Development and optimization of ultra-high performance supercritical fluid chromatography mass spectrometry method for high-throughput determination of tocopherols and tocotrienols in human serum

The goal of this study was to develop an effective supercritical fluid chromatography method using single quadrupole MS for analysis of all isomeric forms of vitamin E. Finally, two fast and effective methods, the high resolution one and the high speed one, for the determination of 8 vitamin E isomers in human serum were developed.     

Properties of microdispersed sintered nanodiamonds as a stationary phase for normal-phase high performance liquid chromatography

The chromatographic properties of microdispersed sintered nanodiamonds (MSND) are studied under conditions of normal-phase HPLC. The retention characteristics of 30 substances representing four classes of aromatic compounds including monoalkylbenzenes, polymethylbenzenes, di-n-alkyl phthalates and polyaromatic hydrocarbons in n-alkane mobile phases have been measured. The selectivity of MSND was compared with literature data for other common adsorbents including silica gel, alumina and porous graphitic carbon (PGC). MSND shows the distinctive adsorption properties especially in a stronger retention of aromatic hydrocarbons and in the better selectivity of the separation of geometric isomers. The significant improvement in separation efficiency up to 45,300 theoretical plates per meter, was achieved for the first time for the columns packed with diamond related materials (DRM).     

Application of a contactless conductometric detector for the simultaneous determination of small anions and cations by capillary electrophoresis with dual-opposite end injection

A contactless conductometric detection (CCD) system for capillary electrophoresis (CE) with a flexible detection cell was applied for the simultaneous determination of small anions and/or cations in rain, surface and drainage water samples. The applied frequency, the amplitude of the input signal, the electrolyte conductivity and electrode distance were found to be the most significant factors affecting the detection sensitivity. 2-(N-Morpholino)ethanesulfonic acid/histidine-based (MES/His) electrolytes were used for direct conductivity detection of anions and cations, while ammonium acetate was selected for indirect conductivity determination of alkylammonium salts. For the simultaneous separation procedure, involving dual-opposite end injection, an electrolyte consisting of 20 mM MES/His, 1.5 mM 18-crown-6 and 20 microM cetyltrimethylammonium bromide provided baseline separation of 13 anions and cations in less than 6 min. The detection limits achieved were 7-30 micrograms/l for direct conductometric detection of various common inorganic cations and anions, excluding F- (62 micrograms/l) and H2PO4- (250 micrograms/l), and 35-178 micrograms/l for indirect conductometric detection of alkyl ammonium cations. The developed electrophoretic method with conductometric detection was compared to ion chromatography.     

“Isocyanide-less” Ugi/Intramolecular Diels-Alder reaction of 5-hydroxymethylfurfural

The one-pot, three-step, four-component Ugi-IMDAF reaction with 5-hydroxymethylfurfural provides simple access to hydroxymethyl-substituted epoxyisoindolones in a diastereoselective and stereospecific manner. The protocol avoids the transfer or isolation of isocyanides, and the broad scope was illustrated by the synthesis of 22 different compounds bearing various substituents on the heterocyclic core.     

Mass measurement and top-down HPLC/MS analysis of intact monoclonal antibodies on a hybrid linear quadrupole ion trap-orbitrap mass spectrometer

Mass and top-down analyses of 150-kDa monoclonal immunoglobulin gamma (IgG) antibodies were performed on an Orbitrap analyzer. Three different sample delivery methods were tested including (1) infusion of an off-line desalted IgG sample using nano-electrospray; (2) on-line desalting followed by a step elution with a high percentage of organic solvent; and (3) reversed-phase HPLC separation and on-line mass and top-down analyses of disulfide isoforms of an IgG2 antibody. The accuracy of mass measurements of intact antibody was within ±2 Da (15 ppm). The glycoforms of intact IgG antibodies separated by 162 Da were baseline resolved. In-source fragmentation of the intact antibodies produced mainly 115 residue fragments including N-terminal variable domains of heavy and light chains. The sequence coverage (the number of cleavages) was greatly increased after reduction of disulfide bonds and HPLC/MS/MS analysis of light and heavy chains using collision-induced dissociation in the ion trap of the LTQ-Orbitrap. This is an attractive alternative to peptide mapping for characterization and monitoring of post-translational modifications attributed to minimal sample preparation, high speed of the mass/top-down analysis, and relatively minor method-induced sample modifications.     

Immobilization of porphyrins in poly(hydroxymethylsiloxane)

Three tetracationic porphyrins differing in the position of charged nitrogen atoms on the peripheral substituents — 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP4), 5,10,15,20-tetrakis(N-methylpyridinium-2-yl)porphyrin (TMPyP2), 5,10,15,20-tetrakis(4-trimethylammoniophenyl) porphyrin (TMAPP), and hydrophobic 5,10,15,20-tetraphenylporphyrin (TPP), were immobilized by adsorption and encapsulation in poly(hydroxymethylsiloxane) (PHOMS). The so prepared porphyrin-PHOMS composites were characterized by porosimetry, scanning electron microscopy, fluorescence and diffuse reflectance UV-VIS spectroscopy. It was found that porphyrins are immobilized in the PHOMS matrix in the free base monomer form Their irradiation produced singlet oxygen O₂(¹Δ_g) with the lifetime of 10–30 μs.     

The Behaviour of Thin Samples of Ferroelectric Liquid Crystals

On a ferroelectric liquid crystal DOBAMBC transitions between helical and twisted structures are observed if changing the temperature. The twisted structure appears when the helical pitch becomes comparable to the sample thickness, From the switching process of the twisted DOBAMBC samples in an electric field the polarity of surface layers is determined. Low signal di- electric permittivity shows an increase below the transition to the ferroelectric phase, which is a consequence of the twisted structure deformation in the electric field.