Selection of a ternary eluant for the determination of fat-soluble vitamins in multivitamin pharmaceutical preparations by high-performance liquid chromatography

A procedure for selecting a ternary eluant for the determination of the synthetic fat-soluble vitamins E acetate, A acetate, K₃, and D₂ in Hexavit, Undevit, and Hendevit multivitamin pharmaceutical preparations was proposed, and the composition of then-hexane-l,2-dichloroethane-n-butanol (86.42 :13.42: 0.16, vol %) eluant was optimized.     

The theoretical basis of mercurimetry in non-aqueous solutions

The methods for thermodynamic calculations of the equilibria in solutions of mercury salts and complexes are presented. The calculations of equilibrium constants in non-aqueous solvents are based on the transfer activity coefficients of mercury ions from water to the non-aqueous solvent. The dismutation and precipitation reaction constants are calculated, and the redox potentials of mercury systems are measured. Examples of analytical use of the thermodynamic functions of mercury salt solvation are given in the text.     

A TEM and XRD study of the SbNbSe3 misfit layer structures

Two new misfit layer structures have been synthesized within the Sb-Nb-Se system. Powder X-ray diffraction and electron microscopy techniques (electron diffraction, HREM, XEDS) have been used to determine the nature of their structure. According to TEM and XEDS data (for more than 15 crystals studied) both phases are monolayer type, i.e. (SbSe)1+delta (NbSe2). Electron microscopy reveals a composite modulated structure that consists of the periodical intergrowth of a pseudotetragonal SbSe layer, denominated as Q, and a pseudohexagonal layer NbSe2, denominated as H. Both layers fit along b, stack along c and do not fit along a (misfit) giving rise to an incommensurate modulation along this direction. The two phases differ in the symmetry of the Q layers being in one case orthorhombic (for delta = 0.17) and monoclinic in the other (for delta = 0.19). After the characterization of the sample by electron microscopy the unit cells of the basic layers could be refined for both phases by powder X-ray diffraction: aQ = 5.824(2) A, bQ = 5.962(5) A, cQ = 23.927(6) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees and aH = 3.415(5) A, bH = 5.962(6) A,, cH = 11.962(1) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees for the orthorhombic phase; aQ = 5.844(2) A, bQ = 5.981(1) A, cQ = 23.919(5) A, alpha = 90 degrees, beta = 90 degrees and gamma = 96.00(3)degrees and aH = 3.439(1) A, bH = 5.994(2) A, cH = 11.956(3) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees for the monoclinic phase. The phase with the monoclinic Q-sublattice often appears as twinned crystals. The more abundant crystals are disordered intergrowths of both monolayer phases.     

Oxymercuric method of organic analysis in non-aqueous solutions

A new method of non-aqueous titration based on the oxymercuration of organic compounds is presented. A kinetic investigation of the oxymercuration of olefin and acetylene bonds has permitted the optimal conditions for quantitative determination to be found. The selectivity and determination are given.     

Headspace gas chromatographic separation of toxic organic impurities from air

Summary To determine toxic organic compounds (methanol, ethanol, n-propanol, acetone, methyl ethyl ketone, methyl isobutyl ketone) in air a method was developed for their headspace gas chromatographic analysis with preconcentration in n-butanol (alcohols) and in n-pentanol (ketones). The distribution coefficients of analytes in the air-absorbent system have been measured: 1051 (MeOH), 5630 (EtOH), 6773 (n-PrOH), 307 (Me₂CO), 580 (MeCOEt), 1035 (MeCOBu-i). The minimum detectable level (mg m⁻³) was determined as low as 0.9 (MeOH), 4.0 (EtOH), 0.9 (n-PrOH), 0.2 (Me₂CO), 0.1 (MeCOEt), 0.4 (MeCOBu-i). The method was effectively used for gas effluent air control in the workplace and in the atmosphere. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996