Miniaturized Method for Chemical Oxygen Demand Determination Using the PhotoMetrix PRO Application.

The analysis of chemical oxygen demand (COD) plays an important role in measuring water pollution, but it normally has a high ecological price. Advances in image acquisition and processing techniques enable the use of mobile devices for analytical purposes. Here, the PhotoMetrix PRO application was used for image acquisition and multivariate analysis. Statistical analysis showed no significant difference in the results compared to the standard method, with no adverse effect of the volume reduction. The cost of analysis and waste generation were reduced by one third, while the analysis time was reduced by one fifth. The miniaturized method was successfully employed in the analysis of several matrices and for the evaluation of advanced oxidation processes. The AGREE score was improved by 25% due to miniaturization. For these reasons, the miniaturized PhotoMetrix PRO method is a suitable option for COD analysis, being less hazardous to the environment due to reductions in the chemicals used and in waste generation.

Protective effects of diet containing rutin against trichlorfon-induced muscle bioenergetics disruption and impairment on fatty acid profile of silver catfish Rhamdia quelen.

Trichlorfon is an organophosphate insecticide that is widely used on fish farms to control parasitic infections. It has been detected in freshwater ecosystems as well as in fishery products. There is a growing body of evidence to suggest that certain feed additives may reduce or prevent pesticide-induced toxicity in fish. The aim of the present study was to determine whether acute exposure to trichlorfon would alter bioenergetic homeostasis and alter fatty acid profiles in muscles of silver catfish (Rhamdia quelen). We also sought to determine whether rutin prevents or reduces these effects. Cytosolic and mitochondrial creatine kinase (CK) and activities of complexes II-III and IV in muscle were significantly inhibited by exposure to 11 mg/L trichlorfon for 48 h compared to effects in the unexposed group. Total content of polyunsaturated fatty acids (omega-3 and omega-6) were significantly lower in muscle of silver catfish exposed to 11 mg/L trichlorfon for 48 h than in the unexposed group. Addition of 3 mg rutin/kg feed increased CK activity and prevented inhibition of complex IV activity, as well as preventing all alterations of muscle fatty acid profiles elicited by exposure to trichlorfon. No significant differences were observed between groups with respect to muscle adenylate kinase or pyruvate kinase activities, as well as total content of saturated and monounsaturated fatty acids. Our findings suggest that exposure (48 h) to 11 mg trichlorfon/L water inhibits cytosolic and mitochondrial CK activity in muscle. Trichlorfon also affects activities of complexes II-III and IV in respiratory chain, with important consequences for adenosine triphosphate production. The pesticide alters fatty acid profiles in the fish and endangers human consumers of the product. The most important finding of the present study is that inclusion of rutin improves bioenergetic homeostasis and muscle fatty acid profiles, suggesting that it reduces trichlorfon-induced muscle damage.

Evaluation of alternative sorbents for dispersive solid-phase extraction clean-up in the QuEChERS method for the determination of pesticide residues in rice by liquid chromatography with tandem mass spectrometry.

Many compounds are used for pest control during the production and storage of rice, making it necessary to employ multiclass methods for pesticide residues determination. For this purpose, QuEChERS-based methods are very efficient, fast and accurate, and improvements in the clean-up step are important, especially for complex matrices, like cereals. In this work, different sorbents such as chitosan, florisil(®) , alumina, diatomaceous earth, graphitized carbon black, besides the commonly used primary secondary amine and octadecylsilane, were evaluated for dispersive solid-phase extraction clean-up in acetate-buffered QuEChERS method for the determination of residues of 20 representative pesticides and one metabolite in rice by liquid chromatography coupled to tandem mass spectrometry. The sorbent C18 presented the best results, however, chitosan showed similar results, and the best performance among the unconventional sorbents evaluated. The method limit of quantification, attending accuracy (70-120% recovery) and precision (RSD ≤20%) criteria, ranged from 5 to 20 µg/kg. Results showed that chitosan is an effective alternative to reduce analysis costs, maintaining the method reliability and accuracy.

Pesticide multiresidue determination in rice paddy water by gas chromatography coupled with triple quadrupole mass spectrometry.

Pollution of water sources by pesticides is a result of intensive use of these compounds, and the establishment of analytical methods for monitoring programs is very important. This paper presents a method for the determination of multiclass pesticide residues in rice paddy water based on SPE and GC/MS/MS. The validation results were satisfactory. All compounds showed adequate linearity (r2 >or= 0.99), and analysis by GC/MS/MS with a triple quadrupole mass spectrometer gave high selectivity and sensitivity. With the proposed SPE step an LOD of 0.06 microg/L was achieved. Recoveries from blank samples spiked at 0.2, 04, and 0.8 microg/L were between 70 and 120% with RSD <20% for most analyzed compounds, despite their different chemical nature, indicating good accuracy and precision. The proposed method is efficient for pesticide residue determination, including some metabolites, and gave good performance when applied to real samples.

Determination of pesticide residues and related compounds in water and industrial effluent by solid-phase extraction and gas chromatography coupled to triple quadrupole mass spectrometry.

Pollution of drinking water supplies from industrial waste is a result of several industrial processes and disposal practices, and the establishment of analytical methods for monitoring organic compounds related to environmental and health problems is very important. In this work, a method using solid-phase extraction (SPE) and gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS) was developed and validated for the simultaneous determination of pesticide residues and related compounds in drinking and surface water as well as in industrial effluent. Optimization of the method was achieved by using a central composite design approach on parameters such as the sample pH and SPE eluent composition. A single SPE consisting of the loading on a polymeric sorbent of 100 mL of sample adjusted to pH 3 and elution with methanol/methylene chloride (10:90, v/v) permitted the obtaining of acceptable recoveries in most cases. The concentration factor associated with sensitivity of the chromatographic analysis permitted the achievement of the method limit of detection values between 0.01 and 0.25 µg L(-1). Recovery assays presented mean recoveries between 70 and 120% for most of the compounds with very good precision, despite the different chemical nature of the compounds analyzed. The selectivity of the method, evaluated through the relative intensity of quantification and qualification ions obtained by GC-QqQ-MS/MS, was considered adequate. The developed method was finally applied to the determination of target analytes in real samples. River water and treated industrial effluent samples presented residues of some compounds, but no detectable residues were found in the drinking water samples evaluated.

Critical Evaluation of Analytical Methods for the Determination of Anthropogenic Organic Contaminants in Edible Oils: An Overview of the Last Five Years.

Anthropogenic contaminants, as pesticides, polycyclic aromatic hydrocarbons (PAHs) and monochloropropanediols (MCPDs), have become important to be controlled in edible oils, since their regular occurrence. In fact, alerts from the Rapid Alert System for Food and Feed (RASFF) in oils normally include these compounds. From a critical point of view, tools used to control these compounds in the last 5 years will be discussed, including sample preparation, analysis and current regulations. Extraction and analysis methods will be discussed next, being liquid-liquid extraction (LLE) and QuEChERS, with or without clean-up step, as well as chromatographic methods coupled to different analyzers (mainly mass spectrometry), the most commonly used for extraction and analysis respectively. Occurrence in samples will also be reviewed and compared with the legal maximum residue limits (MRLs), observing that 4%, 20% and 60% of the analyzed samples exceed the legal limits for pesticides, MCPDs and PAHs respectively.

Comparison of several extraction procedures for the determination of biopesticides in soil samples by ultrahigh pressure LC-MS/MS.

A new procedure has been proposed for the determination of biopesticides (nicotine, sabadine, veratridine, rotenone, azadirachtin, cevadine, deguelin, spynosad D, and pyrethrins) and piperonyl butoxide in agricultural soils. Several extraction procedures such as solid-liquid extraction using mechanical shaking, sonication, pressurized liquid extraction, and modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) have been tested, obtaining better results when QuEChERS procedure without further cleanup steps was applied. The determination of the compounds was carried out by ultra high pressure liquid chromatography coupled to tandem mass spectrometry, using methanol and aqueous solution of ammonium formate 5 mM as mobile phase. The method was validated for all compounds at concentrations ranging from 10 to 100 µg/kg and recoveries ranged from 68 to 116%, except for nicotine and sabadine, with recoveries lower than 50%. Precision was estimated through intra- and inter-day studies, obtaining intra-day precision lower than 20% for most of the compounds, and inter-day precision was lower than 25%. Limits of detection and quantification were also estimated, obtaining limits of quantification equal or lower than 10 µg/kg. Finally, the method was applied to the analysis of 20 real agricultural soil samples and no biopesticide residues were found over the limit of quantification.

Behavioral impairment and neurotoxic responses of silver catfish Rhamdia quelen exposed to organophosphate pesticide trichlorfon: Protective effects of diet containing rutin.

Trichlorfon is an organophosphate pesticide used extensively for controlling ectoparasites in aquaculture. Studies have found that trichlorfon caused environmental pollution and severe neurotoxic effects in several freshwater species. Feed additives such as flavonoids may reduce or prevent pesticide-induced toxicity in fish. The aim of the present study was to determine whether acute exposure to trichlorfon impairs behavior and causes oxidative damage in brains of silver catfish (Rhamdia quelen). We also sought to determine whether rutin would be capable of preventing or reducing these effects. Silver catfish were divided into four groups: groups A and C received basal feed, while groups B and D received feed containing 3 mg rutin/kg diet for 21 days. After 21 days, groups C and D were exposed for 48 h to a nominal concentration of 11 mg trichlorfon/L water. Fish exposed to trichlorfon showed significantly longer distances travelled and swimming performances than did unexposed fish. Cerebral levels of reactive oxygen species and lipid peroxidation were significantly higher in fish exposed to trichlorfon than in unexposed fish, while cerebral superoxide dismutase, catalase, glutathione peroxidase, and acetylcholinesterase (AChE) activities were significantly lower. Taken together, our findings suggest that dietary supplementation rutin completely prevented all alterations elicited by trichlorfon, except for cerebral AChE activity; the latter remained significantly lower compared to the unexposed group. In summary, rutin prevents trichlorfon-induced neurotoxicity in silver catfish.

Miniaturized QuEChERS method for determination of 97 pesticide residues in wine by ultra-high performance liquid chromatography coupled with tandem mass spectrometry.

A miniaturized sample preparation method was developed and validated for the multiresidue determination of 97 pesticides in wine samples. The proposed extraction procedure is based on the QuEChERS acetate method with dispersive solid phase extraction (d-SPE) for the clean-up step. Ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) was used for determination. The extraction and clean-up steps were evaluated to obtain the best conditions for the selected pesticides. Miniaturization of the sample preparation step provided a reduction in the consumption of samples and chemicals. The method limit of quantification was between 10 and 20 µg L-1. Trueness results, obtained by recovery assays at the spike levels 10, 20, 50 and 100 µg L-1, ranged from 70 to 120% with precision in terms of relative standard deviations (RSD) ≤ 20%. The method was successfully applied for the analysis of wine samples and different pesticides were found at concentrations from 14 to 55 µg L-1.

Balls-in-tube matrix solid phase dispersion (BiT-MSPD): An innovative and simplified technique for multiresidue determination of pesticides in fruit samples.

Sample preparation of complex matrices, like food samples, continues to be a challenge demanding great effort for improvements. In this study, a new technique named balls-in-tube matrix solid-phase dispersion (BiT-MSPD) is proposed based on a simplification of the conventional MSPD technique being all sample preparation performed directly in a closed extraction tube with the assistance of steel balls. An innovative method using BiT-MSPD was successfully established for the determination of 133 pesticide residues in apple, peach, pear and plum by ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS). Several sorbents were evaluated as solid support in different proportions with the sample. The homogenization step using mortar, glass rod or steel balls, with methanol and acetonitrile as extraction solvent, was evaluated. Vortex and ultrasound assisted extractions were also tested. Best results were obtained with C18, homogenization with steel balls, acetonitrile as solvent and ultrasound assisted extraction. Validation presented adequate trueness and precision results for the evaluated pesticides with recovery results ranging from 72 to 113% and RSD ≤ 17%. Practical limit of detection (LOD) and quantification (LOQ) for the compounds were 3 and 10 µg kg-1, respectively. The developed method proved to be easier and faster to perform than the MSPD, considering that extraction and clean-up are performed in the same tube without the need to transfer to cartridges, recipients or to use a separate clean-up step. The proposed BiT-MSPD technique was successfully applied to fruit samples and has great potential to be applied in other matrices, like cereals and meat, since the steel balls promote an efficient sample dispersion and extraction of pesticides. The BiT-MSPD permit a fully automation of the entire sample preparation step.

Effective methods for the determination of triphenyltin residues in surface water and soil samples by high-performance liquid chromatography with tandem mass spectrometry.

Monitoring of triphenyltin (TPhT) in the environment, particularly to control its misuse in agriculture, is of great importance because of its high toxicity. In this work, methods for determination of TPhT residues in surface water and soil samples by liquid chromatography with tandem mass spectrometry (LC-MS/MS) were developed and validated. Different sample volumes and pH and elution solvent types and volumes were evaluated for solid phase extraction (SPE) of TPhT in surface water samples. The optimized conditions were 500 mg sorbent Strata C18-E, 100 mL of the sample, pH adjusted to 9.0 and 1 mL of methanol containing acetic acid as the eluent. For a 10 g soil sample, the extraction was established using a modified QuEChERS method with 10 mL of acidified acetonitrile followed by a clean-up step by dispersive solid phase extraction (dSPE) with C18. A full factorial 23 design of experiments was applied to optimize the sample preparation method for soil samples. Practical method limits of quantification were 0.1 µg L-1 and 10 µg kg-1 for surface water and soil samples, respectively. Satisfactory accuracy, with recoveries from 86 to 107% for surface water and 72 to 87% for soil samples, as well as good precision, with an overall relative standard deviation (RSD) from 3 to 8% was observed. The validated methods were applied to real samples and some residues of TPhT were found, especially in soil samples (30 to 190 mg kg-1), indicating the suitability for routine analysis.

Organophosphate pesticide trichlorfon induced neurotoxic effects in freshwater silver catfish Rhamdia quelen via disruption of blood-brain barrier: Implications on oxidative status, cell viability and brain neurotransmitters.

The aim of this study was to evaluate whether rupture on blood-brain barrier (BBB) can be a pathway for trichlorfon-induced neurotoxic effects, and to investigate its implications on oxidative status, cell viability and brain neurotransmitters in silver catfish (Rhamdia quelen). The BBB permeability was increased in fish exposed for 24 h to 22 mg/L of trichlorfon compared to the control group, as well as in those exposed to 11 and 22 mg/L of trichlorfon for 48 h. Compared to the control group, brain reactive oxygen species and lipid peroxide levels were higher when exposed to 22 mg/L of trichlorfon and 11 and 22 mg/L of trichlorfon after 24 h and 48 h, respectively, while the antioxidant capacity against peroxyl radical levels was lower. Exposure to 22 mg/L of trichlorfon for 24 h reduced brain cell viability compared to the control group, together with 11 and 22 mg/L of trichlorfon for 48 h. Also, brain AChE, Na+ and K+-ATPase activities were reduced in those fish exposed to trichlorfon compared to the control group. Thus, the rupture of BBB can be considered an important pathway involved in trichlorfon-induced neurotoxic effects, which contributes to brain oxidative damage and important changes on brain neurotransmitters.

Simultaneous determination of the quaternary ammonium pesticides paraquat, diquat, chlormequat, and mepiquat in barley and wheat using a modified quick polar pesticides method, diluted standard addition calibration and hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry.

In this study, a modified Quick Polar Pesticides (QuPPe) method, optimized by a central composite design, was developed to determine quaternary ammonium pesticides (QUATs) residues in barley and wheat by ultra-high-performance liquid chromatographic tandem mass spectrometry (UHPLC-MS/MS) using a hydrophilic interaction chromatography (HILIC) column. Considering the high polarity of these compounds, special conditions of sample preparation and analysis are required. Different mobile phases, extraction procedure and clean-up were evaluated. An isocratic elution with aqueous solution of ammonium formate 60 mmol L-1 (pH 3.7) and acetonitrile, 40:60 (v/v), was selected. Water and acidified methanol as extraction solvent, without heating, and a clean-up with dichloromethane, chitosan and acetonitrile presented good results. The validated method presented satisfactory selectivity, linearity, matrix effect, trueness and precision, providing recoveries from 93 to 110% with RSD < 13% for barley, and 70 to 115% with RSD < 18% for wheat. The complexity of these matrices requires the calibration in matrix and the diluted standard addition calibration (DSAC) procedure has been shown to be an excellent option to compensate for the matrix effect and the losses of the analytes in the extraction. Real samples of barley and wheat were analyzed and 60% presented concentrations of paraquat above the maximum limits allowed by the European Union. The modified QuPPe method combined with DSAC and HILIC-UHPLC-MS/MS demonstrated to be an effective approach to determine QUATs in barley and wheat, and is a good alternative for routine analysis. The use of the biosorbent chitosan is effective, low cost and more ecological when compared to others conventional sorbents.

Disturbance of energetic homeostasis and oxidative damage provoked by trichlorfon as relevant toxicological mechanisms using silver catfish as experimental model.

Recent evidences have suggested the involvement of phosphoryl transfer, catalyzed by creatine kinase (CK), adenylate kinase (AK) and pyruvate kinase (PK), to metabolic alterations and impairment of bioenergetics homeostasis linked to adenosine triphosphate (ATP) production, and utilization during exposure to pesticides. It is recognized that sublethal concentrations of trichlorfon alter hepatic and branchial metabolism, but the pathways involved in this process remains unknown. Thus, the aim of this study was to evaluate whether phosphoryl transfer network can be a pathway involved in the hepatic and branchial metabolic alterations during exposure to sublethal concentrations of trichlorfon using silver catfish Rhamdia quelen as experimental model. Hepatic and branchial CK (cytosolic and mitochondrial isoforms) and PK activities were inhibited after 48 h of exposure to 11 and 22 mg/L trichlorfon compared to control group, while AK activity did not differ between groups. In addition, sodium-potassium pump (Na+, K+-ATPase) activity was lower after 48 h of exposure to 22 mg/L trichlorfon compared to control group. Thiobarbituric acid reactive substances (TBARS) were higher in liver samples after 24 h of exposure to 22 mg/L trichlorfon compared to control group, as well as after 48 h of exposure to 11 and 22 mg/L trichlorfon in liver and gills. Finally, hepatic and branchial non-protein thiol (NPSH) levels were lower after 48 h of exposure to 11 and 22 mg/L trichlorfon. All evaluated parameters did not recover after 48 h in clean water. Based on these evidence, the impairment of phosphoryl transfer network can be considered a pathway involved in the hepatic and branchial metabolic alterations during exposure to sublethal concentrations of trichlorfon. Moreover, alterations on CK and PK activities provoke an impairment on Na+, K+-ATPase activity, which can be mediated by lipid oxidative damage and reduction of NPSH content.

Optimization of sample preparation by central composite design for multi-class determination of veterinary drugs in bovine muscle, kidney and liver by ultra-high-performance liquid chromatographic-tandem mass spectrometry.

In this study a simple and fast multi-class method for the determination of veterinary drugs in bovine liver, kidney and muscle was developed. The method employed acetonitrile for extraction followed by clean-up with EMR-Lipid® sorbent and trichloracetic acid. Tests indicated that the use of TCA was most effective when added in the final step of the clean-up procedure instead of during extraction. Different sorbents were tested and optimized using central composite design and the analytes determined by ultra-high-performance liquid chromatographic-tandem mass spectrometry (UHPLC-MS/MS). The method was validated according the European Commission Decision 2002/657 presenting satisfactory results for 69 veterinary drugs in bovine liver and 68 compounds in bovine muscle and kidney. The method was applied in real samples and in proficiency tests and proved to be adequate for routine analysis. Residues of abamectin, doramectin, eprinomectin and ivermectin were found in samples of bovine muscle and only ivermectin in bovine liver.

Method validation for the analysis of 169 pesticides in soya grain, without clean up, by liquid chromatography-tandem mass spectrometry using positive and negative electrospray ionization.

Part of a comprehensive study on the comparison of different extraction methods, GC-MS(/MS) and LC-MS/MS detection methods and modes, for the analysis of soya samples is described in this paper. The validation of an acetone-based extraction method for analysis of 169 pesticides in soya, using LC-MS/MS positive and negative electrospray ionisation (ESI) mode, is reported. Samples (5 g) were soaked with 10 g water and subsequently extracted with 100 mL of a mixture of acetone, dichloromethane and light petroleum (1:1:1), in the presence of 15 g anhydrous sodium sulphate. After centrifugation, aliquots of the extract were evaporated and reconstituted in 1.0 mL of methanol, before direct injection of the final extract (corresponding with 0.05 g soya mL(-1)) into the LC-MS/MS system. Linearity, r(2) of calibration curves, instrument limit of detection/quantitation (LOD/LOQ) and matrix effect were evaluated, based on seven concentrations measured in 6-fold. Good linearity (at least r(2)> or =0.99) of the calibration curves was obtained over the range from 0.1 or 0.25 to 10.0 ng mL(-1), corresponding with pesticide concentrations in soya bean extract of 2 or 5-200 microg kg(-1). Instrument LOD values generally were 0.1 or 0.25 ng mL(-1). Matrix effects were negligible for approximately 90% of the pesticides. The accuracy, precision and method LOQ were determined via recovery experiments, spiking soya at 10, 50, 100 microg kg(-1), six replicates per level. In both ESI modes, method LOQ values were mostly 10 or 50 microg kg(-1) and more than 70% of pesticides analysed by each mode met the acceptability criteria of recovery (70-120%) and RSD (< or =20%), at one or more of the three levels studied. A fast, easy and efficient method with acceptable performance was achieved for a difficult matrix as soya, without cleanup.

Evaluation of an alternative fluorinated sorbent for dispersive solid-phase extraction clean-up of the quick, easy, cheap, effective, rugged, and safe method for pesticide residues analysis.

In this study, the efficiency of a new fluorinated sorbent for dispersive solid-phase extraction (d-SPE) clean-up in extracts provided by the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) acetate method from tomato and sweet pepper samples was evaluated by ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). Clean-up using d-SPE technique has been widely used associated with the QuEChERS method. The most commonly sorbents used in d-SPE are primary secondary amine (PSA), octadecylsilane (C18) and graphitized carbon black (GCB), which are indicated to remove sugars, fatty acids, pigments, among others. The performance of an alternative fluorinated sorbent was compared with PSA and C18 sorbents for representative pesticides and better results were obtained when the fluorinated sorbent was used. Validation presented acceptable results for trueness and precision, with method limit of detection between 0.9 and 1.8µgkg-1 and limit of quantification from 2.6 to 5.4µgkg-1. Most of the compounds presented low matrix effect. Results showed that the fluorinated sorbent contribute to the clean-up of the tomato extract and is an effective alternative, with lower costs and greater efficiency. Commercial tomato samples were analyzed using the proposed method and residues of dimethoate, tetraconazole and thiamethoxam were detected.

Evaluation of the rotating disk sorptive extraction technique with polymeric sorbent for multiresidue determination of pesticides in water by ultra-high-performance liquid chromatography-tandem mass spectrometry.

The use of pesticides has been associated with the increase of productivity of crops and control of vectors that cause diseases. However, excessive use of these compounds can cause human health and environmental problems, especially regarding to water resources. In this work, a method for multiresidue determination of 62 pesticides in surface water using the rotating disk sorptive extraction (RDSE) technique for sample preparation and ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) for analysis was optimized and validated. The parameters time and rotational disk velocity for the extraction step, types and amounts of sorbents, sample pH, ionic strength, time and velocity of the rotating disk in the desorption step, as well different desorption solvents were evaluated. The best results were obtained using 50mL of sample, acidified at pH 2.0, and 2.5g of sodium chloride. The selected velocity of rotation in the extraction step was 1600rpm for 80min. Inside the disk cavity, a small amount (20mg) of the polymeric sorbent Oasis® HLB was used. The desorption step was performed immerging the disk in 3mL of methanol and rotating the disk at 1600rpm for 60min. Procedural calibration curves showed linearity between 0.05 or 0.1-2µgL-1, with r2>0.99 for all compounds. The method presented practical limit of quantification of 0.05 or 0.1µgL-1 and suitable accuracy and precision, with recoveries from 70.1 to 119.9% and RSD≤20% for the levels 0.05, 0.1, 0.5 and 2µgL-1. The validated method was applied to surface water samples from different river and residues of atrazine, azoxystrobin, clomazone, difenoconazole, epoxiconazole, propoxur, simazine and tebuconazole were found in the range of 0.06-0.35µgL-1. The results indicate that the proposed method is suitable for the determination of pesticide residues in surface water, allowing an easy and simultaneously preparation of several samples with low material consumption.

Multiresidue determination of pesticides in crop plants by the quick, easy, cheap, effective, rugged, and safe method and ultra-high-performance liquid chromatography tandem mass spectrometry using a calibration based on a single level standard addition in the sample.

In this study, a QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method, optimized by a 23 full factorial design, was developed for the determination of 72 pesticides in plant parts of carrot, corn, melon, rice, soy, silage, tobacco, cassava, lettuce and wheat by ultra-high-performance liquid chromatographic tandem mass spectrometry (UHPLC-MS/MS). Considering the complexity of these matrices and the need of use calibration in matrix, a new calibration approach based on single level standard addition in the sample (SLSAS) was proposed in this work and compared with the matrix-matched calibration (MMC), the procedural standard calibration (PSC) and the diluted standard addition calibration (DSAC). All approaches presented satisfactory validation parameters with recoveries from 70 to 120% and relative standard deviations≤20%. SLSAS was the most practical from the evaluated approaches and proved to be an effective way of calibration. Method limit of detection were between 4.8 and 48µgkg-1 and limit of quantification were from 16 to 160µgkg-1. Method application to different kinds of plants found residues of 20 pesticides that were quantified with z-scores values≤2 in comparison with other calibration approaches. The proposed QuEChERS method combined with UHPLC-MS/MS analysis and using an easy and effective calibration procedure presented satisfactory results for pesticide residues determination in different crop plants and is a good alternative for routine analysis.

An effective method for pesticide residues determination in tobacco by GC-MS/MS and UHPLC-MS/MS employing acetonitrile extraction with low-temperature precipitation and d-SPE clean-up.

An effective method has been developed and validated for the determination of residues of 55 pesticides in tobacco. The proposed sample preparation method is based on acetonitrile extraction, low-temperature precipitation (LTP) and dispersive solid phase extraction (d-SPE) clean-up. Gas chromatography and ultra-high performance liquid chromatography analysis, both coupled to tandem mass spectrometry (GC-MS/MS and UHPLC-MS/MS), were used for determination. LTP is easy to perform and was crucial to obtain a clean extract. Method quantification limit for the pesticides were between 25 and 75µgkg-1. Extraction recoveries obtained for blank samples spiked at 25, 75, 125 and 250µgkg-1 levels ranged from 63 to 161% with relative standard deviations (RSD)≤20%. The method was successfully applied to the analysis of thirteen different tobacco samples, providing to be a robust procedure for routine analysis. The compounds pirimiphos methyl and isofenphos presented residues in the range of 35-51µgkg-1.