Phospholipids of kenaf of variety Opytnyi-1847

The total phospholipids of kenaf of variety Opytnyi-1847 and homogeneous fractions of them have been studied. A known law has been confirmed — positions 2 of the main fractions of phospholipids are esterified predominantly with unsaturated fatty acids and in N-aceylated phospholipids the amide-bound acids are more saturated than the O-acyls.Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 775–777, November–December, 1980.     

Observation of the phosphorescence spectra from the spin sublevels of low emissivity: quinoxaline

A method to observe the phosphorescence emissions from the spin sublevels of low emissivity is proposed, and its application to quinoxaline is attempted. The newly observed phosphorescence spectra from the T_x and T_y sublevels differ considerably in vibrational structures from the usually observed phosphorescence from the T_z sublevel.     

Molecular structures,vibrational assignments and barriers to pseudorotation of gaseous niobium pentachloride and tantalum pentachloride from electron diffraction data

The pentachlorides of niobium and tantalum have trigonal bipyramidal structures (D_3hsymmetry) with thermal average axial bonds, r_α, longer than the equatorial ones by 0.097(9) and 0.142(5) Å, respectively. The equatorial bonds are r(Nb—Cl) = 2.241(4) and r(Ta—Cl) = 2.227(3) Å. Standard deviations are given. Calculated amplitudes of vibration for the e' type of bending frequencies assigned as v₆ (equatorial in-plane bend) < v₇ (axial—equatorial bend) agree significantly better with the experimental vibrational amplitudes than do amplitudes computed for the opposite assignment. Assuming an analytical quartic-harmonic potential for the pseudorotational motion of the molecules, barriers to pseudorotation of 1.5(0.7) and 1.2(0.6) kcal mol^?1 are estimated from the electron diffraction data for NbCl₅ and TaCl₅, respectively. Effects from interatomic multiple scattering are included in the theoretical intensities, and are found to be of some importance to the results.     

Infrared studies of chromones—II Isotopically substituted 5-hydroxychromones

By deuteration of the OH group, it has been shown that two bands, at 1665 and 1630 cm⁻¹ (CCl₄), in the IR spectra of 5-hydroxychromones are associated with the H-bonded CO stretching vibration. Nuclear deuteration of 5-hydroxy-2-methylchromone (1) under acidic conditions gave a tri- and a hexadeutero derivative; the latter, isotopically substituted at C-3, shows a single CO band at 1649 cm⁻¹. Hydrolysis of 3-acetyl-5-hydroxy-2-methylchromone with sodium carbonate in deuterium oxide furnished 5-hydroxy-2-trideuteromethylchromone-3-d which also exhibits a single CO absorption. Partial incorporation of O¹⁸ into the CO group of 1 results in a single ν_C=O¹⁸ at 1593 cm⁻¹. It is suggested that the doublet CO absorption of 5-hydroxychromones arises from a Fermi resonance involving a low-energy vibrational mode of the vinyl proton on the nuclear C-3 position.     

Analytical applications of ternary complexes-V Indirect spectrophotometric determination of cyanide

An indirect spectrophotometric method is proposed for the determination of cyanide down to 0.2 ppm. It is based on the fact that cyanide prevents the formation of the strongly absorbing ternary complex between silver(I), 1,10-phenanthroline and Bromopyrogallol Red in nearly neutral aqueous solution. Among 17 cations examined, only mercury(II) could not be tolerated. Zinc, cadmium and cobalt interfered only when present in large amounts. A 1000-fold molar excess (over cyanide) of 14 anions can also be tolerated. Bromide, iodide and thiocyanate interference is overcome by addition of lead nitrate, ammonium sulphate and barium nitrate, followed by centrifugation.     

Peak distortion in the column liquid chromatographic determination of omeprazole dissolved in borax buffer.

Injection of a sample containing omeprazole dissolved in borax buffer (pH 9.2) into a reversed-phase liquid chromatographic system consisting of a mixture of acetonitrile and phosphate buffer (pH 7.6) as the mobile phase and a C18 surface-modified silica as the solid phase resulted under special conditions in split peaks of omeprazole. The degree of peak split and the retention time of omeprazole varied with the concentration of borax in the sample solution and the ionic strength of the mobile phase buffer as well as with the column used. Borax is eluted from the column in a broad zone starting from the void volume of the column. The retention is probably due to the presence of polyborate ions. The size of the zone varies with the concentration of borax in the sample injected. In the borax zone the pH is increased compared with the pH of the mobile phase, and when omeprazole (a weak acid) is co-eluting in the borax zone its retention is affected. In the front part and in the back part of the borax zone, pH gradients are formed, and these gradients can induce the peak splitting. When the dissolving medium is changed to a phosphate buffer or an ammonium buffer at pH 9 no peak distortion of omeprazole is observed.     

Effect of the specific activity of the tracer on rat luteinizing hormone radioimmunoassay

Rat luteinizing hormone /LH/ was labelled with¹²⁵I by the Chloramine T method.¹²⁵I-LH, used as tracer in radioimmunoassay, was separated from the labelling reaction mixture by gel filtration. By using the proper protein/radioiodine ratio in the labelling reaction mixture the specific activity of¹²⁵I-LH was adjusted to 2.5–20.5 MBq g^–1. The influence of the specific activity on the assay parameters as well as on the tracer stability was investigated.     

Membrane filtration studies of aquatic humic substances and their metal species: a concise overview. Part 2. Evaluation of conditional stability constants by using ultrafiltration

The assessment of conditional stability constants of aquatic humic substance (HS) metal complexes is overviewed with special emphasis on the application of ultrafiltration methods. Fundamentals and limitations of stability functions in the case of macromolecular and polydisperse metal-HS species in aquatic environments are critically discussed. The review summarizes the advantages and application of ultrafiltration for metal-HS complexation studies, discusses the comparibility and reliability of stability constants. The potential of ultrafiltration procedures for characterizing the lability of metal-HS species is also stressed.     

A study of the solubility of yttrium,praseodymium, neodymium,and gadolinium sulfates in the presence of sodium and potassium in sulfuric-phosphoric acid solutions at 20°C

Solubility of yttrium, praseodymium, neodymium, and gadolinium sulfates in the presence of sodium and potassium ions and the composition of solid phases were studied at 20°C in relation to the concentration of acids in sulfuric acid, phosphoric acid, and sulfuric-phosphoric acid solutions containing up to 36 wt % H₂SO₄ and 33.12 g 1^?1 H₃PO₄.