Carbamate Pesticides In Water Samples Research Articles

Dual-use ionization source for direct and sensitive detection of trace carbamates residue

Directly determining trace compounds in actual sample by ambient ionization mass spectrometry (AIMS) has always been a challenge. Due to the excellent adsorption and desorption properties of nanomaterials, AIMS combined with nanomaterials can improve the adsorption and desorption properties of MS. In this work, we developed a molecularly imprinted graphene oxide coated steel sheet (MIGOCS) to be used as a solid phase extraction adsorbent. Graphene oxide was characterized by its strong adsorption abilities, and the surface molecularly imprinted polymer has high selectivity. Here, the MIGOCS coupled with the ambient electrospray ion source was used to detect trace carbamate pesticides in water samples. Meanwhile, the extraction and spray parameters were systematically optimized. The newly developed molecularly imprinted graphene oxide-steel sheet spray-mass spectrometry (MIGO-SS-MS) method has low detection limits (0.05 ∼ 0.4 ng mL−1) and satisfactory recoveries (83.23 ∼ 97.98 %) for carbamates (CMs). The method can be potentially applied to the determination of CMs in water and food samples.

Spherical conjugated microporous polymers for solid phase microextraction of carbamate pesticides from water samples.

Conjugated microporous polymers (CMPs) with uniform morphology have shown fascinating application in the separation science. In this study, metal-free Knoevenagel condensation was adopted to prepare spherical sp2 carbon-conjugated microporous polymers, which used tetrakis(4-formylphenyl)methane and 1,4-phenylenediacetonitrile as monomers. Due to the remarkable extraction capability for carbamate pesticides (CPs), the as-synthesized CMPs were fabricated as the coating for solid-phase microextraction (SPME). After optimized SPME parameters (adsorption time, salt concentration, sample pH, adsorption temperature, desorption time, desorption solvent and desorption volume), ten CPs in water samples were quantified by ultrahigh performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Linearity in the range 0.005-100ng mL-1 with low detection limits of 0.00060-0.017ng mL-1 was obtained. The intra-day and inter-day precisions expressed as relative standard deviations were 1.5-8.1% and 1.1-8.0%, respectively. Fiber-to-fiber reproducibility was below 7.3%. The CMPs-SPME-UPLC-MS/MS method was applied to detect trace CPs in real water samples with relative recoveries from 91.8% to 108%.

Bubble-in-drop microextraction of carbamate pesticides followed by gas chromatography-mass spectrometric analysis

Bubble-in-drop microextraction (BID) is a variation of single-drop microextraction in which an air bubble is deliberately introduced to the solvent to enhance extraction efficiency. Here, BID coupled with GC-MS was developed for the extraction, enrichment and determination of carbamate pesticides in environmental water samples. Conditions affecting BID performance including the type of extraction solvent and its volume, volume of air bubble, extraction time, stirring rate, salt concentration and sample pH were evaluated. Under the most favorable BID conditions, the method provided good linearities from 0.05 to 20.0 μg L−1 with the coefficients of determination higher than 0.99. Enrichment factors were determined to be between 536 and 1097. The limits of detection and limits of quantification were in the ranges of 0.02 to 0.04 μg L−1, and 0.05 to 0.13 μg L−1, respectively. BID-GC-MS was successfully applied to the determination of carbamate pesticides in water samples with satisfactory recoveries from 81.7% to 99.0%, and intra-day and inter-day precision (relative standard deviations of <7% and <8%, respectively).

Graphene-modified TiO2 nanotube arrays as an adsorbent in micro-solid phase extraction for determination of carbamate pesticides in water samples

Graphene is a good adsorbent for organic pollutants, especially for compounds containing benzene rings. When used in TiO2 nanotube arrays for micro-solid phase extraction (μ-SPE), the combination of graphene’s strong adsorptive properties with its good separation capabilities results in excellent sample preconcentration performance. In the present study, graphene-modified TiO2 nanotube arrays were prepared by electrodeposition using a cyclic voltammetric reduction method. Four carbamate pesticides, including metolcarb, carbaryl, isoprocarb, and diethofencarb, were used as model analytes to validate the enrichment properties of the prepared adsorbent in μ-SPE. Factors affecting the enrichment efficiency of the μ-SPE procedure were optimized and included sample pH, elution solvents, salting-out effect, adsorption time and desorption time. Under optimal conditions, graphene-modified TiO2 nanotube arrays exhibited excellent enrichment efficiency for carbamate pesticides. The detection limits of these carbamate pesticides ranged from 2.27 to 3.26μgL−1. The proposed method was validated using four environmental water samples, and yields of pesticides recovered from spiked test samples of the four analytes were in the range of 83.9–108.8%. These results indicate that graphene-modified TiO2 nanotube arrays exhibit good adsorption to the target pollutants, and the method described in this work could be used as a faster and easier alternative procedure for routine analysis of carbamate pesticides in real water samples.

A solid-phase microextraction-gas chromatographic approach combined with triple quadrupole mass spectrometry for the assay of carbamate pesticides in water samples

A simple and sensitive method was developed for the quantification of five carbamate pesticides in water samples using solid phase microextraction (SPME) combined with gas chromatography-triple quadrupole mass spectrometry (GC-QqQ-MS). The performance of five SPME fibers was tested in univariate mode whereas the other variables affecting the efficiency of SPME analysis were optimized by the multivariate approach of design of experiment (DoE) and, in particular, a central composite design (CCD) was applied. The optimum working conditions in terms of response values were achieved by performing analysis with polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber in immersion mode for 45min at room temperature with addition of NaCl (10%). The multivariate chemometric approach was also used to explore the chromatographic behavior of the carbamates and to evaluate the importance of each variable investigated. An overall appraisement of results shows that the factor which gave a statistically significant effect on the response was only the injection temperature. Identification and quantification of carbamates was performed by using a gas chromatography-triple quadrupole mass spectrometry (GC-QqQ-MS) system in multiple reaction monitoring (MRM) acquisition. Since the choice of internal standard represented a crucial step in the development of method to achieve good reproducibility and robustness for the entire analytical protocol, three compounds (2,3,5-trimethacarb, 4-bromo-3,5-dimethylphenyl-n-methylcarbamate (BDMC) and carbaryl-d7) were evaluated as internal standards. Both precision and accuracy of the proposed protocol tested at concentration of 0.08, 5 and 3μgl−1 offered values ranging from 70.8% and 115.7% (except for carbaryl at 3μgl−1) and from 1.0% and 9.0% for accuracy and precision, respectively. Moreover, LOD and LOQ values ranging from 0.04 to 1.7ngl−1 and from 0.64 to 2.9ngl−1, respectively, can be considered very satisfactory.

Ultratrace determination of carbamate pesticides in water samples by temperature controlled ionic liquid dispersive liquid phase microextraction combined with high performance liquid phase chromatography

A simple and sensitive method was developed for the determination of three carbamate pesticides in water samples. It is based on temperature controlled ionic liquid dispersive liquid phase microextraction combined with high-performance liquid chromatography. The ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate was used as the extractant, and the factors affecting the extraction were investigated in detail. The detection limits obtained for isoprocarb, diethofencarb and fenothiocarb are 0.91, 0.45, and 1.40 μgL-1, respectively, and the precisions are in the range between 1.0 and 1.8% (n = 6). The method was validated with environmental water samples and the results indicate that it represents a viable alternative to existing methods.

Ultrasound-assisted surfactant-enhanced emulsification microextraction for the determination of carbamate pesticides in water samples by high performance liquid chromatography

A novel ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) coupled with high performance liquid chromatography-diode array detection has been developed for the extraction and determination of six carbamate pesticides (metolcarb, carbofuran, carbaryl, pirimicarb, isoprocarb and diethofencarb) in water samples. In the UASEME technique, Tween 20 was used as emulsifier, and chlorobenzene and chloroform were used as dual extraction solvent without using any organic dispersive solvent that is normally required in the previously described common dispersive liquid-liquid microextraction method. Parameters that affect the extraction efficiency, such as the kind and volume of the extraction solvent, the type and concentration of the surfactant, ultrasound emulsification time and salt addition, were investigated and optimized for the method. Under the optimum conditions, the enrichment factors were in the range between 170 and 246. The limits of detection of the method were 0.1-0.3 ng mL(-1) and the limits of quantification were between 0.3 and 0.9 ng mL(-1), depending on the compounds. The linearity of the method was obtained in the range of 0.3-200 ng mL(-1) for metolcarb, carbaryl, pirimicarb, and diethofencarb, 0.6-200 ng mL(-1) for carbofuran, and 0.9-200 ng mL(-1) for isoprocarb, with the correlation coefficients (r) ranging from 0.9982 to 0.9998. The relative standard deviations varied from 3.2 to 4.8% (n=5). The recoveries of the method for the six carbamates from water samples at spiking levels of 1.0, 10.0, 50.0 and 100.0 ng mL(-1) were ranged from 81.0 to 97.5%. The proposed UASEME technique has demonstrated to be simple, practical and environmentally friendly for the determination of carbamates residues in river, reservoir and well water samples.

Low-density extraction solvent-based solvent terminated dispersive liquid–liquid microextraction combined with gas chromatography-tandem mass spectrometry for the determination of carbamate pesticides in water samples

A simple and fast method of low-density extraction solvent-based solvent terminated dispersive liquid–liquid microextraction (ST-DLLME) was developed for the highly sensitive determination of carbamate pesticides in the water samples by gas chromatography-tandem mass spectrometry (GC-MSMS). After dispersing, the obtained emulsion cleared into two phases quickly when an aliquot of acetonitrile was introduced as a chemical demulsifier into the aqueous bulk. Therefore, the developed procedure does not need centrifugation to achieve phase separation. It was convenient for the usage of low-density extraction solvents in DLLME. Under the optimized conditions, the limits of detection for all target carbamate pesticides were in range of 0.001–0.50 ng mL −1 and the precisions were in the range of 2.3–6.8% (RSDs, 2 ng mL −1, n = 5). The proposed method has been successfully applied to the analysis of real water samples and good spiked recoveries over the range of 94.5–104% were obtained.

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.

Application of dispersive liquid–liquid microextraction combined with high-performance liquid chromatography to the determination of carbamate pesticides in water samples

A rapid and sensitive method has been established for the determination of four carbamate pesticides (carbofuran, carbaryl, pirimicarb, and diethofencarb) in water samples by using dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography-diode array detection. Parameters that affect the extraction efficiency, such as the kind and volume of the extraction and disperser solvent, extraction time, and salt addition, were investigated and optimized. Under the optimum conditions, the enrichment factors were in the range between 101 and 145. The linearity of the method was obtained in the range of 5-500 ng mL(-1) with the correlation coefficients (r) ranging from 0.9978 to 0.9997. The method detection limits were 0.4-1.0 ng mL(-1). The relative standard deviations varied from 4.7% to 6.5% (n = 5). The relative recoveries of the four carbamates from water samples at spiking levels of 5.0 and 20.0 ng mL(-1) were 84.0-92.0% and 86.5-94.0%, respectively. The proposed method has been successfully applied to the analysis of target carbamate residues in river, rain, well, and tap water samples with satisfactory results.

Novel method for the determination of five carbamate pesticides in water samples by dispersive liquid–liquid microextraction combined with high performance liquid chromatography

A novel method for the determination of five carbamate pesticides (metolcarb, carbofuran, carbaryl, isoprocard and diethofencard) in water samples was developed by dispersive liquid–liquid microextraction (DLLME) coupled with high performance liquid chromatography-diode array detector (HPLC-DAD). Some experimental parameters that influence the extraction efficiency were studied and optimized to obtain the best extraction results. Under the optimum conditions for the method, the calibration curve was linear in the concentration range from 5 to 1000 ng mL −1 for all the five carbamate pesticides, with the correlation coefficients ( r 2) varying from 0.9984 to 0.9994. Good enrichment factors were achieved ranging from 80 to 177-fold, depending on the compound. The limits of detection (LODs) (S/N = 3) were ranged from 0.1 to 0.5 ng mL −1. The method has been successfully applied to the analysis of the pesticide residues in environmental water samples.

Analysis of carbamate pesticides in water samples using single-drop microextraction and gas chromatography–mass spectrometry

Single-drop microextraction (SDME) followed by gas chromatography-mass spectrometry detection was used for the determination of some carbamate pesticides in water samples. The studied pesticides were thiofanox, carbofuran, pirimicarb, methiocarb, carbaryl, propoxur, desmedipham and phenmedipham. Two alternative sample introduction methods have been examined and compared; SDME followed by cool on-column injection (without derivatization) and SDME followed by in-microvial derivatization and splitless injection. Acetic anhydride was used as derivatization reagent. Parameters that affect the derivatization reaction yield and the extraction efficiency of the SDME method were studied and optimized. The analytical performances and possible applications of both approaches were investigated. Relative standard deviations for the studied compounds ranged from 3.2 to 8.3%. The detection limits obtained by the derivatization method were found to be in the range 3-35 ng/L. Using cool on-column injection (without derivatization), the detection limits were between 30 and 80 ng/L.

Application of liquid-phase microextraction and on-column derivatization combined with gas chromatography–mass spectrometry to the determination of carbamate pesticides

A method has been established for the determination of five carbamate pesticides in water samples using liquid-phase microextraction (LPME) followed by on-column derivatization and gas chromatography–mass spectrometric (GC–MS) determination. Trimethylphenylammonium hydroxide (TMPAH) and trimethylsulfonium hydroxide (TMSH) were used as derivatization reagent for extracts prior to GC–MS analysis as carbamate pesticides are thermally labile compounds. Parameters that affect the extraction efficiency (selection of organic solvent and extraction time) and derivatization efficiency (choice of derivatization reagent and concentration of derivatization reagent) were investigated. The proposed method provided good enrichment factors up to 224, with reproducibility ranging from 4.86 to 7.81%, and good linearity from 1 to 400 μg/L. The limits of detection (LODs) ranged between 0.2 and 0.8 μg/L (S/N = 3) using GC–MS with selective ion monitoring. This method was applied to the determination of carbamate pesticides in tap water and waste water.

Semi disposable reactor biosensors for detecting carbamate pesticides in water

Two flow-injection biosensor systems using semi disposable enzyme reactor have been developed to determine carbamate pesticides in water samples. Acetylcholinesterase was immobilized on silica gel by covalent binding. pH and conductivity electrodes were used to detect the ionic change of the sample solution due to hydrolysis of acetylcholine. Carbamate pesticides inhibited acetylcholinesterase and the decrease in the enzyme activity was used to determine these pesticides. Parameters influencing the performance of the systems were optimized to be used in the inhibition procedure. Carbofuran and carbaryl were used to test these systems. Detection limits for the potentiometric and conductimetric systems were both at 10% inhibition corresponding to 0.02 and 0.3 ppm of carbofuran and carbaryl, respectively. Both systems also provided the same linear ranges, 0.02-8.0 ppm for carbofuran, and 0.3-10 ppm for carbaryl. The analysis of pesticides was done a few times before the reactor was disposed. Percentages of inhibition obtained from different reactors were reproducible, therefore, no recalibration was necessary when changing the reactor. The biosensors were used to analyze carbaryl in water samples from six wells in a vegetable growing area. Both systems could detect the presence of carbaryl in the samples and provided good recoveries of the added carbaryl, i.e., 80-106% for the potentiometric system and 75-105% for the conductimetric system. The presence of carbaryl in water samples analyzed by the biosensors was confirmed by gas chromatography-mass spectrometric system. These biosensors do not require any sample preconcentration and are suitable for detecting pesticides in real water samples.

On-line coupling of in-tube solid phase microextraction (SPME) to HPLC for analysis of carbamates in water samples: Comparison of two commercially available autosamplers

In-tube solid phase microextraction (SPME) is a new on-line sample preparation technique that is easily installed on a conventional high-performance liquid chromatography (HPLC) autosampler, and has previously been used with the LC Packings FAMOS autosampler without modification of the autosampler itself. This paper describes the on-line coupling of in-tube SPME to a Hewlett Packard (HP) model 1100 HPLC autosampler, and reports on several fundamental aspects of the technology. The extraction and desorption processes with this system were thoroughly studied for a group of carbamate pesticides in water samples. The similarities and differences of the in-tube SPME technique with the two different autosamplers, FAMOS and Hewlett Packard, were compared during method development. The optimized conditions were successfully applied to extract the carbamates of interest from spiked surface, well, and tap water samples, exhibiting excellent method precision. The % relative standard deviation (RSD) for all the carbamates studied in the different environmental water samples was between 0.8 and 6.0%. There was no noticeable extraction efficiency decrease relative to pure laboratory samples when the method was applied to spiked environmental water samples. The method was found to be linear between 2 and 20,000 μg/L with correlation coefficients in the range of 0.9791 to 0.9991. With respect to the different water samples, the limits of detection (LODs) for all the carbamates studied were in the range of 0.44–17 μg/L. For carbaryl, the LODs were between 0.44 and 0.67 μg/L, which were lower than those obtained using the in-tube SPME method with the FAMOS autosampler. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 125–134, 2000