-
Journal of Separation Science Jul 2011A sequential injection-bead injection-lab-on-valve system was hyphenated to HPLC for online renewable micro-solid-phase extraction of carbamate insecticides. The...
Sequential injection-bead injection-lab-on-valve coupled to high-performance liquid chromatography for online renewable micro-solid-phase extraction of carbamate residues in food and environmental samples.
A sequential injection-bead injection-lab-on-valve system was hyphenated to HPLC for online renewable micro-solid-phase extraction of carbamate insecticides. The carbamates studied were isoprocarb, methomyl, carbaryl, carbofuran, methiocarb, promecarb, and propoxur. LiChroprep(®) RP-18 beads (25-40 μm) were employed as renewable sorbent packing in a microcolumn situated inside the LOV platform mounted above the multiposition valve of the sequential injection system. The analytes sorbed by the microcolumn were eluted using 80% acetonitrile in 0.1% acetic acid before online introduction to the HPLC system. Separation was performed on an Atlantis C-18 column (4.6 × 150 mm, 5 μm) utilizing gradient elution with a flow rate of 1.0 mL/min and a detection wavelength at 270 nm. The sequential injection system offers the means of performing automated handling of sample preconcentration and matrix removal. The enrichment factors ranged between 20 and 125, leading to limits of detection (LODs) in the range of 1-20 μg/L. Good reproducibility was obtained with relative standard deviations of <0.7 and 5.4% for retention time and peak area, respectively. The developed method has been successfully applied to the determination of carbamate residues in fruit, vegetable, and water samples.
Topics: Carbamates; Chromatography, High Pressure Liquid; Food Contamination; Fruit; Insecticides; Pesticide Residues; Solid Phase Extraction; Vegetables; Water Pollutants, Chemical
PubMed: 21557471
DOI: 10.1002/jssc.201100075 -
Journal of Chromatography. A Aug 2010Six selected primary carbamate insecticides, methomyl, carbaryl, carbofuran, propoxur, isoprocarb, and promecarb, were hydrolyzed in alkaline solution, resulting in...
Six selected primary carbamate insecticides, methomyl, carbaryl, carbofuran, propoxur, isoprocarb, and promecarb, were hydrolyzed in alkaline solution, resulting in electroactive derivatives detectable at a platinum (Pt) electrode poised at +0.8 V vs Ag/AgCl (3 M NaCl). The Pt electrode was inserted into a small electrochemical cell and positioned close to the capillary outlet as an end-column detector to detect the carbamate derivatives after electrophoretic separation. Based on their predicted pK(a) values and aqueous solubilities, micellar electrokinetic chromatography (MEKC) was optimized for baseline separation of the derivatives using 20 mM borate, pH 10.2 containing 20 mM sodium dodecyl sulfate as a running buffer. When combined with solid-phase extraction (SPE) on octadecyl silica, a preconcentration factor of 100-fold achieved detection to 0.5 microM methomyl and to 0.01 microM for the remaining five pesticides, significantly below the level regulated by government agencies of most countries. The SPE-MEKC method when applied to the separation and analysis of spiked river water and soil samples, yielded results with excellent reproducibility, recovery and selectivity.
Topics: Borates; Carbamates; Chromatography, Micellar Electrokinetic Capillary; Electrodes; Electrophoresis, Capillary; Environmental Pollutants; Hydrogen-Ion Concentration; Insecticides; Linear Models; Platinum; Reproducibility of Results; Rivers; Sensitivity and Specificity; Sodium Dodecyl Sulfate; Soil Pollutants; Solid Phase Extraction; Solubility; Spectrophotometry, Ultraviolet
PubMed: 20598698
DOI: 10.1016/j.chroma.2010.06.024 -
Analytical and Bioanalytical Chemistry Jul 2010This study describes the use of stationary phases with polar functionality suitable for the chemical analysis of carbamates pesticides and comparing with conventional...
This study describes the use of stationary phases with polar functionality suitable for the chemical analysis of carbamates pesticides and comparing with conventional alkyl C8 and C18 phases. The emphasis of this study was to compare the selectivity and retention of the pesticides on different stationary phases, bonded onto 1.7 microm partially porous silica particles under isocratic separation condition. Four stationary phases including: phenylaminopropyl (PAP) phase, bidentate propylurea-C18 (BPUC(18)), C8 and C18, were successfully bonded on the partially porous silica spheres as evidenced by (29)Si and (13)C solid-state NMR analysis. The phenylaminopropyl phase exhibited smaller retentivity and enhanced selectivity compared to the alkyl C8 phase; the analysis time to run separation of the six carbamate pesticides (i.e., methomyl, propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) on the PAP phase was threefold faster than alkyl C8 phase. In a similar manner, the BPUC(18) phase shows similar selectivity to that of the PAP phase, but with longer retentivity; although the BPUC(18) phase is characterized with a lesser degree of retentivity for the carbamate pesticides than the conventional alkyl C18 phase. We propose that pi-pi and weak polar interactions between the carbamate pesticides and the PAP phase dominates the separation mechanism and providing a superior selectivity; faster separation time was also achieved as a result of smaller retentivity. Whereas the C8 and C18 bonded phases exhibits only hydrophobic interactions with the pesticides, leading to larger retentivity. The BPUC(18) phase is shown to interact via polar-polar interactions in addition to hydrophobic interactions with the pesticides, providing similar selectivity with the PAP phase but with larger retentivity.
Topics: Carbamates; Carbon Isotopes; Chromatography, Liquid; Hydrophobic and Hydrophilic Interactions; Isotopes; Magnetic Resonance Spectroscopy; Pesticides; Silicon
PubMed: 20496174
DOI: 10.1007/s00216-010-3816-3 -
Analytical and Bioanalytical Chemistry Jul 2009A cloud-point extraction (CPE) method using Triton X-114 non-ionic surfactant was developed for the extraction and preconcentration of carbamate insecticide residues...
A cloud-point extraction (CPE) method using Triton X-114 non-ionic surfactant was developed for the extraction and preconcentration of carbamate insecticide residues (i.e., methomyl, propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) in fruit samples. The optimum conditions of CPE were 1.5% (w/v) Triton X-114, 7.0% (w/v) NaCl and 20 min equilibrated at 45 degrees C. The surfactant-rich phase was then analyzed by reversed-phase high-performance liquid chromatography with ultraviolet detection at 270 nm, under gradient separation using methanol and 0.1% (v/v) acetic acid. Under the study conditions, six carbamate insecticides were successfully separated within 27 min. Good reproducibility was obtained with the relative standard deviation of <3% for retention time and <9% for peak area. Limits of detection in the studied fruit samples were in the range of 0.1-1.0 mg kg(-1). No carbamate insecticides were detected in the studied fruit samples. The high recoveries of the spiked fruit samples were obtained in the range 80.0-107%. The CPE method has been shown to be a potential useful methodology for the preconcentration of the target analytes, with a preconcentration factor of 14. Moreover, the method is simple, has high sensitivity, consumes much less solvent than traditional methods, and is environmental friendly.
Topics: Calibration; Carbamates; Centrifugation; Chemical Fractionation; Chromatography, High Pressure Liquid; Fruit; Hydrophobic and Hydrophilic Interactions; Insecticides; Molecular Structure; Pesticide Residues; Polyethylene Glycols; Salts; Temperature; Time Factors
PubMed: 19242683
DOI: 10.1007/s00216-009-2663-6 -
Journal of Chromatography. A Sep 2007An automated solid-phase extraction-high performance liquid chromatography method has been developed to determine trace concentration of N-methylcarbamate pesticides in...
Determination of N-methylcarbamate pesticides in environmental samples by an automated solid-phase extraction and liquid chromatographic method based on post-column photolysis and chemiluminescence detection.
An automated solid-phase extraction-high performance liquid chromatography method has been developed to determine trace concentration of N-methylcarbamate pesticides in water and fruits. The method is based on the post-column conversion of the pesticides into methylamine by irradiation with UV light. The resultant methylamine was subsequently detected by chemiluminescence using tris(2,2'-bipyridyl)ruthenium(III), which was on-line generated by photo-oxidation of the ruthenium(II) complex with peroxydisulfate. Factors affecting the rate of the reactions were optimized so that their contribution to the total band-broadening was negligible. This detection system was used to determine bendiocarb, carbaryl, promecarb and propoxur, which were separated on an ODS C(18) column. The mobile phase consisted of water and acetonitrile using a gradient elution. A linear relationship between peak area and concentration was obtained for all pesticides (r(2)>0.999). Intra- and inter-day precision values of about 0.64-1.3% RSD (n=10) and 2.2-2.8% RSD (n=15), respectively, were obtained. N-Methylcarbamate pesticide residues at ultratrace levels could be determined in environmental samples when an automated solid-phase extraction device was coupled on-line with the HPLC system. Detection limits were within the range 3.9-36.7 ngl(-1) for water samples and 0.5-4.7 microgkg(-1) for fruits.
Topics: Carbamates; Chromatography, High Pressure Liquid; Luminescent Measurements; Pesticides; Photochemistry; Photolysis; Reproducibility of Results; Solid Phase Extraction
PubMed: 17643443
DOI: 10.1016/j.chroma.2007.07.006 -
Analytica Chimica Acta Jan 2007The effect of native cyclodextrins (alpha, beta, or gammaCD with six, seven and eight glucose units, respectively), hydroxypropyl-beta-cyclodextrin (HPCD), chitosan...
The effect of native cyclodextrins (alpha, beta, or gammaCD with six, seven and eight glucose units, respectively), hydroxypropyl-beta-cyclodextrin (HPCD), chitosan (CHT) and glucose in water solution or water with n-propylamine (PA) as co-solvent upon the UV-vis and fluorescence properties of poorly fluorescent N-methyl carbamates pesticides (C) as bendiocarb (2,2-dimethyl-1,3-benzodioxol-4-ol methylcarbamate, BC) and promecarb (3-methyl-5-(1-methylethyl)phenol methylcarbame, PC) was examined. Fluorescent enhancement was found for both substrates with all CDs in water or PA-water except from PC with alphaCD. The addition of CHT increases the fluorescence of BC but decreases the fluorescence of PC, and glucose addition gives in both cases no spectral changes. Host-guest interaction was clearly determined by fluorescence enhancement with betaCD and HPCD with a 1:1 stoichiometry for the complexes (C:CD). The values obtained for the association constants (K(A), M(-1)) were (6+/-2)x10(2) and (2.3+/-0.3)x10(2) for BC:betaCD and BC:HPCD complexes, respectively. For PC:betaCD and PC:HPCD the values of K(A) were (19+/-2)x10(2) and (21+/-2)x10(2), respectively. The ratio of the fluorescence quantum yields for the bound and free substrates (phi(CCD)/phi(C)) was in the range 1.74-3.8. The limits of detection (L(D), microg mL(-1)) for the best conditions were (0.57+/-0.02) for BC with HPCD and (0.091+/-0.002) for PC with betaCD in water. Application to the analysis in pesticide spiked samples of tap water and fruit yields satisfactory apparent recoveries (84-114%), and for the extraction procedure in fruits and a commercial formulation, recoveries were of 81-98% and 104%, respectively. The method is rapid, simple, direct, sensitive and useful for pesticide analysis.
Topics: Carbamates; Cyclodextrins; Glucose; Humans; Indicators and Reagents; Nanotechnology; Pesticides; Spectrometry, Fluorescence; Water
PubMed: 17386527
DOI: 10.1016/j.aca.2006.10.010 -
Journal of Agricultural and Food... Aug 2003The competitive degradation of six carbamate insecticides by membrane anodic Fenton treatment (AFT), a new Fenton treatment technology, was carried out in this study....
The competitive degradation of six carbamate insecticides by membrane anodic Fenton treatment (AFT), a new Fenton treatment technology, was carried out in this study. The carbamates studied were dioxacarb, carbaryl, fenobucarb, promecarb, bendiocarb, and carbofuran. The results indicate that AFT can effectively degrade these insecticides in both single component and multicomponent systems. The carbamates compete for hydroxyl radicals, and their kinetics obey the previously developed AFT kinetic model quite well. Hydroxyl radical reaction rate constants were obtained, and they decrease in the following order: dioxacarb approximately carbaryl > fenobucarb > promecarb > bendiocarb > carbofuran. The AFT is shown to have higher treatment efficiency at higher temperature. Degradation products of the carbamates were determined by gas chromatography/mass spectrometry, and it appears that degradation can be initiated by hydroxyl radical attack at different sites in the molecule, depending on the individual structure of the compound. Substituted phenols are the commonly seen degradation products. The AFT treatment can efficiently remove the chemical oxygen demand of the carbamate mixture, significantly increasing the biodegradability. Earthworm studies show that the AFT is also an effective detoxification process.
Topics: Animals; Biodegradation, Environmental; Carbamates; Hydrogen Peroxide; Hydroxyl Radical; Insecticides; Iron; Kinetics; Oligochaeta; Temperature; Waste Management
PubMed: 12926887
DOI: 10.1021/jf034311f -
The Analyst Nov 2002A flow injection-chemiluminescent method for the determination of carbofuran and promecarb is proposed. The assay was based on the on-line conversion of the pesticides...
A flow injection-chemiluminescent method for the determination of carbofuran and promecarb is proposed. The assay was based on the on-line conversion of the pesticides into methylamine by irradiation with UV light. The methylamine generated was subsequently reacted with tris(2,2'-bipyridine)ruthenium(III), which was generated through the on-line photo-oxidation of tris(2,2'-bipyridine)ruthenium(II) with peroxydisulfate. The emitted light showed a linear relationship with the concentration of the pesticide over the ranges 0.22-11.2 microg ml(-1) for carbofuran and 0.41-16.6 microg ml(-1) for promecarb. The repeatability was 1.6% expressed as relative standard deviation (n = 10) and the reproducibility, studied on five different days, was 2%. The sample throughput was 200 injections per h. The reliability of the method for routine analysis of these pesticides in water, soil and grains is demonstrated.
Topics: Carbamates; Carbofuran; Flow Injection Analysis; Food Contamination; Luminescent Measurements; Pesticide Residues; Photochemistry
PubMed: 12475046
DOI: 10.1039/b207460p -
In-tube solid-phase microextraction coupled to capillary LC for carbamate analysis in water samples.Analytical Chemistry Jul 2000Recently, the on-line sample preparation technique, intube solid-phase microextraction (SPME), was successfully implemented with a Hewlett-Packard 1100 HPLC system for...
Recently, the on-line sample preparation technique, intube solid-phase microextraction (SPME), was successfully implemented with a Hewlett-Packard 1100 HPLC system for analysis of carbamates in water samples. This paper describes the coupling of in-tube SPME to capillary LC and explores its utility as a sample preparation method in that format, relative to conventional LC. The Hewlett-Packard HPLC system was upgraded to a capillary LC system using commercially available accessories from LC Packings. The combination of in-tube SPME with a capillary LC system was expected to build on the merits of both in-tube SPME and the capillary LC to generate a sensitive method with an easy, effective, and efficient sample preparation. Due to the relatively large effective injection volume of the in-tube SPME technique (30-45 microL), on-column focusing was employed in order to achieve good chromatographic efficiency. Excellent sensitivity was achieved with very good method precision. For all carbamates studied, the RSD of retention time was between 0.5 and 0.8% under 4 microL/min microgradient conditions. The RSD of peak area counts was between 1.5 and 4.6%. The detection limits for all carbamates studied were less than 0.3 microg/L and, for carbaryl, just 0.02 microg/L (20 ppt). Compared with the conventional in-tube SPME/LC method, the LODs were lowered for carbaryl, propham, methiocarb, promecarb, chlorpropham, and barban, by factors of 24, 45, 42, 81, 62, and 56, respectively. The optimized method was successfully applied to the analysis of carbamates in surface water samples.
Topics: Carbamates; Chromatography, High Pressure Liquid; Electrophoresis, Capillary; Insecticides; Pesticide Residues; Spectrophotometry, Ultraviolet; Water Pollutants, Chemical; Water Supply
PubMed: 10905306
DOI: 10.1021/ac990726h -
Journal of Food Protection Dec 2000An acetylcholinesterase inhibition method was employed for detection of 21 carbamate pesticides in bananas, peaches, strawberries, and tomatoes. Each of these four...
An acetylcholinesterase inhibition method was employed for detection of 21 carbamate pesticides in bananas, peaches, strawberries, and tomatoes. Each of these four agricultural commodities was spiked with 0.1 to 10 ppm of each of the 21 carbamates and individual detection levels were determined. Similar responses and detection limits were observed for all four produce when tested for a given carbamate. The detection levels ranged from 0.1 ppm for carbofuran and 3-hydroxycarbofuran to 6 ppm for promecarb and aldicarb sulfoxide. These results are generally at or below the tolerances established by the Environmental Protection Agency for these commodities. Positive samples from the enzyme inhibition screening were also analyzed with the carbaryl-specific enzyme-linked immunosorbent assay (ELISA) kit. The detection limits for carbaryl and carbofuran were 2.0 ppb and 8.0 ppb, respectively. The other carbamates did not exhibit cross-reactivity even at high ppb levels. Thus, the enzyme inhibition assay and ELISA are simple and fast screening procedures for the detection of carbamate pesticide residues in food commodities.
Topics: Carbamates; Enzyme Inhibitors; Enzyme-Linked Immunosorbent Assay; Food Analysis; Food Contamination; Fruit; Pesticide Residues
PubMed: 11131904
DOI: 10.4315/0362-028x-63.12.1758