Sorption of aliphatic ketones from aqueous solutions by starch cryotextures

Capillary gas chromatography was applied to study the sorption of aliphatic ketones (C₆—C₁₁), including metamers, from aqueous solutions by corn starch cryotextures. The amount of ketones sorbed by cryotextures depends linearly on their concentrations in the initial sol. Equations describing the concentration dependence of sorption were proposed. The shape of sorption isotherms reflects the strength of sorption. The binding constants and the number of binding sites were determined for weakly sorbed ketones. The length of alkyl substituent and the position of the functional group are the crucial factors governing the sorption of ketones under conditions of excess binding sites. It was found that the degree of sorption increases with an increase in the carbon chain length from 6 to 9 carbon atoms. The presence of cooperation of binding sites for ketone sorption by cryotextures was demonstrated. The major part of ketones is sorbed irreversibly. This fact points to the formation of supramolecular complexes. Ketones with lower molecular masses are better sorbed by cryotextures than by native starch grains.     

Synthesis and study of polydentate ligands that contain a pyrimidine ring

The corresponding hydrazones, azo compounds, and 2,4-bis(1H-pyrazol-1-yl)pyrimidines were synthesized by the reaction of 5-ethyl-2-hydrazino-6-methyl-4(3H)-pyrimidinone, 2-(N-p-butylanilino)-4-hydrazino-6-methylpyrimidine, and 4-hydrazino-2-(1H-pyrazol-1-yl)pyrimidines with salicylaldehyde, isatin, -naphthoquinone, phenanthrenequinone, and acetylacetone. The structures of the synthesized compounds are discussed on the basis of a study of their electronic, IR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1682–1687, December, 1980.     

Sorption of alkyl acetates from aqueous solutions by corn starch cryotextures

Capillary gas chromatography was used to study noncovalent sorption ofn-butyl,n-hexyl, andn-octyl acetates from aqueous solutions by corn starch cryotextures. In the concentration range of 0.5–15.0 mmol L⁻¹, about 38%n-butyl acetate, 70%n-hexyl acetate, and 98%n-octyl acetate are extracted from aqueous solutions. The sorption of the alkyl acetates depends on the alkyl chain length, indicating the hydrophobic character of their interaction with the corn starch cryotexture. No competitive sorption between acetates in the mixture was observed. Binding of alkyl acetates occurs during the cryosponge formation, due probably to the templation at the stage of starch sol, fixation in the cryosponge, and sorption on the surface of its walls. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1943–1945, October, 1998.     

FRee electron model for heteroatomic conjugate molecules

A simple generalization of the free electron model is suggested for describing the heteroatomic conjugate molecules and obtaining analytical equations for the energy levels of these systems. The δ-like potential is used as a potential of a heteroatom in this model, and the energy levels are obtained as corrections for first order perturbation theory.     

Ultrafast photofragmentation dynamics of molecular iodine driven with timed XUV and near-infrared light pulses

Photofragmentation dynamics of molecular iodine was studied as a response to the joint illumination with femtosecond 800 nm near-infrared and 13 nm extreme ultraviolet (XUV) pulses delivered by the free-electron laser facility FLASH. The interaction of the molecular target with two light pulses of different wavelengths but comparable pulse energy elucidates a complex intertwined electronic and nuclear dynamics. To follow distinct pathways out of a multitude of reaction channels, the recoil of created ionic fragments is analyzed. The delayed XUV pulse provides a way of following molecular photodissociation of I(2) with a characteristic time-constant of (55 ± 10) fs after the laser-induced formation of antibonding states. A preceding XUV pulse, on the other hand, preferably creates a 4d(-1) inner-shell vacancy followed by the fast Auger cascade with a revealed characteristic time constant τ(A2)=(23±11) fs for the second Auger decay transition. Some fraction of molecular cationic states undergoes subsequent Coulomb explosion, and the evolution of the launched molecular wave packet on the repulsive Coulomb potential was accessed by the laser-induced postionization. A further unexpected photofragmentation channel, which relies on the collective action of XUV and laser fields, is attributed to a laser-promoted charge transfer transition in the exploding molecule.     

Observation of the Talbot effect for ultrasonic waves

The diffraction of ultrasonic radiation on an amplitude diffraction grating in the near-field area (Fresnel diffraction) has been studied. The effect of self-imaging of the grating (Talbot effect) has been detected for ultrasonic radiation at distances from the grating in the range from z = 0 to z = 2L _T, where L _T is the Talbot length. The fractional Talbot effect, i.e., the ultrasonic image of the grating with the period d/2, has been observed.     

An Enzyme-Linked Immunosorbent Assay (Elisa) for the Detection of Acetochlor

Competitive enzyme-linked immunosorbent assays (ELISAs) were developed in hapten-homologous and hapten-heterologous formats for the detection of the chloroacetanilide herbicide acetochlor. ELISA systems were devised using antibodies generated against acetochlor conjugated to carrier proteins through a thioether moiety replacing the chlorine atom in the parent structure, while haptens modified both on the chloroacetyl moiety and on the ethoxymethyl group of acetochlor have been used for coating antigens. The optimized ELISA systems allowed the detection of acetochlor 0.2-65 µg/L, and cross-reactivity studies revealed high specificity of the immunoassay: only four (propisochlor, butachlor, alachlor and metolachlor) among 18 structurally related acetanilide herbicides, fungicides and intermediates showed significant (> 1%) cross-reactivity, with even the highest value (propisochlor) being below 10%. Assay performance was not affected detrimentally by methanol up to 10% (v/v) and ethanol up to 5% (v/v). Assay performance was tested by measuring acetochlor concentration in water samples and compared favorably ( r 2 = 0.976) with those detected by gas chromatographic method coupled with mass spectrometry (GC-MS) using solid-phase microextraction (SPME) for sample preparation.     

Sorption of aliphatic alcohols, acetates, and their mixtures by corn starch cryotextures depending on concentrations of sorbates and starch in initial sols

The sorption of a mixture ofn-hexanol,n-octanol, andn-hexyl andn-octyl acetates from aqueous solutions by corn starch cryotextures was studied using capillary gas chromatography at different initial concentrations of the sorbates (1–25 mmol L⁻¹) and corn starch (2–6%). The amounts of compounds sorbed by cryotextures are proportional to the increase in their concentration in the initial sol and the length of the alkyl substituent. Linear equations describing the concentration dependence were proposed. The sorption ofn-hexanol from a mixture of substances containingn-octanol increases as compared to that from the individual alcohol. It was shown that the degree of sorption of aroma by cryotextures was independent of the content of starch in the initial sol. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1496–1501, August, 1999.