Comparative study of clean-up and fractionation methods for the determination of organochlorine pesticides in lipids by gas chromatography.

Three of the methods most often used for the clean-up and fractionation of organochlorine pesticides in lipid residue analysis by gas chromatography with electron-capture detection were compared. The overall recoveries of twenty pesticides from spiked samples were higher than 88%, the relative standard deviation being in the range 3-11% (n = 6) at the 36-80 ppb (10(9) level. The three methods were compared by analysis of variance, with no differences in precision at the 0.05 significance level. Differences in recoveries appeared in only two instances. None of the three methods seems to be significantly better than the others for the determination of the pesticides studied.     

Applications of a Novel Sample Preparation Method for the Determination of Sulfonamides in Edible Meat by CZE

A simple, rapid and reliable method based on SPE clean-up and CZE separation was validated for the trace determination of sulfonamides (SAs) in meat. Acetonitrile was used for the extraction of SAs (sulfamethoxazole, sulfamethazine, sulfamerazine, and sulfadimethoxine) from the samples and 1-propanol was used for the denaturing of the proteins present in the sample matrix. SPE procedure was employed for the clean-up and pre-concentration of SAs prior to CZE analysis. Complete separation was achieved by using 45 mmol L^?1 phosphate buffer (pH = 6.3) at an applied voltage of 20 kV. Overall obtained recoveries were from 83.3 to 94.5% for the SAs. The detection limit of each sulfonamide ranges from 4 to 6 μg kg^?1. The presented one step SPE clean-up method is highly applicable for the determination of the SAs at a residue level below the maximum residue limit.     

Multiresidue analysis of pesticides in vegetables and fruits using two-layered column with graphitized carbon and water absorbent polymer

A high-throughput multiresidue analysis of pesticides in non-fatty vegetables and fruits was developed. The method consisted of a single extraction and a single clean-up procedure. Food samples were extracted with ethyl acetate and the mixture of extract and food dregs were poured directly into the clean-up column. The clean-up column consisted of two layers of water-absorbent polymer (upper) and graphitized carbon (lower), which were packed in a reservoir (75 ml ) of a cartridge column. The polymer removed water in the extract while the carbon performed clean-up. In a recovery test, 110 pesticides were spiked and average recoveries were more than 95% from spinach and orange. Most pesticides were recovered in the range 70-115% with RSD usually < 10% for five experiments. The residue analyses were performed by the extraction of 12 pesticides from 13 samples. The two methods resulted in similar residue levels except chlorothalonil in celery, for which the result was lower with the proposed method. The results confirmed that the proposed method could be applied to monitoring of pesticide residue in foods.     

Sample pretreatment method for the determination of polychlorinated biphenyls in bird livers using ultrasonic extraction followed by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A simple and reliable sample methodology based on simultaneous ultrasonic extraction, sulfuric acid clean-up and headspace solid-phase microextraction (SPME)-gas chromatography-mass spectrometry has been developed as an advantageous analytical tool for the determination of seven polychlorinated biphenyl congeners in bird livers at low levels. The influence of several parameters on the efficiency of the proposed method was systematically investigated. The clean-up efficiency of sulfuric acid treatment was tested and compared with those of column chromatography (Flosiril, silica gel and alumina) and solid-phase extraction (SPE) (Supelclean ENVI-Carb cartridge) procedures. The use of sulfuric acid in the clean-up step prior to headspace solid-phase microextraction analysis allows the removal of interfering matrix compounds present in the liver extracts that would otherwise cause severe ionization suppression of the polychlorinated biphenyls (PCBs) during the ionization process. The optimized method had good linearity (R2>0.99) over the range studied (5-500 ng/g wet weight) and showed satisfactory level of precision, with RSD values lower than 10.6%. The obtained relative recoveries ranged between 63 and 94%. The limits of detection (0.06-0.63 ng/g wet weight) were low enough to check for harmful levels of polychlorinated biphenyls in biological samples, and were well below most of the restrictive limits established by European Union regulations. The method was found to be reliable under the operational conditions proposed and was applied successfully to the analysis of individual polychlorinated biphenyls in liver tissues. The results obtained from five bird species from Greece revealed the presence of the target compounds in all samples analyzed, at levels ranging between 0.54 and 39.45 ng/g wet weight.     

Evaluation of an automated clean-up system for the isotope-dilution high-resolution mass spectrometric analysis of PCB, PCDD, and PCDF in food

An automated clean-up system was evaluated for the simultaneous analysis of polychiorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF), and biphenyls (PCB) in different foods. In addition to the seventeen 2,3,7,8-substituted PCDDIPCDF and four non-ortho PCB, by use of the clean-up system studied, it was possible to collect the eight mono-ortho and two di-ortho PCB and the seven indicator PCB in two separate fractions during the same clean-up run. The study was first performed using standard mixtures containing PCDD, PCDF and PCB, and a certified reference material. The recoveries of the 13C-labeled compounds ranged from 51 to 90%, indicating that the PCDD, PCDF, and PCB clean-up worked satisfactorily. Next, the automated system for PCDD, PCDF, and PCB analysis was evaluated for foods such as milk, egg, meat (beef, chicken, and pork), mussel, and olive oil. The recoveries of the 13C-labeled compounds ranged from 40 to 120% for PCB and from 57 to 113% for PCDD/ PCDF, meeting the requirements of well accepted methods. Thus, the automated clean-up system studied is a suitable alternative to conventional clean-up methods.     

大米中多种残留农药的固相萃取-气相色谱-质谱分析

建立了一种同时测定大米中有机氯、有机磷、氨基甲酸酯和拟除虫菊酯等4类农药残留量的分析方法。通过比较二氯甲烷、三氯甲烷、乙腈、乙酸乙酯和不同比例的己烷-丙酮混合溶剂等8种溶剂的提取效果,选择以二氯甲烷为提取溶剂;以Florisil固相萃取小柱净化,通过以不同比例的己烷-丙酮作洗脱溶剂,发现体积比为4∶1的己烷-丙酮的洗脱效果最佳,在选定的洗脱条件下,样品的净化效果良好;用气相色谱-质谱测定,以保留时间、选择离子及其相对丰度定性,以外标法定量。以低限加标样品的3倍信噪比确定方法的检出限(LODs),以两个添加水平测定样品的回收率和相对标准偏差(RSD)。该方法的检出限达到μg/kg水平;除敌敌畏、乐果、pp′-DDT等几种农药外,大多数农药的加标回收率在75%和120%之间,RSD均低于10.4%,r≥0.992。该方法简便、快速、灵敏,能够满足同时测定大米中多种类残留农药的要求,可以作为大米中农药多残留的例行分析和确证分析的方法。     

Automated liquid chromatographic determination of ochratoxin A in cereals and animal products using immunoaffinity column clean-up.

The analysis of the fungal mycotoxin ochratoxin A in cereals and animal products is described using an immunoaffinity column clean-up and high-performance liquid chromatographic determination. The clean-up can be carried out manually or using a commercially available automated sample preparation system. The method has been applied to cereals such as wheat, rye and barley, unprocessed breakfast cereals and animal products such as pigs' kidneys and blood sausages. Recoveries ranged from 70-80% for spiked samples (10 micrograms/kg) and the method had a relative standard deviation of 1.3% (n = 8) for the analysis of a wheat sample naturally contaminated at 13.7 micrograms/kg ochratoxin A and relative standard deviation of 3.0% (n = 8) for a pig kidney sample spiked at 10 micrograms/kg ochratoxin A. The immunoaffinity approach was significantly faster than methods employing conventional chromatographic clean-up, and extracts were freer of co-extractives giving a limit of detection of 0.2 micrograms/kg.     

Analysis of zearalenone and α-zearalenol in animal feed using high-performance liquid chromatography

Different extraction and clean-up techniques used before HPLC analysis were compared in order to obtain a reliable method for the quantitative determination of zearalenone (ZEA) and α-zearalenol (α-ZOL) in animal feed. Immunoaffinity clean-up was compared to C₁₈ and Florisil column clean-up. Extracted samples were analysed by reversed-phase HPLC with fluorescence detection (λ_ex=274 nm, λ_em=440 nm). A mobile phase of acetonitrile:water (50:50 (v/v)) and a flow-rate of 1.0 ml min⁻¹ resulted in a good separation between ZEA and α-ZOL. Using immunoaffinity clean-up the linear range was between 25 and 600 μg kg⁻¹ for ZEA and α-ZOL in maize. Intra-laboratory coefficients of variation (CV) (under repeatability conditions) were 9.16% for ZEA and 2.18% for α-ZOL. Recoveries for spiked ZEA and α-ZOL samples ranged from 89 to 110% with CVs between 5.2 and 11.2% (under within-laboratory reproducibility conditions). Using C₁₈ and Florisil solid-phase clean-up, matrix interference was too high. Therefore, naturally contaminated animal feed samples were analysed using the developed HPLC method coupled to the immunoaffinity clean-up.     

Development of a solid-phase extraction method for the determination of polychlorinated biphenyls in water

Polychlorinated biphenyls (PCBs) in water were extracted with a rebuilt extraction unit using 47 mm C18 solid-phase extraction (SPE) disks. Three types of disks (SPEC, ENVI and Empore) were investigated for the extraction of seven PCBs from 11 reagent water spiked at two concentration levels (20 and 1000 ng/l). The Empore disks produced the best analyte recoveries (91-107% with R.S.D. of 1-8%) at the low concentration level and displayed no leaking tendency. Empore disks were therefore considered superior to ENVI and SPEC disks for the conditions outlined in this work. The obtained extracts were dried and purified in an additional clean-up step using custom-made columns containing Florisil and Na2SO4. For water containing large amounts of organic matter, a pre-filtration was included. Final analysis was carried out on a dual-column GC-electron-capture detection system with on-column injection. The optimised extraction method, including clean-up, was less time-consuming and used less hazardous organic solvents than conventional liquid-liquid extraction (LLE) methods. Recoveries were 92-102% with R.S.D. of 3-8%.     

Determination of closantel and rafoxanide in animal tissues by online anionic mixed-mode solid-phase extraction followed by isotope dilution liquid chromatography tandem mass spectrometry

A rapid and high-throughput isotope dilution LC-MS/MS method with online sample pre-concentration and clean-up using anionic mixed-mode SPE was described for the determination of closantel and rafoxanide in edible bovine and ovine tissues. Tissue samples were extracted with acetonitrile and acetone mixture (60:40, v/v). Sample pre-concentration, clean-up and analysis were completed simultaneously with the online MAX SPE LC-MS/MS system. Closantel-(13) C(6) and rafoxanide-(13) C(6) were used as the internal standards to improve the precision of the method. The method was validated with edible ovine and bovine tissues (muscle, kidney and liver) fortified at three different levels. The accuracy and RSD were 86-106% and ≤14%, respectively. This high-throughput method was suitable for routine quantitative analysis of closantel and rafoxanide in food safety surveillance samples.     

Dispersive solid-phase extraction clean up combined with Soxhlet extraction for the determination of 16 PAHs in soil samples by GC-MS

Dichloromethane soil samples extracts were prepared using Soxhlet extraction technique, and after clean-up step, gas chromatography-mass spectrometry analysis of 16 priority polycyclic aromatic hydrocarbons (PAHs) was carried out. A comparison of dispersive solid-phase extraction (dSPE) and column chromatography (cC), as clean-up techniques, was evaluated. Six different sorbents (silica, diatomaceous earth, primary–secondary amine, C18, clinoptilolite and florisil) were tested as dispersive clean-up sorbents versus activated silica and alumina for cC. Best results for three concentration levels among dSPE were obtained using diatomaceous earth, with recovery values in the range of 75–112% for 13 of 16 analysed compounds, while cC recoveries were in the range of 75–111% for all analysed PAHs. Analysis of 12 soil samples from urban area of Ni? (Serbia) singled out acenaphthene as the most abundant compound.     

Application of ion-exchange cartridge clean-up in food analysis. V. Simultaneous determination of sulphonamide antibacterials in animal liver and kidney using high-performance liquid chromatography with ultraviolet and mass spectrometric detection

A simple, rapid, and reliable method for the determination of residual sulphonamide antibacterials (SAs) (sulfadiazine, sulfamerazine, sulfadimidine, sulfamethoxypiridazine, sulfisozole, sulfamonomethoxine, sulfamethoxazole, sulfisoxazole, sulfadimethoxine, and sulfaquinoxaline) in animal liver and kidney was developed using a combination of clean-up on a Bond Elut PSA cartridge and HPLC with UV detection. The SAs were extracted with ethyl acetate and then dissolved in 5 ml of 50 v/v% ethyl acetate-n-hexane after being evaporated to dryness. For clean-up of the crude sample, the resuspended extract was applied to a Bond Elut PAS (primary/secondary amine cartridge), and then SAs were eluted from the cartridge using 5 ml of 20 v/v% acetonitrile-0.05 M ammonium formate before being analysed by HPLC. Recoveries of the SAs at the levels of 0.5 and 0.1 microg/g were 70.8-98.2%, the rerative standard deviation were less than 7.0%, and the detection limits were 0.03 microg/g. The present analysis method of SAs in animal kidney and liver using HPLC with a clean-up procedure was demonstrated to be highly applicable to the direct LC-MS-MS analysis without any modification.     

An evaluation method for determination of non-polar pesticide residues in animal fat samples by using dispersive solid-phase extraction clean-up and GC-MS

A rapid and easy method has been proposed, optimized and evaluated for quantitative determination at trace level of a representative group of non-polar pesticides in fat samples. The method includes n-hexane-saturated acetonitrile extraction, fat precipitation by cooling pre clean-up followed by dispersive solid-phase extraction (d-SPE) based on QuEChERS procedure clean-up. Determination was performed by gas chromatography?Cmass spectrometry (GC-MS) in selected ion monitoring (SIM) mode. Efficiency of the d-SPE clean-up step was evaluated by comparison with fat oxidation treatment and gel permeation chromatography. Different combinations of d-SPE extraction reagents and sample amounts were tested in order to minimize matrix co-extractives and interferences. Best recoveries were obtained with 1200?mg of MgSO₄, 400?mg of end-capped C₁₈, 400?mg of PSA and 1?g of sample amount. SIM method, matrix effect, precision, and accuracy were evaluated with spiked pork fat samples for 38 representative pesticides. Results of this study showed that this technique is applicable in routine analysis for its application into monitoring programs. It simplifies time-consuming clean-up steps and allows a satisfactory long-term chromatographic performance.     

Rapid method for the determination of 16 organochlorine pesticides in sesame seeds by microwave-assisted extraction and analysis of extracts by gas chromatography-mass spectrometry

A method for the multiresidue analysis of 16 organochlorine insecticides in sesame seeds has been developed. The method is based on the microwave-assisted extraction (MAE) of the sesame seeds by the use of a water-acetonitrile mixture followed by Florisil clean-up of the extracts and subsequent analysis by gas chromatography-mass spectrometry (GC/MS) in the selected ion monitoring (SIM) mode. MAE operational parameters (extraction solvent, temperature and time, extractant volume) were optimized with respect to extraction efficiency of the target compounds from sesame seeds with 46% oil content. Recoveries >80% with relative standard deviations (RSD) <12% were obtained for all compounds under the selected parameters. The Florisil clean-up step proved sufficient for the removal of co-extracted substances so that no adverse effect on the chromatographic system was observed. Limit of quantification (LOQ) values were in the range of 5-10 microg/kg. The proposed method was applied in the analysis of sesame seed samples imported to Greece.     

Development of a selective sample clean-up method based on immuno-ultrafiltration for the determination of deoxynivalenol in maize

This paper describes the development of a highly selective analytical method for the determination of deoxynivalenol (DON) in maize. The developed method is based on immuno-ultrafiltration (IUF) and is the first application of IUF as a clean-up strategy in food analysis. Quantification of DON was carried out by high-performance liquid chromatography with ultraviolet detection. In contrast to immunoaffinity chromatography, in IUF the antibodies are not bound to a solid support material but used in free form, thus making it possible to avoid the critical immobilisation step. Sample clean-up by IUF proved to be as selective as clean-up using commercially available immunoaffinity columns. The limit of detection (S/N=3) of the analytical method was found to be 74 ng DON/g maize. Repeated analysis of a certified maize reference material on four different days resulted in a mean recovery of 93% with a standard deviation of 10%.     

Determination of tetracyclines in bovine kidney by liquid chromatography/tandem mass spectrometry with on-line extraction and clean-up

A novel, sensitive, high performance liquid chromatography/tandem mass spectrometric (i.e. mass spectrometry/mass spectrometry) method with on-line extraction and clean-up for the screening and confirmation of residues of tetracyclines in kidney has been developed. After liquid extraction of homogenised kidney with McIlvain buffer, an aliquot of the extract is directly injected on the LC/MS/MS system with further extraction and clean-up of the sample on-line. Detection of the analytes was achieved by positive electrospray ionization followed by multiple reaction monitoring. For each tetracycline the collisional decomposition of the protonated molecule to a unique, abundant fragment ion was monitored. The method has been validated for tetracycline, oxytetracycline, chlortetracycline and doxycycline. Calibration curves resulting from spiked blank kidney samples at the 100-1200 microgram/kg level showed good linear correlation. At the level of 600 microgram/kg both within- and between-day precision, as measured by relative standard deviation (RSD), were less than 7%. The limits of detection (LODs) for tetracycline, oxytetracycline, chlortetracycline and doxycyline were 18, 23, 24 and 21 microgram/kg, respectively. The limits of quantification (LOQs) for tetracycline, oxytetracycline, chlortetracycline and doxycyline were 36, 46, 47 and 42 microgram/kg, respectively. The recoveries ranged from 71 to 91%. The procedure provides a rapid, reliable and sensitive method for the determination of residues of tetracyclines in bovine kidney. The advantage of this method over existing methods is its decreased sample preparation and analysis time, which makes the method more suitable for routine analysis.     

A rapid and environmental friendly determination of the dithiocarbamate metabolites ethylenethiourea and propylenethiourea in fruit and vegetables by ultra high performance liquid chromatography tandem mass spectrometry

Previous published methods for the analysis of ETU and PTU are time-consuming and furthermore use dichloromethane (DCM) for extraction or clean-up. This study details the development and validation of a rapid method that combines a simple extraction step with UHPLC-ESI(+)-MS/MS. This is the first application of UHPLC-MS/MS to analyse these compounds. Besides that, we replaced DCM with a more environmental-friendly solvent. The analytical performance was evaluated with the analysis of spiked celery samples at 50 μg kg(-1) (LOQ) and 300 μg kg(-1). The recoveries were between 65% and 90% for ETU and between 71% and 127% for PTU with RSDs in repeatability and reproducibility conditions below 10% for ETU. This method is rapid (a chromatographic run time of 2 min) and can easily be performed (no laborious clean-up). The presented method is environmental friendly with significant reduction in solvent consumption.     

Evaluation and optimization of extraction and clean-up methods for the analysis of polycyclic aromatic hydrocarbons in peat samples

The analysis of PAH in peat samples is complicated by the high content of organic matter in peat which affects both extraction efficiency and analytical quality. Therefore, we evaluated the efficiencies of three extraction methods (accelerated solvent extraction (ASE), fluidized bed extraction, ultrasonic extraction) and several clean-up techniques in order to find the best set of methods. ASE proved to be the best extraction method. For clean-up, a procedure using aluminium oxide and silica gel showed the highest efficiency, whereas a method originally developed for soil samples failed to remove the peat matrix satisfactorily. With the optimized extraction and clean-up procedure, 170 samples from Canadian bogs were analysed for PAH. With overall recovery rates between 69?±?14 and 89?±?16% and an inaccuracy of ≤20%, the optimized method was a well suitable tool for the analysis of PAH in peat samples.     

Improvement of chemical analysis of antibiotics. XVII. Application of an amino cartridge to the determination of residual sulphonamide antibacterials in meat, fish and egg

A simple, rapid and reliable method for the determination of residual sulphonamide antibacterials (SAs) (sulphathiazole, sulphisozole, sulphamethoxazole, sulphadiazine, sulphamerazine, sulphadimidine, sulphamonomethoxine, sulphadimethoxine, sulphamethoxypyridazine and sulphaquinoxaline) in meat, fish and egg was developed using a combination of high-performance liquid chromatography (HPLC) and clean-up with an amino-type prepacked cartridge. SAs were extracted with ethyl acetate and applied to a Baker 10 amino cartridge. After elution from the cartridge, SAs were determined by HPLC. The recoveries at the level of 0.5 ppm were 73.7-99.1% and the detection limits were 0.05 ppm. The analysis time per sample was about 45 min.     

Solid-phase extraction of sugar cane soot extract for analysis by gas chromatography with flame ionisation and mass spectrometric detection

The incomplete combustion of biomass is one of the most important sources of emissions of organic compounds into the atmosphere, like polycyclic aromatic hydrocarbons (PAHs) which show genotoxic activity. Since environmental samples generally contain interferents and trace amounts of PAHs of interest, concentration and clean-up procedures are usually required prior to the final chromatographic analysis. This paper discusses the performance of Sep-Pak cartridges (silica gel and RP18) on clean-up of sugar cane soot extract. The best results were obtained with a silica Sep-Pak cartridge. The recoveries ranged from 79% (benzo[b]fluoranthene) to 113% (benzo[e]pyrene).