Miniaturised sample preparation of fatty foodstuffs for the determination of polychlorinated biphenyls

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.

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.

Sample preparation

A panorama of sample preparation methods has been composed from 481 references, with a highlight of some promising methods fast developed during recent years and a somewhat brief introduction on most of the well-developed methods. All the samples were commonly referred to molecular composition, being extendable to particles including cells but not to organs, tissues and larger bodies. Some criteria to evaluate or validate a sample preparation method were proposed for reference. Strategy for integration of several methods to prepare complicated protein samples for proteomic studies was illustrated and discussed.

Development and application of a simplified clean-up procedure for the determination of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in horse fat by gas chromatography-tandem mass spectrometry (GC-MS/MS)

A simplified clean-up procedure was developed in combination with gas chromatography-tandem mass spectrometry (GC-MS/MS) for the determination of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in adipose tissue. Clean-up was performed by the successive application of a Mega Bond Elut silica column and a Bond Elut PCB column. Validation of the method was conducted according to European Union Commission Decision 2002/657/EC. In order to evaluate the applicability of the method, 44 horse fat samples were analysed. The total PCB concentration (sum of PCBs 28, 52, 101, 118, 138, 153 and 180) ranged from 5.35 to 140 ng g(-1) lipid weight. The total PBDE concentration (sum of BDEs 28, 47, 99, 100, 153, 154 and 183) ranged from below the decision limit to 6.34 ng g(-1) lipid weight.

p-Nitro-N-propylaniline/silica: Synthesis, characterization, and its application in matrix solid phase dispersion for multiresidue analysis of pesticides in carrots

A new material for matrix solid phase dispersion (MSPD) was synthesized -- p-nitro-N-propylaniline/silica (pNNPASi) by grafting reactions, characterized by elemental analysis and N(2)-adsorption-desorption isotherms, and tested for multiclass multiresidue analysis of pesticides in wet and freeze-dried carrots. Results obtained applying this new solid phase sorbent to MSPD extraction of ten pesticides (trichlorphon, trifluralin, dicloran, chlorothalonil, prometryn, linuron, captan, procymidone, prochloraz, and deltametrin) in wet carrots showed better results than the ones obtained for freeze-dried samples. Recoveries were in the range of 48-106% and precisions varied from 6 to 20% when wet samples were employed. Comparison between pNNPASi sorbent and C(18) showed better performance of pNNPASi for eight out of ten pesticides tested. The LOQs show that the developed method can be used to detect the pesticides investigated in carrots at concentrations below the maximum residue levels (MRL) established by EU, USEPA, and National Sanitary Surveillance Agency (ANVISA). Linuron, captan, prochloraz, and deltamethrin were found in at least one of the two commercial samples studied in concentrations above the LOQ of this method. Concentrations of the last three pesticides were above the European MRL in one of the commercial samples.

Miniaturised selective pressurised liquid extraction of polychlorinated biphenyls from foodstuffs

The feasibility of miniaturised pressurised liquid extraction (PLE) with in-cell purification and subsequent gas chromatography with micro-electron capture detection (GC-micro-ECD) for the determination of prioritary and toxic polychlorinated biphenyls (PCBs) in a variety of foodstuffs (fat contents in the range 22-49%, w/w, on a freeze-dried basis) has been investigated. After optimisation of the several experimental parameters affecting the efficiency of the selective PLE process, the developed method provided quantitative recoveries of the endogenous PCBs studied and complete fat elimination in a single step using n-hexane as extraction solvent. A total solvent volume of 3.5 mL was used for the two consecutive 7 min static PLEs of 100-mg samples. Detection limits using GC-micro-ECD were below 0.2 ng/g freeze dried sample for all 22 PCBs investigated in real-life foodstuffs, and the repeatability of the complete PLE plus GC-micro-ECD method as calculated for the analysis of the endogenous PCBs in general was better than 14%. Comparison of the miniaturised PLE method developed with either conventional Soxhlet extraction or matrix solid phase dispersion with subsequent (off-line) clean-up for the analysis of non-spiked samples showed that the efficiency of PLE was similar to or better (recoveries in the range 83-133%, as calculated for the endogenous analytes) than for the other two extraction methods assayed.

PCB, DDT, arsenic, and heavy metal (Cd, Cu, Pb, and Zn) concentrations in chameleon (Chamaeleo chamaeleon) eggs from Southwest Spain

This work presents the concentrations of twenty PCB congeners, p,p'-DDT, and its two main metabolites, p,p'-DDE, p,p'-TDE, As, Cd, Cu, Pb, and Zn found in common chameleon eggs from nine different nests located in Southwest Spain. Of the heavy metals and arsenic, Zn and Cu exhibited the highest concentrations in egg contents (ranging from 10100 to 12950 and from 567 to 706 ng g(-1) wet weight basis [w.w.], respectively) and eggshells (ranging from 5605 to 13290 ng g(-1)w.w. for Zn and from 1487 to 4361 ng g(-1)w.w. for Cu). Total PCB concentrations in egg contents ranged from 32 to 52 ng g(-1)w.w. and were higher than total dichlorodiphenylethanes concentrations (ranging from 0.67 to 1.9 ng g(-1)w.w., calculated as the sum of p,p'-DDT plus p,p'-DDE and p,p'-TDE). Comparison of the data from the present study with the data from a study conducted in 1997 revealed a large decrease in Pb concentration and a twofold increase in PCB concentrations. Taking into account all the pollutants investigated, the contamination level found in common chameleon eggs from Southwest Spain was generally lower than has been reported in the literature for eggs of different reptile species. However, it should be borne in mind that most of the data found in the literature refer to highly polluted areas.

Sample handling strategies for the determination of persistent trace organic contaminants from biota samples

Even after emergence of most advanced instrumental techniques for the final separation, detection, identification and determination of analytes, sample handling continues to play a basic role in environmental analysis of complex matrices. In fact, sample preparation steps are often the bottleneck for combined time and efficiency in many overall analytical procedures. Thus, it is not surprising that, in the last two decades, a lot of effort has been devoted to the development of faster, safer, and more environment friendly techniques for sample extraction and extract clean up, prior to actual instrumental analysis. This article focuses on the state of the art in sample preparation of environmental solid biological samples dedicated to persistent organic pollutants (POPs) analysis. Extraction techniques such as Soxhlet extraction, sonication-assisted extraction, supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), pressurised liquid extraction (PLE) and matrix solid-phase dispersion (MSPD) are reviewed and their most recent applications to the determination of POPs in biota samples are provided. Additionally, classical as well as promising novel extraction/clean-up techniques such as solid phase microextraction (SPME) are also summarized. Finally, emerging trends in sample preparation able to integrate analytes extraction and their adequate clean-up are presented.

Feasibility of gas chromatography - ion trap tandem mass spectrometry for the determination of polychlorinated biphenyls in food

The different parameters affecting the ionisation and fragmentation of selected polychlorinated biphenyls (PCBs) in an IT detector working in the MS/MS mode, ITD(MS/MS), have been optimised for maximum selectivity and sensibility. The low LODs (in the range 0.03-0.3 microg/L), the satisfactory repeatability (RSDs in general below 11%) and reproducibility (RSDs below 17%) obtained when analysing standard solutions ensured proper determination of the PCBs studied at the concentrations typically found in food samples. Foodstuffs naturally contaminated with varying levels of PCBs have been analysed using the optimised GC-ITD(MS/MS) method. The results obtained compared favourably with those found using more conventional detectors, such as (micro-)electron capture detection (for ortho-PCBs) and high-resolution MS (for non-ortho-PCBs), as well as with the consensus PCB levels established for these particular samples via an international interlaboratory exercise. The relative merits of these three detectors have been discussed.

Miniaturization in sample treatment for environmental analysis

The increasing demand for faster, more cost-effective and environmentally friendly analytical methods is a major incentive to improve the classical procedures used for sample treatment in environmental analysis. In most classical procedures, the use of rapid and powerful instrumental techniques for the final separation and detection of the analytes contrasts with the time-consuming and usually manual methods used for sample preparation, which slows down the total analytical process. The efforts made in this field in the past ten years have led to the adaptation of existing methods and the development of new techniques to save time and chemicals, and improve overall performance. One route has been to develop at-line or on-line and, frequently, automated systems. In these approaches, miniaturization has been a key factor in designing integrated analytical systems to provide higher sample throughput and/or unattended operation. Selected examples of novel developments in the field of miniaturized sample preparation for environmental analysis are used to evaluate the merits of the various techniques on the basis of published data on real-life analyses of trace-level organic pollutants. Perspectives and trends are briefly discussed.