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N-Methyl carbamates are insecticides that inhibit acetylcholinesterase (AChE) causing same symptomatology in acute and chronic exposures. Traces of them could be found in animal tissues, milk, honey, eggs, etc. because of some foods treatment during growth. There is an increasing interest in fast screening methods for detection of different pollutant groups in the foods. Biosensors are a promising alternative of the existing chromatographic methods such as HPLC, GC, etc. They are fast, easy to use and provide fully acceptable values for the monitoring methods like sensitivity, LOD, LOQ, etc. In order to construct an optical biosensor, AChE is immobilized as a target enzyme for N-methyl carbamates on the surface of new membranes synthesized by a sol-gel technology. The designed biosensensor is tested for determination of methomyl, aldicarb, carbofuran, propoxur in liver samples. An appropriate method for sample preparation is also developed. Further, the new method is validated in accordance with document SANTE/11945/2015 covering the required criteria for N-Methyl carbamates determination. The biosensor could detect levels lower than 10 μg/kg which is the maximum residue limit (MRL) for pesticides in foods. Km of 2,2x10-3 M is calculated for acetylcholine using a 4 month life-time of a biosensor. [ABSTRACT FROM AUTHOR]

Water quality assessment was conducted on the Ruiru River, a tributary of an important tropical river system in Kenya, to determine baseline river conditions for studies on the aquatic fate of N-methyl carbamate (NMC) pesticides. Measurements were taken at the end of the long rainy season in early June 2013. Concentrations of copper (0.21-1.51 ppm), nitrates (2.28-4.89 ppm) and phosphates (0.01-0.50 ppm) were detected at higher values than in uncontaminated waters, and attributed to surface runoff from agricultural activity in the surrounding area. Concentrations of dissolved oxygen (8-10 ppm), ammonia (0.02-0.22 ppm) and phenols (0.19-0.83 ppm) were found to lie within normal ranges. The Ruiru River was found to be slightly basic (pH 7.08-7.70) with a temperature of 17.8-21.2°C. The half-life values for hydrolysis of three NMC pesticides (carbofuran, carbaryl and propoxur) used in the area were measured under laboratory conditions, revealing that rates of decay were influenced by the electronic nature of the NMCs. The hydrolysis half-lives at pH 9 and 18°C decreased in the order carbofuran (57.8 h) > propoxur (38.5 h) > carbaryl (19.3 h). In general, a decrease in the electron density of the NMC aromatic ring increases the acidity of the N-bound proton removed in the rate-limiting step of the hydrolysis mechanism. Our results are consistent with this prediction, and the most electron-poor NMC (carbaryl) hydrolyzed fastest, while the most electron-rich NMC (carbofuran) hydrolyzed slowest. Results from this study should provide baseline data for future studies on NMC pesticide chemical fate in the Ruiru River and similar tropical water systems. [ABSTRACT FROM AUTHOR]

Pyridine-based Factor XIa (FXIa) inhibitor ( S )- 2 was optimized by modifying the P2 prime, P1, and scaffold regions. This work resulted in the discovery of the methyl N -phenyl carbamate P2 prime group which maintained FXIa activity, reduced the number of H-bond donors, and improved the physicochemical properties compared to the amino indazole P2 prime moiety. Compound ( S ) -17 was identified as a potent and selective FXIa inhibitor that was orally bioavailable. Replacement of the basic cyclohexyl methyl amine P1 in ( S )- 17 with the neutral p -chlorophenyltetrazole P1 resulted in the discovery of ( S ) -24 which showed a significant improvement in oral bioavailability compared to the previously reported imidazole ( S )- 23 . Additional improvements in FXIa binding affinity, while maintaining oral bioavailability, was achieved by replacing the pyridine scaffold with either a regioisomeric pyridine or pyrimidine ring system. [ABSTRACT FROM AUTHOR]

Organophosphorus (OP) and N -methylcarbamate pesticides inhibit acetylcholinesterase (AChE), but differences in metabolism and detoxication can influence potency of these pesticides across and within species. Carboxylesterase (CaE) and A-esterase (paraoxonase, PON1) are considered factors underlying age-related sensitivity differences. We used an in vitro system to measure detoxication of AChE-inhibiting pesticides mediated via these esterases. Recombinant human AChE was used as a bioassay of inhibitor concentration following incubation with detoxifying tissue: liver plus Ca +2 (to stimulate PON1s, measuring activity of both esterases) or EGTA (to inhibit PON1s, thereby measuring CaE activity). AChE inhibitory concentrations of aldicarb, chlorpyrifos oxon, malaoxon, methamidophos, oxamyl, paraoxon, and methylparaoxon were incubated with liver homogenates from adult male rat or one of 20 commercially provided human (11–83 years of age) liver samples. Detoxication was defined as the difference in inhibition produced by the pesticide alone and inhibition measured in combination with liver plus Ca +2 or liver plus EGTA. Generally, rat liver produced more detoxication than did the human samples. There were large detoxication differences across human samples for some pesticides (especially malaoxon, chlorpyrifos oxon) but not for others ( e.g. , aldicarb, methamidophos); for the most part these differences did not correlate with age or sex. Chlorpyrifos oxon was fully detoxified only in the presence of Ca +2 in both rat and human livers. Detoxication of paraoxon and methylparaoxon in rat liver was greater with Ca +2 , but humans showed less differentiation than rats between Ca +2 and EGTA conditions. This suggests the importance of PON1 detoxication for these three OPs in the rat, but mostly only for chlorpyrifos oxon in human samples. Malaoxon was detoxified similarly with Ca +2 or EGTA, and the differences across humans correlated with metabolism of p -nitrophenyl acetate, a substrate for CaEs. This suggests the importance of CaEs in malaoxon detoxication. Understanding these individual differences in detoxication can inform human variability in pesticide sensitivity. [ABSTRACT FROM AUTHOR]

A sensitive, economic, rapid and simple method for the determination of fourN-methylcarbamate pesticides: methomyl (2.0–80 μg L−1), aldicarb (5.0–50 μg L−1), butocarboxim (2.0–60 μg L−1) and oxamyl (2.0–60 μg L−1); is reported. It relies on the coupling of photoinduced chemiluminescence (PICL) detection with flow injection (FI) methodology. The automation of FI together with the use of light as a reagent decreased the environmental impact of the analysis. The proposed method was based on the oxidation of these pesticides, previously irradiated on-line with UV light, with cerium(IV), using quinine as a sensitiser. Limits of detection below the legal limits (100 ng L−1) established by the European Union for drinking waters were obtained without the need of preconcentration steps. A good inter-day reproducibility (1.6–6.4%,n = 5), repeatability (rsd = 2.7 %,n = 25) and high throughput (123 h−1) were achieved. The method was successfully applied to the determination of methomyl in natural waters with mean recoveries ranging from 90% to 98%. [ABSTRACT FROM PUBLISHER]

Emerging studies have linked prooxidative carbamate compound exposures with various human pathologies including pancreatic cancer. In these studies, our aim was to examine mitochondrial oxidative stress-mediated aberrant chromatin responses in human pancreatic ductal epithelial cells. Posttranslational histone modifications, promoter DNA methylation, and micro-RNA (miRNA) expression patterns were evaluated following induction of mitochondrial oxidative stress by N-succinimidyl N-methylcarbamate exposure. In treated cells, perturbation in mitochondrial machinery led to hypermethylation of p16 and smad4 gene promoters and downregulation of respective gene products. Posttranslational histone modifications that include hypoacetylation of acetylated histone (AcH) 3 and AcH4, hypermethylation of monomethylated histone 3 at lysine 9 and trimethylated histone 4 at lysine 20 ubiquitinated histone (uH) 2A/uH2B, and increased phosphorylation of H2AX and H3 were observed in the treated cells. Altered expression of miRNAs denoted possible location of corresponding genes at oxidatively damaged fragile sites. Collectively, our results provide a direct role of mitochondrial oxidative stress-mediated epigenetic imbalance to perturbed genomic integrity in oxygen radical-induced pancreatic injury. Further, identification and characterization of molecular switches that affect these epigenomic signatures and targets thereof will be imperative to understand the complex role of redox-regulatory network in pancreatic milieu. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Carbamates were selective for tick & sand fly acetylcholinesterase over that of human & bovine. [•] Tick had 1000-fold lower sensitivity toward tacrine than all previous species tested. [•] In tick, the W384 residue has a structural clash with tacrine and related inhibitors. [•] There is little resistance to coumaphos oxon and carbamates in AChE from field strains. [•] One compound, 2-((2-ethylbutyl)thio)phenyl methylcarbamate, is an excellent new lead. [Copyright &y& Elsevier]

Abstract: A simple, rapid and sensitive method for simultaneous determination of three N-methylcarbamate pesticides (carbaryl, pirimicarb, and isoprocarb) in vegetables was developed by coupling polymer monolith microextraction (PMME) to high-performance liquid chromatography (HPLC). A poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolith was selected as the extraction medium for PMME. To achieve optimum extraction performance, several parameters were investigated, including desorption solvent, desorption flow rate, sample flow rate, sample volume, sample pH values, inorganic salt and organic solvent content of the sample solution. Under the optimum experimental conditions, the method provides an acceptable linearity (5–5000μg/kg), low limits of detection (0.36–2.6μg/kg), good precision (intra-day relative standard deviations<2.53%, inter-day relative standard deviations <6.36%). Finally, the developed method was successfully applied to the determination of N-methylcarbamate pesticides in vegetables, and the trueness was evaluated by recovery experiments. The obtained relative recoveries were in the range of 70.4–98.5%. This PMME method integrates sample extraction, purification, and preconcentration of analytes into one single step and it also has several advantages such as solvent-free extraction, small sample volume, high enrichment, convenience, and flexibility operation. [Copyright &y& Elsevier]

A transferable tight-binding parametrization procedure for extended Hückel approximation is proposed, with the charge self-consistent scheme, that could be applied to the quantum molecular dynamics (MD) simulation for long-time dynamics of large-scale systems. In this procedure, either a target molecule is divided into small molecules or another realistic set of small molecules characterizing chemical bonds in the complicated target molecule is adopted. Then, the parameters for these small molecules are adjusted and compared with reference results of energy levels and wave functions by, for example, density functional theory. Upon application to the large target molecule, these parameters are then readjusted directly in the target molecule. An example is demonstrated with MD simulation applied to the ionic liquid molecule N-methyl-N-propylpiperidinium bis trifluoromethanesulfonyl imide (PP13-TFSI). The origin and stability of HOMO-LUMO gap are discussed. [ABSTRACT FROM AUTHOR]

This study is a small part of a project aimed at performing comprehensive evaluation of the quality of local raw materials and products in the region of Warmia and Mazury in Poland. This study evaluates selected determinants of the health quality and nutritional value of rye bread in relation to origin (small and large scale production). The analytical procedure included determination of the content of acrylamide, organochlorine pesticides and polychlorinated biphenyls, n-methylcarbamates, ochratoxin A, acidity, moisture, protein, glucose, fat, salt, cu, Mn, Fe, Zn, ca, and Mg. The quality of bread produced on a small scale, compared to that produced in large bakeries, differed only in terms of some determinants. Rye bread from local producers contained statistically significantly less (P ≤ 0.05) acrylamide and statistically significantly more copper, manganese and zinc. [ABSTRACT FROM AUTHOR]

Abstract: Detailed insights regarding the inclusion process between β-cyclodextrin and the N-methylcarbamates insecticides like Bendiocarb, Carbaryl, Carbofuran and Promecarb, are proposed in bases of experimental and computational methods. The results from Fourier transform infrared spectroscopy, differential scanning calorimetry, induced circular dichroism and molecular dynamics indicate that only in the case of Promecarb the interaction with the macrocycle is produced by the alkyl rest of the molecule. In all other cases the aromatic moiety is the part of the insecticide that is partially included in the cavity of β-cyclodextrin. [Copyright &y& Elsevier]

Abstract: The aim of this work was to develop a method for the determination of N-methyl carbamates in water involving hollow fibre supported liquid membrane (HFSLM) and solid phase extraction (SPE) as sample preparation methods. Four N-methyl carbamate pesticides, aldicarb, carbaryl, carbofuran and methiocarb sulfoxide, were simultaneously extracted and analysed by a liquid chromatograph with a diode array detector (LC-UV/DAD) and a liquid chromatograph coupled to a ion trap quadrupole mass spectrometer (LC–ESI–MS). The high performance liquid chromatography (HPLC) separation of carabamate extracts was performed on a C18 column with water–acetonitrile as the mobile phase. The mass spectrometry analyses were carried out in the positive mode, operating under both the selected ion monitoring (SIM) and full scan modes. The solid phase recoveries of the extracts ranged between 8% and 98%, with aldicarb having the highest recoveries, followed by carbaryl, carbofuran and methiocarb had the lowest recovery. The HFSLM recovery ranged between 8% and 58% and the order of recovery was similar to the SPE trend. Factors controlling the efficiency of the HFSLM extraction such as sample pH, stripping phase pH, enrichment time, stirring speed as well as organic solvent used for entrapment of analytes, were optimised to achieve the highest enrichment factors. [Copyright &y& Elsevier]

In this paper, orange peel was utilized as low-cost adsorbent to remove carbofuran from aqueous solution by adsorption. All the experiments were conducted at 30°C to investigate the effects of initial concentration, adsorbent dosage, contact time, ionic strength, and pH on carbofuran adsorption. The results showed that it was effective to remove carbofuran in the alkalic medium and the equilibrium adsorption was practically achieved in 60 min. The presence of NaCl inhibited the adsorption of carbofuran onto orange peel. Langmuir model provided the better correlation of the experimental data and could interpret the adsorption process and the maximum monolayer adsorption capacity was found to be 84.49 mg/g at the temperature of 30°C. The pseudo-second-order kinetic model could describe the adsorption kinetics rationally and the rate-limiting step was the intraparticle diffusion process. It was implied that orange peel may be suitable as adsorbent material for adsorption of N-methyl carbamate insecticides from aqueous solution. [ABSTRACT FROM AUTHOR]

Abstract: A new analytical method based on micellar electrokinetic chromatography tandem mass spectrometry (MEKC–ESI–MS/MS) employing a MS friendly surfactant (ammonium perfluorooctanoate) is proposed and validated for the identification and simultaneous quantification of 17 N-methylcarbamate pesticides in environmental and drinking water samples. MS/MS detection using an ion trap as analyzer operating in the multiple reaction monitoring mode was used. Different parameters were optimized in order to obtain an adequate CE separation combined with the highest sensitivity in MS/MS. Dispersive liquid–liquid microextraction (DLLME) using a low-density extraction solvent has been proposed for extraction, obtaining a preconcentration factor of 10. Under optimum conditions, recoveries for fortified samples ranged from 83% to 101%, with relative standard deviations lower than 8%. The limits of detection ranged from 1 to 144ngl−1, demonstrating the sensitivity and applicability of this fast, simple, and environmentally friendly method. [Copyright &y& Elsevier]

Abstract: A rapid and simple method for the extraction and preconcentration of N-methylcarbamates (NMCs) (carbofuran, carbaryl and promecarb) in water samples using dispersive liquid–liquid microextraction (DLLME) using chemometrics was developed. Influence variables such as volume of extracting (CHCl3) and dispersing solvents (ACN), pH and ionic strength, extraction time and centrifugation time and speed were screened in a 27–4 Plackett–Burman design was investigated. The significant variables were optimized by using a central composite design (CCD) combined with desirability function (DF). At optimum conditions values of variables set as 126μL chloroform, 1.5mL acetonitrile, 1min extraction time, 10min centrifugation at 4000rpmmin−1, natural pH, 4.7% (w/v) NaCl, the separation was reached in less than 14min using a C18 column and an isocratic binary mobile phase (acetonitrile: water (50:50, v/v)) with flow rate of 1.0mLmin−1. At optimum conditions method has linear response over 0.001–10μgmL−1 with detection limit between 0.0001 and 0.0005μgmL−1 with relative standard deviations (RSDs) in the range 2.18–5.06% (n =6). [Copyright &y& Elsevier]

Abstract: The in vitro geno- and cytotoxicity exerted by the N-methylcarbamate pesticide carbofuran (CF) and its commercial formulation furadan® (F®) were studied in Chinese hamster ovary (CHOK1) cells by several bioassays for both genotoxicity (e.g., the sister chromatid exchange (SCE) and micronuclei (MNi) frequencies), and cytotoxicity (e.g., cell-cycle progression, mitotic index (MI), 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and neutral red (NR)). Both CF and F® activities were tested within the range of 5–100μg/ml. CF within a 10–100μg/ml concentration-range induced a significant dependent increase of SCE frequency and MNi over control values. At the same concentration-range, F® increased significantly the SCE frequencies over control values although in a non-dependent manner while only an enhanced frequency of MNi was found in those 50μg/ml-treated cultures. No binucleated cytokinesis-block cells were found in 100μg/ml F®-treated cultures. The NDI index revealed a delay in the onset of cell-division with 50 and 100μg/ml of CF and F®, respectively. The delayed rate of nuclear division induced by 100μg/ml of F® was higher than that induced by an equal concentration of CF. CF and F® induced both a significant concentration-dependent delay in cell-cycle progression and a decrease in the proliferative replication index within 5–100μg/ml and 50–100μg/ml concentration-range, respectively. Decreased cell viability was found in up to 26% and 47% in 100μg/ml CF- and F®-treated cultures, respectively. The NR and MTT assays revealed a clear cell growth inhibition when concentrations of 50 and 100μg/ml of either CF or F® were employed. Accordingly, the results highlight that CF by itself and F®, even in a greater extend exerts both genotoxicity and cytotoxicity in mammalian cells in culture, at least in CHOK1 cells. [Copyright &y& Elsevier]

A gas chromatography–tandem mass spectrometric (GC-MS/MS) method has been developed for the determination of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), carbaryl (1-naphthyl-N-methylcarbamate) and their main metabolites in human blood plasma. Optimization of the isolation of the compounds from plasma matrix included the precipitation, denaturation and digestion of plasma proteins. Derivatization was achieved by the use of trifluoroacetic acid anhydride and was optimized for temperature, time and volume of derivatization agent. In the proposed method, a mild precipitation technique was applied using β-mercaptoethanol and ascorbic acid in combination with solid-phase extraction technique using Oasis HLB (Hydrophobic Lipophilic Balance) cartridges for further clean up of samples. Carbamate linkage was not hydrolyzed to its phenol product, but both carbamate phenol and ketones were transformed into trifluoroacetyl derivatives in order to become volatile compounds and were determined using tandem mass spectrometry. The linearity of the method was shown for nine concentrations in the range of 0.50–250 ng mL−1 in fortified plasma aliquots. Limits of detection (LODs) for all compounds ranged from 0.015–0.151 ng mL−1. Inter-day and intra-day assays (RSD) for all compounds, at three concentration levels of 2.5, 25 and 100 ng mL−1 ( n=3) in fortified plasma samples were less than 18%. Accuracy (% E r) was calculated at three concentration levels, 8, 80 and 160 ng mL−1 ( n=3), and ranged from −12.0 to 15.0%. Matrix effect was evaluated so mean recoveries were calculated for all compounds and ranged from 81–107%. Specificity for the use of this method to biological monitoring studies was achieved including four main metabolites of CF, 1-naphthol and 2-naphthol from the naphthalene metabolism pathways, and both the parent compound of carbofuran and carbaryl. The proposed method was applied to plasma samples of pesticide users. [ABSTRACT FROM AUTHOR]

Abstract: A new gas chromatographic–tandem mass spectrometric method has been developed and validated for the determination of two N-methylcarbamates, carbofuran and carbaryl and their metabolites in applicators’ urine specimens. Mild conditions were used for sample preparation based on enzymic hydrolysis and solid-phase extraction using Oasis HLB sorbent cartridges. Amides, phenols and ketones were first converted to volatile derivatives of trifluoroacetic acid anhydride (TFAA) and afterwards were quantitated using tandem mass spectrometry. Linear calibration equations (1–200ngmL−1 urine) were obtained from fortified urine samples for all eight compounds, carbaryl, 1-naphthol, 2-naphthol, and carbofuran, 3-hydroxycarbofuran, 7-phenol, carbofuran-3-keto, 3- hydroxycarbofuranphenol. For all compounds, the limit of detection was lower than 0.1ngmL−1. Precision for all compounds, at the concentrations of 1, 10 and 100ngmL−1 (n =5) in-fortified urine samples ranged from 0.7% to 18%. Accuracy was calculated at two concentrations 8 and 80ngmL−1 (n =5) and ranged from −8.4% to 8.2%. Relative recoveries at concentrations of 1, 10 and 100ngmL−1, ranged from 71% to 116%. The method was successfully applied to five male applicators and 10 non-applicators (including both smokers and non-smokers). [Copyright &y& Elsevier]

Abstract: A new procedure for the screening of total N-methylcarbamate (NMCs) content in water at different concentration levels is here presented. It is based on a previous off-line alkaline hydrolysis of the NMCs, for the production of methylamine (MA), and its subsequent derivatisation with o-phthalaldehyde (OPA). After that, the obtained derivative is involved in the peroxyoxalate chemiluminescent (PO-CL) reaction using imidazole as a catalyst being the CL emission proportional to the total NMC content. The chemiluminescent reaction is carried out in a flow injection analysis (FIA) manifold, employing sodium dodecyl sulphate micellar medium as carrier, which avoids the rapid degradation of POs in water solution. The applicability of the screening method is shown for the monitoring of NMCs in natural waters. Analytical features, as specification limit signal, screening uncertainty, sensitivity and specificity, are calculated. [Copyright &y& Elsevier]

Abstract: Liquid chromatography-pneumatically assisted electrospray mass spectrometry with both negative and positive ionization has been used for the determination of carbamates pesticides and their transformation products in Tunisian surface water. Eight pesticides and four of their hydrolysis products were covered in this study. Optimization of electrospray inlet conditions is described as well as results from investigations of the linearity of the detector response. Conditions for tandem mass spectrometry (MS–MS) detection of characteristic daughter ions formed by collision induced dissociation (CID) of the parent ion are described. Detection limits using MS in the selected ion monitoring (SIM) mode were generally in the order of 0.5μgL-1 or below. A principle of analysis is proposed based on triple quadrupole MS as a method for quantitative determination followed by verification of positive findings by CID–MS–MS. Application of the method for detecting carbamates residues in surface water is demonstrated. [Copyright &y& Elsevier]

A rapid and selective method for the simultaneous determination of triazine herbicides (atrazine, its degradation product desethylatrazine, simazine, prometryn, terbutryn) and N -methylcarbamate insecticides (propoxur, carbaryl and methiocarb) in surface water has been developed. A 0.5 L of the water sample was preconcentrated by passage through a 1 g C 18 solid-phase extraction cartridge. The retained compounds were eluted with 5 mL of methanol from the cartridge. The pesticides were separated and quantified by reversed-phase high-performance liquid chromatography with UV diode-array detection. Analytical separation was performed using a concave gradient elution with acetonitrile and water on a C 18 column. Prometryn and terbutryn were determined at 240 nm; propoxur, methiocarb at 204 nm and the others at 220 nm. Recoveries varied from 85 to 102% over concentrations at 0.025 and 0.2 µg L -1 . The limits of detection for the compounds investigated are in the range of 0.005-0.012 µg L -1 . [ABSTRACT FROM AUTHOR]

A dynamic ultrasound-assisted method for the extraction of N-methylcarbamates (oxamyl, dioxacarb, metolcarb, carbofuran, carbaryl and isoprocarb) from soils and foods is proposed. The main factors affecting the extraction efficiency have been optimised by means of a central composite design. Pure water can be used as leaching agent. A flow injection manifold coupled to the extractor allows automation of the several steps involved in the analytical process. The method allows extraction of the carbamates from soil and food at 1 μg/g spiked level, with recoveries similar to those provided by the EPA 8318 method, without degradation of the target compounds during the extraction and with drastic shortening of the time required for this step (2 min vs. 4 h). Recoveries of the target analytes were 77–95% for spiked soil and 85–101% for spiked food. The detection and quantification limits were 12 and 40 ng/g, respectively, for all analytes, except carbaryl (detection and quantification limits 3 and 10 ng/ng, respectively). The relative standard deviations for repeatability and within-laboratory reproducibility were 3.1 and 7.5%, respectively. [Copyright &y& Elsevier]

A combination of static–dynamic modes of pressurized hot water extraction has been used for the extraction of N-methylcarbamates (namely, oxamyl, dioxacarb, metholcarb, carbofuran and carbaryl) from different fruits and vegetables. The selection of water as leaching agent provides a clean approach which avoids the use of organic solvents. A flow injection manifold coupled to the extractor has allowed the automation of the subsequent steps (namely, filtration, preconcentration, individual chromatographic separation, post-column derivatization and fluorescence detection) involved in the analytical process. Good recoveries, ranging from 80 to 104%, and precision, expressed as relative standard deviation, between 3.0 and 8.4% have been achieved by the proposed method. [Copyright &y& Elsevier]

A sensitive and selective coupled-column liquid chromatography (LC-LC) method was developed for the trace level determination of some N-methylcarbamates and some of their main metabolites as aldicarb, aldicarb-sulphoxide, aldicarb-sulphone, carbofuran and 3-hydroxicarbofuran in drinking and ground waters. The limit of determination can be reduced to 0.1 μg.L−1 by solid phase extraction with a subsequent evaporation step. Environmental samples spiked at 0.1 μg.L−1 were preconcentrated off-line with graphite carbon and then analyzed by LC-LC with UV detection yielding average recoveries between 81–109% (n=5) with RSD between 5–9%. The overall procedure allowed a sample throughput of up to 30 samples per day. [ABSTRACT FROM AUTHOR]

Abstract: Treatment of 4-nitrophenyl chloroformate with alkylammonium hydrochloride salts and solid anhydrous Na2CO3 in either CH2Cl2 or CH3CN gave 4-nitrophenyl N-methylcarbamate and other N-alkylcarbamate analogues in excellent yields. Of particular interest is the observation that 4-nitrophenyl N-methylcarbamate, a safer alternative to the highly toxic methyl isocyanate, is obtained in quantitative yield (⩾95% pure as determined by 1H NMR) after simple filtration and solvent evaporation. [Copyright &y& Elsevier]