Zbyněk Plzák

New carbon adsorbent for high-performance liquid chromatography

Abstract A carbon adsorbent prepared by reduction of poly(tetrafluoroethylene) with alkali-metal amalgams can be used as a mechanically stable packing for high-performance liquid chromatography. Physical properties of the material are presented, and the structure of the particles is discussed. The separations of some aliphatic alcohols, aromatic compounds and isomeric carboranes are used to illustrate the performance of the adsorbent.

A PTFE-based carbon adsorbent in high-performance liquid chromatography

Abstract A new type of carbon adsorbent, prepared by reduction of PTFE, was studied and modified with the aim of obtaining a material with a relatively homogeneous, non-polar surface for applications in high-performance liquid chromatography. Three types of sorbent differing in the specific surface area, oxygen remainder and porosity were investigated. The chromatographic behaviour of various solutes, both in non-polar (e.g., pentane) and polar (aqueous buffer) media, has been studied. The plots of natural logarithm of the capacity factor vs. the carbon number were reasonably parallel for a homologous series with different functional groups. The influence of the ionization of some amino acids on their retention over the whole pH range has been shown.

Reversed-phase ion-pair liquid chromatographic separations of some heteroborane anions

Abstract Separation of 23 heteroborane anions by reversed-phase ion-pair liquid chromatography on C1-bonded-phase columns using C12 or C6 n-alkylamine pairing ion is reported. The elution was monitored with a UV detector at 235, 254 or 280 nm well below microgram sensitivity level. The effects of the concentrations of the pairing ion and the inert salt, the pH, the pairing ion length, the stationary phase material and the methanol—water ratio on retention and selectivity were investigated.

High-performance liquid chromatographic separations of some boranes and their derivatives

Abstract The high-performance liquid chromatographic conditions required for the liquid-solid separation of about 20 higher boranes, heteroboranes and their derivatives were established. The separations were carried out on silica gel using n -heptane and methylene chloride as mobile phases. Except for several closo -boranes, spectrophotometric detection at 254 nm was used for borane compounds. Instead of water, acetonitrile and in some instances isopropanol were used as silica gel modifiers.

Chromatographic behaviour of the closo-[B12H12]2- derivatives on hydroxyethylmethacrylate gels

Abstract Halo derivatives (Cl, Br, I) of the closo -dodecahydro-dodecaborate anion, [B 12 H 12 ] 2− , and their positional isomers were separated on Separon HEMA hydroxyethylmetacrylate sorbents. Different effects on the separation process, including cations and anions in the mobile phase, the electrolyte concentration in the eluent, pH, addition of organic modifier and separation temperature, were studied. Optimum conditions for the separation were accomplished with Separon HEMA BIO 300 and 1000 sorbents using 0.1–0.5 M sodium perchlorate solutions in 0.01 M phosphate buffer (pH 8.5) as the mobile phase. The separated compounds were detected using direct UV detection in the range 200–210 nm.

A general preparative route to compounds containing 10-vertex arachno- and nido-tricarbaborane cages

Two representatives of the 10-vertex family of tricarbaboranes, arachno-µ-6,9-RCH-9-R-5,6,9-C3B7H11(R = H or Me) and nido-5,6,10-Me3-5,6,10-C3B7H8, arise from two different modes of alkyne insertion (acetylene and but-2-yne) into the cage of arachno-4,5-C2B7H13.

Laser photolysis of liquid hexafluorobenzene : graphitic and fluorine-containing carbon formation at ambient temperature

ArF laser photolysis of liquid hexafluorobenzene affords a number of aromatic fluorocarbons, graphitic carbon and a fluorine containing polymeric C/F material. The preponderance of decafluorobiphenyl among the perfluoroaromatic products reveals the importance of the pentafluorophenyl radical combinations in the initial stages of photolysis. The C/F material is judged to arise from polymerization of fluoroalkyne transients. The graphite formation represents a unique mode of photolytic liquid-phase graphitization of perfluoroaromatic compounds.

Purity assay of sodium mercaptododecaborate by high-performance liquid chromatography

Abstract A simple high-performance liqiud chromatographic (HPLC) method for purity monitoring and determination of [B12H11SH]2− (I)_ and its oxidation impurities [B12H11SSB12H11]4− (II) and [B12H11S(O)SB12H11]4− (III is presented. The method is based on the use of the hydroxyethylmethacrylate sorbent Separon HEMA-BIO 300 and 100 mM sodium percholorate in 0.01 M phosphate buffer as mobile phase. Common HPLC equipment with direct spectrophotometric detection in the range 200–210 nm was used throughout. The minimal detectable amounts of the sodium salts of anions I, II and III at 204 nm were 8.6·10−8, 8.8·10−9 and 6.4·10−8 g, respectively. The application of the method to the study of the stability of the sodium salt of I in solution revealed a strong positive effect of trace amounts of Cu+ in enhancing the Na2B12H11SH oxidation rate.