Adsorption-desorption and leaching behavior of kresoxim-methyl in different soils of India: kinetics and thermodynamic studies.

The sorption and leaching behavior of kresoxim-methyl was explored in four different soils, viz., clay, sandy loam, loamy sand, and sandy loam (saline), representing vegetables and fruits growing regions of India. Adsorption of kresoxim-methyl in all the soils reached equilibrium within 48 h. The rate constants for adsorption and desorption at two different temperatures were obtained from the Lindstrom model, which simultaneously evaluated adsorption and desorption kinetics. The data for rate constants, activation energies, enthalpy of activation, entropy of activation, and free energy indicated physical adsorption of kresoxim-methyl on soil. The relative adsorptivity of the test soils could be attributed to different organic matter and clay contents of the soils. A good fit to the linear and Freundlich isotherms was observed for both adsorption as well as desorption. The groundwater ubiquity score (GUS) for different soils varied between 0 and 2.26. The GUS and leaching study indicated moderately low leaching potential of kresoxim-methyl. The adsorption on four soil types largely depended on the soil physicochemical properties such as organic carbon content, cation-exchange capacity, and texture of the soil.

Kresoxim methyl dissipation kinetics and its residue effect on soil extra-cellular and intra-cellular enzymatic activity in four different soils of India.

The rate of degradation of kresoxim methyl and its effect on soil extra-cellular (acid phosphatase, alkaline phosphatase and ß-glucosidase) and intra-cellular (dehydrogenase) enzymes were explored in four different soils of India. In all the tested soils, the degradation rate was faster at the beginning, which slowed down with time indicating a non-linear pattern of degradation. Rate of degradation in black soil was fastest followed by saline, brown and red soils, respectively and followed 1st or 1st + 1st order kinetics with half-life ranging between 1-6 days for natural soil and 1-19 days for sterile soils. The rate of degradation in natural against sterilized soils suggests that microbial degradation might be the major pathway of residue dissipation. Although small changes in enzyme activities were observed, kresoxim methyl did not have any significant deleterious effect on the enzymatic activity of the various test soils in long run. Simple correlation studies between degradation percentage and individual enzyme activities did not establish any significant relationships. The pattern and change of enzyme activity was primarily due to the effect of the incubation period rather than the effect of kresoxim methyl itself.

Dissipation kinetics, safety evaluation, and assessment of pre-harvest interval (PHI) and processing factor for kresoxim methyl residues in grape.

A field dissipation study was conducted to evaluate the pre-harvest interval (PHI) and processing factor (PF) for kresoxim methyl (Ergon 44.3 SC) residues in grapes and during raisin making process at recommended dose (RD) and double the recommended dose (DRD). Kresoxim methyl residues dissipated following 1st-order kinetics with a half-life of 10 and 18 days at RD and DRD, respectively. The PHIs with respect to the European Union maximum residue limit (EU-MRL) of 1 mg kg(-1) for grapes were 13 and 30 days at RD and DRD, respectively. The degradation data during grape to raisin making process were best fitted to nonlinear 1st + 1st-order kinetics with a half-life ranging between 4 and 8 days for both shade drying and with raisin dryer at different doses. The PFs were 1.19 and 1.24 with shade drying and 1.09 and 1.10 with raisin dryer, respectively, which indicates concentration of the residues during raisin making process. The dietary exposure of kresoxim methyl on each sampling day was less than the respective maximum permissible intake both at RD and DRD. The residues of kresoxim methyl in market samples of grapes and raisins were well below the EU-MRL and were also devoid of any risk of acute toxicity related to dietary exposure.

(2Z)-3-(2,4-Di-chloro-phen-yl)-3-hy-droxy-N-phenyl-prop-2-ene-thio-amide.

In the title mol-ecule, C15H11Cl2NOS, the dihedral angle between the phenyl and benzene rings is 72.24 (1)°. In the crystal, pairs of N-H⋯S hydrogen bonds form dimers with twofold rotational symmetry. The dimers are connected by weak C-H⋯O hydrogen bonds, forming a two-dimensional network parallel to (001). An intra-molecular O-H⋯S hydrogen bond is also observed.

9-(4-Hy-droxy-3-meth-oxy-phen-yl)-3,3,6,6-tetra-methyl-1,2,3,4,5,6,7,8,9,10-deca-hydro-acridine-1,8-dione.

In the title mol-ecule, C24H29NO4, the central ring of the acridinedione system adopts a flat boat conformation and the four essentially planar atoms of this ring [maximum deviation = 0.001 (2) Å] form a dihedral angle of 85.99 (12)° with the benzene ring. The two outer rings of the acridinedione system adopt sofa conformations. In the crystal, O-H⋯O and N-H⋯O hydrogen bonds link the mol-ecules, forming a two-dimensional network parallel to (100).

9-(3-Fluoro-phen-yl)-3,3,6,6-tetra-methyl-1,2,3,4,5,6,7,8,9,10-deca-hydro-acridine-1,8-dione.

In the title mol-ecule, C23H26FNO2, the central ring of the acridinedione system adopts a slight boat conformation and the four essentially planar atoms of this ring [maximum deviation = 0.019 (1) Å] form a dihedral angle of 89.98 (6)° with the benzene ring. The two outer rings of the acridinedione system adopt sofa conformations. In the crystal, N-H⋯O hydrogen bonds link the mol-ecules, forming chains along [001].

2-Amino-7,7-dimethyl-5-oxo-4-[3-(trifluoro-meth-yl)phen-yl]-1,4,5,6,7,8-hexa-hydro-quinoline-3-carbonitrile.

In the title mol-ecule, C19H18F3N3O, the dihydro-pyridine and cyclo-hexene rings both adopt sofa conformations. The five essentially planar atoms of the dihydro-pyridine ring [maximum deviation = 0.039 (2) Å] form a dihedral angle of 88.19 (8)° with the benzene ring. The F atoms of the trifluoro-methyl group were refined as disordered over two sets of sites in a 0.840 (3):0.160 (3) ratio. In the crystal, N-H⋯O and N-H⋯N hydrogen bonds link mol-ecules into a two-dimensional network parallel to (100).

2-Amino-7,7-dimethyl-5-oxo-4-[3-(trifluoro-meth-yl)phen-yl]-5,6,7,8-tetra-hydro-4H-chromene-3-carbonitrile.

In the title mol-ecule, C19H17F3N2O2, the fused cyclo-hexene and pyran rings adopt sofa and flattened boat conformations, respectively. The four essentially planar atoms of the pyran ring [maximum deviation = 0.008 (2) Å] form a dihedral angle of 88.13 (9)° with the benzene ring. The F atoms of the trifluoro-methyl group were refined as disordered over three sets of sites in a 0.507 (7):0.330 (7):0.163 (3) ratio. In the crystal, mol-ecules are connected into inversion dimers via pairs of N-H⋯N hydrogen bonds and these dimers are further linked by N-H⋯O hydrogen bonds into a two-dimensional network parallel to (100).

2-[(Dimethyl-amino)-methyl-idene]propane-dinitrile.

In the title moleclue, C6H7N3, the mean plane of the dimethyl-amino group [maximum deviation = 0.006 (2) Å] forms a dihedral angle of 7.95 (18)° with the mean plane of the propane-dinitrile fragment [maximum deviation = 0.008 (2) Å]. In the crystal, weak C-H⋯N hydrogen bonds link the mol-ecules into a three-dimensional network.

5-Benzoyl-4-(4-fluoro-phen-yl)-3,4-dihydro-pyrimidin-2(1H)-one.

In the title mol-ecule, C(17)H(13)FN(2)O(2), the 3,4-dihydro-pyrimidine ring adopts a flattened sofa conformation with the flap atom (which bears the fluoro-phenyl substituent) deviating from the plane defined by the remaining five ring atoms by 0.281 (2) Å. This plane forms dihedral angles of 85.98 (6) and 60.63 (6)° with the 4-fluoro-phenyl and benzoyl-phenyl rings, respectively. The dihedral angle between the 4-fluoro-phenyl group and the benzene ring is 71.78 (6)°. In the crystal, N-H⋯O hydrogen bonds link mol-ecules into inversion dimers that are further connected by another N-H⋯O inter-action into a two-dimensional supra-molecular structure parallel to (101).

9-(3,4-Dimeth-oxy-phen-yl)-3,3,6,6-tetra-methyl-1,2,3,4,5,6,7,8,9,10-deca-hydro-acridine-1,8-dione.

The asymmetric unit of the title compound, C(25)H(31)NO(4), contains two independent mol-ecules. In one mol-ecule, the benzene ring and an attached meth-oxy group were refined as disordered over two sets of sites in a 0.65 (4): 0.35 (4) ratio. In both mol-ecules, the central ring of the acridinedione system adopts a flattened boat conformation. The four essentially planar atoms of this ring [maximum deviations = 0.006 (5) Šin both mol-ecules] forms dihedral angles of 86.8 (2) and 87.6 (2)°, respectively, with the major and minor components in the disordered benzene ring and 87.3 (2)° with the benzene ring in the fully ordered mol-ecule. The two outer rings of the acridinedione system adopt sofa conformations in both mol-ecules. In the crystal, N-H⋯O hydrogen bonds form two independent chains along [100]. C-H⋯O hydrogen bonds link the chains, forming a three-dimensional network.

Poly[µ2-aqua-µ4-(2-{3-[(6-chloro-pyridin-3-yl)meth-yl]-2-oxoimidazolidin-1-yl}acetato)-sodium].

In the title compound, [Na(C11H11ClN3O3)(H2O)](n), there are two independent Na(I) ions, one of which lies on an inversion center and is coordinated in a slightly distorted octa-hedral environment. The other Na(I) ion lies on a twofold rotation axis and is cooordinated in a slightly distorted trigonal-bipyramidal coordination environment. In the organic ligand, the imidazolidine ring adopts a half-chair conformation. The Na(I) ions bridge organic ligands and water mol-ecules, forming a two-dimensional structure parallel to (100). There are inter-molecular O-H⋯O and weak C-H⋯O hydrogen bonds within the two-dimensional structure.

Ethyl 2-{3-[(6-chloro-pyridin-3-yl)meth-yl]-2-(nitro-imino)-imidazolidin-1-yl}acetate.

In the title compound, C(13)H(16)ClN(5)O(4), the imidazole ring is in a slight envelope conformation. The dihedral angle between the pyridine ring and the four essentially planar atoms [maximum deviation 0.015 (2) Å] of the imidazole ring is 80.8 (1)°. In, the crystal, weak C-H⋯O and C-H⋯N hydrogen bonds are present. In addition, there are weak π-π stacking inter-actions between symmetry-related pyridine rings with a centroid-centroid distance of 3.807 (1) Å.

Ethyl 3-[(6-chloro-pyridin-3-yl)meth-yl]-2-oxoimidazolidine-1-carboxyl-ate.

In the title compound, C(12)H(14)ClN(3)O(3), the imidazole ring adopts a half-chair conformation. The dihedral angle between the pyridine and imidazole rings is 70.0 (1)°. In the crystal, the molecules are linked by C-H⋯O inter-actions, forming chains parallel to the c axis.

1-[(6-Chloro-pyridin-3-yl)meth-yl]imidazolidin-2-iminium chloride.

The title compound, C(9)H(12)ClN(4) (+)·Cl(-), is a natural metabolic product of imidacloprid [systematic name: (E)-1-(6-chloro-3-pyridyl-meth-yl)-N-nitro-imidazolidin-2-yl-idene-amine] and was obtained by the reduction of the latter using Fe in HCl. The dihedral angle between the pyridine and imidazole rings is 62.09 (12)°. The crystal structure is stabilized by N-H⋯Cl and C-H⋯Cl inter-actions involving the chloride anion. The pyridine N and the chloride atoms are not involved in inter-molecular inter-actions.

(2E)-3-(Dimethyl-amino)-1-(4-fluoro-phen-yl)prop-2-en-1-one.

In the title compound, C(11)H(12)FNO, the dihedral angle between the prop-2-en-1-one group and the benzene ring is 19.33 (6)°. The configuration of the keto group with respect to the olefinic double bond is s-cis. In the crystal, the mol-ecules form dimers through aromatic π-π stacking inter-actions [centroid-centroid distance = 3.667 (1) Å] and are linked via C-H⋯O inter-actions into chains along the b axis.

Methyl (2E)-2-cyano-3-(dimethyl-amino)-prop-2-enoate.

In the title compound, C(7)H(10)N(2)O(2), the dimethyl-amino group is twisted slightly relative to the acrylate fragment, forming a dihedral angle of 11.6 (1)°. In the crystal, molecules are linked via pairs of bifurcated C-H/H⋯O hydrogen bonds, forming inversion dimers, which are further connected by C-H⋯N hydrogen bonds into chains along the a-axis direction.

3-Meth-oxy-2-[2-({[6-(trifluoro-meth-yl)pyridin-2-yl]-oxy}meth-yl)phen-yl]prop-2-enoic acid.

The title mol-ecule, C(17)H(14)F(3)NO(4), consists of two nearly planar fragments, viz. the 2-benzyl-oxypyridine (r.m.s. deviation 0.016 Å) and (E)-3-meth-oxy-prop2-enoic (r.m.s. deviation 0.004 Å) units, which form a dihedral angle of 84.19 (7)°. In the crystal, pairs of O-H⋯O hydrogen bonds link mol-ecules into dimers that are further connected by C-H⋯O and C-H⋯F inter-actions into (001) layers. In addition, π-π stacking inter-actions are observed within a layer between the pyridine and benzene rings [centroid-centroid distance = 3.768 (2) Å]. The F atoms of the trifluoro-methyl group are disordered over two sets of sites in a 0.53 (4):0.47 (4) ratio.

Multiresidue analysis of 83 pesticides and 12 dioxin-like polychlorinated biphenyls in wine by gas chromatography-time-of-flight mass spectrometry.

A multiresidue method is described for simultaneous estimation of 83 pesticides and 12 dioxin-like polychlorinated biphenyls (PCBs) in red and white wines. The samples (20mL wine, acidified with 20 mL 1% HCl) were extracted with 10 mL ethyl acetate (+20 g sodium sulphate) and cleaned by dispersive solid-phase extraction (DSPE) with anhydrous calcium chloride and Florisil successively. The final extract (5 mL) was solvent exchanged to 1mL of cyclohexane:ethyl acetate (9:1), further cleaned by DSPE with 25mg primary secondary amine sorbent and analyzed by gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS) within 31 min run time. The limits of quantification of most analytes were 80% for most analytes except cyprodinil, buprofezin and iprodione. The expanded uncertainties at 10 ng/mL were <20% for most analytes. Intra-laboratory precision in terms of Horwitz ratio of all the analytes was below 0.5, suggesting ruggedness of the method. Effectively, the method detection limit for most analytes was as low as up to 1 ng/mL in both red and white wine, except for cyfluthrin and cypermethrin.

Degradation kinetics and safety evaluation of buprofezin residues in grape (Vitis vinifera L.) and three different soils of India.

BACKGROUND: This work was undertaken to determine the preharvest interval (PHI) of buprofezin to minimize its residues in grapes and thereby ensure consumer safety and avoid possible non-compliance in terms of residue violations in export markets. Furthermore, the residue dynamics in three grapevine soils of India was explored to assess its environmental safety. RESULTS: Residues dissipated following non-linear two-compartment first + first-order kinetics. In grapes, the PHI was 31 days at both treatments (312.5 and 625 g a.i. ha(-1)), with the residues below the maximum permissible intake even 1 h after foliar spraying. Random sampling of 5 kg comprising small bunchlets (8-10 berries) collected from a 1 ha area gave satisfactory homogeneity and representation of the population. A survey on the samples harvested after the PHI from supervised vineyards that received treatment at the recommended dose showed residues below the maximum residue limit (MRL) of 0.02 mg kg(-1) applicable for the European Union. In soil, the degradation rate was fastest in clay soil, followed by sandy loam and silty clay, with a half-life within 16 days in all the soils. CONCLUSION: The recommendation of the PHI proved to be effective in minimizing buprofezin residues in grapes. Thus, this work is of high practical significance to the domestic and export grape industry of India to ensure safety compliance in respect of buprofezin residues, keeping in view the requirements of international trade.