液相色谱-串联质谱法快速筛查测定浓缩果蔬汁中的156种农药残留

建立了浓缩果蔬汁中156种农药多残留的液相色谱-电喷雾串联质谱(LC-ESI-MS/MS)测定方法。样品用1%醋酸乙腈溶液萃取,经Waters Sep-Pak Vac固相萃取柱净化,乙腈-甲苯(体积比为3∶1)洗脱,旋转蒸发浓缩,用乙腈-水（体积比为3∶2）溶解,以Agilent ZORBAX SB-C18色谱柱分离,以电喷雾电离串联质谱在正离子多反应监测(MRM)模式下进行测定。对156种农药在5种浓缩果蔬汁(橙汁、苹果汁、葡萄汁、白菜汁、胡萝卜汁)中两个添加水平下的回收率进行了测定,回收率范围为57.2%～122.7%,相对标准偏差范围为0.9%～19.8%。方法的检出限(S/N=3)和定量限(S/N=10)范围分别为0.10～56.77 μg/kg和0.33～189.23 μg/kg。该方法样品前处理简单、快速、分析时间短,灵敏度、准确度和精密度均符合农药多残留检测技术的要求,适用于苹果汁、橙汁、葡萄汁、白菜汁、胡萝卜汁等浓缩果蔬汁中156种农药多残留的快速筛查测定。     

Analysis of carbamate and phenylurea pesticide residues in fruit juices by solid-phase microextraction and liquid chromatography-mass spectrometry

A new analysis method to detect carbamates and phenylurea pesticide residues in fruit juices was developed using solid-phase microextraction (SPME) coupled with liquid chromatography-single quadrupole mass spectrometry (LC/MS) and liquid chromatography-quadrupole ion trap mass spectrometry (LC/QIT-MS). The pesticide residues present in watery matrices as fruit juices were extracted using three types of fibers: 50-microm Carbowax/templated resin (CW/TPR), 60-mum poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB) and 85-microm polyacrylate. The different extraction conditions were evaluated choosing as the best parameters 90 min (time), 20 degrees C (temperature) and 1 ml (volume). After extraction, the desorption (in a static mode) was performed in the specific interface chamber SPME/HPLC, previously filled with 70% methanol and 30% water. The best recoveries, evaluated at two fortification levels (0.2 and 0.5 mg kg(-1)) in fruit juices, were obtained using PDMS/DVB and CW/TPR fibers, and ranged from 25 to 82% (monolinuron, diuron and diethofencarb), with relative standard deviations (RSDs) from 1 to 17%. All the limits of quantification (LOQs) were in the range of 0.005-0.05 microg ml(-1) and, in any case, equal to, or lower than, maximum residue limits (MRLs) established by Italian and Spanish legislations. The mass spectrometry analyses were carried out using an electrospray ionization (ESI) source operating in the positive mode both for single quadrupole and for QIT mass analysers, operating in selected ion monitoring (SIM) and in multiple reaction monitoring (MRM) modes, respectively. The proposed new method can be applied to the determination of selected pesticides in real samples of fruit juices.     

Validation of a solid-phase microextraction method for the determination of organophosphorus pesticides in fruits and fruit juice

A method for the determination of organophosphorus pesticides (diazinon, fenitrothion, fenthion, quinalphos, triazophos, phosalon and pyrazophos) in fruit (pears) and fruit juice samples was developed and validated. The samples were diluted with water, extracted by solid-phase microextraction (SPME) and analysed by gas chromatography (GC) using a flame photometric detector in phosphorous mode. Limits of detection of the method for fruit and fruit juice matrices were below 2 micrograms/kg for all pesticides. Relative standard deviations for triplicate analyses of samples fortified at 25 micrograms/kg of each pesticide were not higher than 8.7%. Recovery tests were performed for concentrations between 25 and 250 micrograms/kg. Mean recoveries for each pesticide were all above 75.9% and below 102.6% for juice, and between 70 and 99% for fruit except for pyrazophos in the fruit sample (with mean recovery of 53%). Therefore, the proposed method is applicable in the analysis of pesticides in fruit matrices and the use of the method in routine analysis of pesticide residues is discussed.     

超高效液相色谱-串联质谱法快速测定浓缩果汁中噻菌灵和多菌灵的残留量

建立了同时测定浓缩果汁中噻菌灵和多菌灵残留的超高效液相色谱-串联质谱快速检测法。样品用乙酸乙酯提取,以ACQUITY UPLC BEH C18色谱柱(50 mm×2.1 mm, 1.7 μm)进行超高效液相色谱分离,以电喷雾电离串联质谱正离子多反应监测(MRM)模式进行测定,以基质匹配标准溶液外标法定量。结果表明:在试验条件下,噻菌灵和多菌灵在0.5~10 μg/kg范围内线性关系良好,相关系数大于0.99,不同基质中的检出限(S/N=3)范围为0.12~0.23 μg/kg。在0.5、1.0和5.0 μg/kg 3个水平下噻菌灵和多菌灵的加标回收率为76.98%~108.7%,相对标准偏差(RSD)为2.95%~9.99%。同时,本研究对浓缩果汁中噻菌灵和多菌灵残留检测的基质效应进行了考察。本方法具有操作简便、快速、准确的特点,可用于浓缩果汁中噻菌灵和多菌灵残留量的日常检测。     

Determination of ink photoinitiators in packaged beverages by gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry

A new analytical method, using gas chromatography-mass spectrometry (GC/MS) and liquid chromatography-mass spectrometry (LC/MS) techniques, was developed for the determination in packaged food beverages of five ink photoinitiator residues: 2-isopropylthioxanthone (ITX), benzophenone, 2-ethylhexyl-4-dimethylaminobenzoate (EHDAB), 1-hydroxycyclohexyl-1-phenyl ketone (IRGACURE 184) and ethyl-4-dimethylaminobenzoate (EDAB). Samples were extracted from selected beverages (milk, fruit juices and wine) and relative packagings, using n-hexane and dichloromethane, respectively, purified on solid-phase extraction (SPE) silica gel cartridges, and then analyzed in GC/MS and LC/MS. The recovery percentages, obtained spiking the beverage samples at concentrations of 4 and 10 microgl(-1) with a standard mixture of photoinitiators, were in the range 42-108% (milk), 50-84% (wine), and 48-109% (fruit juices). The repeatability of the method was assessed in all cases by the % of correlation value, that was lower than 19%. The lowest limits of detection (LODs) and limits of quantification (LOQs), obtained using GC/MS, were in the range 0.2-1 and 1-5 microgl(-1), respectively. The method was applied to the analysis of forty packaged food beverages (milk, fruit juices and wine samples). The most significant contamination was that of benzophenone, found in all samples in a concentration range of 5-217mugl(-1). Its presence was confirmed by an LC/Atmospheric-Pressure PhotoIonization (APPI)/MS/MS analysis. The photoinitiator (EHDAB) was found in eleven out of forty beverages in a concentration range of 0.13-0.8 microgl(-1). Less important was the ITX contamination, found in three out of forty samples in a range 0.2-0.24 microgl(-1). The work proposes a new method to analyze ink photoinitiator residues in polycoupled carton packaging and in contained food beverages.     

Application of liquid chromatography with electrospray tandem mass spectrometry to the determination of a new generation of pesticides in processed fruits and vegetables

This paper describes a method for the sensitive and selective determination of 24 new pesticide residues (azoxystrobin, trifloxystrobin, kresoxim-methyl, fenazaquin, indoxacarb, fenothiocarb, furathiocarb, benfuracarb, imidachloprid, dimethomorph, fenpyroximate, hexythiazox, tebufenpyrad, tebufenozide, difeconazole, fenbuconazole, flusilazole, paclobutrazol, tebuconazole, tetraconazole, bromuconazole, etofenprox, fenhexamid, pyridaben) in apple puree, concentrated lemon juice and tomato puree. A miniaturized extraction-partition procedure requiring small amounts of non-chlorinated solvents was used. The extracts are analyzed by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS) without any further clean-up step. The pesticides are separated on a reversed-phase polar column using a gradient elution. Fifty-five simultaneous MS-MS transitions of precursor ions were monitored (two or three for each pesticide). Studies at fortification levels of 0.001-0.020 and 0.010-0.200 mg/kg gave mean recoveries ranging from 76 to 106% for all compounds, except for imidacloprid, with (R.S.D.s) < or = 15%. The excellent sensitivity and selectivity of LC-MS-MS method allowed quantitation and identification at low levels also in difficult matrices with a run time of 20 min. With the developed method almost 100 samples of commercial fruit products (nectars, juices, purees) were analyzed. None of samples contained residues higher than 0.010 mg/kg.     

Evaluation of pesticide residue in grape juices and the effect of natural antioxidants on their degradation rate

Various studies have been drawn toward the beneficial properties of fruit juices because they have several components, such as phenols, vitamins, and flavonoids, with antioxidant effects. However, fruit juices can also contain residues of pesticides used as standard pest control methods in crops. Many of these pesticides are degraded through oxidative mechanisms, and their persistence in juices can be enhanced by antioxidants. This study covers the degradation of four pesticides, aldicarb, demeton-S-methyl, fenamiphos, and methiocarb, to their respective sulfoxide and sulfone in grape juices, water (pH 3.5) and water (pH 3.5) with quercetin (one of the most important flavonoids of grape) added in an attempt to establish whether the presence of antioxidants can affect the degradation rate of pesticides. For this purpose, a multiresidue method based on solid-phase extraction (SPE) was developed for the simultaneous determination of these pesticides and their metabolites in commercial juices. The extraction procedure was carried out in C₁₈ columns. The subsequent elution of pesticides was performed with dichloromethane prior to the determination by liquid chromatography-tandem mass spectrometry (LC-MS/MS), using two precursor-product ion transitions. Average recoveries for all the pesticides studied were higher than 80%, with relative standard deviations lower than 15% in the concentration range 0.005–0.05 μg/mL, and the quantification limits achieved ranged from 0.1 to 4.6 μg/L. The results demonstrated that degradation was slower in fruit juices and aqueous solutions with quercetin than in water. Several commercial grape juices were also analyzed to establish the levels of these pesticides. Methiocarb, fenamiphos, and demeton-S-methyl were found at low levels in some samples.     

Determination of thiabendazole in fruit juices by a new monoclonal enzyme immunoassay

A competitive, indirect enzyme-linked immunosorbent assay (ELISA) for thiabendazole has been developed and applied to the analysis of fruit juices spiked with this fungicide. The immunoassay is based on a new monoclonal antibody derived from a hapten functionalized at the nitrogen atom in the 1-position of the thiabendazole structure. To our knowledge, such a structure has not been previously used to obtain antibodies to thiabendazole. The I50 value and the detection limit of the ELISA for standards were 0.2 and 0.05 ng/mL, respectively. Fruit juices were analyzed by diluting samples in assay buffer, without extraction or cleanup. Samples were not even centrifuged or filtered to remove fruit pulp. Under these conditions, the immunoassay was able to accurately determine thiabendazole down to 1 ng/mL in orange and grapefruit juices, down to 5 ng/mL in banana juice, and down to 20 ng/mL in apple and pear juices. Sensitivity differences of the ELISA were caused by the minimum dilution required by each juice to minimize matrix effects: 1/10 for orange and grapefruit juices, 1/50 for banana juice, and 1/100 for apple and pear juices. In an attempt to further increase the sensitivity of the immunoassay for matrixes showing the strongest interferences, apple and pear juices spiked with thiabendazole at low levels (1-20 ng/mL) were extracted with ethyl acetate before analysis. This simple procedure entailed a significant reduction of matrix effects, which in fact allowed us to determine accurately as low as 5 ng/mL thiabendazole in apple and pear juices. Irrespective of whether samples were analyzed by the direct dilution method or after extraction, the simplicity, sensitivity, and sample throughput of this monoclonal immunoassay makes it a very convenient method for the routine monitoring of thiabendazole residues in fruit juices.     

Determination of five pesticide residues in oranges by matrix solid-phase dispersion and liquid chromatography to estimate daily intake of consumers.

Residues of benzoylphenylurea insecticides (diflubenzuron, hexaflumuron, and flufenuxuron), carboxamide acaricides (hexythiazox), and carbamate insecticides (benfuracarb) were determined in 150 orange fruit samples from September 1998 to June 1999, to estimate exposure of the Valencian population to oranges contaminated with these newly developed pesticides. The method for monitoring these residues is based on matrix solid-phase dispersion and liquid chromatography with UV or atmospheric pressure chemical ionization/mass spectrometry (APCI/MS) detection. Orange samples representing 11 varieties were collected from an agricultural cooperative and examined for the 5 pesticides. In 74.6% of all analyzed samples, the pesticide residues were below detection limits, which ranged from 0.002 to 0.05 mg/kg. Residues were detected in 25.4% of the samples, with higher incidences of diflubenzuron, flufenuxuron, hexythiazox, and benfuracarb; hexaflumuron residues were detected only occasionally. Two different pesticides exceeded maximum residue limits (MRLs) in 4 (2.7%) of the orange samples. Diflubenzuron surpassed 1 mg/kg MRL in 3 samples and flufenuxuron exceeded the 0.3 mg/kg MRL in 3 samples. The estimated daily intake of the 5 pesticide residues during the period was 0.077 microg/kg body weight per day. This value is much lower than the total admissible daily intake proposed by the Food and Agricultural Organization and the World Health Organization.     

Simultaneous determination of 103 pesticide residues in tea samples by LC‐MS/MS

A simple and sensitive method was developed and validated for the simultaneous determination of 103 pesticide residues in tea by LC‐MS/MS. For the analysis of the pesticide with polarity, thermal lability or low volatility, this LC‐MS/MS method has an advantage over GC. In this work, residual pesticides were extracted from the tea sample with ACN and then purified using Carb‐NH₂ SPE cartridges. Using the multiple reaction monitoring mode, the pesticides were quantified and identified by the most abundant and characteristic fragment ions. The recoveries obtained for each pesticide ranged between 65 and 114% at three spiked concentration levels. The intra‐day precisions were lower than 19.6%. Good linear relationships were observed with the correlation coefficients r² >0.996 for all analytes. The established method was successfully applied to the determination of pesticide residues in real tea samples.     

Pesticide Residues in Vegetables and Fruits from Farmer Markets and Associated Dietary Risks

The use of pesticides leads to an increase in agricultural production but also causes harmful effects on human health when excessively used. For safe consumption, pesticide residues should be below the maximum residual limits (MRLs). In this study, the residual levels of pesticides in vegetables and fruits collected from farmers’ markets in Sharkia Governorate, Egypt were investigated using LC-MS/MS and GC-MS/MS. A total number of 40 pesticides were detected in the tested vegetable and fruit samples. Insecticides were the highest group in detection frequency with 85% and 69% appearance in vegetables and fruits, respectively. Cucumber and apple samples were found to have the highest number of pesticide residues. The mean residue levels ranged from 7 to 951 µg kg⁻¹ (in vegetable samples) and from 8 to 775 µg kg⁻¹ (in fruit samples). It was found that 35 (40.7%) out of 86 pesticide residues detected in vegetables and 35 (38.9%) out of 90 pesticide residues detected in fruits exceeded MRLs. Results for lambda-cyhalothrin, fipronil, dimothoate, and omethoate in spinach, zucchini, kaki, and strawberry, respectively, can cause acute or chronic risks when consumed at 0.1 and 0.2 kg day⁻¹. Therefore, it is necessary for food safety and security to continuously monitor pesticide residues in fruits and vegetables in markets.     

液相色谱-串联质谱法测定蔬菜和水果中硝苯菌酯的残留量

建立了一种通过检测硝苯菌酯(2,4-dinitro-6-(1-methylheptyl) phenyl crotonate, 2,4-DNOPC)相应的水解产物2,4-二硝基-6-(1-甲基庚基)苯酚(2,4-dinitro-6-(1-methylheptyl) phenol, 2,4-DNOP)来测定蔬菜和水果中2,4-DNOPC残留量的液相色谱-电喷雾串联质谱(LC-ESI-MS/MS)检测方法。蔬菜和水果样品用丙酮-甲醇-盐酸的混合液进行液-液分配提取,在碱性条件下超声水解后再进行液-液分配提取,然后进行LC-MS/MS测定。2,4-DNOPC在6种蔬菜和水果中的回收率试验结果表明,2,4-DNOPC在甘蓝中的添加回收率为89.7%～93.3%,相对标准偏差(RSD)为6.3%～8.5%;在黄瓜中的添加回收率为87.7%～95.1%, RSD为5.8%～10.4%;在番茄中的添加回收率为89.3%～96.0%, RSD为6.8%～9.2%;在苹果中的添加回收率为92.0%～98.3%, RSD为5.1%～10.3%;在梨中的添加回收率为89.0%～95.0%, RSD为5.3%～10.2%;在葡萄中的添加回收率为81.2%～95.8%, RSD为5.8%～10.4%。2,4-DNOPC在6种蔬菜和水果的最低检测浓度均为0.01 mg/kg。该检测方法样品前处理简单、快速,分析时间短,灵敏度、准确度和精密度均符合农药残留检测要求,适用于蔬菜和水果中硝苯菌酯残留量的检测。     

大体积进样气质联用法测定浓缩果蔬汁中农药的残留量

建立了气相色谱-质谱同时检测果蔬汁中多类农药残留的方法。利用Agilent仪器的保留时间锁定功能（RTL）及相应的质谱农药库，建立了多类农药选择离子监测的分组时间窗，避免了仪器维护后农药保留时间烦琐的更新过程，保证了农药保留时间的重复性；探讨了具有溶剂排空模式的程序升温蒸发（PTV）对大体积进样的作用。通过对分流排空量、吹扫时间、PTV温度及其进样体积等PTV参数的优化，提高了检测灵敏度。通过同位素标汜农药作为内标，GC—MS的定量可靠性得到改善。     

Monitoring multi-class pesticide residues in fresh fruits and vegetables by liquid chromatography with tandem mass spectrometry

A new analytical method was developed using liquid chromatography with tandem mass spectrometry for the routine analysis of 31 multi-class pesticide residues and applied to approximately 50 fresh fruit and vegetable samples (green bean, cucumber, pepper, tomato, eggplant, watermelon, melon and zucchini). Extraction of the pesticides with ethyl acetate was carried out. The optimal ionisation conditions were selected for each pesticide in the same run. The procedure was validated and the values of some merit figures, such as recovery, precision, linear range, detection limit and quantification limit for each pesticide were calculated together with its calculated expanded uncertainty (U). The average recoveries in cucumber obtained for each pesticide ranged between 74 and 105% at two different fortification levels (n = 10 each) that ranged between 9 and 250 ng g(-1) (depending on the pesticide). The uncertainty associated to the analytical method was lower than 23% for all compounds tested. The calculated limits of detection and quantitation were typically <1 ng g(-1) that were much lower than the maximum residue levels established by European legislation.     

Establishment of an LC-MS/MS Method for the Determination of 45 Pesticide Residues in Fruits and Vegetables from Fujian,China

Pesticide residues in food have become an important factor seriously threatening human health. Therefore, this study was conducted to determine the pesticide residues in fruits and vegetables commonly found in Fujian, China, with the aim of constructing a simple and rapid method for pesticide residue monitoring. We collected 5607 samples from local markets and analyzed them for the presence of 45 pesticide residues. A fast, easy, inexpensive, effective, robust, and safe (QuEChERS) multi-residue extraction method followed by liquid chromatography equipped with triple-quadrupole mass spectrometry (LC-MS/MS) was successfully established. This 12-min-long analytical method detects and quantifies pesticide residues with acceptable validation performance parameters in terms of sensitivity, selectivity, linearity, the limit of quantification, accuracy, and precision. The linear range of the calibration curves ranged from 5 to 200 mg/L, the limits of detection for all pesticides ranged from 0.02 to 1.90 μg/kg, and the limits of quantification for the pesticides were 10 μg/kg. The recovery rates for the three levels of fortification ranged from 72.0% to 118.0%, with precision values (expressed as RSD%) less than 20% for all of the investigated analytes. The results showed that 726 (12.95%) samples were contaminated with pesticide residues, 94 (1.68%) samples exceeded the maximum residue limit (MRL) of the national standard (GB 2763-2021, China), 632 (11.23%) samples were contaminated with residues below the MRL, and 4881 (87.05%) samples were pesticide residue-free. In addition, the highest number of multiple pesticide residues was observed in bananas and peppers, which were contaminated with acetamiprid, imidacloprid, pyraclostrobin, and thiacloprid.     

Development of GC–MS/MS method for environmental monitoring of 49 pesticide residues in food commodities in Al-Rass,Al-Qassim region,Saudi Arabia

The harmful effects of pesticide residues are a threat to our health. Therefore, the current study aimed to validate a simple method for the determination of pesticide residues in commonly consumed fruits and vegetables from Al-Rass, Al-Qassim region, Saudi Arabia. A total of 1430 samples were collected from a local market and then analyzed for monitoring of 49 pesticide residues. A quick, easy, cheap, effective, rugged, and safe (QuEChERS) multi-residue extraction method followed by gas chromatography equipped with triple-quadrupole mass spectrometry (GC–MS/MS) was successfully implemented. This 17-min-run analytical method detects and quantifies pesticide residues with acceptable validation performance parameters in terms of sensitivity, selectivity, linearity, the limit of quantification, accuracy, and precision. The linear range of the calibration curves ranged from 10 to 300 µg/L, all the pesticide LODs ranged from 0.0005 to 0.0024 mg/kg, and the pesticide LOQs ranged from 0.0011 to 0.0047 mg/kg. The recovery values at the three fortification levels ranged from 78 % to 107 %, and the precision values (expressed as RSD%) were less than 20 % for all of the investigated analytes. The results showed that 138 (9.65 %) of the analyzed samples were contaminated with pesticide residues, 40 (2.80 %) of the analyzed samples exceeded the maximum residue limit (MRL) of the European Commission regulations (EC) for pesticides residues, 98 (6.85 %) of the analyzed samples were contaminated with residues below the MRL, and 1292 (90.35 %) of the analyzed samples were pesticide residue-free. Coriander contained the highest percentage (46.88 %) of pesticide residues, particularly tetradifon that representing 18.75 % noncompliance with the MRL, followed by parsley, with 20.59 % pesticide residues (10.29 % non-compliance). Multiple pesticide residues were observed most frequently in tomatoes and dates which were contaminated with buprofezin and ethion respectively.     

分散固相萃取-超高效液相色谱-串联质谱法测定果蔬、牛奶、植物油和动物肌肉中残留的61种有机磷农药

建立了果蔬、牛奶、植物油和动物肌肉中61种有机磷农药多残留的分析方法。果蔬和牛奶样品用乙腈均质提取,盐析分配;植物油样品用正己烷溶解,乙腈萃取;动物肌肉样品用正己烷配合乙腈-水溶液均质提取,盐析分配。各提取法得到的提取液采用C18和Primary Secondary Amine (PSA)粉末分散固相萃取净化,超高效液相色谱-串联质谱仪(UPLC-MS/MS)分析,采用电喷雾离子化正离子方式(ESI+)及多反应监测模式(MRM)测定,基质匹配标准溶液外标法定量。方法的定量限(S/N≥10)均达到0.01 mg/kg;回收率为62.8%～107%,相对标准偏差为4.2%～19%。该方法准确、灵敏、快速,可满足多种食品中有机磷农药残留的检测要求。     

Rapid determination of carbendazim in complex matrices by electrospray ionization mass spectrometry with syringe filter needle

The determination of pesticide residues is an indispensable task in controlling food safety and environment protection. Carbendazim is one of the extensive uses of pesticides in the agricultural industry. In this study, a simple method utilizing syringe filter has been applied as electrospray ionization emitter for mass spectrometric identification and quantification of carbendazim in complex matrices including soil, natural water, and fruit juice samples, which contain many insoluble materials. With online syringe filter of the complex samples, most of insoluble materials such as soil were excluded in spray ionization process due to the filter effect, and analytes were subsequently sprayed out from syringe needle for mass spectrometric detection. The pore sizes of filters and diameters of syringe needles also were investigated. The analytical performances, including the linear range (1–200 ng·mL⁻¹), limit of detection (0.2–0.6 ng·mL⁻¹, S/N > 3), limit of quantitation (3.5–8.6 ng·mL⁻¹, S/N > 10), reproducibility (6.4%–12.5%, n = 6), and recoveries (72.1%–91.0%, n = 6) were well acceptable for direct analysis of raw samples. Matrix effect for detection of carbendazim in soil samples also was experimentally investigated. This study demonstrated that syringe filter needle coupled with electrospray ionization mass spectrometry is a simple, efficient, and sensitive method for detection of pesticide residues in water, soil, and fruit juice for risk assessment.     

Pesticide residues on fruits and vegetables from Ontario, Canada, 1991-1995

For the 5-year period 1991 to 1995, 1536 vegetable and 802 fruit samples were analyzed. The purpose of this study was to determine if pesticides were present on Ontario-produced fruits and vegetables, and if so, to determine if residues violated maximum residue limits (MRLs). Overall, 31.5% of the samples had no detectable pesticide residues, whereas 68.5% contained one or more residues. Most of the residues were present at very low concentrations; 48% of the detections were < 0.1 parts per million (ppm), and 86% were < 1 ppm. However, violations of MRL were observed in only 3.2% of the vegetables samples and 3.1% of the fruit samples. In addition, 4.8% of the samples contained a "technical" violation, that is, there was no specified MRL for the pesticide-commodity combination and the residues exceeded 0.1 ppm. Of the detectable residues, 63% were < 10% of the MRL, whereas 89% were < 50% of the MRL. More fruit samples (91.4%) had a detectable residue, compared with vegetable samples (56.6%). Fruit is often treated close to harvest or post harvest to ensure that wholesome produce reaches the consumer. Forty-six percent of the samples contained 2 or more residues, and 2% of all samples had more than 5 different pesticides detected; fruit samples tended to have more multiple residues. The most frequently found pesticides were captan, the dithiocarbamate fungicides, endosulfan, azinphos-methyl, phosmet, parathion, and iprodione. These pesticides were also used in the greatest quantity for crop production. Overall, the data agree fairly closely with those reported for the U.S. Department of Agriculture Pesticide Data Program because the 2 programs have similar analytical goals and objectives.     

Simultaneous enrichment of aluminium and lead with cupferron on activated carbon for determination in milk and fruit juices by atomic absorption spectrometry

An enrichment method has been modified for the determination of Al in animal milk and fruit juices by flame atomic absorption spectrometry (FAAS). The samples were digested by wet ashing. 8-Hydroxyquinoline and cupferron were used as complexing reagents for adsorption of the Al complexes on activated carbon. The pH values for maximum recovery of Al were in the ranges 4.4–6.0 for cupferron and 8.0–9.0 for oxine. The relative standard deviation was 4% for an aluminium concentration of 120 gL^–1 using cupferron. Optimum conditions for lead enrichment were taken from previous work on the cupferronactivated carbon enrichment method. The optimized procedure was applied to the determination of Al and Pb in animal milk and fruit juices by FAAS. Simultaneous enrichment of these two elements was achieved at the same pH.