Multi-residue method for rapid screening and confirmation of pesticides in crude extracts of fruits and vegetables using isocratic liquid chromatography with electrospray tandem mass spectrometry

A LC-MS-MS method capable of the quantitative determination of a range of pesticide residues present in crude extracts from a variety of fruit and vegetables has been developed. Isocratic LC conditions have been used in conjunction with electrospray ionisation tandem mass spectrometry to detect and identify up to 38 pesticides presented as various mixtures in different matrices. The utility of the method is demonstrated by the analysis of crude extracts, with no sample clean up, from grape, kiwi fruit, strawberry, spinach, lemon, peach and nectarine. Mean recoveries ranging from 63 to 96% with relative standard deviations < 20% were obtained for 30 of the 38 pesticides following analysis of organic produce fortified at concentrations between 0.01 and 0.8 mg/kg. Detected residues were quantified from interpolation against calibration data generated using matrix-matched standards that covered analyte concentration ranges between 0.005 and 0.8 microg/ml. Conditions suitable for the qualitative and quantitative confirmation of residues detected in samples are specified.     

Spectroscopic studies of lewis acid—base complexes: IV. An infrared study of oriented single crystals and normal coordinate analyses of trimethylamine—boron halide adducts

A total of 19 isotopic species of various (CH₃)₃NBX₃ complexes have been prepared and their IR spectra studied in the solid state in the region 40–4000 cm^?1. The isotopes involved are deuterium, boron-10, boron-11, and nitrogen-15 with X = F, CI, Br and I. C_3v symmetry has been preserved in all cases. Symmetry classifications of the fundamental molecular frequencies have been derived from polarized IR measurements on oriented single crystals in the range 250–4000 cm^?1. Errors and inconsistencies in previous studies have been resolved and revised vibrational assignments are proposed on the basis of the new data. Normal coordinate analyses have been carried out utilizing symmetry compliance constants without the assumption of point mass methyl groups. A common potential function containing 22 parameters for the A₁ class and 26 for the E class was utilized. The results support the proposed frequency assignments. B-N force constants obtained by inversion of the compliance matrices vary systematically from the chloro to the iodo complex. However, the B-N force constant for the fluoro complex falls between that for the chloro and bromo species; no systematic trend appears for the B-N compliance constants.     

Synthesis of alpha-fluorosulfonamides by electrophilic fluorination

Alpha-fluorosulfonamides were prepared by electrophilic fluorination of tertiary sulfonamides using N-fluorobenzenesulfonimide as fluorinating agent and utilizing the dimethoxybenzyl group (DMB) as a new sulfonamide protecting group. Removal of the DMB group with TFA/CH(2)Cl(2) gave primary and secondary alpha-fluorosulfonamides.     

A diatropic ring current in a fluorofullerene trannulene

Ipsocentric current-density maps for a fluorofullerene derivative, C60F15H3, modelling the addition pattern of the experimentally characterised C60F15[CBr(CO2Et)2]3 which contains an [18]trans-annulene system, reveal a diamagnetic ring current dominated by the contribution of the four HOMO electrons, as in a classical (4n + 2) aromatic annulene.