苹果中多菌灵、噻菌灵和甲基托布津的高效液相色谱法分析

建立了同时检测苹果中多菌灵、噻菌灵和甲基托布津残留量的高效液相色谱(HPLC)分析方法.样品经乙酸乙酯提取,旋转蒸发仪浓缩,氮气吹干甲醇定容后,采用配有二极管阵列检测器(DAD)的HPLC测定,外标法定量.在添加不同浓度的标准品时,多菌灵、噻菌灵和甲基托布津的添加回收率分别为87.7%～118.7%、72.8%～80.3%、64.0%～66.8%.方法对多菌灵、噻菌灵和甲基托布津3种农药的检出限较低,分别为0.134、0.230和0.250mg/L,可以满足苹果汁中多菌灵、噻菌灵和甲基托布津的残留限量检测要求.检测果皮样品中的农药残留量,多菌灵的残留量为7.24×10-2mg/kg,噻菌灵和甲基托布津未检出,低于国标中规定的残留限量标准.     

On-line automated sample preparation for liquid chromatography using parallel supported liquid membrane extraction and microporous membrane liquid-liquid extraction

An automated system was developed for analysis of non-polar and polar ionisable compounds at trace levels in natural water. Sample work-up was performed in a flow system using two parallel membrane extraction units. This system was connected on-line to a reversed-phase HPLC system for final determination. One of the membrane units was used for supported liquid membrane (SLM) extraction, which is suitable for ionisable or permanently charged compounds. The other unit was used for microporous membrane liquid-liquid extraction (MMLLE) suitable for uncharged compounds. The fungicide thiophanate methyl and its polar metabolites carbendazim and 2-aminobenzimidazole were used as model compounds. The whole system was controlled by means of four syringe pumps. While extracting one part of the sample using the SLM technique. the extract from the MMLLE extraction was analysed and vice versa. This gave a total analysis time of 63 min for each sample resulting in a sample throughput of 22 samples per 24 h.     

Liquid chromatographic-mass spectrometric determination of post-harvest fungicides in citrus fruits

Liquid chromatography (LC)-atmospheric pressure ionisation (API)-mass spectrometry (MS) has been used to determine residues of five fungicides in oranges with a minimum sample cleanup. Atmospheric pressure chemical ionisation (APCI) and electrospray (ES) were compared and both gave similar results in terms of sensitivity and structural information. The main ions were [M+H]+ for carbendazim, imazalil, thiophanate methyl and thiabendazole, and [M+H-C4H9NHCO]+ for benomyl. Samples were extracted with sodium sulphate and ethyl acetate. Although benomyl and thiophanate methyl were transformed through the extraction procedure to carbendazim, the method showed good precision (<13%) and recovery (>70%), except for thiophanate methyl (50%), whilst also yielding limits of detection (<0.03 mg kg(-1)) that are adequate for the determination of the studied fungicides in oranges.     

Determination of carbendazim in blueberries by reversed-phase high-performance liquid chromatography.

A fluorescent reversed-phase high-performance liquid chromatographic method was developed for the analysis of carbendazim in blueberries. Recoveries of fortified blueberries at 27 and 810 ng/g were more than adequate with good precision. Forty commercial blueberry samples were analyzed and the amount of carbendazim ranged from none detected (detection limit of 15 ng/g) to 155 ng/g. Confirmation of carbendazim in the blueberry samples was made by enzyme immunoassay and UV photodiode array.     

Liquid chromatographic determination of carbendazim in the presence of some normal soil constituents with photodiode-array detection

A reversed-phase high-performance liquid chromatographic method was developed for the determination of carbendazim in the presence of some normal soil constituents (kaolinite, montmorillonite and peat). Spiked aqueous soil samples were injected after centrifugation and filtration. Quantitative recoveries were observed and good precision was obtained. The concentration range studied, 1.6716-8.3580 mg/l, is the most suitable for adsorption-desorption studies of carbendazim on soil and soil constituents.     

Optimization of the extraction of azo colorants used in toy products

Azo dyes are widely used in formulations intended for children use. But their potential toxicity raised the need of an efficient and fast method of analysis. A study for the optimization of the extraction of some azo colorants used in toys was conducted. Several extraction methods for the selected analytes were evaluated and compared, i.e., supercritical fluid extraction (SFE), microwave-assisted extraction (MAE) and Soxhlet extraction. Poly(vinyl chloride) samples spiked with known quantities of the studied dyes were prepared. The influence of critical variables on analyte recoveries in SFE and MAE was investigated by using a full-level factorial design, where most significant parameters as well as order interactions were studied in each case. The analytes were subsequently detected by high-performance liquid chromatography with UV detection. The three extraction techniques were compared in terms of reproducibility, selectivity and analyte recoveries. MAE showed higher recoveries (above 98%), except for the diazo dye (nearly 60%). Reproducibilities were generally good for the three methods (relative standard deviation lower than 2.0%).     

Determination of five pesticides in juice,fruit and vegetable samples by means of liquid chromatography combined with multivariate curve resolution

The aim of this work was to quantify five commonly used pesticides (propoxur, carbaryl, carbendazim, thiabendazole and fuberidazole) in real samples as: tomato, orange juice, grapefruit juice, lemon and tangerine. The method used for the determination of these analytes in the complex matrices was high-performance liquid chromatography with diode array detection. In order to work under isocratic conditions and to complete each run in less than 10 min, the analysis was carried out applying multivariate curve resolution coupled to alternating least-squares (MCR–ALS). The flexibility of this applied multivariate model allowed the prediction of the concentrations of the five analytes in complex samples including strongly coeluting analytes, elution time shifts, band shape changes and presence of uncalibrated interferents. The obtained limits of detection (in μg L⁻¹) using the proposed methodology were 2.3 (carbendazim), 0.90 (thiabendazole), 12 (propoxur), 0.46 (fuberidazole) and 0.32 (carbaryl).     

Optimization of the extraction of polycyclic aromatic hydrocarbons from wood samples by the use of microwave energy

A simple and rapid microwave-assisted extraction (MAE) procedure was developed and optimized for benzo[a]anthracene, benzo[e]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene and benzo[a]pyrene in wood samples. The spiked wood used was prepared 3 months before analysis to simulate weathering processes and to allow the formation of analyte-matrix interaction. The samples, immersed in acetonitrile were irradiated with microwaves in a closed-vessel system. Optimization of the method was achieved by using a factorial design approach on parameters such as extraction time, temperature and sample amount. The analysis of extracts has been carried out by reversed-phase high-performance liquid chromatography with fluorescence detection for quantification and UV-diode-array detection for confirmation. The MAE procedure yielded extracts that could be analyzed directly without any preliminary clean-up or solvent exchange steps.     

Analysis of free and esterified sterols in vegetable oil methyl esters by capillary GC

The introduction of quality standards for vegetable oil methyl esters is gaining in importance due to their increased use as diesel fuel substitutes and as technical products. Free and esterified sterols, the main constituents of the unsaponifiable matter in vegetable oils, are recovered in vegetable oil methyl esters and may influence the technical properties of vegetable oil methyl ester products. A rapid gas chromatographic method for the qualitative and quantitative determination of free and esterified sterols in vegetable oil methyl esters has therefore been developed. The concentration of the free sterols as well as their qualitative and quantitative composition and the concentration of the sterol esters have been determined in rape seed oil methyl ester samples by GC–FID. Prior to analysis, the free sterols were silylated with N,O-bis(trimethylsilyl)trifluoroacetamide with 1% of trimethylchlorosilane; betulinol was used as an internal standard. Calibration was performed by analysis of standard solutions containing β-sitosterol, cholesteryl stearate, and betulinol. The reproducibility of the quantitative results has been evaluated by repeated injections of the same test solution and by repeated complete analysis of the same sample.     

Optimization of the extraction of paclitaxel from Taxus baccata L. by the use of microwave energy

A simple and rapid microwave-assisted extraction (MAE) procedure was developed and optimized for the extraction of paclitaxel (Taxol) from the needles of yew trees Taxus baccata L. grown in Iranian habitats. The samples, immersed in a methanol-water mixture, were irradiated with microwaves in a closed-vessel system. The method was evaluated using a factorial design approach based on parameters such as extraction time, temperature, methanol concentration in water (v/v), and the ratio of grams of sample to 10 mL of solvent. Statistical treatment of the results revealed that the selected parameters were all significant except the extraction time. Optimum conditions would be 1.5 g samples in 10 mL solvent (90% methanol), an extraction temperature of 95 degrees C, and an extraction time of 7 min. The extracts has been analyzed by reverse-phase high-performance liquid chromatography with UV detection (LC/UV) at 227 nm for quantification. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for confirmation. The main advantage of the proposed MAE method versus conventional solvent extraction (CSE) are the considerable reductions in time (7 min versus 16 h) and in solvent consumption (20 mL versus 150 mL). The MAE procedure yielded extracts that could be analyzed directly without any preliminary clean-up or solvent exchange steps. Both extraction methods show RSDs lower than 10% and lead to comparable recoveries of paclitaxel (87-92%).     

微波辅助萃取新鲜芦荟叶中芦荟甙的研究

应用密闭微波萃取装置对芦荟中的有效成分芦荟甙进行了微波萃取研究,并利用透射电子显微镜对微波萃取机理进行了初步探讨.讨论了不同萃取剂、溶剂浓度、萃取时间和微波功率等对提取率的影响.在萃取剂为乙醇-水体系,溶剂(乙醇)体积分数为70%、萃取时间为4min及微波功率为340W的条件下,萃取效果最佳.与索氏提取及超声波萃取法相比,本法具有萃取速度快、提取率高及溶剂用量少等特点.     

Determination of trans octadecenoic acids by silver-ion chromatography-gas liquid chromatography: an intercomparison of methods

Several silver-ion chromatography-gas liquid chromatography (GLC) techniques for the determination of trans octadecenoic acids in partially hydrogenated vegetable fats were collaboratively evaluated. Twelve laboratories participated in the study. All collaborators used high polarity fused silica capillary columns for the separation of fatty acid methyl esters by GLC; 7 collaborators isolated trans monoenes by silver-ion liquid chromatography (Ag-LC) and the remainder used silver-ion thin-layer chromatography (Ag-TLC). Eight artificially prepared materials [soybean oil spiked with either methyl elaidate, trielaidin, or trans octadecenoates isolated from partially hydrogenated sunflower oil (PHSO)] and 2 matrix materials (PHSO and a blend of PHSO and palm oil) served as test samples. Ag-TLC and Ag-LC proved to be equivalent techniques for the prefractionation of trans monoenes. Recovery of methyl elaidate, trielaidin, or trans octadecenoates isolated from PHSO varied between 97.9-103.7% over a concentration range of 1 to 30 g trans fatty acids/100 g. Reproducibility relative standard deviation (RSDR) for the spiked samples were in the range of 3.1-8.6% for 30-1% trans monoene content. For the 2 matrix samples (mean 3.75 and 19.08% trans monoene content) RSDR was 13.2 and 3.6%. The hyphenated techniques tested proved to be highly accurate and sufficiently precise methods for the determination of trans monoenes in partially hydrogenated vegetable fats. Procedural variations of the silver-ion chromatography prefractionation step (separation mode, mobile phase, and detection systems) did not significantly influence the results of the test. Therefore, silver-ion chromatography is a robust method, which does not need rigorous standardization to achieve high precision of test results. A further benefit of the hyphenated technique is that any type of efficient polar capillary column can be used.     

微波辅助萃取/气相色谱-质谱联用分析蔬菜中的有机磷农药

建立了微波辅助萃取（MAE）/气相色谱-质谱联用法（GC-MS）测定蔬菜样品中二嗪磷、水胺硫磷的分析方法，研究了不同溶剂的萃取效率。选择二氯甲烷为萃取溶剂，采用二因素三水平的正交设计实验优化了萃取溶剂体积和萃取时间。方法的线性范围分别为二嗪磷和对硫磷4ng/g-400ng/g，水胺硫磷20ng/g-400ng/g，检出限分别为二嗪磷和对硫磷4ng/g-400ng/g、水胺硫磷20ng/g-400ng/g，检出限分别为二嗪磷0.29ng/g、对硫磷1.70ng/g、水胺硫磷2.30ng/g。测定200.0ng/g和50.0ng/g加标蔬菜样品，回收率为72.2%-102.0%,RSD为1.5%-11.0%。与传统的机械振荡萃取法相比，不仅萃取效率相当，而且还具有省时省溶剂的优点。     

Phenolic-compound-extraction systems for fruit and vegetable samples

This paper reviews the phenolic-compound-extraction systems used to analyse fruit and vegetable samples over the last 10 years. Phenolic compounds are naturally occurring antioxidants, usually found in fruits and vegetables. Sample preparation for analytical studies is necessary to determine the polyphenolic composition in these matrices. The most widely used extraction system is liquid-liquid extraction (LLE), which is an inexpensive method since it involves the use of organic solvents, but it requires long extraction times, giving rise to possible extract degradation. Likewise, solid-phase extraction (SPE) can be used in liquid samples. Modern techniques, which have been replacing conventional ones, include: supercritical fluid extraction (SFE), pressurized liquid extraction (PLE), microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE). These alternative techniques reduce considerably the use of solvents and accelerate the extraction process.     

Evaluation of microwave-assisted extraction for the analysis of polychlorinated biphenyls and organochlorine pesticides in fish

The efficiency of microwave-assisted extraction (MAE) was evaluated for the analysis of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in fish. An isotope dilution method was used for quantification via analysis of the samples by gas chromatography and mass spectrometry. MAE solvent, temperature, and time were optimized, and observed concentrations were compared. The MAE results were also compared to those of other extraction techniques (Soxhlet extraction, pressurized liquid extraction, saponification, and homogenization). Concentrations of PCBs and OCPs obtained by MAE at 120 degrees C for 10 min were comparable to those by the other techniques. The results suggest that MAE can be used for the analysis of PCBs and OCPs in fish.     

Liquid chromatographic determination of benomyl in water samples after dispersive liquid–liquid microextraction

A dispersive liquid–liquid microextraction (DLLME) method combined with solvolysis reaction for extraction of the carbamate fungicide benomyl as carbendazim from water samples is described. The method is based on the extraction of benomyl from acidified sample solution and its conversion into carbendazim via solvolysis reaction with DMF as organic solvent. The proposed DLLME method was followed by HPLC with fluorimetric detection for determination of benomyl. The proposed method has good linearity (0.998) with wide linear dynamic range (0.01–25 mg/L) and low detection limit (0.0033 mg/L), making it suitable for benomyl determination in water samples.     

Pressurized liquid extraction and microwave-assisted extraction in the determination of organochlorine pesticides in fish muscle samples

This paper describes a comparative study of 2 extraction methods, pressurized liquid extraction (PLE) and microwave-assisted extraction (MAE), for the determination of organochlorine pesticides (OCPs) in fish muscle samples. In both cases, samples were extracted with hexane-acetone (50 + 50), and the extracts were purified by solid-phase extraction using a carbon cartridge as the adsorbent. Pesticides were eluted with hexane-ethyl acetate (80 + 20) and determined by gas chromatography with electron-capture detection. Both methods demonstrated good linearity over the range studied (0.005-0.100 microg/mL). Detection limits ranged from 0.029 to 0.295 mg/kg for PLE and from 0.003 to 0.054 mg/kg for MAE. For most of the pesticides, analytical recoveries with both methods were between 80 and 120%, and the relative standard deviations were < 10%. The proposed methods were shown to be powerful techniques for the extraction of OCPs from fish muscle samples. Although good recovery rates were obtained with both extraction methods, MAE provided advantages with regard to sample handling, cost, analysis time, and solvent consumption. Acceptable validation parameters were obtained although MAE was shown to be more sensitive than PLE.     

Optimization of microwave-assisted extraction for alizarin and purpurin in Rubiaceae plants and its comparison with conventional extraction methods

A simple and rapid microwave-assisted extraction (MAE) procedure was developed and optimized for two common color pigments, alizarin and purpurin, in various samples of Rubiaceae plants. Several variables that can potentially affect the extraction efficiency, namely temperature, methanol concentration in the extractant mixture, time, and solvent volume were optimized by means of a central composite design approach. The results suggest that temperature and methanol concentration in the solvent mixture are statistically the most significant factors. The separation and quantitative determination of the pigments was carried out in less than 6 min by a developed high-performance liquid chromatographic method with UV detection at 250 nm. Under optimum operating conditions, MAE showed significantly higher recoveries than those obtained by the conventional extraction methods (ultrasonic and reflux extraction), ranging from 84 to 94%. In addition, a drastic reduction of the extraction time (20 min versus 6 h) and solvent consumption (20 versus 100 mL) was achieved with a reproducibility (RSDs < 10%) comparable with that provided by the reflux extraction as a reference method.     

Optimized separation and determination of methyl sulfone metabolites of polychlorinated biphenyls (PCBs) and p,p'-DDE in biota samples

An optimised method is described for the determination of 27 methyl sulfone polychlorobiphenyls (PCBs) and DDE in biota samples. Initially, the samples were extracted by hot Soxhlet and the methyl sulfones were separated by liquid/liquid extraction with concentrated sulfuric acid and back-extracted with hexane. The parameters of the back-extraction were studied and it was found that for a quantitative extraction of the methyl sulfones from the concentrated acid layer, a 50% dilution with cold water should be done. The hexane layer containing the methyl sulfones was further cleaned-up on basic silica (33% KOH) and Florisil. After concentration, the extract was analysed by gas chromatography-mass spectrometry (GC-MS) with electron capture negative ionisation (ECNI) in selected ion monitoring mode (SIM). It was shown that, for methyl sulfones, the ion formation was dependent on the chlorine substitution, position of the MeSO2-group and the ion source temperature. If the ion source temperature was higher than 200 degrees C, [M-CH3]- was the predominant ion for most methyl sulfones. Therefore, for increased sensitivity, quantitation of most congeners was done using [M-CH3]- ions instead of the molecular ion as used in previously reported methods. The method was validated for the determination of 26 tri- to hepta- 3- and 4-substituted MeSO2-PCBs and 3-MeSO2-DDE in animal and human tissues. Good sensitivity and selectivity of the method were obtained. Limits of detection (LODs) ranged from 0.06 to 0.10 ng g(-1) lipid weight. Average recoveries of individual congeners from vegetable oil spiked with individual standards (3.33 ng g(-1)) ranged from 73 to 112% with a mean value of 89%. The coefficients of variation ranged from 5.2 to 12.2%, which is within the acceptable range for environmental analyses.     

Degradation study of benomyl and carbendazim in water by liquid chromatography and multivariate curve resolution methods

Summary The degradation of benomyl and carbendazim in different organic solvents, distilled and ground waters was studied by on-line solid-phase extraction (SPE) followed by liquid chromatography (LC), diode array detection (DAD) or atmospheric pressure chemicalionization mass spectrometry detection (APCI-MS), UV spectrophotometry and multivariate curve resolution. Stability studies were performed in different organic solvents, such as acetonitrile and methanol, and in aqueous solution at different pH. Samples were stored in dark conditions at 4 °C and analysed by LC-DAD over 10 days. Photodegradation products of benomyl were resolved by spectrophotometry and multivariate curve resolution between pH 3 to 9. These results were correlated with those from LC-DAD and LC-APCI-MS. Photolysis studies were carried out at low concentration levels (2 μg L⁻¹) of carbendazim under different storage conditions in order to evaluate the effect of parameters, such as pH, temperature and sunlight exposure. Water samples (50 mL) were preconcentrated using on-line SPEC-LC-DAD. Photodegradation products of benomyl and carbendazim were identified by on-line-SPE-LC-DAD and SPE-LC-APCI-MS, leading to identification DAD and SPE-LC-APCI-MS, leading to identification of carbendazim, 3-butyl-2,4-dioxo-s-triazino1,2-abenzimidazole (STB) and 2-aminobenzimidazole (2-AB). Dedicated to Professor W. Haerdi on the occasion of his 70^th birthday.