Ion-pairing high-performance liquid chromatography determination of amitrole in apple after solid-phase extraction and precolumn derivatization

Electrocatalytic detection of herbicide, amitrole at WO3·0.33H2O modified carbon paste electrode for environmental applications

Environmental pollution by the heavy usage of pesticides has been a pandemic issue in view of the rising farming operations for increasing the crop yield to meet the requirements of food chain supply. Throughout the world, environmental pollution by the presence of pesticides, particularly the use of herbicides in large quantities to protect the crops, has posed many environmental issues. In this research, an electrochemical sensor based on tungsten oxide hydrates (WO₃·0.33H₂O) nanorod modified carbon paste electrode (CPE) was developed for the detection of herbicide, amitrole (AMT) by the cyclic voltammeter. Hydrothermally synthesized and characterized WO₃·0.33H₂O nanorod was found to be sensitive towards the detection of AMT due to its superior sensing property as the sensor showed enhanced current and catalytic property when used in phosphate buffer solution (PBS) of pH 5.0 by the cyclic voltammetric (CV) and square wave voltammetric (SWV) techniques. The influence of electro kinetic parameters viz., scan rate, pH, accumulation time and temperature with respect to AMT oxidation was studied using CV. The linearity range was in between 1.0 × 10^-8 M and 24 × 10^-5 M and limit of detection (LOD) and limit of quantification (LOQ) was calculated to be 2.33 nM and 7.8 nM respectively. The proposed simple method demonstrated the potential applicability to detect AMT from the soil and water samples.

Development of a Multiresidue Method for Endocrine-Disrupting Pesticides by Solid Phase Extraction and Determination by UHPLC-MS/MS from Drinking Water Samples

A rapid and efficient method based on solid phase extraction and liquid chromatography–tandem mass spectrometry was validated, allowing the determination of the endocrine-disrupting herbicides (acetochlor, alachlor, amitrole and atrazine), fungicides (carbendazim, triadimefon, penconazole and propiconazole), and insecticides (carbaryl and carbofuran) in drinking water. Low method detection limits (0.01–0.64 ng/L) and method quantification limits (0.03–2.13 ng/L) were obtained with satisfactory recoveries and precision for the endocrine-disrupting pesticides. The method was applied for real drinking water samples collected in the area of the city of Hangzhou (Zhejiang, China); the results showed that carbendazim, atrazine and acetochlor were detected in the drinking water samples and acetochlor was the most detected analyte.

Rapid determination of polar pesticides and plant growth regulators in fruits and vegetables by liquid chromatography/tandem mass spectrometry

A simple high-throughput liquid chromatography/tandem mass spectrometry (LC-MS/MS) multiresidue analysis method was developed for the simultaneous determination of polar pesticides, plant growth regulators and other polar compounds. These included amitrole, chlormequat, mepiquat, cyromazine, ETU, PTU, perchlorate, and daminozide using a mixed-mode column. A 10 g test portion was shaken with acidified methanol for 10 min. After centrifugation, the sample extract was injected and analyzed within 11 min by LC-MS-MS. This column eliminated the need for derivatization or the use of ion paring reagent. Two MS-MS transitions were monitored in the method for each target compound to achieve true positive identification. Eight isotopically-labeled internal standards corresponding to each analyte were used to correct for matrix suppression effect and/or instrument signal drift. The average recovery for all analytes at 20, 40, and 250 ng/g (n = 6) ranged from 73-136%, with a relative standard deviation of ≤ 20%.

A simple electrochemical platform based on pectin stabilized gold nanoparticles for picomolar detection of biologically toxic amitrole

Amitrole is a biologically toxic nonselective herbicide which contaminates surface and ground waters at unprecedented rates. All reported modified electrodes that detect amitrole within sub-micromolar to nanomolar levels were based on the electro-oxidation of amitrole. Herein, we developed a new conceptual idea to detect picomolar concentrations of amitrole based on calcium cross linked pectin stabilized gold nanoparticle (CCLP-GNP) film modified electrode which was prepared by electrodeposition. When the electrochemical behavior of amitrole was investigated at the CCLP-GNP film, the reduction peak current of the GNPs linearly decreased as the concentration of amitrole increases. We have designed a determination platform based on the amitrole dependent decrease of the GNP cathodic peak. The described concept and high sensitivity of square wave voltammetry together facilitate the great sensing ability; as a result the described approach is able to reach a low detection limit of 36 pM which surpassed the detection limits of existing protocols. The sensor presents a good ability to determine amitrole in two linear concentration ranges: (1) 100 pM-1500 pM with a detection limit of 36 pM; (2) 100 nM-1500 nM with a detection limit of 20 nM. The preparation of CCLP-GNPs is simple, rapid and does not require any reducing agents.

Biosensor based on ds-DNA decorated chitosan modified multiwall carbon nanotubes for voltammetric biodetection of herbicide amitrole

The interaction of amitrole and salmon sperm ds-DNA was studied using UV-vis and differential pulse voltammetry (DPV) at both bare and DNA-modified electrodes. Amitrole showed an oxidation peak at 0.445 V at a bare pencil graphite electrode (PGE). When ds-DNA was added into the amitrole solution, the peak current of amitrole decreased and the peak potential underwent a shift. UV-vis spectra showed that the absorption intensity of the ds-DNA at 260 nm decreased with increasing amitrole concentration, proving the interaction between amitrole and the ds-DNA. The results also showed that amitrole could interact with the ds-DNA molecules via the intercalative binding mode. Finally, a pretreated pencil graphite electrode (PGE) modified with multiwall carbon nanotubes (MWCNTs) and chitosan (CHIT) decorated with the ds-DNA were tested in order to determine amitrole content in solution. Electrochemical oxidation of amitrole bonded on DNA/MWCNTs-CHIT/PGE was used to obtain an analytical signal. A linear dependence was observed to exist between the peak current and 0.025-2.4 ng mL(-1) amitrole with a detection limit of 0.017 ng mL(-1). The sensor showed a good selectivity and precision for the determination of amitrole. Finally, applicability of the biosensor was evaluated by measuring the analyte in soil and water samples with good selectivity.

High-performance liquid chromatographic method for determination of amino acids by precolumn derivatization with 4-chloro-3,5-dinitrobenzotrifluoride

This work presents an high-performance liquid chromatography method for the determination of amino acids after precolumn derivatization with 4-chloro-3,5-dinitrobenzotrifluoride (CNBF) which can readily react with both primary and secondary amines. The precolumn derivatization conditions, including the CNBF concentration, reaction pH, temperature and reaction time were investigated for method optimization. In pH 9.0 borate buffer, the reaction of amino acids with CNBF was carried out at 60 degrees C for 30min, the optimized concentration of CNBF was 70mmol L(-1) and the molar ratio of amino acids to CNBF was 1:5.25. The chromatographic separation of 19 amino acids derivatives was performed on a Kromasil ODS C(18) column (250mm x 4.6mm, 5microm) with good reproducibility, and ultraviolet detection was applied at 260 nm. The mobile phase was a mixture of phase A (acetonitrile) and phase B (acetate buffer, acetonitrile, triethylamine; 82.8:17:0.2, pH 4.9), and the flow rate was 0.4mL min(-1). The separation of all the labeled amino acids was achieved within 45min at room temperature by gradient elution mode. The method linearity, calculated for each amino acid, had a correlation coefficient higher than 0.9979, in concentrations ranging from 9.60 to 3330.00 micromol L(-1). The detection limits of amino acids were 2.40-6.50micromol L(-1), at a signal-to-noise ratio of 3. The proposed method was applied for the determination of amino acids in beer with recoveries of 97.0-103.9% and relative standard deviations of 2.62-4.22%, respectively. This method showed good accuracy and repeatability that can be used for the quantification of amino acids in real samples.