Ramen Kumar Kole

Photodegradation of metsulfuron methyl in aqueous solution

Metsulfuron methyl (1) was effectively degraded by ultra violet light in aqueous solution. About 50% of 1 was degraded within 15 hours. A new metabolite (2) of metsulfuron methyl was isolated and characterised along with phenyl sulfonamide (3) and an unidentified photometabolite (4). The pathway of photodegradation of metsulfuron methyl has been proposed.

Phototransformation of bifenox in aqueous isopropanol

Phototransformation of bifenox was studied under UV and sunlight in aqueous isopropanol using TiO2 as photocatalyst. The rate of photodegradation of bifenox in aqueous isopropanol (10 µg mL−1) followed first-order kinetics under UV (T1/2 = 15 h) and sunlight (T1/2 = 28 h). UV-irradiated bifenox solution yielded five metabolites F1, F2, F3, F4, and F5 and sunlight irradiated solution delivered four metabolites F1, F2, F6, and F7. The metabolite F1 was isolated as yellow crystalline solid (m.p. 91–93°C) and characterized as methyl (2,4-dichlorophenoxy) anthranilate by direct comparison with an authentic sample prepared in the laboratory. The other metabolites were identified as 3-carboxymethyl-4-nitrophenol (F2), 2,4-dihydroxy phenoxy aniline (F3), 4-hydroxy hydroxyl-aminobenzene (F4), isopropyl 2,4-dichlorophenolate (F5), 4-isopropyloxy-4′-nitrosodiphenyl ether (F6), and 2,4-di-isopropyloxy hydroxyl aminobenzene (F7) by GC-MS. The relative amounts of the products were found to be 18–20% for F1, 11–17% for F2, and 1–3% for F3–F7. The mechanism of phototransformation involved reduction, dechlorination, hydrolysis as well as nucleophilic displacement reactions.

Validation of multiresidue method for analysis of 31 pesticides in rice using gas chromatography-tandem mass spectrometry

Five modified QuEChERS were tested for the multiresidue analysis of 31 pesticides in rice. Rice was spiked with mixture solution of pesticides at 10 ng/g. Method selection was based on the LODs (sensitivity) and recovery tests (accuracy) of the pesticides. Analysis was done in GC-tandem MS in multiple reaction monitoring mode with a total run time of approximately 37 min. The selected method was validated after spiking rice at 20 and 100 ng/g in rice. The performance characteristics of the method impacted for all selected pesticides were acceptable according to the guidelines for method validation (recovery of 70-120% with an RSD of <20% and r2 value of ≥0.99). For rice, matrix effect on the signals of the compounds was corrected by using matrix-matched calibration standards. The LOQs met the requirements of the maximum residue limits for pesticides in rice. The developed method allowed for the simultaneous determination and confirmation of a large number of different groups of pesticides and was fast, simple, inexpensive, and useful for the routine analysis of rice.

Antifungal activity of plant extracts against Colletotrichum musae, the post harvest anthracnose pathogen of banana cv. Martaman

Purpose – The purpose of this paper was to determine the antifungal activities of different solvent extracts of common plants in vitro and in vivo against banana anthracnose fungus Colletotrichum musae (Berk & M.A. Curtis) Arx, and to investigate its effects on the pathogen and identify the bio active component(s). Design/methodology/approach – Extracts were obtained from leaves, tender shoots, rhizomes, bulbs, seeds and fruits of 42 naturally growing plant species following hot sequential extraction. Preliminary screening of the solvent extracts was done based on the inhibition of radial mycelial growth of C. musae following poison food technique and conidial germination inhibition by cavity slide technique. The selected extracts were assessed for their effect on harvested banana in reducing anthracnose during storage. The active components in the bio-active fractions of plant extract were identified by gas chromatography-mass spectroscopy. Findings – Methanol extracted a larger quantity of material (between 6.9 and 12.5 per cent) than hexane or chloroform, and all its extracts were active against the test pathogen with mycelial growth inhibition ranging from 13.70 to 88.89 per cent. Zingiberofficinale rhizome extract as well as Polyalthia longifolia and Clerodendrum inerme leaf extracts exhibited more than 80 per cent inhibition of mycelial growth. Total inhibition of spore germination of C. musae was recorded in Z. officinale and P. longifolia extracts at 0.3 per cent w/v and 0.5 per cent w/v concentration, respectively, while only 68 per cent spore inhibition was recorded in C. inerme at 0.5 per cent w/v concentration. Of the three plant species, Z. officinale had the best antifungal activity (18.0 per cent disease incidence; 2.2 disease severity scale) when banana fruits were dipped in the extract at a concentration of 0.5 per cent w/v at 5 days of storage in ambient condition (80-82 per cent R.H., 27 ± 1°C). The bio-active compounds in the extract of Z. officinale were identified as alpha-curcumene and zingerone. Originality/value – Based on the antifungal activity, plant extract of Z. officinale can be used as an effective alternative to chemicals in controlling anthracnose pathogen in harvested banana.

Simultaneous determination and risk assessment of fipronil and its metabolites in sugarcane, using GC-ECD and confirmation by GC-MS/MS

A sensitive gas chromatographic method using a modified QuEChERS technique is reported for simultaneous determination, dissipation and risk assessment of fipronil and its metabolites in sugarcane and soil. Recoveries were 80.7-98.5% with precision within 1.4-16.5% estimated at the limits of detection (LOD) 0.0015-0.002 µg g-1 and limits of quantification (LOQ) 0.005 µg g-1. Fipronil dissipated with half-life (T1/2) of 2.8-4.3 days while for total fipronil it was 3.7-6.0 days following application of fipronil (5% SC) in sugarcane fields at recommended (100 g a.i. ha-1) and double the recommended (200 g a.i. ha-1) doses. Estimated pre-harvest intervals (PHI) for fipronil were 20.3-27.0 days in sugarcane plants, and for total fipronil the corresponding values were 28.2-37.8 days. No dietary risk was observed due to fipronil (RQd < 1) 5 days after application. Potential risk exists towards algae and soil macro-organism (RQs > 1), but for earthworms it was safe (RQs < 1).

GC-MS/MS determination and ecological risk assessment of pesticides in aquatic system: A case study in Hooghly River basin in West Bengal, India

A liquid-liquid extraction (LLE) for water and modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method for sediment combined with gas chromatography-tandem mass spectrometry (GC-MS/MS) detection in multiple reaction monitoring (MRM) mode was standardized for determination of 31 pesticides. Performance characteristics for the selected pesticides were acceptable according to European Commissions (EC) guidelines for method validation (recovery 70-120%, RSD <20% and R2 value ≥ 0.99). River, pond and tubewell water and river sediment samples (64 nos.) were collected from Hooghly River basin in West Bengal, India during 2014-2016. About 42% of the samples showed the presence of 19 pesticides with the highest loading of total pesticides (T-pesticides) in river water (3.01 ng mL-1) followed by sediment (1.25 ng g-1), pond (0.40 ng mL-1) and tubewell (0.02 ng mL-1) water. The non-agricultural OC (organochlorine) insecticides were detected in all river water and sediment samples mainly due to HCHs (hexachlorocyclohexane) from old source and fresh use of DDTs (dichlorodiphenyltrichloroethane) in local areas. No OC insecticides were detected in pond and tubewell water. Maximum residues of some recommended pesticides in agriculture were obtained in pond water. Most of the river water samples (93.7%) were in excess of EC limit (0.50 ng mL-1) of T-pesticides for drinking followed by pond water samples (56.2%). Tubewell water samples were free from T-pesticide threat but exceeded the EC limit (0.10 ng mL-1) for single pesticide in case of chlorpyrifos only. Ecological risk on aquatic animals was observed for OCs in river and chlorpyrifos in pond aquatic ecosystem.

Response of gill ATPase and liver esterase of pseudorasobora parva to a two month exposure to glyphosate and metsulfuron methyl

Responses of gill ATPase and liver esterase of topmouth gudgeon, Pseudorasobora parva under sublethal exposure to glyphosate (WSC 41% as isopropyl amine salt) at 1.0, 5.0 and 25 mg/L and metsulfuron methyl (technical 98.2%) at 0.0095, 0.085 and 0.85 mg/L of water were measured at 8th, 16th, 24th and 65th days of exposure. Two way analysis of variance (ANOVA) followed by least significant difference (LSD) test and parameter estimates indicated a significant inhibitory effect on gill ATPase activity (max. 57%) by metsulfuron methyl and liver esterase activity by glyphosate (max. 43%) as compared to the control, but the differences in the residual activities among the concentration levels of the herbicides were not significant. The activities changed significantly with the sampling times except gill ATPase activity under metsulfuron methyl exposure. In most of the cases, the maximum inhibitory effect on the enzymes was recorded on the 8th day and over-recovering appeared with time.