Rapid screening of amitraz and its metabolite residues in honey using a quick, easy, cheap, effective, rugged, and safe extraction method coupled with UHPLC and Q Exactive.

A method for determining amitraz and 2,4-dimethylaniline in honey was established by using ultra-high-performance liquid chromatoghaphy and Q Exactive after applying quick, easy, cheap, effective, rugged, and safe extracting process. A suitable extraction method was designed to extract the amitraz and 2,4-dimethylaniline after a suitable amount of honey samples was dissolved. A Thermo Syncronis C18 column (100 × 2.1 mm, 1.7 µm) was used for chromatographic separation of the samples. Then the two compounds were quantitatively analyzed via a program of Q Exactive. The linearity of amitraz and 2,4-dimethylaniline was good in the concentration range of 0.5-100 µg/L, and the correlation coefficient R2 was >0.99. The average recovery and relative standard deviation of each component were 81.3-90.0% and 5.1-7.2%. The 24- and 48-h test results showed that the sample needed to be tested within 24 h. The limit of detection was 0.1 µg/kg for amitraz and 2,4-dimethylaniline, whereas for both the limit of quantitation was 0.3 µg/kg.

Rapid and efficient removal of acetochlor from environmental water using Cr-MIL-101 sorbent modified with 3, 5-Bis(trifluoromethyl)phenyl isocyanate.

The excessive use of acetochlor (ACT), a commonly used herbicide with latent endocrine disrupting functions, causes surface water pollution. The efficient removal of ACT from contaminated water supplies is of paramount importance. In the current work, 3,5-Bis(trifluoromethyl)phenyl isocyanate (BTP) was successfully anchored onto Cr-MIL-101 walls via covalent incorporation to afford Cr-MIL-101-BTP as a novel adsorbent for the high-efficiency removal of ACT in aqueous solutions. The kinetic adsorption process, adsorption isotherms, adsorbent regeneration, and key parameters, such as adsorbent dosage, pH value, and ionic strength, for the adsorption of ACT were studied. Results showed that a pseudo-second-order rate equation effectively describes the adsorption kinetics. The Langmuir model exhibited a better fit to adsorption isotherm than the Freundlich model. Given the π-π stacking and hydrogen bond interaction, the adsorption capacity in Cr-MIL-101-BTP approached a maximum of 312.5 mg/g for ACT, which was considerably higher than the adsorption capacities of many other reported adsorbents. The excellent adsorption characteristics of Cr-MIL-101-BTP toward ACT were preserved in a wide pH range and high concentration of background electrolytes. In addition, the result showed that partition coefficient (PC) of Cr-MIL-101-BTP was 356.14 mg/g/µM at 5 mg/L of ACT concentration, which was found as the outperformer in all tested subjects. The ACT adsorption capacity of Cr-MIL-101-BTP at the breakthrough point was greatly influenced by initial concentration, and could be described by the Thomas model. Regeneration experiments indicated that the Cr-MIL-101-BTP was recycled at least six times without significant loss of adsorption capacity. Moreover, Cr-MIL-101-BTP did not show cytotoxic activity against the tested HepG2 cell lines and did not pose serious risks to Daphnia carinata survival (48 h LC50 = 446.6 µg/mL). These results prefigured the promising potential of Cr-MIL-101-BTP as a novel adsorbent for the efficient removal of ACT from aqueous solutions.

Enantioseparation of four amide herbicide stereoisomers using high-performance liquid chromatography.

The chirality of herbicides has been the focus of research. However, there is little information on the enantioseparation of amide herbicides with different chiral elements. In this study, the need for different chiral stationary phases (CSPs), mobile phases, temperatures and flow rates for the separation of napropamide, acetochlor and propisochlor was discussed in detail and compared to metolachlor. Resolution of C-chiral enantiomers was easier than that of axial-chiral enantiomers. Metolachlor and acetochlor could achieve baseline separation only on AY-H and AS-H columns, respectively. Propisochlor had satisfactory separations on OD-H and AS-H columns. Napropamide was separated on OJ-H, AY-H and AS-H columns. Both the structures of the compounds and CSPs and the interactions between them played significant roles in the enantioseparations. Molecule dockings were also used to elucidate the separation mechanisms. C-chiral enantiomers had perfect symmetry in their optical properties, whereas the axial-chiral enantiomers did not. The elution order for napropamide, acetochlor and propisochlor, with a single chiral location, was R- prior to S-. These results were the first that compare the enantioseparations of four amide herbicides with different chirality, and they provided the absolute configurations for the herbicides. The paper also illustrated certain mechanisms for enantioseparations.

Effect of the iron oxide catalyst on o-toluidine oxidation by the fluidized-bed fenton process.

This study investigates the effects of the Fe2+ concentration and synthetic iron oxide catalysts on o-toluidine degradation using a fluidized-bed Fenton process. The mineralization ofo-toluidine in the synthetic catalyst system is also examined. The H3.5 and H7.3 Fe/SiO2 and A7.8 and A 12.5 Fe/SiO2 catalysts were successfully synthesized by adding H202 and injecting air process, respectively. The optimum initial ferrous ion concentration for degradation of 1 mM o-toluidine was 1 mM. Experimental results reveal that 1 mM o-toluidine can be 100% degraded at 60 and 120 min in the modified fluidized-bed Fenton process with A7.8 Fe/SiO2 and the conventional fluidized-bed Fenton process with SiO2 carrier, respectively, when the optimum conditions of 1mM Fe2+ and 17mM H202 at pH 3 were used. The A7.8 Fe/SiO2 catalyst had a stronger oxidation ability than the H3.5 Fe/SiO2, H7.3 Fe/SiO2 and A12.5 Fe/SiO2 catalysts, and was attributed to the high iron content on the surface of the SiO2 support. The Fenton and Fenton-like reactions occurred in the A7.8 Fe/SiO2 catalyst system. Degradation of o-toluidine in the Fenton-like process follows pseudo-first-order kinetics. The A7.8 Fe/SiO2 catalyst efficiently enhanced o-toluidine oxidation under the pH range of 2-4.

Determination of amitraz and its metabolites in whole blood using solid-phase extraction and liquid chromatography-tandem mass spectrometry.

A method was developed for determination of amitraz and its metabolites, N-[2,4-(dimethylphenyl)-N'-methylformamidine (DMPF), 2,4-dimethylformamidine (DMF), 2,4-dimethylaniline (DMA) in whole blood. The analytes were extracted by solid-phase extraction (SPE) using dichloromethane, acetonitrile and methanol (2:1:1) mixture as elute solution. Analysis was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the positive ion mode using multiple reaction monitoring (MRM) technique. Collision-induced dissociation (CID) of amitraz at the electrospray source in MS/MS was observed in the analytic conditions. The method was validated in human whole blood spiked at three concentration levels. The low limit of detection (LOD) and the low limit of quantification (LOQ) for all the analytes were below 0.5µg/L and 2µg/L, respectively. Recoveries were between 90.2% and 104.5%, Bias and relative standard deviation (RSD) were below 15% (n=6). The good linear relationships were obtained in certain concentration ranges of amitraz and its metabolites. The results demonstrated the method is exclusive, sensitive and accurate, and can be applied in forensic toxicology.

Degradation of o-toluidine by fluidized-bed Fenton process: statistical and kinetic study.

BACKGROUND, AIM, AND SCOPE: The optimal conditions of o-toluidine degradation by fluidized-bed Fenton process were determined using Box-Behnken designs (BBD). The BBD can be used to find the optimal conditions in multivariable systems. The optimal conditions obtained by the design were further applied in the kinetic analysis of o-toluidine oxidation in fluidized-bed Fenton process. MATERIALS AND METHODS: The 1.35-L fluidized-bed reactor used in all experiments was a cylindrical vessel with an inlet, outlet, and recirculation pump. The o-toluidine was determined by high-performance liquid chromatography. RESULTS AND DISCUSSION: Analytical results indicated that pH, Fe(2+), and H(2)O(2) were significant factors in o-toluidine and chemical oxygen demand (COD) removal, but loading carrier was not. The pH significantly affected not only o-toluidine degradation, but also total iron removal. The predicted conditions for optimal removal of 1 mM of o-toluidine using 100 g of carriers were pH 3 ± 0.5, 1 mM of Fe(2+), and 17 mM of H(2)O(2). Removal of o-toluidine and COD in the actual experiment was higher than predicted, whereas removal of total iron was slightly lower. The kinetic study showed that the initial rate and rate constant (k) of o-toluidine degradation in the fluidized-bed Fenton process correlated Fe(2+) concentration. In the Fe(2+)/H(2)O(2) stage, high concentration of H(2)O(2) produced a scavenging effect. CONCLUSIONS: The predicted removal efficiencies of o-toluidine and COD were 90.2% and 41.4%, respectively. Moreover, the removals of o-toluidine and COD in the actual experiment were 99.8% and 61.8%, respectively.

Comparison of o-toluidine degradation by Fenton, electro-Fenton and photoelectro-Fenton processes.

A Box-Behnken design (BBD) statistical experimental design was used to investigate the degradation of o-toluidine by the electro-Fenton process. This method can be used to determine the optimal conditions in multivariable systems. Fe(2+) concentration (0.2-1.0mM), H(2)O(2) concentration (1-5mM), pH (2-4), and current (1-4A) were selected as independent variables. The removal efficiencies for o-toluidine and chemical oxygen demand (COD) were represented by the response function. Result by 2-level factorial design show that the pH and the Fe(2+) and H(2)O(2) concentrations were the principal parameters. Among the main parameters, the removal efficiencies for o-toluidine and COD were significantly affected by pH and Fe(2+) concentration. From the Box-Behnken design predictions, the optimal conditions in the electro-Fenton process for removing 90.8% of o-toluidine and 40.9% of COD were found to be 1mM of Fe(2+) and 4.85 mM of H(2)O(2) at pH 2. Under these optimal conditions, the experimental data showed that the removal efficiencies for o-toluidine and COD in the electro-Fenton process and the photoelectro-Fenton process were more than 91% and 43%, respectively, after 60 min of reaction. The removal efficiencies for o-toluidine and COD in the Fenton process are 56% and 27%, respectively.

[Isolation and degradation characteristics of acetochlor-degrading strain A-3].

The strain A-3 which could use acetochlor as the sole nitrogen source was isolated from soils contaminated with acetochlor and the sludge of pesticide factory by enrichment culture. The strain was identified as Ensifer adhaerens according to the results of morphology, physiology,and the phylogenetical analyses of 16S rRNA sequence. It was observed that the degradation rate of acetochlor by strain A-3 was 33.6% after 10 days culture at the concentration of 10 mg/L. The composition of the culture could affect the growth of A-3 and the degradation of acetochlor. The growth and degradation ability of strain A-3 were different with the different carbon sources. The strain had the strangest growth capability with the D600 value of 0.55, but the degradation rate was only 9.4% when using sucrose as carbon source. However, the strain A-3 had the highest degradation rate up to 29.2%, although the D600 value was only 0.3 when using glucose as carbon source. When the NaCl concentration was 0.5%, the strain A-3 grew best and had the highest degradation rate of 35%, but when the NaCl concentration was higher than 7%, the growth of A-3 was inhibited and the degradation rate was reduced to 2.6%. The results showed that the strain A-3 could degrade acetochlor effectively and the growth and degradation process was affected by environmental media, and the degradation of acetochlor could be controlled by changing the composition of the culture.

Simultaneous determination of acetochlor and propisochlor residues in corn and soil by solid phase extraction and gas chromatography with electron capture detection.

A sensitive and simple method for simultaneous analysis of acetochlor and propisochlor in corn and soil has been developed. Two herbicides were extracted from soil and corn matrices with methanol/water and acetone, respectively, followed by solid phase extraction (SPE) to remove co extractives, prior to analysis by gas chromatography with electron capture detection (GC-ECD). Primary secondary amine (PSA) SPE cartridges (500 mg, 3 mL) were used for sample preparation. The analytes from corn and soil matrices were eluted with 5 mL petroleum ether-acetic ether (95/5, v/v) and 3 mL petroleum ether-acetic ether (95/5, v/v), respectively. The recoveries of two pesticides ranged from 73.8% to 115.5% with relative standard deviations (RSD) less than 11.1% and sensitivity of 0.01 mg/kg, in agreement with directives for method validation in residue analysis. The method was successfully applied to determine the fate of acetochlor and propisochlor in real corn and soil samples. For acetochlor and propisochlor, the half-life times (t1/2) in soil was 5.541 and 6.074 days, respectively. No acetochlor and propisochlor residues (<0.01 mg/kg) were detected in corn at harvest time withholding period of 2.5 months after treatments of the pesticides. Direct confirmation of the analytes in samples was achieved by gas chromatography-mass spectrometry (GC-MS).

Development and validation of an analytical method for total amitraz in fruit and honey with quantification by gas chromatography-mass spectrometry.

The EU maximum residue limit (MRL) definition for amitraz is 'the sum of amitraz plus all its metabolites containing the 2,4-aniline moiety, expressed as amitraz'. A rapid and sensitive method has been developed and validated in-house for the determination of total amitraz in pears, strawberries, oranges and honey. Samples were hydrolysed (under acidic followed by alkaline conditions) to convert amitraz to 2,4-dimethyaniline, which was then partitioned into 2,2,4-trimethylpentane prior to quantification by gas chromatography-mass spectrometry. The method was validated at 0.02 and 0.1 mg kg(-1) amitraz (well below MRL requirements) with a lowest calibrated level (LCL) for 2,4-dimethylaniline of 0.002 mg kg(-1) (equivalent to 0.0024 mg kg(-1) amitraz). A single partition step yielded recoveries of approximately 60% (with % CV values in the range 3.3-8.2), which is satisfactory for screening purposes. A second partition increased recoveries by 10-20%, making the method suitable for the quantification of residues.

A novel sol-gel calix[4]arene-modified capillary column for open-tubular capillary electrochromatography.

A novel open-tubular CEC (OT-CEC) column was prepared by immobilized 5,11,17,23-tetra-tert-butyl-25,27-diethoxy-26,28-dihydroxy-calix[4]arene (Calix[4]) on fused-silica capillary column with sol-gel technology. Calix[4] was initially reacted with gamma-glycidoxypropyltrimethoxysilane (KH-560) to form a new sol-gel precursor (calix[4]-KH-560), and then mixed with another precursor, namely tetraethoxysilane (TEOS). After hydrolysis and condensation, a sol-gel matrix was obtained, in which calix[4] was incorporated. Successful calix[4]-modified sol-gel coating was suggested by infrared (IR) spectra and greatly decreased EOF. In comparison with OT columns prepared by the sol-gel method with TEOS and KH-560 only, the calix[4]-modified sol-gel column showed greatly improved separation of isomeric toluidines, nitrophenols, picolines and neurotransmitters with structural similarity. Migration time and theoretical plate number reproducibility were satisfactory with RSDs less than 1 and 6% each for within column runs and not more than 3 and 7% each for column-to-column measurements, using toluidine and nitrophenol isomers as test solutes on this column. High separation efficiencies (96,000-300,000 plates/m) for basic toluidine isomers were obtained. This column was also successfully employed to combine extraction procedure for the determination of dopamine (DA) and norepinephrine (NE) in Portulaca oleracea L. The recoveries of DA and NE were 93.3 and 94.2%, respectively.

Fabrication and performance of a three-dimensionally adjustable device for the amperometric detection of microchip capillary electrophoresis.

A microchip CE-amperometric detection (AD) system has been fabricated by integrating a two-dimensionally adjustable CE microchip and an AD cell containing a one-dimensionally adjustable disk detection electrode in a Plexiglas holder. It facilitates the precise 3-D alignment between the channel outlet and the detection electrode without a complicated 3-D manipulator. The performance of this unique system was demonstrated by separating five aromatic amines (1,4-phenyldiamine, aniline, 2-methylaniline, 4-chloroaniline, and 1-naphthylamine) of environmental concern. Factors influencing their separation and detection processes were examined and optimized. The five analytes have been well separated within 140 s in a 74 cm long separation channel at a separation voltage of +2500 V using a 10 mM phosphate buffer (pH 3.5). Highly linear response is obtained for the five analytes over the range 20-200 microM with the detection limits ranging from 0.46 to 1.44 microM, respectively. The present system demonstrated long-term stability and reproducibility with RSDs of less than 5% for the peak current (n = 9). The new approach for the microchannel-electrode alignment should find a wide range of applications in CE, flowing injection analysis, and other microfluidic analysis systems.

Subcritical water extraction to evaluate desorption behavior of organic pesticides in soil.

We evaluated the feasibility of extracting organic pesticides in soil using a hot-water percolation apparatus at 105 degrees C and 120 kPa pressure. Efficiency of the method was assessed by extracting six selected pesticides (acetochlor, atrazine, diazinon, carbendazim, imidacloprid, and isoproturon) from previously equilibrated soil at 13.6-65.8 mg/kg concentration range. Studies were performed on brown forest soil with clay alluviation (Luvisol). The method developed was compared to the traditional batch equilibrium method in terms of desorbed amount of pesticides from soil and extraction time. Pesticides in the liquid phase from the batch sorption experiment and in the effluent from the hot-water percolation were quantified by high-performance liquid chromatography with UV detection. The results of the percolation experiment are in close correlation with those of the conventional soil testing method. Desorbed quantities by hot-water percolation were 85% acetochlor, 62% atrazine, 65% carbendazim, 44% diazinon, 95% imidacloprid, and 84% isoproturon, whereas using batch equilibrium method 101, 66, 64, 37, 81, and 90% were desorbed, expressed as the percentage of the adsorbed amount of pesticide on soil following equilibration. The average time for hot-water extraction was 3.45 min, in contrast to the 16 h time consumption of the traditional batch method. The effect of temperature on stability of selected compounds was also evaluated using pesticide-spiked sand without soil. Recoveries of analytes ranged between 84.6 and 91.1% with reproducibility of 7.9-10.2%, except for diazinon, for which recovery was 59.4% with 14.4% relative standard deviation since decomposition occurred at elevated temperature. The percolation process has been described by a first-order kinetic equation. The parameters calculated from the equation provide an opportunity to estimate the amount of compound available for desorption, the rate of desorption processes in the studied soil-pesticide-water system, and modeling the leaching process to obtain additional information on the environmental behavior of the examined pesticide.

[Separation and determination of metsulfuron, bensulfuron, acetochlor by high performance liquid chromatography].

In this paper a high performance liquid chromatographic method for the separation and determination of metsulfuron, bensulfuron and acetochlor in the composite herbicide "Nongjiayi" is described. The concentration of methanol in the mobile phase and the temperature of the column affected the k' factor and the separation of the three active ingredients. Impurities in the "Nongjiayi" did not interfere with the determination. Chromatographic conditions were Shim-Pack CLC-C8 (150 mm x 6 mm i.d., 5 microm), mobile phase of methanol-water (60:40, V/V) and UV detector at 240 nm. Quantification was carried out with the three external standards. The average recovery was 98.81% with RSD=0.80% for metsulfuron, 99.10% with RSD=0.78% for bensulfuron and 99.72% with RSD=0.69% for acetochlor. The linear range of this method was 0.10-0.40 microg (r=0.9994) for metsulfuron, 0.40-1.60 microg (r=0.9995) for bensulfuron and 10-40 microg (r=0.9987) for acetochlor. The method is accurate, rapid and reproducible and can be applied to quality control for the "Nongjiayi".

Capillary electrophoretic separation of TNT and its transformation products.

2,4,6-Trinitrotoluene (TNT), 2-aminodinitrotoluene (2ADNT), 4-aminodinitrotoluene (4ADNT), and diamino-6-nitrotoluene (DA6NT) in a variety of matrices (including chemical, microbial, and plant extract) were successfully separated and quantified using micellar electrokinetic capillary electrophoresis (MEKC). The method used a buffer solution of 20 mM in borax, 50 mM in sodium dodecyl sulfate (SDS), and of pH 8.5. Voltage applied across the capillary was 20 kV and temperature was maintained at 25 degrees C. Compounds eluted within approximately 6-11 min and were identified by both their migration times and spectra.

Separation of fuchsin homologs using high performance liquid chromatography.

Commercial samples of basic fuchsin contain variable proportions of four homologs, pararosaniline, rosaniline, magenta II, and new fuchsin. That different samples of dyes give variable staining is documented in the literature. Three commercial samples of basic fuchsin were investigated using high performance liquid chromatography. Separation of homologs was achieved using a C18 adsorbant and a solvent system of methanol:water:glacial acetic acid (66:24:10).