Authors:P. Yu, Z. Tan, S. Meng, S. Lu, X. Lan, L. Sun, F. Xu, T. Zhang, and S. Hu
Isoproturon [N'-(p-cumenyl)-N,N-dimethylurea] was synthesized, and the low-temperature heat capacities were measured with a small sample precise
automatic adiabatic calorimeter over the temperature range from 78 to 342 K. No thermal anomaly or phase transition was observed
in this temperature range. The melting and thermal decomposition behavior of isoproturon was investigated by thermogravimetric
analysis (TG) and differential scanning calorimetry (DSC). The melting point and decomposition temperature of isoproturon
were determined to be 152.4 and 239.0C. The molar melting enthalpy, and entropy of isoproturon, ΔHm and ΔSm, were determined to be 21.33 and 50.13 J K-1 mol-1, respectively. The fundamental thermodynamic functions of isoproturon relative to standard reference temperature, 298.15
K, were derived from the heat capacity data.
Yaduraju, N. T., Kulshrestha, G., Sharma, R. P., Ahuja, K. N. (1993): Isoproturon for weed control in potato (Solanum tuberosum) and its residue in soil and tuber. Indian J. Agric. Sci. , 63, 731-733.
Isoproturon for weed control
Authors:Ali Mohammad, Arshi Amin, and Abdul Moheman
The chromatographic behavior of eight pesticides has been examined on cationic-micelles impregnated silica layers using mixed organic solvent (different combinations of hexane-acetone, v/v) systems. The chromatographic system constituting 0.01% CTAB (N-cetyl-N,N,N-trimethyl ammonium bromide) impregnated silica gel as stationary phase, and hexane-acetone in 1:1 ratio (v/v) as mobile phase was most favorable for on-plate identification of pesticides with preliminary separation. Surface modification of silica gel on impregnation, as indicated by SEM and FTIR studies was responsible for improved chromatographic performance. The results obtained on 0.01% CTAB impregnated silica layers were compared with those achieved on 0.01% CTAB impregnated kieselguhr, cellulose, or alumina layers. With selected chromatographic system, fivecomponent mixtures of pesticides (glyphosate, acephate, chlorpyrifos, malathion/methyl parathion, and isoproturon) were successfully resolved. The interference of metal cations as impurities on separation of pesticides from their mixtures was also examined. The developed method was successfully applied to the identification of pesticides in cereals, vegetables, and fruit grains. The applicability of the proposed method for the identification of five-component mixture of pesticides present in maize grains was also tested after separation on TLC plates. The limit of detection of glyphosate, acephate, chlorpyrifos, malathion, methyl parathion, and isoproturon was ≈20 μg per zone. For validation and reproducibility of the developed method, standard deviation (SD), ΔRF, and separation factor (α) were calculated.
Fifteen urea pesticides have been separated on RP-18WF
plates with methanol-water and mixed organic (acetonitrile-methanol, 1:1
)-0.1% aqueous orthophosphoric acid (H
) mobile phases (RP-HPTLC), and on silica gel 60F
plates with benzene-methanol and benzene-ethanol mobile phases (NP-TLC). The pesticides could be classified into three groups:
monolinuron (1), chlorotoluron (2), diuron (3), isoproturon (4), and linuron (5)
dimefuron (6), diflubenzuron (7), teflubenzuron (8), and lufenuron (9); and
thifensulfuron methyl (10), triasulfuron (11), chlorsulfuron (12), rimsulfuron (13), amidosulfuron (14), and tribenuron methyl (15).
values and mobile phase composition were determined for the pesticides. Δ
values, separation factors (
), and constants for separation of pairs of compounds (
) were used to determine optimum chromatographic conditions for the separations. Comparison of results from normal and reversed-phase TLC revealed the pesticides in the first group (except for isoproturon and chlorotoluron) were best separated by RP-TLC. Those in the second group could be separated by NP or RP-TLC. The sulfonylurea herbicides in the third group were best separated by NP-TLC, although chlorsulfuron could not be completely separated from thifensulfuron methyl by use of this technique. Separation of chlorsulfuron from thifensulfuron methyl could be achieved by RP-TLC with a mobile phase in which the volume fraction of organic modifier was 0.70.
The phenylurea herbicides chlortoluron, diuron, fluometuron, isoproturon, linuron, methabenzthiazuron, and neburon have been separated by use of three different thin-layer chromatographic systems and quantified densitometrically at nanogram levels. Calibration plots were linear between 50 and 2500 ng for all the herbicides; correlation coefficients,
, were between 0.9962 and 0.9999. For determination of the herbicides in drinking water the substances were enriched from water samples by solid phase extraction (SPE) on C
cartridges. Recovery rates were between 91 and 102% except for methabenzthiazuron (87%); relative standard deviations were ±1.2–2.9%. A rapid fluorodensitometric screening method, involving thermal hydrolysis and subsequent derivatization with fluorescamine, was also developed for the phenylureas. This improved the limit of detection 25-fold.