Catalytic polarographic prewave of cobalt(II) induced by carbendazim. Application to the voltammetric determination of benomyl

Methyl 1H-benzimidazol-2-ylcarbamate (carbendazim or MBC) catalyzes the reduction of Co^II at mercury electrodes in sodium barbital/nitric acid/sodium chloride media. On the basis of a detailed study of the Co^II prewave induced by carbendazim, a mechanism for the electrode reaction is proposed and adequate conditions for the analytical determination of carbendazim by differential pulse voltammetry are established. Based on this finding, a voltammetric method for the indirect determination of methyl[1-(butylcarbamoyl)-1H-benzimidazol-2yl]carbamate (benomyl) is described, following the conversion of benomyl to carbendazim.     

液相色谱法直接测定可湿性制剂苯菌灵

研究了苯菌灵浓度在低温下的相对稳定性，提出了一种简单的直接测定可湿性制剂苯菌灵的高效液相色谱方法。该法的前处理是将有机溶剂冷却到－１５℃，然后用此溶剂来配制苯灵菌灵试液，并在每次进样后都将此试液保存在－１５℃的低温下，从而使得分析结果良好。定量方法的线性范围为０．１￣３ｇ／Ｌ，相对标准偏差为０．４％。     

Gel-surface enhanced fluorescence sensing system coupled to a continuous-flow assembly for simultaneous monitoring of benomyl and carbendazim

A novel, versatile and sensitive continuous-flow on-line solid phase fluorescence based system is proposed for the simultaneous determination of benomyl and carbendazim. The continuous-flow system is based on the on-line preconcentration and resolution of the pesticides on a solid sensing zone, followed by the sequential measure of their native fluorescence, monitored at 235/306 and 293/398 nm (λ_exc/λ_em for carbendazim and benomyl, respectively), and later desorption of these analytes (from the flow-through cell filled with C₁₈ silica gel) using aqueous methanol mixtures as carrier and eluent solutions.A double discrimination is used for the simultaneous monitoring of these analytes: (1) the usage of two pair of excitation/emision wavelengths, performed by the use of a multiwavelength fluorescence detection mode and (2) a temporary sequentiation in the arrival of the analytes to the sensing system by on-line separation due to the different kinetics showed by the analytes in the sorption-desorption process performed just in the solid support placed in the flow-through cell. Carbendazim is determined the first, because it shows a weaker retention in the C₁₈ bonded phase silica beads, while benomyl is strongly fixed. Then, benomyl is conveniently eluted from the flow-through sensing zone and its native fluorescence signal is measured (at 398 nm). The sensor was calibrated for two different injection volumes: 400 and 2000 μl. Using a 2000 μl sample volume, the analytical signal showed linearity in the range 0.050-1.0 and 0.020-0.50 μg ml⁻¹ with detection limits of 3.0 and 7.5 ng ml⁻¹ for carbendazim and benomyl, respectively, and R.S.D. values smaller than 2% for both analytes. A recovery study was performed on four different spiked environmental water samples at concentration levels from 0.05 to 0.35 μg ml⁻¹. The recovery percentage ranged from 97 to 104%, and from 98 to 104%, for benomyl and carbendazim, respectively.     

Determination of some benzimidazole fungicides in tomato puree by high performance liquid chromatography with SampliQ polymer SCX solid phase extraction

High performance liquid chromatography (HPLC) coupled with solid phase extraction (SPE) was optimized for extraction and quantification of two benzimidazoles fungicides (carbendazim and benomyl) in tomato puree. Results indicate that HPLC using an Agilent ZORBAX Eclipse plus C18 column (4.5 mm × 100 mm, 3.5 μm) and SPE using Agilent SampliQ SCX (55 mg, 3 mL) is an excellent combination for extraction and analysis of these compounds. Recoveries ranged from 90.0 to 95.5 percent with RSDs below 5 percent and limit of detections of 5 μg/kg.     

Degradation study of benomyl and carbendazim in water by liquid chromatography and multivariate curve resolution methods

Summary The degradation of benomyl and carbendazim in different organic solvents, distilled and ground waters was studied by on-line solid-phase extraction (SPE) followed by liquid chromatography (LC), diode array detection (DAD) or atmospheric pressure chemicalionization mass spectrometry detection (APCI-MS), UV spectrophotometry and multivariate curve resolution. Stability studies were performed in different organic solvents, such as acetonitrile and methanol, and in aqueous solution at different pH. Samples were stored in dark conditions at 4 °C and analysed by LC-DAD over 10 days. Photodegradation products of benomyl were resolved by spectrophotometry and multivariate curve resolution between pH 3 to 9. These results were correlated with those from LC-DAD and LC-APCI-MS. Photolysis studies were carried out at low concentration levels (2 μg L⁻¹) of carbendazim under different storage conditions in order to evaluate the effect of parameters, such as pH, temperature and sunlight exposure. Water samples (50 mL) were preconcentrated using on-line SPEC-LC-DAD. Photodegradation products of benomyl and carbendazim were identified by on-line-SPE-LC-DAD and SPE-LC-APCI-MS, leading to identification DAD and SPE-LC-APCI-MS, leading to identification of carbendazim, 3-butyl-2,4-dioxo-s-triazino1,2-abenzimidazole (STB) and 2-aminobenzimidazole (2-AB). Dedicated to Professor W. Haerdi on the occasion of his 70^th birthday.     

Simultaneous determination of benomyl and morestan residues in waters by synchronous solid-phase spectrofluorimetry

In this paper a new, sensitive, and simple method for simultaneous determination of pesticides morestan and benomyl at trace levels in waters is reported. Both chemicals, showing native fluorescence in solution at neutral medium, were fixed on C-18 silica gel at pH 1, giving a fluorescent system. The benomyl-morestan-silica gel system, after dry, was packed in a 1-mm silica cell and its synchronous fluorescence spectra were recorded at =80 nm for determination of benomyl and =25 nm for determination of morestan. Measurements of fluorescence were performed at ₁=289 nm and ₂=367 nm for benomyl and morestan analysis, respectively. The applicable concentration ranges were from 0.5 to 15.0 ng·ml^–1 for benomyl and from 0.6 to 15.0 ng·ml^–1 for morestan, with relative standard deviations of 1.2 and 1.5% for benomyl and morestan, respectively, being 0.15 and 0.18 ng·ml^–1 its respective detection limits. The method was applied to the simultaneous determination of residues of both pesticides in water of different provenances.     

Dissipation of carbendazim and its metabolites in cucumber using liquid chromatography tandem mass spectrometry

Currently, there is growing interest in the degradation pathways of organic contaminants such as pesticides. In the case of pesticides, the determination of metabolites in agricultural products and environment is necessary as some of them could present similar toxicity to or even higher toxicity than the parent compound. The development of analytical methodology for the identification and quantification of carbendazim fungicide and its metabolites in cucumber was studied. Cucumber (cucumis sativus) is a global food in terms of economic importance and nutritional quality. Careful optimisation of the liquid chromatography–mass spectrometry (LC-MS)/MS parameters was achieved in order to attain a fast separation with the best sensitivity. The detection was carried out on an Ion-Trap tandem mass spectrometer (MS/MS) by electrospray ionisation in positive ion mode (ESI+) with multiple reaction monitoring (MRM).     

Liquid chromatographic determination of benomyl in water samples after dispersive liquid–liquid microextraction

A dispersive liquid–liquid microextraction (DLLME) method combined with solvolysis reaction for extraction of the carbamate fungicide benomyl as carbendazim from water samples is described. The method is based on the extraction of benomyl from acidified sample solution and its conversion into carbendazim via solvolysis reaction with DMF as organic solvent. The proposed DLLME method was followed by HPLC with fluorimetric detection for determination of benomyl. The proposed method has good linearity (0.998) with wide linear dynamic range (0.01–25 mg/L) and low detection limit (0.0033 mg/L), making it suitable for benomyl determination in water samples.