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.     

固相萃取-离子交换色谱法测定浓缩苹果汁中残留的苯菌灵、多菌灵、噻菌灵

建立固相萃取-离子交换色谱法测定浓缩苹果汁中苯菌灵、多菌灵和噻菌灵的残留量。样品直接用水稀释后,于80 ℃下将苯菌灵完全转化为多菌灵,再经SCX固相萃取柱富集,采用LC-SCX离子交换色谱柱(25 cm×4.6 mm,5 μm)分离,二极管阵列检测器检测,以0.1 mol/L KH2PO4溶液(pH 2.5)-乙腈(体积比为70 ∶30)为流动相,在1.0 mL/min下等度洗脱,于282 nm波长下检测。在0.02～2.0 mg/L范围内,多菌灵和噻菌灵的峰面积与其浓度呈良好的线性关系,最低检出限均可达到0.004 mg/kg,回收率为94.2%～100.4%,相对标准偏差低于4.2%。该方法简便、快速、灵敏、准确,可用于浓缩苹果汁中苯菌灵、多菌灵和噻菌灵残留量的检测。     

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.     

基于细菌纤维素的毛细管电泳法同时测定果蔬中3种苯并咪唑类杀菌剂

建立了高效毛细管电泳同时测定果蔬中3种常见的苯并咪唑类杀菌剂(甲基硫菌灵、多菌灵和苯菌灵)的分析方法。以细菌纤维素(BC)为电泳缓冲液添加剂来提高毛细管电泳的分离能力。系统考察了检测波长、缓冲液离子强度、缓冲液pH、分离电压及BC添加量对3种苯并咪唑类杀菌剂分离效果的影响。最终的优化条件:H3BO3/Na2B4O7缓冲液(4 mmol/L,pH 9.0);BC添加质量分数0.3%;运行电压15 kV;分离柱温25℃;检测波长275 nm。3种苯并咪唑类杀菌剂在8 min之内可实现基线分离及准确定量。结果显示:3种苯并咪唑类杀菌剂在各自线性范围内线性关系良好,相关系数(r2)≥0.997;检出限为5.0~10.0μg/L;保留时间及峰面积的日间相对标准偏差(n=5)分别为0.82%~1.0%和2.4%~2.9%。该法用于葡萄、番茄及黄瓜中3种苯并咪唑类杀菌剂的测定,加标回收率为93.5%~103.0%,RSD≤8.0%。该法可作为果蔬中甲基硫菌灵、多菌灵和苯菌灵同时检测的有效手段。     

Determination of carbendazim,thiabendazole, and<Emphasis Type="Italic"> o-</Emphasis>phenylphenol residues in lemons by HPLC following sample clean-up by ion-pairing

An efficient analytical method is presented involving effective sample clean-up with solid-phase extraction and HPLC-UV analysis for the simultaneous determination of carbendazim, thiabendazole, and o-phenylphenol residues in lemons. Sample preparation involves extraction with acetonitrile acidified with trifluoroacetic acid and an ethyl acetate/petroleum ether mixture. Purification of the crude extract was carried out with liquid–liquid partitioning after addition of an aqueous ammonia solution. Final clean-up was performed on polymeric reversed-phase cartridges pretreated with sodium dodecyl sulfate. Chromatographic analysis was performed on a reversed-phase HPLC column isocratically eluted with an acetonitrile/water/ammonia mixture and UV detection at 254 nm. The chromatographic method is repeatable, reproducible, and sensitive. Fungicide recoveries from lemon samples fortified at levels of 5 and 1 mg kg^–1 were 81–85% for carbendazim, 96–98% for thiabendazole, and 81–106% for o-phenylphenol with coefficients of variation of 2.5–7.4%. Detection limits for carbendazim, thiabendazole, and o-phenylphenol in lemons were 0.21, 0.27, and 0.51 mg kg^–1, respectively.     

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.     

Molecularly imprinted solid-phase extraction of naphthalene sulfonates from water

A new polymeric sorbent synthesised by exploiting molecular imprinting technology has been used to selectively extract naphthalene sulfonates (NSs) directly from aqueous samples. In the non-covalent molecular imprinting approach used to prepare this polymer, 1-naphthalene sulfonic acid (1-NS) and 4-vinylpyridine (4-VP) were used as a template molecule and functional monomer, respectively, and both dissolved in a mixture of methanol/water (4:1) as porogen together with the cross-linker ethylene glycol dimethacrylate. The new non-covalent molecularly imprinted polymer (MIP) prepared in aqueous environment was used as a sorbent in solid-phase extraction (SPE) to selectively extract a group of naphthalene mono- and disulfonates. When one litre of a standard aqueous solution, which contained a mixture of eight NSs, was percolated through the SPE cartridge, all the NSs were retained on the MIP because of the cross-reactivity of the polymer. Recoveries were higher than 80% for all the compounds even after a clean-up step with methanol (MeOH). The MIP was also used to analyse water from the Ebro river.     

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.     

Fast solid phase extraction of polychlorobiphenyls and chlorinated pesticide residues from mussels using sep-pak cartridges

Summary A rapid method for the determination of chlorinated pesticides and polychlorinated biphenyls in mussels (Mytilus sp.) is reported. The mussel sample is homogenized and extracted with acetonitrile. The organic solution is concentrated and successively diluted with distilled water solution (12 g L⁻¹ NaCl). The organic compounds from water solution are adsorbed onto a NH₂ Sep-Pak cartridge. The clean-up step, in which the polychlorobiphenyls and chiorinated pesticides are separated in different eluates, is achieved by passing 25 mL of a 40% methanol aqueous solution through the NH₂ Sep-Pak and the C₁₈ Sep-Pak cartridges connected in series. The polychloroblphenyls are desorbed from the NH₂ Sep-Pak cartridge whilst the chlorinated peslicides are recovered from the C₁₈ Sep-Pak cartridge. In the separation of polychlorobiphenyls from the chlorinated pesticides tested in this work, only aldrin, hepatachlor and 4,4′-DDD are partially adsorbed with the polychlorobiphenyls onto the NH₂ Sep-Pak cartridge. The average recovery is ≥95.0% with a relative standard deviation ≤5.0%. The limits of detection for different pesticides and polychlorobiphenyl congeners are 0.01 and 0.008 μg Kg⁻¹. The final determination is carried out by capillary gas chromatography with ECD.     

Analysis of carbendazim and thiabendazole in lemons by CE-DAD

Summary A capillary electrophoretic method for the determination of two benzimidazole fungicides, carbendazim and thiabendazole, in lemons has been developed. The two fungicides were separated in a law-pH phosphate buffer containing acetonitrile. Reproducibility tests measuring both migration times and peak areas gave low relative standard-deviation values. Calibration graphs were linear and the detection limits, defined as a signal-to-noise ratio of 3:1, were 2.3 and 2.0 μg mL⁻¹ for thiabendazole and carbendazim, respectively. Analysis of carbendazim and thiabendazole residues in lemons was performed after lemon homogenization, extraction with ethyl acetate and purification through a series of separatory-funnel, acid-base partitions. This lemon clean-up procedure ensured no interference in the capillary electrophoretic analysis from lemon endogenous ingredients.     

Determination of some benzimidazole fungicides in tomato puree by high performance liquid chromatography with SampliQ polymer SCX solid phase extraction

High performance liquid chromatography (HPLC) coupled with solid phase extraction (SPE) was optimized for extraction and quantification of two benzimidazoles fungicides (carbendazim and benomyl) in tomato puree. Results indicate that HPLC using an Agilent ZORBAX Eclipse plus C18 column (4.5 mm × 100 mm, 3.5 μm) and SPE using Agilent SampliQ SCX (55 mg, 3 mL) is an excellent combination for extraction and analysis of these compounds. Recoveries ranged from 90.0 to 95.5 percent with RSDs below 5 percent and limit of detections of 5 μg/kg.     

Catalytic polarographic prewave of cobalt(II) induced by carbendazim. Application to the voltammetric determination of benomyl

Methyl 1H-benzimidazol-2-ylcarbamate (carbendazim or MBC) catalyzes the reduction of Co^II at mercury electrodes in sodium barbital/nitric acid/sodium chloride media. On the basis of a detailed study of the Co^II prewave induced by carbendazim, a mechanism for the electrode reaction is proposed and adequate conditions for the analytical determination of carbendazim by differential pulse voltammetry are established. Based on this finding, a voltammetric method for the indirect determination of methyl[1-(butylcarbamoyl)-1H-benzimidazol-2yl]carbamate (benomyl) is described, following the conversion of benomyl to carbendazim.     

In-house validation of an improved sample extraction and clean-up method for GC determination of isomers of nervonic acid in meat products

An improved extraction and clean-up method for determination of brain-specific fatty acids, in particular lignoceric acid (C24:0) and the cis/ trans isomers of nervonic acid (15 c-t C24:1), in meat products has been developed. The method is based on isolation of the polar lipids of interest from the bulk lipids by solid-phase extraction. The fatty acids, derivatised to their fatty acid methyl esters, are quantified by GC in a DB5 column. Fresh meat samples were extracted by using a mixture of n-butanol:hexane (1:9) as solvent. The extract was loaded in a silica gel cartridge column previously equilibrated with hexane. The first fraction containing the major part of the fat was eluted with hexane while acetone and methanol allowed the elution of fatty acids bound to polar moieties such as nervonic and lignoceric acids. This second fraction containing the analyte was methylated and injected into the GC for quantification after addition octacosane (C(28)) as internal standard.     

气相色谱法同时测定玉米中12种三嗪类除草剂的残留量

建立了气相色谱-氮磷检测器同时检测玉米中12种三嗪类除草剂（西玛通、西玛津、阿特拉津、扑灭津、特丁通、特丁津、环丙津、西草净、扑草净、特丁净、甲氧丙净、环嗪酮）残留量的方法。玉米样品用乙腈萃取,强阳离子交换(SCX)固相萃取柱净化后,用DB-5弹性石英毛细管柱(30 m×0.25 mm i.d.×0.25 μm)分离样品,氮磷检测器测定。12种三嗪类除草剂在0.01～2.0 mg/L范围内线性关系关系良好,相关系数均大于0.998;最低检测限为0.01 mg/kg;添加回收率为84.0%～106.8%;相对标准偏差为0.9%～4.7%。     

固相萃取-液相色谱-飞行时间质谱法快速筛查与确证谷物和果蔬中25种杀菌剂残留

利用固相萃取-液相色谱-飞行时间质谱(SPE-LC-Q-TOF/MS)技术建立了谷物、 蔬菜和水果中25种杀菌剂农药残留的快速筛查和确证检测方法.样品经1%(V/V)乙酸-乙腈溶液提取,经Crabon/NH2柱净化,乙腈-甲苯(3∶1, V/V)洗脱,C18色谱柱分离,乙腈和0.1% 甲酸溶液(含5 mmol/L乙酸铵)梯度洗脱,采用LC-Q-TOF/MS检测,外标法定量.建立了25种杀菌剂的一级精确质量数据库和二级谱图库,通过化合物的精确质量数、 保留时间、 同位素峰分布、 同位素比例等信息对检测结果进行自动检索,在无对照标准品的情况下实现了25种农药的定性鉴定.结果表明,25种杀菌剂在0.02~200 μg/L范围内线性关系良好,相关系数R2≥0.9950, 加标回收率在71.8%~114.0%之间,相对标准偏差(RSD)为0.1%~21.3% (n=3).25种杀菌剂检出限为0.01~5.00 μg/kg,定量限为0.02~20.00 μg/kg.本方法简便、 快速、 可靠,可用于谷物、 蔬菜、 水果中25种杀菌剂的快速筛查.     

固相萃取-气相色谱/质谱法同时测定涂料中的8种有机锡

建立了一种固相萃取（SPE）前处理、气相色谱-质谱（GC-MS）法同时测定涂料中8种有机锡的方法。样品采用阳离子交换固相萃取小柱净化,最佳固相萃取条件为：固相萃取小柱分别用5mL甲醇、7mL洗脱液（氯化铵、甲醇、冰乙酸的混合溶液）预洗,10mL甲醇活化;将用甲醇稀释的涂料样品上样后,用5mL甲醇淋洗,抽干2min,7mL乙酸-氯化铵甲醇溶液（10：90,V／V）洗脱溶液洗脱。洗脱液用四乙基硼化钠溶液衍生后,气相色谱-质谱法进行定性定量分析。结果表明：以标准加入法计算回收率,在1.68％-16.84%添加范围内,平均回收率在85％-105％之间,相对标准偏差均小于12％。     

Rapid determination of citrinin in corn by fluorescence liquid chromatography and enzyme immunoassay

A rapid assay procedure was developed for mycotoxin citrinin in corn using liquid-liquid extraction (LLE) cartridges. Ground corn was extracted with methylene chloride and 0.5 N phosphoric acid. The extract was added to an LLE cartridge containing a diatomaceous-earth adsorbant, previously impregnated with sodium bicarbonate solution. After aspiration to dryness, the cartridge was eluted with methanol-water (4 + 1), and aliquots were taken for quantitation by reversed-phase liquid chromatography with fluorescence detection. Recoveries of citrinin added to ground corn at 200-1600 ng/g ranged from 71.2 to 86.3%, with coefficients of variation between 4.1 and 10.6%. An indirect enzyme immunoassay was also evaluated, using sodium carbonate solution for extraction. Recoveries of citrinin added to ground corn at 200-2000 ng/g ranged from 53.2 to 67.2%, but the coefficients of variation varied between 18.4 and 51.5%. The LLE cartridge procedure offers the advantages of low solvent consumption and speed, and is amenable to automation.     

Comparison of commercial solid-phase extraction sorbents for the sample preparation of potato glycoalkaloids

In this study five different commercial sorbents C18, SCX, CN, Certify and Oasis HLB were compared for the solid-phase extraction of potato glycoalkaloids. The recoveries were determined using alpha-solanine, alpha-chaconine and alpha-tomatine, which contained dehydrotomatine as an impurity, as standard compounds. The samples were analysed by reversed-phase liquid chromatography under gradient elution conditions using a Zorbax Rx-C18 column and acetonitrile-25 mM triethylammonium phosphate buffer (pH 3.0) as the mobile phase. The highest recovery (approximately 100%) was achieved with Oasis HLB (60 mg) cartridges. An acetic acid extract of wild Solanum brevidens leaf material was used for the testing of a clean-up procedure. The SCX proved to be the most selective and efficient for removing the undesired components from the leaf extract.     

Aflatoxin M1 determination in cheese by liquid chromatography-tandem mass spectrometry

A new method for determining aflatoxin M1 (AFM1) in cheese by liquid chromatography-tandem mass spectrometry has been developed. Two methodologies were compared for sample extraction. The first one involves sample extraction with dichloromethane for hard, aged cheese or acetone for fresh cheese and includes a preliminary matrix solid-phase dispersion-extraction step before solid-phase extraction (SPE) clean-up by a Carbograph-4 cartridge. The second method uses a water/methanol solution (90:10, v/v) extraction at 150 degrees C before clean-up. The average recoveries of AFM1 from samples spiked at levels of 0.25-0.45 microg/kg, were 81-92% and the precision (RSD) ranged from 3 to 7% with the first method, whilst the average recoveries were 79-84%, and RSD ranged from 7 to 15% for the second method. Due to different matrix effect, the quantification limits were 0.019-0.025 microg/kg in the first case and 0.048-0.143 microg/kg in the second one, depending on cheese typology.     

Determination of benomyl residues in shiitake mushrooms (Lentinula edodes) by liquid chromatography with UV detection

A method is optimized to determine benomyl (as carbendazim derivative) in shiitake mushrooms. It is based on the extraction of the fungicide with an ethyl acetate-hexane mixture and a further analysis of the extract by high-performance liquid chromatography-UV. Mean recoveries are evaluated and range from 76% to 86% with relative standard deviation between 1.1% and 5.8%. The limit of quantitation (0.5 mg/Kg) is lower than the maximum residue level established by European legislation. The method is successfully applied to the analysis of shiitake mushrooms cultivated on eucalyptus logs treated with Benlate 500 (benomyl as active ingredient) under natural environmental conditions.