Fast and easy multiresidue method employing acetonitrile extraction/partitioning and "dispersive solid-phase extraction" for the determination of pesticide residues in produce

A simple, fast, and inexpensive method for the determination of pesticide residues in fruits and vegetables is introduced. The procedure involves initial single-phase extraction of 10 g sample with 10 mL acetonitrile, followed by liquid-liquid partitioning formed by addition of 4 g anhydrous MgSO4 plus 1 g NaCl. Removal of residual water and cleanup are performed simultaneously by using a rapid procedure called dispersive solid-phase extraction (dispersive-SPE), in which 150 mg anhydrous MgSO4 and 25 mg primary secondary amine (PSA) sorbent are simply mixed with 1 mL acetonitrile extract. The dispersive-SPE with PSA effectively removes many polar matrix components, such as organic acids, certain polar pigments, and sugars, to some extent from the food extracts. Gas chromatography/mass spectrometry (GC/MS) is then used for quantitative and confirmatory analysis of GC-amenable pesticides. Recoveries between 85 and 101% (mostly > 95%) and repeatabilities typically < 5% have been achieved for a wide range of fortified pesticides, including very polar and basic compounds such as methamidophos, acephate, omethoate, imazalil, and thiabendazole. Using this method, a single chemist can prepare a batch of 6 previously chopped samples in < 30 min with approximately 1 dollar (U.S.) of materials per sample.     

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.     

A rapid multiresidue method for determination of pesticides in fruits and vegetables by using acetonitrile extraction/partitioning and solid-phase extraction column cleanup

A modification of a rapid and inexpensive multiresidue method for determination of pesticides in fruits and vegetables (QuEChERS method) is presented. Samples were extracted by shaking with acetic acid-acetonitrile (1 + 99). Water was removed by liquid-liquid partitioning with magnesium sulfate and sodium acetate. The extract was subjected to a single solid-phase extraction (SPE) column cleanup, which produced a cleaner extract than did the dispersive SPE cleanup used in the original QuEChERS method. Recovery data were obtained for 316 pesticide residues, at levels ranging from 20 ppb to 1.0 ppm. Data were provided by 3 different laboratories. The modified QuEChERS method resulted in a 65% reduction in solvent usage, when compared with the traditional multiresidue methods previously used in our laboratories.     

Development and application of a dispersive solid-phase extraction method for the simultaneous determination of chloroacetamide herbicide residues in soil by gas chromatography-tandem mass spectrometry (GC-MS/MS)

In this study, a convenient and sensitive analytical method based on dispersive solid-phase extraction (dSPE) and gas chromatography-tandem mass spectrometry in tandem was developed for the simultaneous determination of six chloroacetamide herbicides (acetochlor, alachlor, metolachlor, metazachlor, butachlor and pretilachlor) in soil. Parameters that could influence the extraction efficiency such as the varieties of solvents, the amount of solvents and sorbents were investigated. The optimized extractions were performed by mixing 5.0 g of dried soil with 10.0 mL acetonitrile, 10.0 mL deionized water and 4.0 g sodium chloride, and then the extract was purified with 50.0 mg N-propyl ethylenediamine (PSA), 50.0 mg C18, 10.0 mg graphitized carbon black (GCB) and 100.0 mg MgSO₄ (5:5:1:10). At 5.0, 25.0 and 100.0 ng g^?1 fortification levels for each analyte, the average obtained recoveries ranged from 87.7% to 108.0% with relative standard deviation (RSD) between 3.8% and 10.9%. The soil matrix effect of the six compounds were lower than 11.0%. The linear relation was observed in the range of 5.0–500.0 ng g^?1 and the correlation coefficient (R²) of these compounds were higher than 0.998. The detection limits (LODs) were in the range of 0.2–1.0 ng g^?1, and the limits of quantification (LOQs) were between 0.8 and 2.2 ng g^?1. Comparing with the gas chromatography-electron capture detector (GC-ECD), the GC-tandem mass spectrometry (MS/MS) method can improve the anti-interference ability and thus get better separation of the chloroacetamide herbicides. Additionally, this method was verified to fit for soil samples with broad organic matter range (16.2 to 83.0 g kg^?1). The developed method was successfully applied for analysing 26 field soil samples collected from Dianchi lake basin in the southeast of China. About 42.0% soil samples were detected with these herbicides, of which butachlor was the most frequently detected and the highest concentration was up to 137.0 ng g^?1 in rape soil.     

Development and validation of a solid-phase extraction method coupled to high-performance liquid chromatography with ultraviolet-diode array detection for the determination of sulfonylurea herbicide residues in bovine milk samples

This study proposes a fast, simple and sensitive liquid chromatography diode array detector (LC/UV-DAD)-based method for the simultaneous determination of eight sulfonylurea herbicides (bensulfuron methyl, chlorsulfuron, metsulfuron methyl, primisulfuron methyl, rimsulfuron, thifensulfuron methyl, triasulfuron and tribenuron methyl) in bovine whole milk at concentrations lower than the default limit of 0.01 mg kg(-1) allowed by current legislation (Regulation EC/396/2005 and following Annexes). An effective one-step solid phase extraction (SPE) and clean up procedure was defined with use of Chem Elut cartridges, providing good recoveries for all the analytes tested and with no matrix effects affecting method accuracy. Separation of herbicides was obtained on a C(18) column by acetonitrile- water gradient elution. Method validation has been performed according to European Commission Decision 2002/657/EC criteria, in terms of linearity, recovery, precision, specificity, decision limit (CC(α)) and detection capability (CC(β)). Typical recoveries ranged between 78.4% and 99.7%, at the maximum residue limits (MRLs) levels established by Regulation EC/396/2005, with relative standard deviations (RSD) no larger than 10%.     

Determination of pesticide residues in foods by acetonitrile extraction and partitioning with magnesium sulfate: collaborative study

A collaborative study was conducted to determine multiple pesticide residues in fruits and vegetables using a quick, simple, inexpensive, and effective sample preparation method followed by concurrent analysis with gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/ tandem mass spectrometry (LC/MS/MS). For short, the method is known as QuEChERS, which stands for quick, easy, cheap, effective, rugged, and safe. Twenty representative pesticides were fortified in 3 matrixes (grapes, lettuces, and oranges) at 3 duplicate levels unknown to the collaborators ranging from 10 to 1000 ng/g. Additionally, 8 incurred pesticide residues were determined. Thirteen laboratories from 7 countries provided results in the study, and a variety of different instruments were used by collaborators. The QuEChERS procedure simply entails 3 main steps: (1) a 15 g homogenized sample is weighed into a 50 mL centrifuge tube to which 15 mL acetonitrile containing 1% HOAc is added along with 6 g MgSO4 and 1.5 g NaOAc, and the tube is shaken and centrifuged; (2) a portion of the extract is mixed with 3 + 1 (w/w) MgSO4-primary secondary amine sorbent (200 mg/mL extract) and centrifuged; and (3) the final extract is analyzed by GC/MS and LC/MS/MS. To detect residues <10 ng/g in GC/MS, large-volume injection of 8 microL is typically needed, or the extract can be concentrated to 4 g/mL in toluene, in which case 2 microL splitless injection is used. In the study, the averaged results for data from 7-13 laboratories (not using internal standardization) for the 18 blind duplicates at the 9 spiking levels in the 3 matrixes are as follows [%recovery and reproducibility relative standard deviation (RSD(R), %)]: atrazine, 92 (18); azoxystrobin, 93 (15); bifenthrin, 90 (16); carbaryl, 96 (20); chlorothalonil, 70 (34); chlorpyrifos, 89 (25); cyprodinil, 89 (19); o,p'-DDD, 89 (18); dichlorvos, 82 (21); endosulfan sulfate, 80 (27); imazalil, 77 (33); imidacloprid, 96 (16); linuron, 89 (19); methamidophos, 87 (17); methomyl, 96 (17); procymidone, 91 (20); pymetrozine, 69 (19); tebuconazole, 89 (15); tolylfluanid (in grapes and oranges), 68 (33); and trifluralin, 85 (20). For incurred pesticides, kresoxim-methyl (9.2 +/- 3.2 ng/g) and cyprodinil (112 +/- 18) were found in the grapes; permethrins (112 +/- 41), lamda-cyhalothrin (58 +/- 11), and imidacloprid (12 +/- 2) were determined in the lettuces; and ethion (198 +/- 36), thiabendazole (53 +/- 8), and imazalil (13 +/- 4) were determined in the oranges. Chlorpyrifosmethyl (200 ng/g) was used as a quality control standard added during sample homogenization and yielded 86% recovery and 19% RSD(R). Intralaboratory repeatabilities for the method averaged 9.8% RSD for all analytes. The results demonstrate that the method is fit-for-purpose to monitor many pesticide residues in fruits and vegetables, and the Study Director recommends that it be adopted Official First Action.     

Determination of the nucleosides and nucleobases in Tuber samples by dispersive solid-phase extraction combined with liquid chromatography-mass spectrometry

A simple, fast and inexpensive method based on dispersive solid phase extraction (DSPE) combined with LC–MS was developed for simultaneous determination of 7 nucleosides and nucleobases (i.e., adenine, hypoxanthine, uridine, adenosine, guanine, guanosine, and inosine) in Tuber fruiting-bodies and fermentation mycelia. The DSPE procedure was firstly introduced to remove the protein interference from sample solutions, and D3520 macroporous resin was chosen as the DSPE sorbent because of its high removal capability on protein interferences, but low adsorption rate on analytes. Besides, key parameters on DSPE procedure (i.e., macroporous resin type, macroporous resin amount, methanol concentration, and vortex time) were optimized, and the protein removal efficacy could achieve about 95% after the process optimization. Though the method validation test, the DSPE-LC–MS method was confirmed to be precise, accurate and sensitive, and the column blinding problem was solved successfully. By using this established method, the total amount of nucleosides and nucleobases in the fermentation mycelia was determined to range from 4881.5 to 12,592.9 μg g⁻¹, which was about 2–25 times higher than the fruiting-bodies (from 498.1 to 2274.1 μg g⁻¹). The formulation of nucleosides and nucleobases in the fermentation mycelia maintained relatively constant, while the formulation in Tuber fruiting-bodies varied significantly with their species. Hierarchical cluster analysis (HCA) showed the formulation similarity of nucleosides and nucleobases between Tuber fermentation mycelia and the fruiting-bodies of Tuber indicum and Tuber himalayense. From the viewpoint of nucleosides and nucleobases, this work confirms the potentiality of Tuber fermentation mycelia as the alternative resource for its fruiting-bodies.     

Comparison of solvent extraction and solid-phase extraction for the determination of organochlorine pesticide residues in water.

Solid-phase extraction (SPE) of organochlorine pesticide residues from environmental water samples was evaluated using octadecyl (C18)-bonded porous silica. The efficiency of SPE of these pesticide residues from reagent water samples at 1-5 micrograms dm-3 levels was compared with those obtained by solvent extraction with hexane and Freon TF (trichlorotrifluoroethane). Average recoveries exceeding 80% for these organochlorine pesticides were obtained via the SPE method using small cartridges containing 100 mg of 40 microns C18-bonded porous silica. The average recovery by solvent extraction with hexane and Freon TF exceeded 90% in both instances. It was concluded that the recoveries and precision for the SPE of organochlorine pesticides were poorer than those for the solvent extraction method. Organochlorine pesticide residue levels in environmental water samples from two major rivers flowing through predominantly rice-growing areas were monitored by gas chromatography using the solvent extraction method with hexane. Exceptionally high levels of organochlorine pesticide residues such as BHC, DDT, heptachlor, endosulfan and dieldrin were found in these water samples.     

聚多巴胺涂敷的聚酰胺-胺功能化二氧化硅复合材料用于水样中苯甲酰脲类杀虫剂的分散微固相萃取北大核心CSCD

近年来,由农药残留导致的环境污染问题已引起社会的广泛关注,开发便捷高效的分析方法对农药残留进行检测和监测十分必要。研究设计并成功制备了聚多巴胺涂敷的聚酰胺-胺树状分子功能化的二氧化硅复合材料(SiO-PAMAM-PDA),并采用透射电镜对其进行表征。开发了以此复合材料为吸附剂的分散微固相萃取方法(D-μ-SPE),并结合高效液相色谱对水基质中的4种苯甲酰脲类杀虫剂(BUs)残留进行了富集检测。多巴胺结构中含有丰富的苯环、氨基及羟基,可与目标物形成氢键、π-π相互作用,从而增强了材料对苯甲酰脲的萃取能力。对吸附剂用量、萃取时间等可能影响萃取效率的条件进行了单因素优化。在最优条件下,该方法的线性范围在10~500μg/L之间,根据3倍信噪比(S/N)计算所得的检出限(LOD)为1.1~2.1μg/L,回收率为82.8%~94.1%,相对标准偏差(RSD)为2.1%~8.0%。将建立的方法与已报道的以苯甲酰脲作为目标物的方法进行了对比,发现方法样品用量及萃取剂用量均较少,且所需前处理时间较短,有机溶剂消耗也较少,为苯甲酰脲类农药的检测提供了更快速、绿色的选择。为评估所开发方法的实际样品适用性,将其应用于3种河水样品中4种苯甲酰脲类杀虫剂的分析检测,所得回收率及RSD分别为69.5%~99.4%和0.2%~9.5%,表明此方法在实际样品中同样具有较高的准确性和精密度。     

Comparison of solid-phase extraction and micro-solid-phase extraction for liquid chromatography/mass spectrometry analysis of pesticides in water samples

Our recent on-line solid-phase extraction (SPE) device for micro-liquid chromatography, known as micro-solid-phase extraction (microSPE), was compared with traditional SPE for the analysis, from aqueous samples, of 4 pesticides belonging to different classes. Two different kinds of adsorbents, C18 and graphitized carbon black, were tested. A 2-stage ion trap mass spectrometer, equipped with homemade microflow electrospray ion (ESI) source, was used. Detection limits with a signal-to-noise ratio of 3:1 for both extraction methods were in the range of 0.1 microg/L for all compounds. However, better recoveries were obtained when microSPE traps were used.     

Development of solid-phase extraction and solid-phase microextraction methods for the determination of chlorophenols in cork macerate and wine samples

Tri-, tetra- and pentachlorophenol (TCP, TeCP and PCP) can be considered the precursors in the formation of corresponding chloroanisoles, known to be powerful odorants in corks and wine. Determining the presence of these chlorophenolic compounds in cork soaking solutions (ethanol/water mixtures, 12% (v/v) ethanol used for cork quality control testing), or in wine can be achieved by acetylation/gas chromatography electron-capture detection. In order to reach the required sensitivity, a previous preconcentration step is necessary. Solid-phase extraction (SPE) and headspace solid-phase microextraction (HS-SPME) have given good results for the preconcentration of TCP, TeCP and PCP in such matrices. The use of Oasis HLB cartridges gives acceptable recoveries for the three compounds when different volumes (50-250 mL) of cork macerate with concentrations ranging from 20 to 150 ng/L are processed. Preconcentration based on HS-SPME has also been optimised with a 100 microm polydimethylsiloxane fibre and in situ derivatization. The HS-SPME method allows chlorophenols in a cork soaking solution and in wine to be determined with a limit of detection of 1 ng/L for each compound (in cork macerate) and a repeatability of around 0.5%-5% (n=8) for a concentration level of 30 ng/L.     

Development of a solid-phase microextraction method for direct determination of pentachlorophenol in paper and board samples: Comparison with conventional extraction method

A solid-phase microextraction (SPME) method has been developed for the determination of pentachlorophenol (PCP) in paper and board samples. The analytical procedure involves direct extraction of PCP from paper and board samples and determination by gas chromatography with electron capture detection (GC-ECD). Two kinds of commercially available fibres; 100 microm polydimethylsiloxane (PDMS), apolar, and 85 microm polyacrylate (PA), quite polar, were evaluated to determine the extraction efficiency of pentachlorophenol. Parameters affecting the extraction process, such as temperature and time, were studied. Moreover, time of desorption and the effect of addition of salt were also investigated. The optimized procedure was applied to the analysis of pentachlorophenol (PCP) in five samples of virgin and recycled paper and board. The PCP content was determined by GC-ECD. To evaluate the effectiveness of the proposed method, it was compared with conventional extraction method with liquid-liquid extraction and derivatization. Detection limit of 0.015 microg/g for PCP in paper was achieved with a RSD of 14%.     

Molecularly imprinted solid-phase extraction combined with ultrasound-assisted dispersive liquid-liquid microextraction for the determination of four Sudan dyes in sausage samples

A simple and highly selective molecularly imprinted solid-phase extraction (MISPE) combined with ultrasound-assisted dispersive liquid-liquid microextraction (DLLME) was developed for the determination of four Sudan dye (I, II, III, and IV) residues in sausage products. The novel molecularly imprinted microspheres (MIMs) synthesized by aqueous suspension polymerization using phenylamine-naphthol as the dummy template show high affinity to the four Sudan dyes and were applied as selective sorbents of MISPE-DLLME to overcome the drawbacks of template leakage in quantitative analysis. Good linearity was obtained in a range of 0.005-2.0 μg g(-1) and the average recoveries of the four Sudan dyes at three spiked levels ranged from 86.3 to 107.5%. The MISPE-DLLME-HPLC protocol significantly improved the purification and enrichment of the analytes and eliminated the template leakage of the conventional MISPE on quantitative analysis.     

Comparison of the efficiency of different GLC multi-residue methods on crops containing pesticide residues

Summary The efficiency of the extraction methods with acetone and with ethyl acetate are compared with regard to the multi-pesticide residue determination in fruits and vegetables. The ethyl acetate-method gave higher recoveries for polar pesticides and seems somewhat easier, quicker and cheaper in handling but some co-extractives in the GC-extract are observed. In general, both methods gave acceptable and equivalent recoveries for the pesticides tested.     

Development of a multiresidue method for analyzing herbicide and fungicide residues in bovine milk based on solid-phase extraction and liquid chromatography-tandem mass spectrometry

The adverse effect of reactive chemical residues on the quality of drug products has necessitated the determination of low-molecular-weight aldehydes in pharmaceutical excipients. An analytical methodology for the detection of trace amounts of C1-C8 aliphatic aldehydes and benzaldehyde in excipients is described. The proposed procedure is based on the derivatization of aldehydes in aqueous solution with O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA), followed by static headspace gas chromatographic (SHS-GC) analysis of PFBHA aldehyde oximes with negative chemical ionization (NCI) MS detection. The method developed was demonstrated to be simple, selective, sensitive, and was successfully applied to the screening of aldehydes at sub-microg/g levels in over 30 typical excipients. The most abundant aldehydes found in the samples were formaldehyde and acetaldehyde, for which a rapid and reliable routine quantification method by readily available SHS-GC instrumentation coupled with flame-ionization detection was also developed and validated.     

Dispersive solid-phase extraction cleanup combined with accelerated solvent extraction for the determination of carbamate pesticide residues in Radix Glycyrrhizae samples by UPLC-MS-MS

Dispersive solid-phase extraction (DSPE) cleanup combined with accelerated solvent extraction (ASE) is described here as a new approach for the extraction of carbamate pesticides in Radix Glycyrrhizae samples prior to UPLC-MS-MS. In the DSPE-ASE method, 15 carbamate pesticides were extracted from Radix Glycyrrhizae samples with acetonitrile by the ASE method at 60 °C with a 5 min heating time and two static cycles. Cleanup of a 1 mL aliquot of the extract by the DSPE method used 20 mg PSA (primary secondary amine), 50 mg Al(2)O(3)-N, and 20 mg GCB (graphitized carbon black) (as cleanup sorbents) under the determined optimum conditions. The linearity of the method was in the range of 10 to 200 ng/mL with correlation coefficients (r(2)) of more than 0.996. The limits of detection were approximately 0.2 to 5.0 μg/kg. The method was successfully used for the analysis of target pesticides in Radix Glycyrrhizae samples. The recoveries of the carbamate pesticides at the spiking levels of 50, 100, and 200 μg/kg ranged from 79.7% to 99.3% with relative standard deviations lower than 10%. This multi-residue analytical method allows for a rapid, efficient, sensitive and reliable determination of target pesticides in Radix Glycyrrhizae and other medicinal herbs.     

Determination of nitrate esters in water samples Comparison of efficiency of solid-phase extraction and solid-phase microextraction

This paper deals with comparison of efficiency of extraction techniques (solid-phase extraction, SPE and solid-phase microextraction, SPME) used for extraction of nitrate esters (ethyleneglycoldinitrate, EGDN and nitroglycerin, NG), representing the first step of the method of quantitative determination of trace concentrations of nitrate esters in water samples. EGDN and NG are subsequently determined by means of high-performance liquid chromatography with ultraviolet detection (HPLC-UV). Optimization of SPE and SPME conditions was carried out using model water samples. Seven SPE cartridges were tested and the conditions were optimized (type of sorbent, type and volume of solvent to be used as eluent). For both nitrate esters the limit of detection (LOD) and the limit of quantification (LOQ) obtained using SPE/HPLC-UV were 0.23 microg mL(-1) and 0.70 microg mL(-1), respectively. Optimization of SPME conditions: type of SPME fibre (four fibres were tested), type and time of sorption/desorption, temperature of sorption. PDMS/DVB (polydimethylsiloxane/divinylbenzene) fibre coating proved to be suitable for extraction of EGDN and NG. For this fibre the LOD and the LOQ for both nitrate esters were 0.16 microg mL(-1) and 0.50 microg mL(-1), respectively. Optimized methods SPE/HPLC-UV and SPME/HPLC-UV were then used for quantitative determination of nitrate esters content in real water samples from the production of EGDN and NG.     

分散固相萃取-气相色谱-串联质谱法测定蔬菜中107种农药的残留量

采用分散固相萃取-气相色谱-串联质谱(QuEChERS-GC-MS/MS)建立了蔬菜中107种农药残留量的分析方法。样品由含1%冰醋酸的正己烷饱和乙腈提取、分散固相萃取法净化,采用气相色谱-串联质谱方法在分时段选择反应监测模式下进行测定,外标法定量。所有农药在0.05～1 mg/L范围内线性关系均良好;所有农药的方法定量限(LOQ)均低于10 μg/kg;在10 μg/kg的添加水平下,大蒜、青刀豆、萝卜和菠菜4种基质中绝大多数农药的平均回收率处于60%～130%之间,相对标准偏差(RSD)不大于15.3%。该方法不仅能用于多种蔬菜基质中107种农药残留的检测,而且还能较好地解决本底成分相当复杂的大蒜基质极易出现的干扰问题。     

Derivative spectrum chromatographic method for the determination of trimethoprim in honey samples using an on-line solid-phase extraction technique

A simple, selective and rapid analytical method for determination of trimethoprim (TMP) in honey samples was developed and validated. This method is based on a SPE technique followed by HPLC with photodiode array detection. After dilution and filtration, aliquots of 500 μL honey samples were directly injected to an on-line SPE HPLC system. TMP was extracted on an RP SPE column, and separated on a hydrophilic interaction chromatography column during HPLC analysis. At the first detection step, the noise level of the photodiode array data was reduced with two-dimensional equalizer filtering, and then the smoothed data were subjected to derivative spectrum chromatography. On the second-derivative chromatogram at 254 nm, the limit of detection and the limit of quantification of TMP in a honey sample were 5 and 10 ng/g, respectively. The proposed method showed high accuracy (60-103%) with adequate sensitivity for TMP monitoring in honey samples.