diniconazole and uniconazole

The amylose-tris(3,5-dimethylphenylcarbamate) chiral stationary phase was synthesized and used to separate the enantiomers of triazole pesticides by high-performance liquid chromatography. The mobile phase was n-hexane-isopropanol applying a flow rate of 1.0 mL/min. Six triazole pesticides were enantioselectively separated. Myclobutanil, paclobutrazol, tebuconazole, and uniconazole obtained complete separation with the resolution factors of 5.73, 2.99, 1.72, and 2.07, respectively, and imazalil and diniconazole obtained partial separation with the resolution factors of 0.79 and 0.77 under the optimized conditions. The effect of the content of isopropanol as well as column temperature on the separation was investigated. A circular dichroism detector was used to identify the enantiomers and determine the elution orders. The results showed the low temperature was good for the chiral separation except for diniconazole. The thermodynamic parameters calculated based on linear Van't Hoff plots showed the chiral separations were controlled by enthalpy.

Topics: Amylose; Chromatography, High Pressure Liquid; Imidazoles; Nitriles; Pesticides; Phenylcarbamates; Stereoisomerism; Temperature; Thermodynamics; Triazoles

An NMR method for discriminating among enantiomers by using a chiral liquid crystalline solution was applied to chiral triazole compounds, uniconazole (1) and diniconazole (2), which exhibit antifungal and plant growth regulating activities. These chiral compounds were dissolved in PBLG (poly-gamma-benzyl-L-glutamate)--CDCl3 chiral liquid crystalline solvent for measurements of 13C NMR. The enantiomeric separations were primarily observed in the signals of aromatic carbons owing to differences in chemical shift anisotropies. The enantiomeric excess (ee) was determined from the integral scale of the separated peaks. The resulting ee values are in fair agreement with the actual values. The extrasplittings due to residual dipolar couplings were also measured using Het2DJ spectra for 1S and R, and 2R, and the results are discussed.

Topics: Anisotropy; Fungicides, Industrial; Magnetic Resonance Spectroscopy; Molecular Structure; Solvents; Stereoisomerism; Triazoles

Dermal absorption experiments form an important component in the assessment of risk from exposure to pesticides and other substances. Much dermal absorption data is gathered in rat experiments carried out using a certain standard protocol. Uncertainties in these data arise from many sources and can be quite large. For example, measurements of the systemic absorption of hexaconazole differed by more than an order of magnitude within a single experiment. Two diniconazole studies produced quite different results, due to minor differences in protocol and in chemical formulation. Limits of detection can also prevent accurate measurement when the amounts absorbed are small. These examples illustrate the need for measuring and reporting uncertainties in estimates that are based on these data. The most direct way to estimate uncertainty is to compute the sample standard deviations of replicate measurements. By pooling these estimates across dose and duration groups for which they are similar, the number of degrees of freedom is increased, and more precise confidence intervals can be obtained. In particular, the ratio of upper to lower 95% confidence limits was reduced by as much as ten-fold for hexaconazole, seven-fold for uniconazole, and nearly four-fold for propiconazole.

Topics: Absorption; Animals; Confidence Intervals; Male; Models, Biological; Pesticides; Rats; Risk Assessment; Skin; Triazoles

Enantiomeric separation of the structural analogs, diniconazole and uniconazole, can be achieved by cyclodextrin (CD)-modified micellar electrokinetic chromatography (MEKC). The elution behavior of other structurally related compounds was therefore investigated and compared with that in high-performance liquid chromatography (HPLC) using a CD-bonded stationary phase. From the results, it was concluded that the benzene ring of the solute plays an important role in formation of CD complexes and chiral recognition in MEKC as well as in HPLC, although the enantioselectivity with the two methods was different. Nuclear magnetic resonance (NMR) data revealed different CD effects on the solute between the MEKC and HPLC models.

Topics: Chromatography; Chromatography, High Pressure Liquid; Cyclodextrins; Electrochemistry; Electrophoresis; Fungicides, Industrial; Magnetic Resonance Spectroscopy; Micelles; Plant Growth Regulators; Stereoisomerism; Triazoles