Determination Of Carbamate Pesticides Research Articles

A Green Bridge: Enhancing a Multi-Pesticide Test for Food by Phase-Transfer Sample Treatment Coupled with LC/MS.

The preparation and treatment of the sample has become an important part of the determination process, which directly affects the accuracy of detection. The preparation of the sample for final detection is actually a process of separation and transfer of the target to be tested from the sample matrix. The phase-transfer process of analysis and detection is the process of transferring the target substance to be measured from a complex multiphase system to a simple homogeneous system. This study shows a new phase-transfer process for food sample pretreatment in the determination of carbamate pesticides. Edible gum, xanthan gum, carrageenan, and gelatin were selected for purification testing from the perspective of eco-friendliness and safety. Phase-transfer purification process research was carried out on spinach and other foods. Compared with the commonly used QuEChERS method, the LC/MS results indicate that the straightforward carrageenan treatment process can significantly diminish the detection matrix effect and yield similarly superior detection parameters. The phase-transfer purification method with carrageenan has similar sensitivity and systematic error. The limits of detection and limits of quantitation of each pesticide compound in six plant sample substrates were 0.02-0.36 μg/kg and 0.06-1.9 μg/kg, respectively, which were lower than the residue limits here and abroad. Supplemental recoveries in six blank samples at 5, 20, and 100 μg/kg with the phase-transfer process method were better than those for the QuEChERS method. Positive determination results of actual samples using carrageenan phase-transfer purification proved that this method can be used for related detection from a practical point of view.

Determination of 10 carbamate pesticide residues in liquid milk by ultra performance liquid chromatography-tandem mass spectrometry with pass-through solid-phase extraction purification

Carbamates are used in broad-spectrum insecticides and herbicides, and have highly efficient, low-residue, and long-lasting characteristics. However, this type of pesticide exerts mutagenic, teratogenic, carcinogenic, and other adverse effects, and its frequent use can exceed the recommended scope and limits. Research on the determination of carbamate pesticides mainly focuses on foods of plant origin and pays less attention to foods of animal origin. The methods for carbamate determination described in the current national standards have complicated operating procedures and low efficiency. Therefore, highly efficient and accurate methods for carbamate detection in milk must be established. In this work, a rapid method based on pass-through solid-phase extraction (SPE) purification coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of 10 carbamate pesticides in liquid milk. The pretreatment and instrument methods were systematically optimized. The milk sample was extracted with acetonitrile, and then purified using a Captiva EMR-Lipid filtration kit. The purified extract was separated on an ACQUITY UPLC BEH C18 column with mobile phase of methanol and 0.1% formic acid aqueous solution in gradient elution. The flow rate was 0.3 mL/min. Column temperature was 35 ℃. Quantitative analysis was performed using the external standard method with matrix matching curves. The 10 carbamate pesticides showed good linear relationships in the mass concentration range of 2-200 μg/L, with correlation coefficients greater than 0.999. The limits of detection (LODs) and quantification (LOQs) for the 10 carbamate pesticides were 0.045-0.23 and 0.15-0.77 μg/kg, respectively. Recovery tests were conducted using the blank-matrix method at three spiked levels of 15, 50, and 100 μg/kg, and good recoveries for the 10 carbamate pesticides were obtained. In particular, the recoveries for the three spiked levels of 15, 50, and 100 μg/kg were 68.7%-93.3% with relative standard deviations (RSDs) of 1.8%-8.0%. The proposed method is efficient, convenient, accurate, and suitable for the rapid detection of the 10 carbamate pesticides in liquid milk. Compared with the conventional NH2 and ENVITM-18 SPE columns used in the national standard determination method, the proposed method demonstrated better purification effects. The recoveries for aldicarb sulfoxide, aldicarb sulfone, methomyl, and carbaryl after purification using the Captiva EMR-Lipid kit increased from 60% to 80%. Thus, the proposed method is suitable for targets with strong polarity and gives measurement results with good repeatability and accuracy.

Efficient Extraction and Determination of Carbamate Pesticides in Vegetables Based on a Covalent Organic Frameworks with Acylamide Sites

It is an important challenge to effectively extract and determine pesticides in complex samples. Covalent organic frameworks (COFs) are burgeoning porous crystalline organic materials with good environmental resistance, thus demonstrating great potential as adsorbents in contaminants detection. In this work, we design and synthesize a novel COF-TpDB via 1,3,5-triformylphloroglucinol (Tp) and 4,4′-diaminobenzoylanilide (DB) as well as its packed cartridge for solid phase extraction (SPE) of carbamate pesticides. Simulation calculations showed H-bonding facilitates the adsorption interactions between the carbamate pesticides and TpDB. A method was developed by coupling TpDB as SPE sorbents with high performance liquid chromatography-ultraviolet (HPLC-UV) detection to determine trace carbamate pesticides in vegetables. The established method showed a wide linear range of 0.1–200 ng mL−1 and low limit of detections (0.005–0.05 ng mL−1) for four carbamate pesticides. The applicability of TpDB as adsorbent was investigated for determination of trace carbamate pesticides residue in vegetables with satisfactory recoveries of four carbamates in the range of 80.4–101.2%. The results demonstrated that the COF-TpDB offer great potential for efficient extraction of carbamate pesticides from complicate matrices.

Elevated Temperature Homogeneous Liquid Phase Extraction Coupled to Ionic Liquid–Based Dispersive Liquid–Liquid Microextraction Followed by High-Performance Liquid Chromatography: Application of Water-Miscible Ionic Liquids as Extraction Solvent in Determination of Carbamate Pesticides

In the present study, an elevated temperature homogeneous liquid extraction coupled with ionic liquid‑based dispersive liquid–liquid microextraction was developed to extract five carbamate pesticides (pirimicarb, carbaryl, methiocarb, aldicarb, and carbofuran) from packed fruit juice samples. The method consisted of a two-step procedure in which cyclohexylamine was used in order to extract the target analytes. In the first step, the analytes were extracted from a sample solution thermostated at elevated temperature (80 °C) into a water-immiscible organic solvent (cyclohexylamine). In the second step, the separated organic phase was mixed with 1-butyl-3-methylimidazolium chloride (as the solvent for extraction) and the mixture was spread into deionized water. In this step, cyclohexylamine controlled the solubility of 1-butyl-3-methylimidazolium chloride in the aqueous phase and acted as a dispersive solvent and a phase separation agent, simultaneously. After centrifugation, we removed all the gathered organic phases and analyzed them by using high-performance liquid chromatography diode-array detector. Figure of merits of the method including the limits of detection and quantification, enrichment factors, extraction recoveries, and relative standard deviations were obtained within ranges 0.4–3.9 and 1.5–13.2 ng mL−1, 147–217, 59–87%, and 3.3–5.5%, respectively, indicating that the method was successful in determining the analytes.

Standard addition method based on four-way PARAFAC decomposition to solve the matrix interferences in the determination of carbamate pesticides in lettuce using excitation–emission fluorescence data

The simultaneous determination of two carbamate pesticides (carbaryl and carbendazim) and of the degradation product of carbaryl (1-naphthol) in iceberg lettuce was achieved by means of PARAFAC decomposition and excitation–emission fluorescence matrices. A standard addition method for a calibration based on four-way data was applied using different dilutions of the extract from iceberg lettuce as a fourth way that provided the enough variation of the matrix to carry out the four-way analysis. A high fluorescent overlapping existed between the three analytes and the fluorophores of the matrix. The identification of two fluorescent matrix constituents through the four-way model enabled to know the matrix contribution in each dilution of the extract. This contribution was subtracted from the previous signals and a subsequent three-way analysis was carried out with the tensors corresponding to each dilution. The PARAFAC decomposition of these resulting tensors showed a CORCONDIA index equal to 99%. For the identification of the analytes, the correlation between the PARAFAC spectral loadings and the reference spectra has been used. The trueness of the method, in the concentration range studied, was guaranteed because there was neither constant nor proportional bias according to the appropriate hypothesis tests. The best recovery percentages were obtained with the data from the most diluted extract, being the results: 127.6% for carbaryl, 125.55% for carbendazim and 87.6% for 1-naphthol. When the solvent calibration was performed, the decision limit (CCα) and the capability of detection (CCβ) values, in x0=0, were 2.21 and 4.38μgL−1 for carbaryl, 4.87 and 9.64μgL−1 for carbendazim; and 3.22 and 6.38μgL−1 for 1-naphthol, respectively, for probabilities of false positive and false negative fixed at 0.05. However, these values were 5.30 and 10.49μgL−1 for carbaryl, 18.05 and 35.73μgL−1 for carbendazim; and 1.92 and 3.79μgL−1 for 1-naphthol, respectively, when the matrix-matched calibration using the most diluted extract was carried out in the recovery study.

Determination of Carbamate Pesticides in Vegetables by Octadecyl Modified Graphene Reinforced Hollow Fiber Liquid Phase Microextraction Combined with High-Performance Liquid Chromatography

A novel adsorbent, octadecyl modified graphene, was prepared for hollow fiber liquid phase microextraction to increase the efficiency of the preconcentration process. The modified material was employed for the isolation of metolcarb, carbaryl, isoprocarb, and diethofencarb from vegetables prior to determination by high-performance liquid chromatography with diode array detection. Octadecyl modified graphene dispersed in 1-octanol served as the acceptor phase of the sorbent, resulting in enhanced efficiency. The optimization of several parameters was carried out to achieve the maximum efficiency. Under the optimized conditions, the calibration curve was linear from 0.5 to 100.0 nanograms per gram for carbaryl and 1.0 to 100.0 nanograms per gram for the other analytes with correlation coefficients (r) between 0.9952 and 0.9990. The limits of detection for the carbamates were from 0.2 to 0.6 nanogram per gram. The recoveries of the analytes ranged from 90.3 to 107.4 percent, indicating the excellent performance of the method for the determination of carbamates in vegetables.

Determination of Carbamate Pesticides and Phthalates in Vegetables by a Cloud Point Extraction Process Using Tergitol 15-s-7 and High Performance Liquid Chromatography

An efficient and environmentally friendly analytical process based on cloud point extraction (CPE) has been developed for the determination of carbamate pesticides and phthalates in vegetables by high performance liquid chromatography (HPLC) separation and ultraviolet detection (UV). The readily biodegradable nonionic surfactant Tergitol 15-S-7 was chosen as the extraction solvent. To obtain optimum extraction efficiency, several experimental parameters including surfactant concentration, salt concentration, equilibration temperature, equilibration time, and sample pH were identified. Under the optimum conditions, the linear regression coefficients of the standard curves were greater than 0.9984. The limits of detection for carbaryl, pirimicarb, dimethyl phthalate (DMP), and diethyl phthalate (DEP) are 0.003, 0.015, 0.012, and 0.006 µg mL−1, respectively. The intra-day and inter-day relative standard deviations are less than 5.75% and 6.97%. The proposed method has been proven to be an efficient, green, rapid, and inexpensive approach for extraction and determination of target analytes present in vegetable samples.

Ionic liquid magnetic bar microextraction and HPLC determination of carbamate pesticides in real water samples

We have developed a simple method for the microextraction of the carbamate pesticides carbofuran, pirimicarb, and carbaryl. It is termed ionic liquid magnetic bar microextraction (ILMB-ME) and based on an ionic liquid deposited on a magnetic stirrer bar placed in a sealed short PCR tube into which microholes where pinned. When placed in a vial containing the aqueous sample solution, the ILMB tumbles freely in the aqueous solution and the carbamates are extracted into the ionic liquid phase which then was determined by HPLC. The enrichment factors for carbofuran, pirimicarb, and carbaryl are 107, 94, 95, respectively. The limits of detection, calculated as three times the signal-to-noise ratio (S/N), are 1.4 μg L−1 for carbofuran, 3.4 μg L−1 for pirimicarb, and 1.7 μg L−1 for carbaryl. The repeatability, carried out by extracting water samples spiked with carbamate levels of 200 μg L−1, yielded relative standard deviations between 2.9 and 6.0 %, (for n = 5). The recoveries of all the three fungicides from tap, lake and rain water samples at spiking levels of 5 and 50 μg L−1 are in the range from 86 to 98 %, and from 80 to 96 %, respectively. We conclude that this is a simple, practical and efficient method for the determination of fungicide residues in real water samples.

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 carbamates at trace levels in water and cucumber by capillary liquid chromatography

A sensitive and reliable method using capillary HPLC with UV-diode array detection (DAD) has been developed and validated for trace determination of carbamate pesticides in cucumber and environmental water samples. The analytes, including carbofuran, carbaryl, methiocarb, promecarb, benthiocarb and fenoxycarb, present legal residue levels regulated by the EU Council Directive 98/83/EC on drinking water and by the Regulation (EC) No. 396/2005 on vegetables. A previous off-line solid-phase extraction (SPE) procedure was required for preconcentration and sample clean-up. The separation was achieved using a C18 column (150 mm × 0.5 mm I.D, 5 µm particle size) and a mobile phase consisting of ACN : water using gradient mode, with a flow rate of 10 µl min−1. Taking advantages of the characteristics of capillary HPLC, low volume of sample and solvents were required, achieving limits of detection for the studied compounds ranged from 10.0–29.6 ng l−1 for water samples and 1.8–5.6 µg kg−1 for cucumber, using UV-detection. Recoveries studies for fortified samples, at three different concentration levels, were carried out obtaining recoveries ranging from 70.0 to 111.1% and relative standard deviations (RSDs) lower than 10.6%.

Simultaneous enzymatic kinetic determination of carbamate pesticides with the aid of chemometrics

A method for the simultaneous enzymatic kinetic determination of the pesticides, oxamyl, aldicarb and aminocarb in fruit, vegetables and water samples, has been researched and developed. It was based on enzymatic reaction kinetics and spectrophotometric measurements, and results were interpreted with the aid of chemometrics. The analytical method relies on the inhibitory effect of the pesticides on acetylcholinesterase (AChE), and the use of 5,5′-dithiobis (2-nitrobenzoic) acid (DTNB) as a chromogenic reagent for the thiocholine iodide (TChI) released from the acetylthiocholine iodide (ATChI) substrate. The complex rate equation for the formation of the chromogenic product, P, was solved under certain experimental conditions, and this enabled the absorbance (A p, at λ max = 412 nm) from the mixtures of the three pesticide inhibitors to be directly related to their concentrations. The detection limits of the enzymatic kinetic spectrophotometric procedures for the determination of the oxamyl, aldicarb and aminocarb were 0.81, 2.13 and 1.25 ng mL−1, respectively. Calibration models were constructed for principal component regression (PCR), partial least squares (PLS), and radial basis function-artificial neural network (RBF-ANN), and verified with synthetic samples of the three pesticides. The prediction performance of these models showed generally satisfactory results, and the RBF-ANN one performed slightly better than the other two (RPET = 7.59% and average %recovery = 99%). This model was then successfully applied to estimate the amounts of the three compounds in fruit, vegetables and water with satisfactory results.

Dispersive liquid–liquid microextraction followed by high-performance liquid chromatography for the determination of three carbamate pesticides in water samples

A simple, rapid and efficient method, dispersive liquid–liquid microextraction (DLLME) in conjunction with high-performance liquid chromatography (HPLC), has been developed for the determination of three carbamate pesticides (methomyl, carbofuran and carbaryl) in water samples. In this extraction process, a mixture of 35 µL chlorobenzene (extraction solvent) and 1.0 mL acetonitrile (disperser solvent) was rapidly injected into the 5.0 mL aqueous sample containing the analytes. After centrifuging (5 min at 4000 rpm), the fine droplets of chlorobenzene were sedimented in the bottom of the conical test tube. Sedimented phase (20 µL) was injected into the HPLC for analysis. Some important parameters, such as kind and volume of extraction and disperser solvent, extraction time and salt addition were investigated and optimised. Under the optimum extraction condition, the enrichment factors and extraction recoveries ranged from 148% to 189% and 74.2% to 94.4%, respectively. The methods yielded a linear range in the concentration from 1 to 1000 µg L−1 for carbofuran and carbaryl, 5 to 1000 µg L−1 for methomyl, and the limits of detection were 0.5, 0.9 and 0.1 µg L−1, respectively. The relative standard deviations (RSD) for the extraction of 500 µg L−1 carbamate pesticides were in the range of 1.8–4.6% (n = 6). This method could be successfully applied for the determination of carbamate pesticides in tap water, river water and rain water.

Determination of carbamate pesticides using micro-solid-phase extraction combined with high-performance liquid chromatography

We describe a simple and sensitive porous polypropylene membrane-protected micro-solid-phase extraction (μ-SPE) approach for the sample preparation and determination of carbamate pesticides in soil samples by high-performance liquid chromatography. The μ-SPE device consisted of C 18 sorbent held within a porous polypropylene envelope. In order to achieve optimum performance, several extraction parameters were optimized. Under the most favorable conditions, the extraction efficiency of the μ-SPE was very high, with detection limits in the range of 0.01–0.40 ng g −1. This is more than two orders of magnitude lower than the limits obtained by the United States Environmental Protection Agency Methods 8321A and 8318. A linear relationship was obtained for each analyte in the range of 2 and 200 ng g −1. The relative standard deviation for the analysis of aged soil samples spiked at 5 ng g −1 was ≤11%. The reproducibility of separate μ-SPE device used for experiments was satisfactory (relative standard deviations ranged from 4 to 11%), indicating that the method is reliable for routine environmental analysis.

Determination of carbamate pesticides in environmental samples as their trifluoroacetyl or methyl derivatives by using gas chromatography–mass spectrometry

A method for the determination of seven carbamate pesticides in water and sediment samples is reported. Samples, after extraction and/or a clean-up procedure, were treated with trifluoroacetic anhydride or diazomethane. The resulting trifluoroacetyl or methyl derivatives were determined by capillary GC–MS with selected-ion monitoring. The carbamates could be determined to levels of 0.05–1.00 ng ml–1 in water with relative standard deviations (sr) or 2.6–22.6% and 10 ng g–1 in sediment with sr values of 5.0–20.3%. The detection limits of the carbamates in water and sediment were 0.014–0.18 ng ml–1 and 1.6–4.6 ng g–1, respectively. Their recoveries from water and sediment were 83–127% and 55–129%, respectively.

Examination of Conditions for the Determination of Carbamate Pesticides in Soils

The procedure for the determination of carbamate pesticides in soil was optimized. The following factors affecting the final results were investigated: extracting solvent, extraction procedure, extract purification procedure, and soil type. Triple extraction with acetone and purification of the extract on a two-stage purification column containing an activated carbon-silica gel 1+1 mixture were found optimal. The extracts after treatment were analyzed by RP-HPLC with UV detection. The method developed allows carbamate pesticides in soil to be determined at concentrations in excess of 30 μg kg-1.

Extraction, Cleanup and Liquid Chromatographic‐Diode Array Determination of Carbamate Pesticides in Soil Samples

Abstract Significant analytical problems occur during the isolation and assay of carbamate insecticide residues in soils. Nonetheless, liquid‐chromatographic diode array can be used to measure species concentrations (e.g., carbofuran, chlorpropham, carbaryl, propoxur, pirimicarb, and oxamyl) in the low ppm range. Low concentrations of the soil‐matrix breakdown product, 1‐naphthol, can also be measured. Several different extraction mixtures (e.g., acetone‐ethyl acetate, acetone‐dichloromethane, acetone‐methanol, and methanol alone) are compared. Cleanup procedures use Florisil column chromatography and several eluents, mixtures of acetone and dichloromethane. Aminopropyl‐silica and Florisil cartridges give promising results for routine analyses. Diode array detection is useful for obtaining UV‐spectral information of matrix interferences and blanks. Co‐eluted peaks may be differentiated using the second derivatives of spectra. The methodology is validated by analyzing residue levels of pirimicarb in real s...

Determination of carbamate pesticides and some urea pesticides after derivatization with acetic anhydride by means of GC-MSD

A simple method for the determination of several thermolabile carbamate and urea pesticides as acetyl derivatives by means of capillary gas chromatography is described. 10 carbamate and 6 urea pesticides yielded thermostable derivatives which can easily be analysed by GC-MSD at the relevant residue levels as demonstrated with food samples. The method was designed to be used in addition to a popular multimethod (S19 — DFG Pesticide Commission).

Determination of carbamate pesticides in fruits and vegetables by multi-dimensional high pressure liquid chromatography (author's transl)

Carbamatpesticide können auch in sehr komplex zusammengesetzten Obst- und Gemüsearten mit Hilfe der mehrdimensionalen Hochdruckflüssigkeitschromatographie im ppm-Bereich nachgewiesen werden. Dabei wird eine Fraktion des Effluents der ersten Säule, die das von Matrixbestandteilen nur unvollständig getrennte Pesticid enthält, mittels eines Schalthahns auf eine zweite Säule mit einer anderen stationären Phase gebracht, wo die Trennung vervollständigt wird. Die erhöhte Auflösung im Zweisäulen Betrieb wird durch die unterschiedlichen Selektivitätskoeffizienten von Wirkstoff und störenden Pflanzenbestandteilen in den beiden Phasensystemen bewirkt. Daneben kann man bei geeigneter Wahl der Fraktionsgrenzen eine relative Anreicherung des Carbamateserreichen. Da bei den verwendeten Phasensystemen die meisten Pflanzenbestandteile relativ schnell eluiert werden, gelingt besonders bei Carbamaten mit hohem Kapazitätskoeffizienten eine eindeutige Identifizierung und Quantifizierung manchmal schon mit der ersten chromatographischen Säule allein. Wegen der hohen Trennkapazität der mehrdimensionalen Hochdruckflüssigkeitschromatographie besteht die Probenvorbereitung nur aus einer Extraktion des Pflanzenmaterials mit Dichlormethan. Nach Ersatz des Extraktionsmittels durch die mobile Phase kann die Lösung direkt in den Flüssigkeitschromatographen injiziert werden.