Simultaneous determination of dimethoate and its metabolite omethoate in curry leaf using LC-MS/MS and risk assessment

This study presents the method development, validation, and simultaneous determination of dimethoate and its metabolite omethoate in curry leaf. Samples were extracted following modified quick, easy, cheap, effective, rugged, and safe extraction protocol and analyzed using liquid chromatography-tandem mass spectrometry. The limit of quantification in the matrix was 0.005 μg g⁻¹ for dimethoate and omethoate. Extraction using acetonitrile recorded the average recoveries in the range of 82.25 to 112.97% for dimethoate and 85.57 to 107.22% for omethoate at 0.005, 0.025 and 0.050 μg g⁻¹ fortification levels and relative standard deviation less than 5%. Similarly, the relative standard deviation values for intraday (Repeatability) and interday (Reproducibility) tests were less than 15%. Dissipation kinetics of dimethoate 30% emulsifiable concentrate at 200 and 400 g a.i h⁻¹ recorded initial deposits of 5.20 and 10.05 μg g⁻¹ and 0.33 and 0.48 μg g⁻¹ for dimethoate and omethoate, respectively, and half-life of 3.07 and 3.34 days. The estimated hazard index value found more than one at a day after dimethoate application. It is not safe for consumer health to use curry leaves in the initial days after application.     

Laser flash photolysis generation and kinetic studies of corrole-manganese(V)-oxo intermediates

Corrole-manganese(V)-oxo intermediates were produced by laser flash photolysis of the corresponding corrole-manganese(IV) chlorate complexes, and the kinetics of their decay reactions in CH2Cl2 and their reactions with organic reductants were studied. The corrole ligands studied were 5,10,15-tris(pentafluorophenyl)corrole (H3TPFC), 5,10,15-triphenylcorrole (H3TPC), and 5,15-bis(pentafluorophenyl)-10-(p-methoxyphenyl)corrole (H3BPFMC). In self-decay reactions and in reactions with substrates, the order of reactivity of (Cor)Mn(V)(O) was TPC > BPFMC > TPFC, which is inverted from that expected based on the electron-demand of the ligands. The rates of reactions of (Cor)Mn(V)(O) were dependent on the concentration of the oxidant and other manganese species, with increasing concentrations of various manganese species resulting in decreasing rates of reactions, and the apparent rate constant for reaction of (TPFC)Mn(V)(O) with triphenylamine was found to display fractional order with respect to the manganese-oxo species. The kinetic results are consistent in part with a reaction model involving disproportionation of (Cor)Mn(V)(O) to give (Cor)Mn(IV) and (Cor)Mn(VI)(O) species, the latter of which is the active oxidant. Alternatively, the results are consistent with oxidation by (Cor)Mn(V)(O) which is reversibly sequestered in non-reactive complexes by various manganese species.     

A secretory phospholipase A2-mediated neuroprotection and anti-apoptosis

Background  

Phospholipase A₂ liberates free fatty acids and lysophospholipids upon hydrolysis of phospholipids and these products are often associated with detrimental effects such as inflammation and cerebral ischemia. The neuroprotective effect of neutral phospholipase from snake venom has been investigated.     

Determination of 77 Multiclass Pesticides and Their Metabolitesin Capsicum and Tomato Using GC-MS/MS and LC-MS/MS

A quick, sensitive, and reproducible analytical method for the determination of 77 multiclass pesticides and their metabolites in Capsicum and tomato by gas and liquid chromatography tandem mass spectrometry was standardized and validated. The limit of detection of 0.19 to 10.91 and limit of quantification of 0.63 to 36.34 µg·kg⁻¹ for Capsicum and 0.10 to 9.55 µg·kg⁻¹ (LOD) and 0.35 to 33.43 µg·kg⁻¹ (LOQ) for tomato. The method involves extraction of sample with acetonitrile, purification by dispersive solid phase extraction using primary secondary amine and graphitized carbon black. The recoveries of all pesticides were in the range of 75 to 110% with a relative standard deviation of less than 20%. Similarly, the method precision was evaluated interms of repeatability (RSDr) and reproducibility (RSD_wR) by spiking of mixed pesticides standards at 100 µg·kg⁻¹ recorded anRSD of less than 20%. The matrix effect was acceptable and no significant variation was observed in both the matrices except for few pesticides. The estimated measurement uncertainty found acceptable for all the pesticides. This method found suitable for analysis of vegetable samples drawn from market and farm gates.     

Photochemical generation of a highly reactive iron-oxo intermediate. A true iron(V)-oxo species?

Laser flash photolysis of 5,10,15-tris(pentafluorophenyl)corrole-iron(IV) chlorate or nitrate, prepared from the corresponding chloride, gave a highly reactive iron-oxo transient identified as an iron(V)-oxo species on the basis of its UV-visible spectrum and high reactivity as well as by analogy to photochemical ligand cleavage reactions of related manganese species. The transient was shown to be an oxo transfer agent in a preparative reaction with cis-cyclooctene. Representative rate constants for oxidation reactions by the new transient at ambient temperature were k = 5900 M-1 s-1 for cyclooctene and k = 570 M-1 s-1 for ethylbenzene. The new transient is more than 6 orders of magnitude more reactive with typical organic reductants than expected for an iron(IV)-oxo corrole radical cation and 100 times more reactive than an analogous positively charged iron(IV)-oxo porphyrin radical cation. Slow electron transfer isomerization of ligand iron(V)-oxo species to iron(IV)-oxo ligand radical cations might be important in reactions of porphyrin-iron catalysts in the laboratory and in nature.