSD values of 13% and 5%, respectively.

To date, solid-phase microextraction (SPME) fibers used for in vivo bioanalysis can be too fragile and flexible, which limits suitability for direct tissue sampling. As a result, these devices often require a sheathing needle to prepuncture robust sample matrixes and protect the extraction phase from mechanical damage. To address this limitation, a new SPME device is herein presented which incorporates an extraction phase recessed into the body of a solid needle. This device requires no additional support or shielding during puncture events through protective tissue. The presented device was thoroughly tested, being fired at 90 m·s through fish scales, forced through vial septa, and employed in a targeted study of polyunsaturated fatty acids in salmon where the protective outer skin was repetitively punctured during sampling. Finally, the recessed SPME device was applied to an on-site application for the tissue analysis of wild muskellunge. With this advancement, rapid, minimally invasive, and easily executed in vivo SPME is now possible opening the door to near endless sampling opportunities.