J. Szulc

Chromatographic analysis of chemical warfare agents

The usefulness and applications of the particular types of chromatography in the analysis of chemical warfare agents have been reviewed. A major problem in the chromatographic analysis of chemical warfare agents is the collection and preparation of the samples. The importance of this problem differs for the various types of chromatography. Significant differences occur in the way in which samples are collected from air, water, soil, vegetables or animal organisms. The analyses are characterized by the main groups of chemical warfare agents, e.g., organophosphorus, vesicants, irritants, etc. Account has been taken of the relationships between their properties and the possibilities of their chromatographic analysis. The advantages and disadvantages of particular types of chromatography in the analysis of the particular groups and individual agents have been considered. The detectability of particular chemical warfare agents has been assessed, together with the separating efficiency for their mixtures. Examples of applications of chromatographic systems and conditions of chromatographing are summarized in tables. It is concluded that chromatography is a very useful tool in the analysis of chemical warfare agents; GC and TLC have the most advantageous properties, HPLC being slightly inferior.

The Stability of the Smectic C Phase in Mixtures: An Influence of a Dopant on the Phase Sequence and the Tilt Angle

Abstract The paper describes methods for obtaining mixtures with a broad range of the smectic C phase and with the smectic A phase above the smectic C phase. It was demonstrated that doping is a very useful method for modification of the smectic C mixtures and for adjusting the tilt angle. It was also shown that smectic C mixture may be composed of compounds having no smectic C phase and that the concentration of these compounds can be large.

Properties of single and mixed liquid-crystalline stationary phases : I. Single liquid-crystalline stationary phases

Abstract The polarities and selectivities of twelve liquid-crystalline stationary phases have been tested as well as their column efficiencies. The effect of these properties on the separating ability of the liquid-crystalline stationary phases with respect to di-substituted benzene isomers is discussed. The separating properties of the individual stationary phases have been predicted, and experimentally confirmed by carrying out separations of mixtures of isomers of disubstituted benzene derivatives.

Properties of liquid crystalline cyanoazoxybenzene alkyl carbonates as stationary phases in gas chromatography

Abstract Seven liquid crystalline azoxybenzene p-cyano-p′-alkyl carbonates have been tested as stationary phases, using Chromosorb W as the support and xylene isomers as the solutes. The data obtained on the effect of the properties of the liquid crystal-support system on column selectivity and efficiency were utilized in the separation of mixtures of disubstituted benzene isomers.

Comparison of Methods for Determining the Eutectic Compositions of Ternary Liquid - Crystalline Mixtures

Abstract Three methods of determining the eutectic compositions of ternary liquid crystal mixtures used as stationary phases in gas chromatography were compared. The method involving the heats of melting of the pure components of the mixtures and CSL equation, the method involving substitution of heats of melting of the components determined in binary mixtures into the CSL equation and a new, own method in which the eutectic composition of the mixture was determined by high-performance liquid chromatography.

Investigations of the properties of liquid–crystalline stationary phases containing naphthalene fragments in their molecules

Abstract Six new liquid–crystalline stationary phases have been produced containing naphthalene fragments in their molecules. The mesophase range lies between 45 and 132°C, the highest clearing temperature being 295°C and the lowest melting point 126°C. The physicochemical properties of these stationary phases have been tested, and the usefulness of the phases for the analysis of polycyclic aromatic hydrocarbons, naphthylamines, naphthols and methylnaphthalene isomers has been demonstrated.

Synthesis and testing of new high-temperature liquid crystalline stationary phases

Abstract Three new liquid crystalline Schiffs bases were synthesized that show wide mesophase ranges. The properties of these compounds as stationary phases and their separating capacities towards polynuclear hydrocarbons were tested.

Smectic C compounds with bicyclo[2,2,2]octane ring

Abstract Homologous series of 4-[2-(4-alkylbicyclo[2,2,2]octyl)ethyl]phenyl 4-alkoxybenzoates were synthetized and their mesomorphic properties were investigated. These compounds exhibit smectic C phase and are useful as components of mixtures with ferroelectric properties. The influence of dopants on the tilt of the molecules in the smectic C layer of the mixtures containing mentioned compounds were studied.

Three ring dioxanes as dopants enhancing the stability of the smectic C phase

Abstract Searching for compounds which could be useful as modifiers of smectic C mixtures, we have synthesized four homologous series of three ring dioxanes, 2BBD, 5BBD, 2CBD, and 5CBD. Their phase transition temperatures and enthalpies were measured and their liquid crystal phases identified. Compounds belonging to series n-BBD form smectic Bcr phases for shorter alkyl chains, and smectic Bcr and A phases, for longer chains. Compounds belonging to the n-CBD series exhibit the smectic A phase, but those with longer alkyl chains have exclusively smectic B phases and those with short tails have other low temperature, highly ordered smectic phases. The compounds were added to smectic C mixture and it was found that some can be useful as dopants. Compounds with longer alkyl tails in the molecule are more suitable for this purpose; the type of ring in the core is less important.

Disc-like liquid crystalline stationary phases from the triphenylene derivatives group

Abstract Disc-like liquid crystals belonging to the triphenylene derivatives group have been tested as stationary phases. Some relationships were determined as a function of the column temperature and separations a few substances were studied. Differences were found in the behaviour of disc-like and rod-like liquid crystalline stationary phases. On disc-like liquid crystals, compounds with a linear molecular structure are easily separated from those with a cyclic structure having similar boiling temperatures.