Browsing by Author "Taylor, Bradley M."

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    Characteristics of a novel on-line micro pressurized liquid extraction method
    (2020-10-05) Taylor, Bradley M.; Thurbide, Kevin B.
    A novel on-line micro pressurized liquid extraction (μPLE) method is introduced, which directly interfaces miniaturized solid sample preparation with HPLC for fast analysis. The technique employs rapid heating to remove analytes from 5-10 mg samples in typically 20-40 seconds using only about 300 μL of solvent. The resulting extract is then internally transferred to an HPLC injector for chromatographic analysis. Results show that good analyte recoveries can be achieved, similar to conventional PLE and off-line μPLE approaches, without manual sample handling. For example, 103 ± 3% (n= 4) of the acetylsalicylic acid present in pharmaceutical tablets was extracted into methanol after 20 seconds at 180 oC. Further, 105 ± 9% (n= 4) of the caffeine present in a green tea sample was extracted into methanol after 40 seconds at 275 oC. Typical time to analysis was about 95 seconds total for most samples and solvents could also be easily alternated during trials to increase extract selectivity. The on-line μPLE system was applied to the extraction of model PAHs from a biochar matrix and was found to extract 97 ± 5% (n= 4) of anthracene present in the sample after a 30 second static and 60 second dynamic extraction at 220 oC. This yield is much better than results obtained by previous approaches and is attributed to the small size, high temperature, low thermal mass, and dynamic flow of the system. Findings indicate that the on-line μPLE system can greatly assist in such extractions and provide a useful method for rapidly preparing solid samples for analysis using little solvent.
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    On-Line Coupling of a Micro-Pressurized Liquid Extraction Method to Liquid Chromatography Via Solid-Phase Trapping
    (2020-10-13) Taylor, Bradley M.; Thurbide, Kevin B.
    A novel method is introduced which employs fast on-line micro pressurized liquid extraction (μPLE) directly interfaced with HPLC via a solid-phase extraction (SPE) trap. The technique utilizes rapid heating to remove analytes from 5-10 mg samples in typically 20 seconds using only about 200 μL of solvent. The resulting extract is then internally transferred to an SPE trap, where the analyte is absorbed/concentrated, and then later completely desorbed/injected to an HPLC for chromatographic analysis. Test extractions of caffeine from Ottawa sand show that analyte in the 200 μL μPLE extract can be quantitatively trapped by SPE (100 ± 4%; n=3), whereas even moderately larger extract volumes (e.g. 1 mL), still well below those normally used in conventional PLE, led to poor recoveries and precision (1.0 ± 0.5% recovery; n=3). As a result, it was found that the on-line μPLE-SPE system could provide near 400-fold analyte enrichment factors that enhanced the analysis of samples with low analyte levels. For instance, application of the method showed that it can facilitate the analysis of impurities in pharmaceutical tablets and pesticide residues in fruit flesh. The on-line μPLE-SPE system also provided relatively rapid quantitative results in this regard. For example, the technique respectively recovered 95 ± 3% (n=5) and 99 ± 3% (n=4) of a phenoxypropionic acid herbicide from strawberry and apple samples, and was about 10-30 times faster than a conventional ultrasonic extraction method. The findings indicate that on-line μPLE-SPE can facilitate coupling to HPLC and provide very rapid sample preparation/preconcentration using little solvent.