Miniaturised selective pressurised liquid extraction of polychlorinated biphenyls from foodstuffs

Characteristics of a novel on-line micro pressurized liquid extraction method

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 s 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 s at 180 °C. Further, 105% ± 9% (n = 4) of the caffeine present in a green tea sample was extracted into methanol after 40 s at 275 °C. Typical time to analysis was about 95 s 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 s static and 60 s dynamic extraction at 220 °C. 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.

Field confirmation of modified pressurized solvent extraction vessels for the analysis of polychlorinated biphenyl congeners in blood samples from Great Lakes Mallards (Anas platyrhynchos)

Miniaturized pressurized solvent extraction vessels were used to examine polychlorinated biphenyl congener (PCB) concentrations in 0.2 g sample sizes of whole blood, liver, heart and breast tissue sampled from twelve Great Lakes Mallard ducks (Anas platyrhynchos). This study successfully supported the blood extraction method, previously validated only using laboratory prepared blood samples, using field samples. In situ clean-up offered excellent sample throughput without degradation of GC-MS performance; using this method, extraction, instrument analysis and data interpretation for 100 samples could be accomplished within a one to two week time period. Results indicated contamination in the blood (∑PCB = 1.9-13 ng g(-1) ww), liver (∑PCB = 0.8-11 ng g(-1) ww), breast (∑PCB = <0.1-9 ng g(-1) ww) and heart tissue (∑PCB = <0.1-6 ng g(-1) ww). Quality control included the analysis of blank samples, NIST SRM 1589a and a duplicate of each sample type (blood or tissue). All blank samples were below the method detection limit, SRM values were within 70% of their certified values and duplicates were within 70% of each other. Correlations were examined for the suite of analysed congeners between blood and various tissues; within select individuals a strong and significant correlation was observed. TEQs were calculated and compared against known toxicity data for bird species. Based on the PCB levels found in this study, no adverse health effects are expected in the birds themselves. ∑PCB concentrations in the breast tissue were also compared against both the Canadian and American guidelines for the consumption of edible poultry and based on these values, the Mallards used in this research would be safe for human consumption.

Use of advanced techniques for the extraction of phenolic compounds from Tunisian olive leaves: phenolic composition and cytotoxicity against human breast cancer cells

A comparison among different advanced extraction techniques such as microwave-assisted extraction (MAE), supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE), together with traditional solid-liquid extraction, was performed to test their efficiency towards the extraction of phenolic compounds from leaves of six Tunisian olive varieties. Extractions were carried out at the best selected conditions for each technique; the obtained extracts were chemically characterized using high-performance liquid chromatography (HPLC) coupled to electrospray time-of-flight mass spectrometry (ESI-TOF-MS) and electrospray ion trap tandem mass spectrometry (ESI-IT-MS(2)). As expected, higher extraction yields were obtained for PLE while phenolic profiles were mainly influenced by the solvent used as optimum in the different extraction methods. A larger number of phenolic compounds, mostly of a polar character, were found in the extracts obtained by using MAE. Best extraction yields do not correlate with highest cytotoxic activity against breast cancer cells, indicating that cytotoxicity is highly dependent on the presence of certain compounds in the extracts, although not exclusively on a single compound. Therefore, a multifactorial behavior is proposed for the anticancer activity of olive leaf compounds.

Miniaturization of Analytical Methods

This chapter highlights miniaturization in sample preparation as a valuable alternative for green analytical chemistry. The current state of the art is discussed on the basis of examples selected from representative application areas, including biomedical, environmental and food analysis, and involving conventional instrumental techniques for final determination of the target compounds. The emphasis is on those techniques and approaches that have already demonstrated their practicality by the analysis of real-life samples, and in particular on those dealing with the accurate determination of minor organic components. The potential of recent developments in this field for sample treatment simplification and complete hyphenation of analytical processes are discussed and the most pressing remaining limitations evaluated.

Modifications of commercial pressurized solvent extraction (PSE) systems for the analysis of polychlorinated biphenyls in avian whole blood and serum

The present study considers simple and cost-effective modifications to commercial pressurised solvent extraction cells to extract polychlorinated biphenyls (PCBs) from avian blood and serum. Blood and serum samples of mass 0.2 g were examined. Such masses are consistent with those which may be obtained from many avian species without sacrificing individuals or compromising breeding and (or) migratory success. Extraction vessels are modified by the use of Teflon inserts, which are readily fabricated at low cost. These inserts reduce internal cell volume and surface area. Thus, background contamination is reduced whilst extraction and rinse solvent is used more effectively to afford a small extract volume. Packing of the cell void with sodium sulfate and florisil achieves in situ sample dehydration and lipid removal. When combined with extraction concentration and large volume injection gas chromatography – ion-trap mass spectrometry (LVI-GC–ITMS), the extraction method is capable of polychlorinated biphenyl analysis without post-extraction clean-up. Validation was accomplished using commercial chicken whole blood and serum, and PCB congeners 28, 77, 105, 126, 153, 167, 170, 180, 183, and 194. Surrogate corrected recoveries in the range of 75% to120% for whole blood and 80% to115% for serum were obtained. Detection limits were in the range of 0.01 to 0.22 ng g–1 for whole blood and 0.03 to 0.45 ng g–1 for serum. The relative standard deviations for all congeners investigated were better than 15%.

Novel pressurized solvent extraction vessels for the analysis of polychlorinated biphenyl congeners in avian whole blood

Persistent organic pollutants remain a serious threat to many food-chain systems. New pollutants continue to emerge. The present study has created novel extraction vessels which are compatible with readily available commercial instrumentation to validate the analysis of one class of persistent organic pollutants, polychlorinated biphenyls (PCBs), in avian blood. The volumes used can be reasonably sampled without sacrificing individuals, or comprising breeding or migratorial success. The procedure consists of the pressurized solvent extraction (PSE) of analytes in a novel PSE extraction vessel. The new extraction cell contains a 38-cm long, coiled, re-packable, in situ clean-up column. Lipid elimination, using Florisil, occurs within the coiled region of the extraction vessel, eliminating the requirement for post extraction clean-up. For development, 0.2 g samples of chicken whole blood have been used. Extract volumes are reduced from (30 to 10) cm(3), compared to unmodified systems. The new PSE vessel with its integrated clean-up method showed satisfactory performance for the analysis of ten environmentally relevant PCB congeners in chicken whole blood samples with recoveries in the range of (70-130)%. Detection limits using gas chromatography coupled with large volume injection ion-trap mass spectrometry (GC-LVI-ITMS-MS) were in the range of (0.05-0.5) ng g(-1). The relative standard deviations for all congeners investigated were better than 5%. This is the first PSE validation to have been conducted on unaltered whole blood samples.

Simultaneous extraction and clean-up of polychlorinated biphenyls and their metabolites from small tissue samples using pressurized liquid extraction

A pressurized liquid extraction-based method for the simultaneous extraction and in situ clean-up of polychlorinated biphenyls (PCBs), hydroxylated (OH)-PCBs and methylsulfonyl (MeSO(2))-PCBs from small (<0.5 g) tissue samples was developed and validated. Extraction of a laboratory reference material with hexane-dichloromethane-methanol (48:43:9, v/v) and Florisil as fat retainer allowed an efficient recovery of PCBs (78-112%; RSD: 13-37%), OH-PCBs (46+/-2%; RSD: 4%) and MeSO(2)-PCBs (89+/-21%; RSD: 24%). Comparable results were obtained with an established analysis method for PCBs, OH-PCBs and MeSO(2)-PCBs.

Fractionation of honey carbohydrates using pressurized liquid extraction with activated charcoal

This article describes the development of a new procedure that combines the use of activated charcoal and pressurized liquid extraction (PLE) to obtain enriched fractions of di- and trisaccharides from honey. Honey was adsorbed onto activated charcoal and packed into a PLE extraction cell. Optimum results were obtained at 10 MPa and 40 degrees C using two consecutive PLE cycles: first, 1:99 (v/v) ethanol/water for 5 min and second, 50:50 (v/v) ethanol/water for 10 min. Di- and trisaccharide fractions were enriched after PLE treatment, accounting for 73% and 8% of total carbohydrates, respectively. This procedure was also compared with other methodologies reported in the literature for the fractionation of honey carbohydrates (yeast treatment and extraction from activated charcoal). While the removal of monosaccharides was more efficient with yeast treatment, recovery of di- and trisaccharides was higher when either the PLE or the activated charcoal treatment was used. PLE was found to be the faster technique; it also required less solvent volume and minimized handling of the sample.