High temperature stationary phase of polysiloxane containing N,N′-bis(diphenylsilyl) tetramethylcyclodisilazane for gas chromatography

A polysiloxane copolymer (P(BPTMC)-alt-ODMS) containing N,N′-bis(diphenyl-silyl) tetramethylcyclodisilazane (BPTMC) was used as stationary phase in gas chromatography with high thermal stability.

Quality assurance of commercial beeswax

The use of low-temperature capillary gas chromatography coupled to electron impact mass spectrometry for the characterization of crude beeswaxes yielded by Apis mellifera is described. The system allows the identification of a great number of compounds, some of them not reported till now in beeswax, such as a family of ethyl esters, tetracosyl oleate, and several saturated and unsaturated hydrocarbons. The information acquired makes possible the differentiation between pure beeswax and some foundation beeswax samples where mixture of pure beeswax with another substances is suspected.

Characterization of stationary phases for gas chromatography by 29Si NMR spectroscopy. II. Silphenylene-siloxane copolymers

A series of tetramethyl-p-silphenylene-siloxane copolymers with dimethyl, 1H,1H,2H,2H-perfluorodecylmethyl and diphenyl siloxy groups was prepared. 1H and 29Si nuclear magnetic resonance spectroscopy showed that the chosen reaction conditions provided polymers with diphenyl content up to 85%. The theoretical content of the monomer units correlated well with the measured content. Signal assignments of the copolymers and their corresponding chemical shifts are summarized. Information about alternating, randomized or block sequences was obtained by 29Si nuclear magnetic resonance spectroscopy. Limitations of the method for the determination of microstructure parameters are discussed.

Investigation of combwax of honeybees with high-temperature gas chromatography and high-temperature gas chromatography-chemical ionization mass spectrometry. II: High-temperature gas chromatography-chemical ionization mass spectrometry

Crude combwax of six various honey bee species have been analyzed by high-temperature gas chromatography (HTGC)-chemical ionization mass spectrometry after a two-step silylation procedure. An optimized chromatographic procedure, described previously, enables the separation of high-molecular mass lipid compounds resulting in a characteristic fingerprint of the combwaxes of different honeybee species. The coupling of HTGC to mass spectrometry requires appropriate instrumentation in order to achieve sufficient sensitivity at high elution temperatures and avoid loss of chromatographic resolution. Chemical ionization was carried out using methane as reagent gas in order to determine the molecular mass of the individual compounds by means of abundant quasi molecular ions. To confirm the presence of unsaturated wax esters, ammonia was used as reagent gas. More than 80 lipid constituents were separated and characterized by their mass spectra. Representative chemical ionization mass spectra of individual compounds are presented. Both, HTGC-flame ionization detection data and the results of the HTGC-mass spectrometric investigations enabled a rapid profiling of the individual classes of compounds in crude combwaxes.

Investigation of combwax of honeybees with high-temperature gas chromatography and high-temperature gas chromatography-chemical ionization mass spectrometry. I. High-temperature gas chromatography

The combwaxes of the honeybee species Apis mellifera, Apis cerana, Apis dorsata, Apis laboriosa, Apis florea and Apis andreniformis have been examined by high-temperature gas chromatography. Combwax consists of a complex mixture of homologous neutral lipids. These compounds containing up to 64 carbons were chromatographed intact on a 10 m x 0.2 mm high-temperature stable SOP-50-PFD (50%-diphenyl/50%-1H,1H,2H,2H-perfluorodecylmethylpolysiloxane)-co ated Duran glass capillary column. The use of this stationary phase results in lower retention values and, at last, in lower thermal stress of the analytes. In order to minimize the discrimination effect due to adsorption and/or degradation, a two-step derivatization was performed resulting in the formation of tert.-butyldimethylsilyl esters of the long chain fatty acids and trimethylsilyl ethers of complex hydroxyesters, respectively. The derivatization procedure was optimized using a modification of the extended Donike test. In addition this test allows the quantification of the thermal stability of the derivatives performed. The derivatization procedure was applied for combwax analysis. More than 80 compounds were separated and their peak areas semiquantitatively exploited.