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Acta Veterinaria Hungarica
Authors: Tihomira Gojmerac, Marija Uremović, Z. Uremović, S. Ćurić, and Nina Bilandžić

The aim of the study was to assess the effect of subacute treatment with a low dose of atrazine (1,3,5-triazine-2,4-diamine, 6-chloro-N-ethyl-N'-(1-methylethyl), an s-triazine herbicide, on endocrine oestrus regulation in gilts. A group of nine gilts (F1generation of Swedish Landrace à Large Yorkshire) were treated with 1 mg atrazine/kg body mass daily, mixed to the feed for 19 days before the onset of expected oestrus. Blood samples were obtained by cranial vena cava puncture three times daily at 3-h intervals on five post-treatment days, i.e. before and during oestrus. The serum concentration of oestradiol-17β (E2) was determined by the fluoroimmunochemical method. On Day -2 before the onset of expected oestrus, a significantly lower (P < 0.001) E2concentration was measured in the serum of treated gilts (31.25 ± 1.95 and 39.32 ± 1.38 pg/mL) than in the control pigs (51.43 ± 1.29 and 68.59 ± 2.99 pg/mL). In contrast, the E2concentration measured in the serum of treated animals was significantly higher (P < 0.001) on the day of the expected onset of oestrus and on the subsequent two days (35.43 ± 1.85, 53.92 ± 1.98 and 60.32 ± 2.35 pg/mL, respectively) than in the control animals (13.52 ± 1.79, 21.53 ± 1.35 and 20.05 ± 1.46 pg/mL, respectively). Insufficient serum E2concentration of the treated gilts resulted in a failure of expected oestrus, as indicated also by the state of dioestrus demonstrated by histopathological examination of the uterus.

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The chromatographic behavior of four groups of s -triazine derivatives (14 compounds) has been studied by TLC on silica gel impregnated with paraffin oil; water-acetone (ϕ acetone = 0.5−0.8), water-acetonitrile (ϕ acetonitrile = 0.2−0.6), and water-dioxane (ϕ dioxane = 0.5−0.8) were used as mobile phases. Investigation of the retention mechanism showed that reversed-phase chromatography occurred under these conditions. Retention constants, R M 0 , were determined by extrapolation and good correlation was obtained between R M 0 and the slope, m , of equations expressing the dependence of retention on mobile phase composition. There was also satisfactory correlation between these retention constants and log P of the s -triazines investigated. Better correlation was obtained between lipophilicity, C 0 , and log P. C 0 can be used as a measure of the lipophilicity of the compounds investigated.

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The chromatographic behavior of four groups of s -triazine derivatives (15 compounds) has been studied on aminoplast and cellulose thin layers with two mobile phases, methanol-water-acetonitrile, 30 + 20 + X , where X = 1–10 ( v/v ), and methanol-dilute acetic acid, 30 + 20 ( v/v ). The mechanism of retention was investigated by changing of volume fraction of acetonitrile in the first mobile phase. Reversed-phase chromatography occurs on both supports. Retention constants, R M o were determined by extrapolation and good correlation was obtained between retention constants, R M o and log P . These retention constants can be used as the measure of the lipophilicity of compounds. The effect of mobile phase pH on the chromatographic retention of s -triazine derivatives was examined and approximate protonation constants, pK a , were determined on the basis of the dependence of retention on pH. These constants correlated well with Hammett substituent constants σ .

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Quantitative structure-retention relationships (QSRR) have been used to study the chromatographic behavior of some s -triazines. Retention factors, R M 0 , on C 18 layers corresponding to zero percent organic modifier in the aqueous mobile phase were determined for five mobile phase mixtures: methanol-water, acetone-water, acetonitrile-water, 2-propanol-water, and tetrahydrofuran-water and relationships between R M 0 values obtained with different organic mobile phase modifiers were examined.A variety of partition coefficients ( A log P , IA log P , C log P , X log P , log P Kowin , and ACD log P ) were calculated by use of different software products. The correlation between partition coefficients and chromatographically obtained lipophilicity was analyzed. On the basis of correlations between R M 0 and log P , C 18 with methanol-water as mobile phase was selected as the best RP HPTLC system for determination of the octanol/water partition coefficient and thus the lipophilicity of the molecules.

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The retention factor in pure water, log k w , is proposed as a measure of the hydrophobicity of s -triazine derivatives. In these studies two reversed-phase techniques, thin-layer chromatography (TLC) and overpressured-layer chromatography (OPLC), were used. The effects of the chromatographic system, i.e. mobile and stationary phase properties, on log k w were analyzed to select the best system for determination of the hydrophobicity of the compounds. In TLC the chemically bonded phases RP-18 and RP-CN were used as stationary phases and acetone, acetonitrile, tetrahydrofuran, and dioxane as organic modifiers of the mobile phases. In OPLC RP-8 and RP-18 stationary phases and water-acetonitrile mobile phases were used. The values of log k w , determined by linear extrapolation and by the new method based on Ościk’s equation, were compared with log P values calculated by different theoretical methods. In TLC the best linear correlations between log P and log k w were observed for water-dioxane as mobile phase on both RP-18 and RP-CN stationary phases whereas in OPLC very good relationships were obtained for all the systems applied. Better functions for correlation of log P with log k w were obtained for log k w values determined by the method developed from Ościk’s equation.

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Retention factors in pure water, log k w , determined by linear extrapolation and by a numerical method based on Ościk’s equation, and calculated values of log P have been compared as hydrophobicity indices for nine homologous s -triazines. In chromatographic studies thin-layer and over-pressured-layer chromatography were used. The effect of mobile phase pH on solute retention was investigated by use of different buffer-methanol mixtures. The effect of mobile and stationary phase properties on chromatographic behavior was also studied; three different organic modifiers (dioxane, acetonitrile, and tetrahydrofuran) and two stationary phases (RP-8 and RP-18) were used. Correlations of calculated log P values and log k w with carbon number, n C , confirm the usefulness of chromatographic techniques for studying the hydrophobicity of organic compounds.

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The chromatographic behavior of nine newly synthesized s -triazines has been studied by thin-layer chromatography on C 18 /UV 254 , HPTLC Nano-Sil-CN/UV 254 , and HPTLC Nano-Sil NH 2 /UV 254 HPTLC plates. Relationships between the R M values of the s -triazines and mobile phase composition were determined for water-tetrahydrofuran, water-dioxane, and water-acetonitrile mobile phases. Retention data observed with different mobile-phase modifiers and different stationary phases were compared. The correlation between the retention of the compounds in reversed-phase liquid chromatography and their octanol-water partition coefficients, expressed as log P , was examined.

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Estimation of retention data by use of correlation equations and physicochemical properties is a useful tool in liquid chromatography. In this work, relationships between physicochemical structural properties and the HPTLC retention of an homologous series of s -triazines on C 18 , cyano, and amino layers has been investigated. Comparisons based on partial least-squares (PLS) regression have been used to model R M 0 values by means of 30 different descriptors. Significant results were obtained in the prediction of retention indices.

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Abstract  

Solid-gas phase transition processes of some triazines were studied from kinetic and thermodynamic viewpoint. DSC measurements and Clausius-Clapeyron equation were used to determine enthalpy values related to these processes. Model-fitting methods (based on Arrhenius, Šatava equations and Šestk-Berggren equations) and model-free methods (based on Ozawa-Flynn-Wall and Kissinger equations) allow to hypothesis R2 mechanism. An attempt to determine the activation parameters (ΔH #, ΔG #, ΔS #) related to these processes was carried out. Accordance between the activation enthalpy values with those of activation energy obtained by means of kinetic methods and with the experimental (DSC) and calculated (Clausius-Clapeyron) enthalpy values was found.

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Abstract  

Adsorption of the herbicide terbuthylazine by a soil from the Jezreel Valley was investigated by thermo-IR-spectroscopy. The adsorption took place mainly by the clay mineral montmorillonite. The adsorbed molecule was hydrogen bonded via the aniline groups to water molecules which were coordinated to the exchangeable metallic cations. When the sample was thermally treated at 115°C interlayer water was evolved, part of the herbicide decomposed and the other part became directly coordinated to the exchangeable metallic cations. The decomposition product contained a CO group.

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