Authors:Feng Tang, Shimei Ge, Yongde Yue, Rimao Hua, and Rong Zhang
A high-performance thin-layer chromatographic method has been developed for determination of four carbamate residues in vegetables. The method uses two mobile phases on silica gel 60 F
GLP HPTLC layers, and detection at
= 243 nm and 207 nm, the average wavelengths of maximum adsorption of pirimicarb and methomyl, and carbaryl and carbofuran, respectively. Recovery of 1.0–5.0 mg kg
of the four mixed carbamates from wax gourd and potatoes was 70.05–103.7%. The accuracy and precision of the method were confirmed by means of fortification experiments.
Authors:Daniela-Crina Marinescu, Elena Pincu, and Viorica Meltzer
of binary mixtures in condensed phase [ 3 – 5 ].
In this paper, we present aspects regarding phase diagram, thermochemistry, and structure of binary mixtures of cholesteril p -phenoxi phenyl carbamate and cholesteril p -biphenyl carbamate
The thermal properties of cellulose carbamate with various nitrogen content are discussed. Thermal analysis was performed in air and under nitrogen atmosphere. The increase in the nitrogen content in cellulose carbamate brings about only a shift of the maximum decomposition rate towards lower temperatures. It can be concluded that cellulose carbamate heated to 320 °C is readily dehydrated and cross-linked, which results in the formation of aromatic structure.
Authors:Anna Sobeková, Katarína Holovská, Viera Lenártová, Slávka Flešárová, and P. Javorský
Bendiocarb, C. O. Pesticide residues in food: 1982 evaluations; file: //E:\Lymfatic\legath\ carbamates\bendiocarb.htm.
Bradford, M. M. (1976) A rapid and sensitive method for the quantification of microgram quantities of
Enrichment of 13C by chemical exchange between CO2 and amine carbamate in nonaqueous solvents has been mathematically modelled in two ways. The height equivalent to a theoretical plate and steady-state separation, based on the two models, have been obtained. If only the isotopic exchange between CO2 gas and amine carbamate is considered, the model can estimate the process performance for pressures close to the atmospheric one and room temperature. For process analysis at pressures higher than the atmospheric one and lower temperatures, a two-step model has been used. Using the two models the effects of pressure have been studied.
Authors:P. Devi, P. Rao, K. Seshaiah, and G. Naidu
Isotope exchange behaviour of bis/diethyl dithio carbamate/cadmium/II/ complex has been studied at 25°C and 35°C varying the concentrations of both metal ion and the complex. The results show that the complex is kinetically labile and the concentration has a significant effect on the rate of the reaction. Increase in temperature also effects the rate of exchange.
A microextraction procedure based on ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) was optimized and validated for preconcentration of carbamate pesticides prior to fast determination using high-performance liquid chromatography (HPLC) with monolithic column. The nonionic surfactant (Tween 20) was used as an emulsifier, and chloroform was selected as an extraction solvent. The experimental parameters affecting the extraction efficiency, such as the kind, concentration, and volume of surfactant, the kind of extraction solvent and its volume, salt addition, ultrasonic extraction time, and centrifugation time, were optimized. Under the selected UASEME and HPLC conditions, separation of five carbamate pesticides (carbofuran, carbaryl, isoprocarb, methiocarb, and promecarb) was achieved within 10 min. The linearity of the method was obtained in the wide range of 2–5000 μg L−1, with correlation coefficients of 0.9931–0.9970. The limits of detection were in the range of 0.4–7.0 μg L−1. The relative standard deviations (n = 5) were less than 0.59% and 4.86% for retention time and peak area, respectively. The enrichment factors of the developed UASEME method were in the range of 33–166. The fruit juice samples (at fortified levels of 0.25, 0.50, and 1.00 mg L−1) were successfully analyzed, and the relative recoveries were obtained in the range of 81–115%.
Authors:M. Lalia-Kantouri, A. Christofides, and G. Manoussakis
Simultaneous TG/DTG/DTA studies under non-isothermal conditions have been carried out in air and nitrogen on some halo-dithiocarbamates of the general formula XM[S2CN(CH2)5]2 (X=Cl, Br and I; andM=As, Sb and Bi).E* values for the 1st stage of decomposition were determined by graphical methods and the TTN temperatures were calculated from the TG profiles. A possible mechanism of the decomposition reaction is suggested, based on the thermoanalytical and pyrolysis results and the mass spectral data. The kinetic analysis data on five of the above dithiocarbamates and nine complexes of the general formula M[S2CN<]3 (M=As, Sb and Bi; and N<=NEt2, N(CH2)5 and N(CH2)4O) were studied by the QIA (quasi-isothermal analysis) technique in air atmosphere. An example of kinetic parameter (k andn) estimation for the first decomposition stage is given for Bi[S2CN(CH2)5]3, with the assumption of different kinetic equations.