Analysis of pesticide residues in bananas harvested in the Canary Islands (Spain)

In this work, 11 pesticides (ethoprofos, dimethoate, diazinon, malaoxon, chlorpyrifos-methyl, fenitrothion, malathion, chlorpyrifos, fenamiphos, buprofezin and phosmet) were analysed in 57 banana samples taken from the local markets of the Canary Islands (Spain). Analyses were carried out by the QuEChERS approach developed for pesticide residue analysis in food, using gas chromatography (GC) with nitrogen–phosphorus detection (NPD). Triphenylphosphate (TPP) was used as internal standard. Recoveries ranged between 67% and 118% with RSD values below 16%. Typical limits of quantification (LOQs) of the method were 0.01–0.14 mg/kg, which are below the EU maximum residue limits (MRLs) established for these compounds in bananas. Chlorpyrifos was detected in 50 samples (88%) in the concentration range 0.03–0.65 mg/kg, malathion in five samples (8.8%) in the concentration range 0.16–0.17 mg/kg, fenitrothion in four samples (7.0%) in the concentration range 0.02–0.10 mg/kg and buprofezin in one sample (1.8%) at 0.15 mg/kg. All these values are below the MRLs established for these compounds except for two samples containing fenitrothion. Among the studied pesticides only chlorpyrifos has a high occurrence in the samples. However, the levels of these residues cannot be considered a serious public health problem according to EU regulations. Because of the high occurrence of chlorpyrifos, its distribution between the pulp and the peel was also investigated. Results show that most of the pesticide remains in the peel and that only amounts between 0.07 and 0.12 mg/kg occur in the pulp even at concentrations in the peel as high as 0.87 mg/kg.     

A validated matrix solid-phase dispersion method for the extraction of organophosphorus pesticides from bovine samples

A method based on matrix solid-phase dispersion (MSPD) was developed for the quantitative extraction of five organophosphorus (OPPs) pesticides from bovine samples. The determination was carried out by high performance liquid chromatography (HPLC) with diode array spectrophotometric UV detection. The MSPD extraction with octadecylsilyl (C18) sorbent combined with a silica gel clean-up and acetonitrile elution was optimised for chlorpyrifos, chlorfenvinphos, diazinon, fenitrothion, and parathion-methyl. The method was validated, yielding recovery values higher than 94%, except for chlorfenvinphos in liver (55%), and precision values, expressed as relative standard deviations (RSDs), which were less than or equal to 15% in liver and 11.5% in muscle at spiking levels of 0.25, 2.5 and 5 μg g⁻¹. Linearity was studied from 0.5 to 15 μg g⁻¹, and the limits of detection (LODs) were found to be lower than 0.1 μg g⁻¹_. This method was applied to the analysis of real samples with confirmative analyses performed using gas chromatography–mass spectrometry (GC–MS) in selected ion monitoring mode (SIM).     

Sample preparation method for the analysis of some organophosphorus pesticides residues in tomato by ultrasound-assisted solvent extraction followed by dispersive liquid–liquid microextraction

A very simple and economic method for organophosphorus pesticides (OPPs) residues analysis in tomato by means of gas chromatography–flame photometric detection (GC–FPD) has been developed. The method involves a rapid and small-scale extraction. The sample was homogenised and extraction of the OPPs with acetone was carried out assisted by sonication. No clean-up or evaporation were required after extraction. Pre-concentration of the OPPs from the acetone extract was done by using dispersive liquid–liquid microextraction (DLLME) technique. Chlorobenzene was added in micro-level volume as extraction solvent and triphenylphosphate as internal standard in DLLME procedure. The method showed good linearity over the range assayed (0.5–1000 μg kg⁻¹) and the detection limits for the pesticides studied varied from 0.1 to 0.5 μg kg⁻¹. Repeatability studies resulted a relative standard deviation lower than 10% in all cases. The proposed method was used to determine pesticides levels in tomatoes grown in open field.     

Multiresidue method for analysis of pesticides in pepper and tomato by gas chromatography with nitrogen–phosphorus detection

An analytical multiresidue method for the simultaneous determination of various classes of pesticides in vegetables (pepper and tomato) was developed. Vegetable samples are extracted with acetone and the pesticides are partitioned into ethyl acetate/cyclohexane. Final determination was made by gas chromatography with nitrogen–phosphorus detection. Confirmation analysis of pesticides was carried out by gas chromatography coupled with mass spectrometry in the selected ion monitoring (SIM) mode. The identification of compounds was based on retention time and on comparison of the primary and secondary ions. Recovery studies were performed at 0.05, 0.1 and 0.02 mg kg⁻¹ fortification levels of each compound and the recoveries obtained ranged from 70.1% to 128.5% with relative standard deviations lower than 7%. The method showed good linearity over the range assayed 50–1500 μg l⁻¹ and the detection and quantification limits for the pesticides studied varied from 0.1 to 4.4 μg kg⁻¹ and 0.4 to 14.5 μg kg⁻¹, respectively. The proposed method was used to determine pesticides levels in peppers and tomatoes grown in experimental greenhouses.     

Analysis of pesticide residues in seaweeds using matrix solid-phase dispersion and gas chromatography–mass spectrometry detection

Products containing organophosphates, carbamates and pyrethroids pesticides, employed as chemotherapeutants in aquaculture, can remain as residues in the marine environment. Matrix solid-phase dispersion (MSPD) was developed to extract seventeen pesticides from seaweed samples using Florisil and graphitized carbon black as clean-up adsorbents prior to gas chromatography–mass spectrometry (GC–MS) determination. The extraction has been optimised by a Box–Behnken design. The optimal conditions were 1 g of seaweed sample, 4 g of anhydrous sodium sulphate as dispersant, 3.6 g of Florisil and 0.4 g of GCB and an elution volume of 14 mL of a hexane:ethyl acetate mixture containing 40% ethyl acetate. The recoveries ranged from 81.6% to 113.2% with relative standard deviations (RSDs) ranging from 1.6% to 13.2%. The limits of detection (LOD) ranged from 0.5 to 2.9 ngg⁻¹. Internal quality control was successfully carried out to verify the quality of the data obtained in the analysis of these pesticides in seaweed samples.     

Dissipation rates of insecticides and fungicides in peppers grown in greenhouse and under cold storage conditions

The dissipation of three insecticides (pirimicarb, pyriproxyfen and buprofezin) and three fungicides (cyprodinil, fludioxonil and tebuconazole) in peppers was evaluated in a study carried out on an experimental greenhouse. Pepper samples were collected during 6 week period in which two successive applications of these pesticides were performed. Gas chromatography (GC) with nitrogen–phosphorus detection (NPD) was used to study the disappearance of these compounds in peppers. Confirmation analysis of pesticides was carried out by capillary gas chromatography coupled with mass spectrometry in the selected ion monitoring (SIM) mode. At the preharvest interval the residue levels were below the legal limit established in Spain. The disappearance rates of these compounds on peppers were described as pseudo-first-order kinetics (r between 0.953 and 0.997) and half-life in the range of 4.41 and 21.47 days. After thirty days under cold and darkness storage conditions, dissipation of buprofezin and pyriproxyfen were not observed. However, dissipation rate in pepper of pirimicarb cyprodinil, fludioxonil and tebuconazole in refrigerated were observed. This, the half-lives for these pesticides were 5–9 times greater under refrigeration.     

Assessment of DFG-S19 method for the determination of common endocrine disruptor pesticides in wine samples with an estimation of the uncertainty of the analytical results

A gas chromatographic method for the determination of endocrine disruptor pesticides (Chlorpyrifos, Penconazole, Procymidone, Iprodione, Bromopropylate and Lambda-Cyhalothrin) in wine samples is described. A general DFG-S19 method for residual pesticide determination in all kind of food stuff was investigated to simplify and adopt for wine samples in this work. Alternative sample preparation routes were elucidated and compared according to their recovery values. Four different separation techniques were tested and the method employing florosil column after a LLE procedure was applied for wine samples with satisfactory recovery ratios (72–97%). The pesticides were extracted from the sample by cyclohexane–ethyl acetate mixture (1:1 v/v) and cleaned up by florosil column. The regression coefficients were at least 0.99 and relative standard deviations were no higher than 16%. Detection limits were in the range of 0.6–2.9 ng/mL and the relative expanded measurement uncertainties were calculated in the 7–22% range.     

基质固相分散-气相色谱检测菊花中有机磷农药残留

建立菊花中14种有机磷农药残留量的气相色谱分析方法。样品用乙腈-丙酮(4:1,V/V)提取,经基质固相分散技术净化,以乙腈-甲苯(3:1,V/V)洗脱,气相色谱-火焰光度检测,外标法定量。在0.05～1.0mg/kg的添加水平,14种有机磷的平均回收率在84.54%～108.54%之间,相对标准偏差在0.66%～6.31%,该方法的检出限为0.01～0.04mg/kg。该方法的灵敏度、准确度和精密度均符合农药残留测定的技术要求。采用所建立方法测定了黄山贡菊、杭白菊和胎菊3种代表性菊花中14种有机磷农药残留量,结果表明,黄山贡菊检出乐果1.68mg/kg、毒死蜱0.17mg/kg、硫环磷0.28mg/kg,杭白菊检出毒死蜱0.09mg/kg,胎菊检出乐果0.25mg/kg、毒死蜱0.14mg/kg、伏杀磷0.08mg/kg。     

Cloud point extraction coupled with ultrasonic-assisted back-extraction for the determination of organophosphorus pesticides in concentrated fruit juice by gas chromatography with flame photometric detection

A new method for the determination of nine organophosphorus pesticides (OPPs): Dichlorvos, methamidophos, acephate, diazinon, dimethoate, chlorpyrifos, parathion-methyl, malathion and parathion-ethyl in concentrated fruit juice was developed using the cloud point extraction coupled with ultrasonic-assisted back-extraction prior to gas chromatography with flame photometric detection (GC-FPD) analysis. The parameters and variables that affect the extraction were investigated. Under optimum conditions: a solution containing 6% (W/V) polyethylene glycol 6000 (PEG 6000) and 20% (W/V) Na₂SO₄ for the extraction of the OPPs. The coacervation phase obtained was back extracted with ethyl acetate. The upper ethyl acetate solution was centrifugated simply for further cleanup for the sake of automatic injection. A preconcentration factor of 50 was obtained for these nine pesticides. Using this method, the limits of detection (LOD) and limits of quantification (LOQ) were in the range of 0.5–3.0 and 1.5–9.0 μg kg⁻¹ in concentrated fruit juice, respectively; the relative standard deviations (RSD) were <9%.     

Monitoring multi-class pesticide residues in fresh grape by hollow fibre sorptive extraction combined with gas chromatography–mass spectrometry

A fast and sensitive multi-residue analysis method is reported for simultaneous determination of 25 pesticides of chemical classes which are spiked into fresh grape. The sample pretreatment method involves extraction and clean-up in one step with SiO₂ hollow fibre from 1.0 mL fresh grape slurry to minimise the matrix effects, and determination by gas chromatography–mass spectrometry with selective ion monitoring mode. The validation of the optimised method in terms of linearity, precision, recovery and repeatability showed that the proposed procedure is sensitive (the limits of detection were in the range of 0.0009–0.0084 μg mL⁻¹ for 25 pesticides), precise and repeatable (average recoveries were between 61% and 108% with relative standard deviations from 4.0% to 12.4 %). The proposed method was also applied to the analysis of these groups of pesticides in fresh grape sample purchased from the local markets of Lanzhou (China), while no residues of the selected pesticides were detected in the sample.     

Headspace gas chromatography–mass spectrometry determination of alkylpyrazines in cocoa liquor samples

This paper proposes a fast, accurate, and quantitative method for alkylpyrazines determination in cocoa liquors samples using gas chromatography with ion trap mass spectrometry detection (GC/IT-MS) and on-line headspace (HS) sample introduction. The optimization of the experimental conditions of the headspace gas chromatography–mass spectrometry (HS–GC–MS) system was carried out using the univariate method, aiming to find a compromise between time of the analysis, sensitivity and pyrazine resolution in a Carbowax (AV-WAX) fused silica capillary column. The procedure was validated through accuracy and precision studies. The results showed a highly satisfactory accuracy rate for the method with a relative standard deviation (RSD) during 1 day and between days of <5.0% (n = 5). On the other hand, the recovery percentages (94–99%) were quantitative in all cases, with a RSD of <4.0% (n = 5). Finally, the use the on-line headspace extraction step simultaneously with the analytes separation and detection of the previous sample injection increased the analysis frequency to 3 samples/h. A total of 120 cocoa liquor samples were analyzed.     

Multiresidue method for determination of 88 pesticides in berry fruits using solid-phase extraction and gas chromatography–mass spectrometry: Determination of 88 pesticides in berries using SPE and GC–MS

A method using solid phase extraction (SPE) cleanup followed by gas chromatography–mass spectrometry (GC–MS) has been established for quantitative determination of 88 pesticide residues in berry fruits including raspberry, strawberry, blueberry and grape. Based on an appraisal of the characteristics of GC–MS, validation experiments were conducted for 88 pesticides. In the method, solid-phase extraction was carried out using Envi-Carb cartridge coupled with NH₂-LC cartridge with acetonitrile–toluene (3:1, v/v) as the eluted solvent. In the linear range of each pesticide, the correlation coefficient was R² ? 0.99. At the low, medium and high three fortification levels of 0.05–0.5 mg kg⁻¹, recoveries fell within 63–137%. The relative standard deviation was between 1% and 19% for all 88 pesticides. Low limits of detection (0.006–0.05 mg kg⁻¹) and quantification (0.02–0.15 mg kg⁻¹) were readily achieved with this method for all tested pesticides.     

Distribution and migration study of pesticides between peel and pulp in grape by online gel permeation chromatography–gas chromatography/mass spectrometry

A multi-residue method for the analysis of 175 pesticides was developed by online gel permeation chromatography–gas chromatography/mass spectrometry (GPC–GC/MS) to study pesticide distribution and migration between peel and pulp in grape. The separated peel and pulp samples were extracted by acetonitrile after fortified with chlorpyrifos-d₁₀ isotope internal standard. The extract was first purified by solid phase distribution sorbent of primary secondary amine (PSA) and then detected by online GPC–GC/MS. At the spiking levels of 10, 50 and 200 μg kg⁻¹, 73.7%, 94.3% and 98.9% of the pesticides, respectively, presented recoveries between 70% and 120%. The ratios were 91.4%, 94.9% and 92.0%, respectively, for the relative standard deviations (RSDs) bellow 15%. Limits of detection (LODs) for the pesticides in pulp were below 10 μg kg⁻¹. Pesticides were separated to four groups according to the distribution ratios (peel/whole grape) of 100%, 80–99.9%, 50–80% and 0–50% in peel. Relationship between the pesticide distribution and corresponding regulation of EU maximum residue level (MRL) was discussed. Six factors influencing the pesticides distribution and migration between peel and pulp were discussed. Weak linear correlation between the pesticide solubility in water (20 °C) and the distribution ratios (lowest and average) in peel was found for most of the detected pesticides with solubility less than 200 mg L⁻¹.     

Electrochemical detection of carbamate pesticides in fruit and vegetables with a biosensor based on acetylcholinesterase immobilised on a composite of polyaniline-carbon nanotubes

A sensitive electrochemical acetylcholinesterase (AChE) biosensor was successfully developed on polyaniline (PANI) and multi-walled carbon nanotubes (MWCNTs) core-shell modified glassy carbon electrode (GC), and used to detect carbamate pesticides in fruit and vegetables (apple, broccoli and cabbage). The pesticide biosensors were applied in the detection of carbaryl and methomyl pesticides in food samples using chronoamperometry (CA). The GC/MWCNT/PANI/AChE biosensor exhibited detection limits of 1.4 and 0.95μmolL(-1), respectively, for carbaryl and methomyl. These detection limits were below the allowable concentrations set by Brazilian regulation standards for the samples in which these pesticides were analysed. Reproducibility and repeatability values of 2.6% and 3.2%, respectively, were obtained in the conventional procedure. The proposed biosensor was successfully applied in the determination of carbamate pesticides in cabbage, broccoli and apple samples without any spiking procedure. The obtained results were in full agreement with those from the HPLC procedure.     

Determination of organophosphorus pesticides in pakchoi samples by headspace solid-phase microextraction coupled with gas chromatography using home-made fiber

A home-made sol-gel-derived co-poly (hydroxy-terminated silicone divinylbenzene) (OH-TSO/DVB) coating fiber has firstly been applied for headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography (GC)—nitrogen-phosphorus detector (NPD) to determine five organophosphorus pesticides (OPPs) in pakchoi samples. The following parameters influencing on the extraction efficiency of HS-SPME were optimized statistically: extraction temperature, extraction time, ionic strength, constant agitation, effect of sample matrix, desorption temperature, and desorption time. Compared with commercial available fibers and OH-TSO SPME fiber, this fiber showed statistically better enrichment capability for these pesticides. For the developed HS-SPME-GC method, it was found that the linearity was all two orders of magnitude, with the limits of detection (LOD) ranging from 0.007 to 0.07 ng g⁻¹, and relative standard deviations (RSD) varying between 4.1 and 8.7% (n = 5). Recoveries of spiked pakchoi samples ranged from 80.74 to 101.47% for every pesticide at each investigated concentration. Overall, it indicated that the obtained method is a validated and accurate procedure for determination of OPPs in pakchoi samples.     

Automatic determination of nickel in foods by flame atomic absorption spectrometry

A new sensitive and low cost flow injection method that combines acid extraction, preconcentration and flame atomic absorption spectrometric determination of nickel in food samples at μg/g levels is described. The dynamic acid extraction step was carried out by using a continuous ultrasound-assisted extraction system. The acid extract was preconcentrated on-line on a minicolumn packed with a chelating resin (Serdolit Che, with iminodiacetic groups) and nickel was eluted with diluted hydrochloric acid, being continuously monitored by flame atomic absorption spectrometry. An experimental design (Plackett-Burman 2⁶ × 3/16) is used to optimise the methodology proposed. The method allowed a total sampling frequency of 13–28 samples per hour. Good precision of the whole procedure (1.9–3.6% expressed as relative standard deviation) and a detection limit of 0.12 μg/g, for 60 mg of sample were achieved. The method was successfully applied to the determination of trace amounts of nickel in food samples.     

Effects of home preparation on organophosphorus pesticide residues in raw cucumber

The effects of washing with tap water and different detergent solutions, storage at different temperatures and ultrasonic cleaning on organophosphorus pesticide (trichlorfon, dimethoate, dichlorvos, fenitrothion, and chlorpyrifos) residue levels in raw cucumber was investigated. Analysis was carried out by liquid chromatography–tandem mass spectrometry. Washing with detergent solutions proved more effective than tap water. The organophosphorus pesticides reduced from 31.1% to 98.8% after washing with detergent solutions for 20 min. Among detergent solutions, 5% sodium carbonate solution caused the greatest loss in trichlorfon and dimethoate, and 5% sodium bicarbonate solution caused the greatest loss in dichlorvos, fenitrothion and chlorpyrifos. Storage at 4 °C for 48 h caused pesticides reduction by 60.9–90.2%. Ultrasonic cleaning for 20 min lowered pesticides by 49.8–84.4%. The data indicated that home preparation is effective for the reduction of organophosphorus pesticide residues in raw cucumber and it is useful for reducing the dietary exposure.     

凝胶渗透色谱净化联合气相色谱-串联质谱法同时测定番石榴中3种农药残留

目的建立一种同时测定番石榴中3种常用农药的凝胶渗透色谱净化联合气相色谱-串联质谱法(gel permeation chromatography-gas chromatography-tandem mass spectrometry,GPC-GC-MS/MS)分析方法。方法番石榴样品经乙腈提取,凝胶渗透色谱净化,毛细管气相色谱柱分离后,采用三重串联四极杆多反应监测模式测定。结果 3种农药在0.05~0.50 mg/L范围内线性关系良好,相关系数均不低于0.9990;毒死蜱、克螨特、氟氯氰菊酯的定量限分别为0.002、0.005、0.01 mg/kg;在0.05、0.10、0.50 mg/kg 3个加标水平下,3种农药的回收率在83.3%~104.8%之间,相对标准差为2.9%~7.9%。结论该方法处理简便,能满足番石榴中3种常用农药毒死蜱、克螨特、氟氯氰菊酯残留检测的要求。     

Analytical methods for the determination of pesticide residues using gas chromatograghy with nitrogen-phosphorus detector

The analysis methods for 3 pesticides (ametryn, cyanophos, and fonofos) were developed and validated. One 1,3,5-triazine herbicide (ametryn), and 2 organophosphorus insecticides (cyanophos and fonofos) were tested. Three kinds of residual pesticides were classified into 2 groups according to the chemical structure and separation method. Solid-phase extraction (SPE) cartridge was used for sample purification and isolation of analytes. Final solution was analyzed with GC with nitrogen-phosphorus detection (NPD). Confirmation analysis of pesticides was carried out by GC-MS in the selected ion monitoring (SIM) mode. Correlation coefficient was ranged from 0.999 to 1.0, depending on sample analytes. Rice, apple, and soybean samples were selected for recovery experiment. Overall recovery rates from blank samples spiked at 3 fortification levels ranged from 76.29 to 107.4% with relative standard deviations lower than 20.2%. The limit of quantification was <3–5 μg/L depending on the analytes, and the reporting level of the method, defined as lower than the maximum residue levels established by Korea Food & Drug Administration (KFDA).     

Determination of selected pesticides in fruit juices by matrix solid-phase dispersion and liquid chromatography–tandem mass spectrometry

A rapid and sensitive liquid chromatography–tandem mass spectrometry method has been developed for the analysis of acephate, monocrotophos, carbendazim, acetamiprid, dimethoate, simazine, carbofuran, atrazine, diuron, DNOC (4,6-dinitro-o-cresol), malathion and tebufenozide in fruit juices. Extracts were obtained by matrix solid-phase dispersion using diatomaceous earth as dispersant and dichloromethane as eluent. Significant matrix effects observed for most of the pesticides tested were eliminated using matrix-matched standards. The quantification of the analytes was carried out using the most sensitive transition. The confirmation of residues detected in real samples was performed by repeated injection and acquiring additional transitions to that used for quantification. Recoveries were in the range 71–118%. Repeatability of the method, expressed as the relative standard deviation, was in general between 5–15%. Low limits of detection (0.01–0.94 ng ml⁻¹) and quantification (0.03–3.12 ng ml⁻¹) were readily achieved with this method for all tested pesticides.