Preparation and evaluation of OV-240-OH coated glass capillary columns for isomer specific determination of PCDDs and PCDFs

Glass capillaries were leached, dehydrated, persilylated with 1, 3-bis (3-cyanopropyl) tetramethyldisiloxane, and coated with OV-240-OH. After crosslinking and binding the phase to the glass surface the columns showed high separation efficiency, high temperature stability, and inertness comparable to persilylated apolar columns. Column performance is shown to be superior to liquid phase cyanopropyl columns such as SP 2330. The excellent separation capabilities together with the selectivity of the phase makes OV-240-OH coated columns a valuable tool for the determination of toxic isomers in complex mixtures of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). The order of elution of individual TCDD isomers was found to be similar to that described for SP 2330 or Silar 10c. The detection of PCDDs and PCDFs in a fly ash extract further illustrates the utility of OV-240-OH coated columns. The high temperature limit of these columns opens the way for the analysis of high boiling compounds such as mixed brominated/chlorinated dibenzo-p-dioxins and dibenzofurans.     

Immobilization of stationary phase films by gamma radiation. Part 1. Nonpolar phases,regular and thick-film capillaries

Borosilicate glass capillaries, silylated and coated with OV-1 or SE-54, were irradiated by a ⁶⁰Co gamma source. The effect of radiation on chromatographic performance was determined for a series of dosages and was evaluated before and after rinsing with solvent. Results for both regular and thick films were obtained.     

Preparation and chromatographic characteristics of calix[4]arene polysiloxane as stationary phases for capillary gas chromatography

Summary Two new kinds of calix[4]arene derivatives, 5, 11, 17, 23-tetra-tert-butyl-25,27-bis(isopropylcarbamoyl-methoxy)-26,28-diundecenyloxy calix[4]arene (C[4]A) and 25,27-dibutoxy-5, 11, 17, 23-tetra-tert-butyl-26,28-diundecenyloxy calix[4]arene (C[4]B0, are prepared and then are polymized by two different processes. Three calix[4]arene polysiloxane stationary phases for capillary gas chromatography are obtained. Their chromatographic characteristics, including column efficiency, polarity, selectivity, glass-transition temperature and thermal stability are studied. Retention mechanisms are also discussed.     

Chromatographic separation of simulants of nerve and blister agents by combining one‐ and two‐channel columns with different stationary phases

A two‐channel gas chromatography column and a single‐channel column were made by deep reactive‐ion etching technology. The two short columns were coated with different stationary phases, and then linked without a modulator. This is to aim at increasing the sample capacity and achieving a higher separation efficiency in complex environments. The results show that the capacity of the connected column is approximately 4 and 1.5 times larger than that of the single‐ and two‐channel columns, respectively. The linked column was utilized to separate a six‐component mixture, composed of three simulants of nerve and blister agents and three interfering vapors. The results demonstrate that the combined column has a remarkably higher separation efficiency than the individual columns, and an acceptable resolution is achieved although the total length of the linked column is only 1.5 m.     

Synthesis of siloxane stationary phases for capillary gas chromatography and supercritical fluid chromatography

A comparison is made between dichlorosilanes and cyclic siloxanes as starting materials in the synthesis of stationary phases for capillary gas chromatography (CGC) and supercritical fluid chromatography (SFC). Siloxanes containing one or more of the side groups methyl, vinyl, phenyl, and cyanoethyl in various ratios were synthesized and compared. These phases were characterized by chromatographic (gel permeation, GPC), spectroscopic (IR, ¹H NMR, ²⁹Si NMR), and thermal (DSC) methods. Coated fused silica columns were evaluated with respect to polarity, crosslinkability with several free-radical initiators, and thermal stability. A new liquid phase, 7% cyanoethyl, 7% phenyl, 1% vinyl methyl polysiloxane is shown to be more polar than OV-1701, more temperature stable, easily crosslinked and suitable for use in supercritical fluid chromatography.     

Preparation,evaluation, and comparison of wide bore (320 μm) and narrow bore (50 μm) cyanosilicone-coated capillary columns for gas chromatography

The preparation of wide bore (320 μm) and narrow bore (50 μm) fused silica capillary columns is described for immobilized cyanopropyl substituted silicones containing 60 and 88% substitution. The effect of high temperature deactivation with cyanopropylcyclosiloxanes was studied with a special test mixture. Curing was achieved with dicumyl peroxide or azo-tert-butane. The columns were evaluated and compared in terms of efficiency, activity, polarity, and temperature stability. Different coating methods were compared for the narrow bore columns. The activity of the 60% cyanopropyl columns that had been immobilized with dicumyl peroxide was significantly larger than for azo-tert-butane immobilized columns. The polarity of polar columns appeared to depend greatly on column temperature and is completely different for wide and narrow bore columns.     

(S)-O-acetyllactyl chloride – a versatile chiral auxiliary in stereodifferentiation of enantiomeric flavor components

The stereodifferentiation of chiral secondary alcohols, 4(5)-alkyl-substituted γ (δ)-lactones via corresponding 1, 4(1, 5)-diols, chiral 1, 3-diols, and 1-thioalkan-3-ols was carried out by diastereomeric derivatization with (S)-O-acetyllactyl chloride as a chiral auxiliary. This procedure is a convenient and reliable method for screening the enantiomeric composition of these naturally occurring flavor volatiles.     

Open tubular capillary column of 50 μm internal diameter with a very high separation efficiency for the separation of peptides in CEC and LC

A specially designed long open tubular capillary column (50 μm internal diameter and 112 cm effective length) was prepared by fabrication of a thin three‐component co‐polymer layer on the inner surface of silica capillary. A pretreated silica capillary was reacted with 4‐(chloromethyl)phenyl isocyanate in the presence of dibutyltin dichloride as catalyst followed by sodium diethyl dithiocarbamate. Then a thin polymer layer was made on the inner surface of capillary by reversible addition‐fragmentation transfer polymerization of styrene, N‐phenylacrylamide, and methacrylic acid. A carefully adjusted formulation of reaction mixture and elaborated procedures were adopted to secure formation of the co‐polymer layer of enhanced separation performance. The co‐polymer immobilized open tubular capillary column was used for the separation of a synthetic mixture of five peptides and excellent separation efficiency (over 1.7 million per column) was obtained in the capillary electrochromatography mode. Such excellent separation efficiencies of ca. 1 m column have not been obtained in the isocratic elution mode so far. The column was also used for separation of the peptides in the liquid chromatography mode to show very good separation efficiency (average 286 700 per column).