[Use of the analytical method LC-MS/MS for finding dinoseb and dinoterb in agricultural products, livestock products and seafood].

A simple determination method of dinoseb and dinoterb in agricultural products, livestock products and seafood by LC-MS/MS was developed. Agricultural samples were extracted with acetone (in the case of rice, soybean and tea leaf, phosphoric acid was added). An aliquot of crude extract was partitioned with hexane and sat. sodium chloride solution. In the case of livestock products and seafood, samples were extracted with a mixture of acetone, hexane, water and sodium chloride, and the organic layer was collected. Clean-up was performed using a PSA mini column. The LC separation was performed on a C18 column with methanol-water (19 : 1) containing 0.005 v/v% acetic acid as a mobile phase, and MS with negative ion electrospray ionization was used for detection. The calibration curve was linear between 0.0005 to 0.04 µg/mL for each compound. Average recoveries (n=5) of dinoseb and dinoterb from 20 kinds of agricultural products, livestock products and seafood fortified at the MRLs were 77-111%, and the relative standard deviations were 2-15%. The limits of quantitation were 0.001 µg/g for both compounds.

Dynamic hollow-fibre liquid phase microextraction of dinitrophenols from human plasma: optimization of an extraction flow system using experimental design methodology.

The utility of a dynamic hollow-fibre liquid phase microextraction method (optimized using a four-variable experimental design and response surface modelling) for extracting dinitrophenolic compounds from human plasma samples was evaluated. The investigated variables were donor phase salt concentration (10-400 mM), donor phase pH (2-6), acceptor phase pH (7-12), and donor/acceptor phase flow rates (30/7.5 to 70/17.5 microL min(-1)). Four dinitrophenol pesticides were used as model substances at concentrations of 0.1 microg mL(-1) in spiked human plasma samples. Extraction efficiencies ranging from 42 to 77% with RSDs below 9 were achieved with the optimized method. The flow rate and acceptor pH were shown to strongly affect the extraction efficiency for all compounds, while the donor phase pH and salt concentration had minor effects. With a well-defined acceptor phase pH and flow rate the system exhibited high robustness. The limits of quantification for the investigated compounds, using the presented extraction method followed by liquid chromatography/electrospray ionization mass spectrometry in selected ion monitoring mode, ranged from 0.05 to 0.1 microg mL(-1) plasma.

Computational models for structure-hydrophobicity relationships of 4-carboxyl-2,6-dinitrophenyl azo hydroxynaphthalenes.

Some phenyl azo hydroxynaphthalene dyes (e.g., sunset yellow) are certified as approved colorants for food, cosmetics, and drug formulations. The hydrophobicity of 4 newly synthesized azo dyes of the phenyl azo hydroxynaphthalene class was investigated, as a training set, with the goal of developing models for quantitative structure-property relationships (QSPR). Retention behavior of the molecules reversed-phase thin-layer chromatography (RPTLC) was investigated using liquid paraffin-coated silica gel as the stationary phase. Mobile phases consisted of aqueous mixtures of methanol, acetone, and dimethylformamide (DMF). Basic hydrophobicity parameter (Rmw), specific hydrophobic surface area (S), and isocratic chromatographic hydrophobicity index (phio) were computed from the chromatographic data. The hydrophobicity index (Rm) decreased linearly with increasing concentration of organic modifiers. Extrapolated Rmw values obtained by using DMF and acetone differ significantly from the value obtained by using methanol as organic modifier [P < 0.05, 1-way analysis of variance (ANOVA), Tukey's multiple comparison test]. Structure-property relationships showed that hydrophobicity was dependent on type and position of naphthalene ring substituents. Rm decreased with the presence of a highly polar substituent (e.g., COOH). Owing to intramolecular interaction, Rm increased when the common hydroxyl group (OH) is positioned ortho to the azo group, relative to para positioning, in 2 positional isomers. Pattern recognition data analysis underscores the utility of phio as a more accurate hydrophobicity descriptor than Rmw. Phio is negatively correlated with theoretically calculated density, surface tension, and refractive index for the molecules. These models could be used to predict toxicity (absorption, distribution, metabolism, excretion, toxicity; ADMET) properties of the azo dyes and may also play useful roles in computer-assisted molecular discovery of nontoxic azo dyes.

Development of a simple hollow fibre supported liquid membrane extraction method to extract and preconcentrate dinitrophenols in environmental samples at ng L(-1) level by liquid chromatography.

An easy and rapid hollow-fibre supported liquid membrane method (HFSLM) has been developed to extract and determinate the total concentration of four dinitrophenols in environmental water at ng L(-1) level. This extraction method provides a high selectivity, short extraction time and very low cost for real samples. It is a three-phase system, aqueous-organic-aqueous, where the organic solvent is held into the fibre pores, being in contact with the two other phases. The organic phase is formed by two different organic solvents, with two different polarities, n-undecane and toluene (1:1). The optimization step was performed using a three-variable Doehler design, involving three factors, stirring speed, fibre length and sample volume. The organic phase composition, as well as the pH of the acceptor and donor phases was also optimized. The extraction equilibrium was reached after 30 min, after which essentially the total amount (90-80%) of the four dinitrophenolic compounds were extracted from the sample. Better repeatability and reproducibility at the expense of lower enrichment factors was obtained compared with other methods, employing incomplete extraction during a fixed time. The matrix effect was tested by performing extractions from leachate water and river water. This method is linear in the range 0.1-100 microgL(-1) in different matrices, with detection limit around 100 ng L(-1), after extraction of 6 mL of sample and using high performance liquid chromatography for final analysis.

Separation of amino acids, their derivatives and enantiomers by impregnated TLC.

The present state of TLC with respect to separation of amino acids, their different derivatives and their enantiomers by the technique of impregnation is discussed. The main approaches to impregnation viz. mixing of a suitable reagent with the adsorbent prior to plate-making, immersion of the untreated plate in the solution of impregnating reagent prior to development, and modification of the adsorbent, have been identified and discussed for each class of these compounds. The role of impregnation in resolving enantiomers or in improving the separation of mixtures of amino acids or their derivatives in terms of ion pairing, complex formation, ligand exchange or other steric interactions has been elaborated in each category.

Toroidal coil counter-current chromatography. Achievement of high resolution by optimizing flow-rate, rotation speed, sample volume and tube length.

This paper deals with optimization of a new seal-free compact toroidal coil centrifuge to achieve high resolution in analytical counter-current chromatography (CCC). Toroidal coil CCC (hydrostatic motion) has advantages compared with high-speed CCC (efficiently mixing solution with planetary motion) in the separation of protein or easily emulsified samples. A toroidal coil separation column of 0.4 mm I.D. PTFE tubing was accommodated around the periphery of the cylindrical centrifuge bowl. Using a two-phase solvent system composed of chloroform-acetic acid-0.1 M hydrochloric acid (2:2:1, v/v/v) and a set of dinitrophenyl-amino acids as test samples, a series of experiments was performed with parameters such as the column length, sample volume, flow-rate, elution mode of the mobile phase and rotation speed. The highest efficiency, over 10,000 theoretical plates, was achieved with a 100 m long coiled tube and an 11 ml total capacity at a flow-rate of 0.01 ml/min at 800 rpm.

Resolution of DL-amino acids on a native cellulose column and a plausible mechanism for their resolution.

We have studied the resolution of DL-amino acids on a native cellulose column. All the DL-amino acids related to protein and their 16 DNP-DL-amino acids were separated. The resolution capability depends mainly upon the bulkiness of the side group attached to the alpha-carbon, but also on structural and functional interaction of amino acid with cellulose. We propose a plausible resolution mechanism that is thought to be governed by a so-called key and lock relation between an amino acid and cellulose. Then, the affinity of each enantiomer for cellulose was calculated based on the resolution factor, which was known to be some 10(-2) -10(-3) eV.

[The determination of toxic compounds with a dinitrophenol structure in the forensic chemical study of cadaveric material]. / Opredelenie toksicheskikh soedinenii dinitrofenol'noi struktury pri sudebno-khimicheskom issledovanii trupnogo materiala.

A method for forensic chemical assessment of dinitrophenol toxic compounds has been developed. Acetone was used as the isolating agent. The isolates were purified by extraction followed by adsorption in a column packed with silica gel. The analyzed substances are analyzed by chromogenic reactions, from UV and visible spectra in alkali and DMPA, and by thin-layer and high-pressure chromatography. The method allows the detection of 47-83% dinitrophenols in artificial mixtures with liver tissue (with 50 mg of analyzed substance per 100 g of the object). The detection minimum for this group of compounds is 0.5 to 1.0 mg per 100 g of cadaveric material.

[Isolation of alkyl dinitrophenol compounds from cadaver material]. / Izolirovanie alkildinitrofenol'nykh soedinenii iz trupnovo materiala.

Acetone was used in isolation of alkyl dinitrophenol compounds from cadaveric material. The authors assess the results of isolation of these substances from model mixtures with cadaveric liver tissue.

Dinitrophenylated thiols in tryptic fragments of the heavy chain from chicken gizzard myosin.

Trypsin digestion of phosphorylated and 3H-labeled dinitrophenylated chicken gizzard myosin released major fragments of Mr 29,000, 50,000 and 66,000 in a ratio of close to one to one. They contained 58% of the label bound to thiols of the heavy chains; 28% of the label was bound to the light chains. The heavy chain fragments of Mr 29,000 and Mr 66,000 were dinitrophenylated when the enzyme activity was inhibited. The 3H-labeled dinitrophenylated myosin alone followed a somewhat different pattern in that the label was bound to the light chains predominantly. Thiolysis of the phosphorylated and dinitrophenylated myosin with 2-mercaptoethanol restored the K+ -ATPase (ATP phosphohydrolase, EC 3.6.1.32) activity and the dinitrophenyl group was removed from the N-terminal fragment of Mr 29,000 of the heavy chain, predominantly. In contrast, restoration of the enzymic activity occurred in thiolyzed dinitrophenylated myosin alone when the label was removed from the light chains rather than the tryptic fragments of the heavy chain. Phosphorylation induced conformational changes in gizzard myosin that altered the reactivity of the thiols in fragments of the globular heavy chain region.