Applications of matrix solid-phase dispersion in food analysis

Determination of organochlorine pesticides and polychlorinated biphenyls in chicken eggs by matrix solid phase dispersion

A multiresidue method for the determination of 20 organochlorine pesticides (aldrin, endrin, dieldrin, alpha-BHC, beta-BHC, gamma-BHC, delta-BHC, alpha-chlordane, gamma-chlordane, 4,4'-DDE, 4,4'-DDT, 4,4'-DDD, endosulfan I, endosulfan II, endosulfan sulfate, endrin aldehyde, heptachlor, heptachlor epoxide, endrin ketone and methoxychlor) and eight PCB congeners (PCB 20, 28, 52, 101, 118, 138, 153, 180) in chicken eggs has been developed and validated. The samples were extracted by a simple and fast matrix solid-phase dispersion (MSPD) method using Florisil as the sorbent material and dichloromethane/hexane (1:1) as the eluting system. Further purification of the extracts was conducted using a conventional clean-up procedure with concentrated sulphuric acid. Determination and quantitation of PCBs and OCs residues was carried out using a gas chromatograph equipped with an electron capture detector (GC-ECD). A mass spectrometric detector (GC-MS) in the selected ion monitoring (SIM) mode was used for confirmation purposes. The method detection limits were <0.7 ng g(-1) for all PCBs and OCs and the relative standard deviations for analyses of samples fortified over the range of 10-200 ng g(-1) were <8%. All compounds provided average recoveries (spiked at five concentration levels) ranging from 82% to 110%. The proposed method was used to analyze 30 commercial products taken from local markets in the course of a 3-month sampling campaign.

Evaluation of different sample treatments for determining pesticide residues in fat vegetable matrices like avocado by low-pressure gas chromatography–tandem mass spectrometry

A multi-residue method has been developed for determining 65 pesticide residues in greasy vegetable matrices such as avocado. Conventional organic solvent extraction assisted by a high-speed homogenizer was compared to pressurized liquid extraction (PLE) as extraction techniques. Following this, the lipophilic extract was purified using gel permeation chromatography (GPC). Alternative clean-up methods were also evaluated, as solid-phase extraction cartridges individually used and downstream coupled, but less effective lipophilic separation was archived. The pesticide residue determination was carried out using low-pressure gas chromatography coupled to tandem mass spectrometry (LP-GC-MS-MS), showing the applicability of this type of GC columns for the analysis of fat vegetable matrices. The proposed methodology was validated in avocado matrix. The recoveries were in the range 70-110%, with RSD values lower than 19%, at 12 and 50 microg/kg spiking levels. The limits of quantitation (LOQs) were in the range 0.04-8.33 microg/kg and the limits of detection (LODs) were between 0.01 and 2.50 microg/kg. All of them were lower than the maximum residue levels (MRLs) set by the European Union (EU) in avocado. The proposed method was evaluated analyzing pesticide residues in real avocado samples.

Determination of sulfonylurea herbicides in water and food samples using sol-gel glass-based immunoaffinity extraction and liquid chromatography-ultraviolet/diode array detection or liquid chromatography-tandem mass spectrometry

Immunoaffinity supports (IAS) were prepared using broad specific polyclonal anti-sulfonylurea (SU) antibodies immobilized in sol-gel glass. Two different kinds of supports were applied, crushed sol-gel monoliths and sol-gel-coated highly porous silica particles. Both were used for the quantitative enrichment of SUs in natural water and food samples followed by high-performance liquid chromatography-ultraviolet/diode array detection (HPLC-UV/DAD) and tandem mass spectrometry (LC-MS/MS), respectively. Loading, washing, and elution conditions of IAS were optimized. The capacity of supports was determined for 30 SUs and compared with the cross-reactivity pattern of the direct competitive enzyme-linked immunosorbent assay. The capacities correlated well with the affinity to individual SU compounds. Even analytes to which the polyclonal antibodies showed only a lower cross-reactivity could be enriched to a certain degree, if a sufficient capacity of IAS was provided. The IAS could be reused at least 10 times without a loss of effectiveness. Recovery of 16 selected SUs extracted from spiked water and food samples was dependent on the affinity of both immobilized antibodies to single compounds and matrix interferences. In water, 13 SUs showed recoveries higher than 80% when immunoaffinity extraction was used in combination with LC-UV/DAD. On the basis of the enrichment of 200 mL of aqueous sample, corresponding limit of detection (LOD) values ranged between 20 and 100 ng/L. The recoveries of 10 SUs, which were extracted from 10 g of potato spiked at a 10 microg/kg level, were higher than 75%. For grain samples, recoveries were at the same order for at least five SU herbicides. The LOD of LC-MS/MS measurements was about 1 order of magnitude higher, i.e., gave LODs between 1.1 and 6.9 microg/kg of food sample, depending on the compound and extraction procedure. These LODs provide evidence that the main advantage of the prepared IAS is their high selectivity for group specific recognition of SUs as compared to other nonspecific solid phase extraction materials.

Approaches for the Simultaneous Extraction of Tetrabromobisphenol A, Tetrachlorobisphenol A, and Related Phenolic Compounds from Sewage Sludge and Sediment Samples Based on Matrix Solid-Phase Dispersion

A procedure based on matrix solid-phase dispersion (MSPD) for sample preparation in the analysis of some bromophenols and halogenated bisphenols in sediments and sludges has been developed. For the first time ever, MSPD was applied for the extraction of organic contaminants from sediment and sewage sludge samples. The influence of experimental conditions on the yield of the extraction process and on the efficiency of the built-in cleanup step was thoroughly evaluated. Analysis of the extracts was performed by nonaqueous capillary electrophoresis coupled with photodiode array ultraviolet detection, using large-volume sample stacking injection based on the electroosmotic flow pump as an on-column preconcentration technique. The method was applied to the analysis of real sludges from urban sewage treatment plants, as well as river and marine sediment samples.

High- and low-resolution mass spectrometry coupled to liquid chromatography as confirmatory methods of anabolic residues in crude meat and infant foods

Within the European Union the use of anabolic steroids for promoting growth and improving meat-to-fat ratio in food-producing animals has been banned since 1988. For the unequivocal identification of hormone residues in a complex matrix such as meat we have developed a rapid, specific and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method, in combination with a simple extraction procedure based on the matrix solid-phase dispersion (MSPD). The performances of a triple quadrupole (QqQ) and a quadrupole/time-of-flight (QqTOF) were compared: the QqQ mass spectrometer was found to be more sensitive for almost all studied analytes, but the selectivity was superior using the QqTOF system; the full-scan spectra (acquired without losing sensitivity), mass accuracy and resolution of the hybrid instrument enabled a more probatory analyte identification than that obtained selecting two multiple-reaction monitoring (MRM) transitions with a QqQ. Average recoveries ranged from 80 to 100%, and the detection capabilities (CCbetas) were less than 1.06 ppb with the QqQ instrument and less than 5.20 ppb with the QqTOF instrument for the bovine meat, which proved to be the most complex matrix.

Matrix solid phase dispersion-Soxhlet simultaneous extraction clean-up for determination of organochlorine pesticide residues in tobacco

A novel method combining matrix solid phase dispersion (MSPD) with Soxhlet simultaneous extraction clean-up (SSEC) was developed. Being a single-step extraction and clean-up procedure, it could be used instead of multistep solvent extraction and Florisol column clean-up. It not only reduces sample contamination during the procedure, but it also decreases the amount of organic solvent needed. The retention times of standards were used to qualitatively assess the method, and the external standard method was used to quantitatively assess it. Residues of organochlorine pesticides (OCP) in tobaccos were determined by gas chromatography-electron capture detection (GC-ECD), and their identities were confirmed by the standard addition method (SAM). The performance of the method was evaluated and validated: the detection limit was 0.01-0.02 microg g(-1), relative standard deviations were 5-26%, and recoveries were 72-99% at fortification levels of 0.10, 1.00 and 10.0 microg g(-1). The analytical characteristics of MSPD-SSEC compared very favorably with the results from the classical multistep solvent extraction and Florisol column clean-up method.

Routine application using single quadrupole liquid chromatography–mass spectrometry to pesticides analysis in citrus fruits

A rapid and sensitive liquid chromatography-electrospray ionization-mass spectrometry method has been developed for the routine analysis of buprofezin, bupirimate, hexaflumuron, tebufenpyrad, fluvalinate and pyriproxyfen in citrus fruits. Extracts were obtained by matrix solid-phase dispersion (MSPD) using C18 as dispersant and dichloromethane-methanol (80:20, v/v) as eluent. Matrix effects were tested for all matrices by addition of standard to sample blank extracts (samples containing no detectable residues). Mean recoveries obtained at fortification levels between 0.01 and 5 mg kg(-1) were 57-97% with relative standard deviations (RSDs) from 5 to 19%. The limits of quantification (LOQ) were in the range of 0.01-0.2 mg kg(-1) and lower than maximum residue limits (MRLs) established by the Spanish legislation. The MSPD was compared with conventional ethyl acetate extraction, showing equivalent recoveries and precision. Although the sample is more concentrated (5-fold) by solid-liquid extraction (SLE) with ethyl acetate than by MSPD, LOQs obtained by both techniques, were almost equal, because MSPD reduces matrix effects, baseline noise, and interfering peaks from the matrix. The proposed method has been applied to the determination of selected pesticides in real samples. Liquid chromatography-tandem mass spectrometry (LC-MS-MS) with quadrupole ion trap (QIT) and triple quadrupole (TQ) have been used as confirmatory tool for positive samples according to a recent No. SANCO/10476/2003 European Union Guideline.

Hyphenation of capillary high-performance liquid chromatography to microcoil magnetic resonance spectroscopy—determination of various carotenoids in a small-sized spinach sample

The development of miniaturized hyphenated systems such as capillary high-performance liquid chromatography--and nuclear magnetic resonance spectroscopy (HPLC-NMR) remains challenging in the field of structure elucidation. In combination with a highly specific sample preparation technique, matrix solid-phase dispersion (MSPD), and a highly selective C30 reverse phase HPLC-NMR enables the identification of small amounts of natural compounds. Here, the investigation of five carotenoids in a standard solution and two carotenoids from a spinach sample demonstrate the potential of this new development. The separation of the carotenoids is performed with self-packed fused-silica capillaries with a binary solvent gradient consisting of acetone and water. The miniaturized system allows the use of fully deuterated solvents for on-line HPLC-NMR coupling. The 1H NMR spectra of the various carotenoids obtained in stopped-flow mode gave a high signal-to-noise ratio with a sample amount in the low nanogram range. All necessary parameters for structure elucidation such as multiplet structure, coupling constants and integration values can be detected unambiguously.

Application of matrix solid-phase dispersion in the analysis of priority polycyclic aromatic hydrocarbons in fish samples

The performance of matrix solid-phase dispersion (MSPD) for the extraction of polycyclic aromatic hydrocarbons (PAHs) in fish tissue is described. The suitability of different solid supports was tested as well as the influence on the extraction efficiency of the natural fat content in samples. Under optimal conditions 0.6-0.8 g of tissue sample, are dispersed with 2 g of octadecylsiloxane (C18) and 0.5 g of anhydrous sodium sulphate and transferred to the top of a polyethylene solid-phase extraction cartridge which already contains 2 g of florisil and 1 g of C18. Cartridges were eluted with acetonitrile. The analysis of the extracts was carried out by high-performance liquid chromatography (HPLC) coupled with fluorescence detection. The proposed method provides detection limits between 0.04 and 0.32 ng/g for the different considered PAHs, below the maximum levels established by the some regulatory bodies for the six PAHs after recent oil spill episodes and European Union regulations. Recoveries over 80% were obtained for all compounds. Accuracy validation was carried out using the US National Institute of Standards and Technology (NIST) SRM 2977 reference material.

Determination of 266 pesticide residues in apple juice by matrix solid-phase dispersion and gas chromatography-mass selective detection

A macro matrix solid-phase dispersion (MSPD) method was developed to extract 266 pesticides from apple juice samples prior to gas chromatography-mass selective detection (GC-MSD) determination. A 10 g samples was mixed with 20 g diatomaceous earth. The mixture was transferred into a glass column. Pesticide residues were leached with a 160 mL hexane-dichloromethane (1:1) at 5 mL/min. Two hundred and sixty-six pesticides were divided into three groups and detected by GC-MSD under selective ion monitoring. The proposed method takes advantage of both liquid-liquid extraction and conventional MSPD methods. Application was illustrated by the analysis of 236 apple juice samples produced in Shaanxi province China mainland this year.

Rapid assay for analyzing biogenic amines in cheese: matrix solid-phase dispersion followed by liquid chromatography-electrospray-tandem mass spectrometry

A new rapid and sensitive method based on matrix solid-phase dispersion (MSPD) followed by liquid chromatography-electrospray-tandem mass spectrometry was devised for the determination of biogenic amines at trace levels in cheese samples. The method required 0.25 g of sample, CN-bonded silica as a dispersant sorbent, and a formic acid aqueous solution/methanol mixture as an eluting solvent. Extraction recoveries from soft cheese products were calculated in the 98 +/- 4-110 +/- 6% range. A procedure based on solid-phase extraction was also evaluated for the extraction of these compounds in cheese. Chromatographic separation was performed using a C18 column with an aqueous ammonium acetate/methanol mixture as the mobile phase under gradient conditions. The method was validated in terms of detection limits (LOD), quantitation limits (LOQ), linearity, recovery, precision, and trueness. Results in the 0.05-0.25 mg kg(-1) range were obtained for the LOD of histamine, tyramine, and beta-phenylethylamine in soft cheese samples. Linearity was established over 2 orders of magnitude. Excellent precision in terms of intra-day repeatability was calculated (RSD% < 5). The applicability of the method to the determination of biogenic amines in cheese products was demonstrated.

Simultaneous determination of thyreostatic residues in animal tissues by matrix solid-phase dispersion and gas chromatography–mass spectrometry

A method for determination of thyreostatic residues in animal tissues by matrix solid-phase dispersion (MSPD) and gas chromatography-mass spectrometry in selected ion detection mode was developed. Thyreostatic compounds in different matrices were extracted and purified by combination of MSPD and subsequent solid-phase extraction. Silica gel was selected as the solid support of both procedures and the conditions of the procedures were optimized. Thyreostats were derivatized with pentafluorobenzylbromide (PFBBr) in strong basic medium and then with N-methyl-N-(trimethylsilyl)-trifluoroacetamide (MSTFA), which can improve the yields of derivatization for thyreostats, the repeatability, and therefore the limits of detection (LOD) of thyreostats. The limits of detection reached 10 microg/kg (2-thiouracil, 6-methyl-2-thiouracil and 6-propyl-2-thiouracil), 20 microg/kg (6-phenyl-2-thiouracil) and 50 microg/kg (tapazole) with high recoveries (more than 70% for most of thyreostats) and relative standard deviations between 4.5% and 8.7%.

Multi-residue screening of chlorinated and brominated compounds from aquaculture samples using matrix solid-phase dispersion—gas chromatography–mass spectrometry

An effective multiresidual method for the trace analysis of fifteen compounds from a diverse group of pesticides, polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyl (PCBs) and polybrominated biphenyl (PBBs) in aquaculture feed is described. The analytical procedure is based on the matrix solid-phase dispersion (MSPD) of feed sample and subsequent elution with hexane. The MSPD process was evaluated using an asymmetrical experimental design 2(3)3(2)//9. Factors such as C18 sorbent amount, kind of adsorbents, solvent volume and elution mode were considered. The results suggest that the operational MSPD conditions are elution with pressure, 1 g of C18, basic alumina as adsorbent and 30 mL of hexane. The overall method including MSPD procedure and GC coupled to mass spectrometry (MS/MS) has been applied to several samples of aquaculture feed and marine species. Precision and accuracy of the analytical method were determined using the reference material from the International Atomic Energy Agency (IAEA-406), showing a good agreement to the referenced values.

Determination of pesticide residues in olives and olive oil by matrix solid-phase dispersion followed by gas chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry

A novel analytical approach has been developed and evaluated for the quantitative analysis of a selected group of widely used pesticides (dimethoate, simazine, atrazine, diuron, terbuthylazine, methyl-parathion, methyl-pirimiphos, endosulfan I, endosulfan II, endosulfan sulphate, cypermethrin and deltamethrin), which can be found at trace levels in olive oil and olives. The proposed methodology is based on matrix solid-phase dispersion (MSPD), (with a preliminary liquid-liquid extraction in olive oil samples) using aminopropyl as sorbent material with a clean-up performed in the elution step with Florisil, followed by mass spectrometric identification and quantitation of the selected pesticides using both gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode and liquid chromatography tandem mass spectrometry (LC-MS-MS) in positive ionization mode. The recoveries obtained (with mean values between 85 and 115% (obtained at different fortification levels) with RSD values below 10% in most cases, confirm the usefulness of the proposed methodology for the analyses of these kind of complex samples with a high fat content. Moreover, the obtained detection limits, which were below 5 microg kg(-1) by LC-MS analyses and ranged from 10 to 60 microg kg(-1) by GC-MS meet the requirements established by the olive oil pesticide regulatory programs. The method was satisfactorily applied to different olives and olive oil samples.

Liquid chromatography-electrospray quadrupole ion-trap mass spectrometry of nine pesticides in fruits

A liquid chromatographic method, with electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS), has been developed for determining acrinathrin, carbosulfan, cyproconazole, lambda-cyhalothrin, kresoxim methyl, pyrifenox, pyriproxyfen, propanil, and tebufenpyrad in fruits. The ions prominent in ESI spectra were [M + H]+ and [M + Na]+. In the mass analyzer, collision-induced dissociation fragmentation involved common pathways, for example, product ions of [M + H]+ resulted from the cleavage of the carbamic group or an oxygen bound. The utility of the method is demonstrated by the analysis of crude extracts obtained by matrix solid-phase dispersion (MSPD) using C18 as dispersant and dichloromethane-methanol as eluent, and by solid-liquid extraction (SLE) with ethyl acetate and anhydrous sodium sulfate. Mean recoveries ranged from 51.5 to 108%, with relative standard deviations <16%, were obtained for MSPD and from 59 to 101% with relative standard deviation <17% for SLE. However, for most compounds, limits of quantification are better by SLE (0.01-4.4 mg kg(-1)) than by MSPD (0.05-2 mg kg(-1)). During the validation process, the procedure was tested for matrix effects, blanks and stability of the system. Considerably matrix effects in the ESI ionization process were detected by comparing standard calibration, and matrix calibration. Because of this, detected residues were quantified from interpolation against calibration data obtained using matrix matched standards.

Analytical strategies for residue analysis of veterinary drugs and growth-promoting agents in food-producing animals—a review

After a brief introduction into the field of veterinary drugs and growth-promoting agents, the most important EU regulations and directives for the inspection of food-producing animals and animal products regarding the residue control of these substances are presented and discussed. Main attention in the review is on the methods of analysis in use today for the most important classes of veterinary drugs and growth-promoting agents viz. anthelmintics, antibiotics, coccidiostats, hormones, beta-agonists and tranquillizers. Emphasis is given to the potential, and limitations, of state-of-the-art analytical procedures and their performance characteristics. The most obvious conclusion is that, today (reversed-phase) liquid chromatography combined with tandem mass spectrometric detection--either triple-quadrupole or ion-trap multi-stage--is the preferred technique in a large majority of all cases. In the field of sample treatment, the combined use of liquid extraction--i.e., liquid partitioning or liquid-liquid extraction--and liquid-solid extraction--primary on- or off-line solid-phase extraction--is most popular. Finally, while the analytical tools required to meet the demands typically formulated by governments and international organizations today, generally speaking are available, several problems still do exist. To quote three examples, problems are encountered in the area of simultaneously extracting and pre-treating groups of analytes with mutually widely different polarities, with regard to identification-point--based confirmation of analyte identity, and regarding quantification errors caused by ion-suppression effects. Improving the speed of analysis is another aspect that should, and will, receive dedicated interest in the near future.

Novel methods to extract flavanones and xanthones from the root bark of Maclura pomifera

A comparison between the extraction yields of xanthones and flavanones from the root bark of the Maclura pomifera by solid-liquid extraction (SLE), matrix solid phase dispersion (MSPD), and an alternative method using sea sand as a sample disruptor, is presented here. Two extraction solvents were used for all extraction techniques, dichloromethane and methanol:water, (9:1, v/v). The extraction procedures were reproducible as the R.S.D. values were less than 5% for almost all compounds. A recovery above 80% was obtained for macluraxanthone using the sea sand extraction procedure. Statistical treatment, ANOVA-single factor, was used to evaluate the different extraction procedures, and homogenization of plant material with sand followed by elution with dichloromethane provided the most efficient and rapid extraction method.

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.

Accelerated solvent extraction and confirmatory analysis of sulfonamide residues in raw meat and infant foods by liquid chromatography electrospray tandem mass spectrometry

This paper describes a new method for the rapid extraction and unequivocal confirmation of 13 sulfonamides (SAs) in raw meat and infant foods. The highly automated extraction procedure is based on accelerated solvent extraction followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) as a confirmatory analysis. After 1 g of food matrix was blended with 2 g of C18 as a solid support material, the mixture was packed into the extraction cell and the SAs were extracted with 10 mL of hot water at 160 degrees C and 100 atm; 100 microL of the extract was directly injected into the LC-MS system. The analytes were ionized in an electrospray interface operating in the positive ion mode and were identified by selecting two multireaction monitoring transitions, which guaranteed method specificity. Typical recoveries from crude meat and baby food samples ranged from 70 to 101% at a fortification level of 100 ppb, corresponding to the maximum residue limits established by the European Union and the U.S. Food and Drug Administration. The interday method precision was less than 8.5%, and the limits of detection were below 2.6 ppb. This study has taken matrix-induced suppression of ionization into account, by comparing standard and matrix-matched calibration curves. Four of the 13 monitored SAs have been detected in some baby foods and raw meat samples, bought from Roman supermarkets and butchers' shops, using the described methodology.

Determination and identification of isoflavonoids in Radix astragali by matrix solid-phase dispersion extraction and high-performance liquid chromatography with photodiode array and mass spectrometric detection

The isoflavonoids in Radix astragali were determined and identified by HPLC-photodiode array detection-MS after extraction employing matrix solid-phase dispersion (MSPD). As a new sample preparation method for R. astragali, the MSPD procedure was optimized, validated and compared with conventional methods including ultrasonic and Soxhlet extraction. The amounts of two major components in this herb, formononetin (6) and ononin (2), were determined based on their authentic standards. Four major isoflavonoids, formononetin (6), ononin (2), calycosin (5) and its glycoside (1), and three minor isoflavonoids, (6aR,11aR)-3-hydroxy-9, 10-dimethoxypterocarpan (7), its glycoside (3), and (3R)-7,2'-dihydroxy-3',4'-dimethoxyisoflavone-7-O-beta-D-glycoside (4), were identified based on their characteristic two-band UV spectra and [M + H], [aglycone + H]+ and [A1 + H]+ ions, etc. The combined MSPD and HPLC-DAD-MS method was suitable for quantitative and qualitative determination of the isoflavonoids in R. astragali.

Optimization of a matrix solid-phase dispersion method for the determination analysis of carbendazim residue in plant material

The objective of this paper was to prove that matrix solid-phase dispersion (MSPD) coupled with high performance liquid chromatography (HPLC) and column switching could be used for the determination and quantification of carbendazim residue in plant samples. By comparing results obtained after optimization of the extraction conditions on an acidic silica gel column, it was determined that sorption and retention of carbendazim were achieved via specific interactions. The method of standard additions was used for quantitative analysis. Its performance was evaluated and validated: the detection limit (UV-Vis detection at lambda=279 nm) was 0.02 microg/g, the relative standard deviations (R.S.D.) were between 2.7 and 4.1% and the recoveries were ranging from 84.3 to 90.7% at the 0.04, 0.08 and 0.1 microg/g fortification levels. The method was successfully tested on cereal samples, and the results obtained with the present off-line MSPD-HPLC procedure were found to compare well with those obtained with procedure involving LLE.

Determination of aflatoxins in peanuts by matrix solid-phase dispersion and liquid chromatography

A new method based on matrix solid-phase dispersion (MSPD) extraction was studied to determine aflatoxin B1, B2, G1 and G2 from peanuts. Optimization of different parameters, such as type of solid supports for matrix dispersion and elution solvents were carried out. The method used 2 g of peanut sample, 2 g of C18 bonded silica as MSPD sorbent and acetonitrile as eluting solvent. Recoveries of each aflatoxin spiked to peanut samples at 2.5 ng/g (5 ng/g for aflatoxin G2) level were between 78 and 86% with relative standard deviations ranging from 4 to 7%. The limits of quantification ranged from 0.125 to 2.5 ng/g for the four studied aflatoxins using liquid chromatography (LC) with fluorescence detection. In addition, LC coupled to mass spectrometry with an electrospray interface was used for confirmation of aflatoxins present in real samples. Eleven peanut samples from different countries were analyzed by the proposed method and by using an enzyme-linked immunosorbent assay (ELISA). ELISA test is a good screening method for investigation of these mycotoxins in peanut samples.

Before the injection--modern methods of sample preparation for separation techniques

The importance of sample preparation methods as the first stage in an analytical procedure is emphasised and examined. Examples are given of the extraction and concentration of analytes from solid, liquid and gas phase matrices, including solvent phase extractions, such as supercritical fluids and superheated water extraction, solid-phase extraction and solid-phase microextraction, headspace analysis and vapour trapping. The potential role of selective extraction methods, including molecular imprinted phases and affinity columns, are considered. For problem samples alternative approaches, such as derivatisation are discussed, and potential new approaches minimising sample preparation are noted.

Matrix solid-phase dispersion extraction and gas chromatographic determination of chloramphenicol in muscle tissue

A method based on matrix solid-phase dispersion (MSPD) was developed for the gas chromatographic (GC) determination of chloramphenicol (CAP) residues in animal muscle tissue. Muscle tissue was blended with octadecylsilyl-derivatized silica (C(18)). A column made from the C(18)/muscle tissue matrix was washed with n-hexane and acetonitrile/water (5 + 95), after which CAP was eluted with acetonitrile/water (50 + 50) and partitioned into ethyl acetate. The final extract was evaporated, and a trimethylsilyl derivative of CAP was prepared with Sylon HTP and detected by GC with an electron capture detector (ECD) and a mass spectrometer. For quantitation, the internal standard used was the meta isomer of CAP (m-CAP) for GC-ECD. Muscle tissue samples were fortified at three concentration levels. At 5, 10, and 15 microg/kg levels the respective mean recoveries were 93, 96, and 98%, and the repeatabilities were 13, 11, and 3%. The detection and quantitation limits with ECD were 1.6 and 4.0 microg/kg, respectively. No statistically significant difference was observed in the efficiency of CAP extraction from muscle tissue of various animals (bovine, porcine, and poultry) by the MSPD technique.

Matrix solid-phase dispersion for the liquid chromatographic determination of phenolic acids in Melissa officinalis

Matrix solid-phase dispersion (MSPD) was used for sample preparation of plant material (Melissa officinalis, Lemon Balm) prior to liquid chromatography of rosmarinic, caffeic and protocatechuic acids, phenolic compounds present in this herb. Different MSPD sorbents and various elution agents were tested and the optimal extraction conditions determined with the aim to obtain extraction recoveries greater than 90% for all analytes.

Simple method for the determination of trace levels of pesticides in honeybees using matrix solid-phase dispersion and gas chromatography

A simple multiresidue method for the determination of insecticides in honeybees is described. The developed method is based on the matrix solid-phase dispersion technique. A total number of 12 insecticides (azinfos-methyl, buprofezin, chlorpyriphos, chlorpyriphos-methyl, diazinon, ethion, fenitrothion, fipronil, methidathion, phosalone, pirimicarb, propoxur) used on flowering fields are determined by this method. The method uses Florisil and silica as dispersing agents, alumina and silica as cleanup adsorbents and a low polarity solvent system to elute pesticide residues from the honeybee samples. The insecticides were quantified using capillary gas chromatography with a nitrogen-phosphorus detector. The method has shown good recovery (70-110%) for various levels of spiked samples (0.01-1.0 mg/kg). The relative standard deviations were in the range of 2-8% for all pesticides studied. The limits of detection were in the range of 0.005-0.05 mg/kg. The procedure can be applied for the determination of residues of low-polarity and medium polarity pesticides in honeybee samples.

Fast and precise determination of phenthoate and its enantiomeric ratio in soil by the matrix solid-phase dispersion method and liquid chromatography

A fast and precise method was developed for the determination of phenthoate and its enantiomeric ratio (ER) in three soil samples. A recently developed sample pretreatment technology--matrix solid-phase dispersion (MSPD) was used to extract phenthoate simply and effectively. MSPD conditions, i.e. solid-phase Florisil amount, water content of Florisil-soil mixture, the constituent and volume of the eluting solvent, were optimized stepwise. The MSPD extract was directly used for quantitative determination of phenthoate by silica-based high-performance liquid chromatography (HPLC) with UV detection. The recoveries of phenthoate from three different types of soils fortified at three levels of 0.1, 1, 10 microg/g ranged from 75 to 94% with RSDs of 1.5-6.5%. On this basis, phenthoate was further isolated from the remainder of MSPD extract by silica-based HPLC and then ER determined on HPLC with cellulose tris-3, 5-dimethylphenylcarbamate as chiral stationary phase. The ERs determined in the soils spiked with racemic or enantiomer-enriched phenthoate agreed sufficiently well with those in the corresponding standard solutions. Finally, the proposed method was successfully applied to the study of enantioselective degradation of phenthoate in the three soils under laboratory conditions. High enantioselectivity was observed in the two alkaline soils with (+)-enantiomer degrading faster than the (-)-enantiomer, while there was little to no enantioselectivity in the acidic soil. The methodology can be used to study the enantioselective environmental behavior of chiral pollutants.

Qualitative and quantitative analysis of tocopherols in toothpastes and gingival tissue employing HPLC NMR and HPLC MS coupling

Gingival samples treated with toothpastes containing tocopherols (vitamin E) were investigated employing HPLC chromatography. The aim was to verify that vitamin E is actually enriched in the tissue, which could have beneficial effects on oral health. After determination of the tocopherols available in the toothpastes, control samples from healthy test persons and subjects suffering from gingivitis were analyzed. Subsequently, gingival tissues from diseased test persons who treated their teeth with the toothpastes containing tocopherols using various kinds of concentrations or applications were investigated. The first step of the analysis was a fast and careful extraction employing matrix solid-phase dispersion (MSPD). Afterward, the separation of the different tocopherol homologues existing was performed by HPLC chromatography on highly selective C30 RP phases. The identification of the tocopherol homologues was performed using the on-line coupling of HPLC with NMR spectroscopy and mass spectrometry.

Determination of fungicide residues in fruits and vegetables by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

A liquid chromatography (LC) method for the quantitative determination of five fungicide residues (dichloran, flutriafol, o-phenylphenol, prochloraz and tolclofos methyl) in oranges, lemons, bananas, peppers, chards and onions is described. The residues were extracted by matrix solid-phase dispersion (MSPD) using C8. Quantitative analysis was performed by isocratic LC coupled to quadrupole mass spectrometer using atmospheric pressure chemical ionization in the negative ionization mode. The limit of quantification was 0.01 mg kgmicro for flutriafol, o-phenylphenol and dichloran, and 0.1 mg kg(-1) for prochloraz and tolclofos methyl. The MSPD method is also suitable for LC-UV analysis but higher limits of quantification (between 1 and 5 mg kg(-1)) were obtained. Validation of the method was performed between 0.01 and 25 mg kg(-1). Recoveries for fungicides ranged from 52.5 to 91.1% with relative standard deviations between 6.1 and 11.9%. The method was applied to the determination of residues in samples taken from agricultural cooperatives. The fungicides most often detected were o-phenylphenol and prochloraz.

Ethanol-modified subcritical water extraction combined with solid-phase microextraction for determining atrazine in beef kidney

The determination of the levels of pesticides in food products has prompted the development of sensitive and rapid methods of analysis that are solvent-free or utilize solvents that are benign to the environment and laboratory worker. In this study we have developed a novel extraction method that utilizes ethanol-modified subcritical water in combination with solid-phase microextraction (SPME) for the removal of atrazine from beef kidney. In situ sample cleanup was achieved using the technique of matrix solid-phase dispersion. A cross-linked polymer, XAD-7 HP, was utilized as a dispersing material for kidney samples. Subcritical water extractions were performed with a pressurized solvent extraction unit at 100 degrees C and 50 atm. Experimental parameters investigated were the volume of solvent and amount of modifier required for the complete extraction of atrazine and optimization of the extraction time. It was determined that 30% ethanol in water (v/v) is adequate for the complete extraction of atrazine. A Carbowax-divinylbenzene SPME fiber was used to sample the aqueous extracts. Analysis of the fiber contents was by ion-trap GC/MS utilizing the single ion mode. The total time of analysis for a single kidney sample is 90 min. The average percent recoveries from samples spiked to the concentrations of 2 and 0.2 microg/g were 104 and 111, respectively. The average relative standard deviations were 10 and 9, respectively. The method limit of detection for beef kidney spiked with atrazine was found to be 20 ng/g of sample.

Combined HPLC-MS and HPLC-NMR on-line coupling for the separation and determination of lutein and zeaxanthin stereoisomers in spinach and in retina

The determination and unambiguous identification of carotenoid stereoisomers from biological tissues, avoiding isomerization and oxidation due to the extraction process, is still a major challenge. Particularly, the analysis of lutein and zeaxanthin stereoisomers is of great importance, as these are the main constituents of the macula lutea, the central part of the human retina, and act as possible agents in the prevention and treatment of age-related macular degeneration (AMD). By combining a mild and quick extraction technique such as matrix solid-phase dispersion together with high-performance liquid chromatography (HPLC), the extremely light and oxygen sensitive lutein and zeaxanthin stereoisomers are extracted, enriched, and separated directly from the solid plant or tissue samples, excluding preparation of artifacts. HPLC separations are performed with C30 phases due to their enhanced shape selectivity compared to C18 phases and on-line coupled to mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy. By using HPLC-MS with atmospheric pressure chemical ionization, the lutein stereoisomers can be distinguished from the zeaxanthin stereoisomers within one chromatographic run in the upper picogram range, whereas HPLC-NMR coupling allows the unequivocal identification of each stereoisomer with a concentration in the upper nanogram range. This article provides an analytical method for the artifact-free determination of lutein and zeaxanthin stereoisomers directly from the solid biological tissue spinach as a source of carotenoids and retina as the sphere of activity for AMD. In addition, the structures of these stereoisomers were unambiguously elucidated by employing hyphenated analytical techniques.