Wall coated capillary

Wallach transformation orgchem By the use of concentrated sulfuric acid, an azoxy-benzene is converted into a pura-hydroxyazobenzene. wal ak. tranz-far.ma-shan wall-coated capillary column analychem Acaplllary column characterized bya layer of stationary liquid coated directly on the Inner wall of a colled capillary tube. wol kod-3d kap-3 ler-e. kal am )... 

A recent modification of the atmospheric pressure ionization technique involving a special low dead volume interface was described by Thomson etal. [27]. They employed packed microbore columns (170 p, 320 p, and 500 p I. D. with lengths ranging from 5 to 15 cm) in conjunction with a low-volume, wall-coated capillary column as an interface. The total ion current chromatogram of the tryptic digest sample of about 1 picomole of human growth hormone is shown in figure 29. The column was packed with an octadecyl bonded phase... 

Jama, M.A. E)elmas, M.P.F., Ruthven, D.M., Diffusion of linear and branched C6 hydrocarbons in silicalite studied by the wall-coated capillary diromatographic Method. Zeolites 18 (1997) pp. 200-204. 

A comparison of efficiency of HPLC and GC columns was made by Wldmer et al (20). For example, 3 ym packed 10 cm column gives 15,000 plates or 150,000 plates/meter. This compares with 11,880 plates obtained with 0.1 mm l.d. wall coated capillary GC columns. These data suggest that greater efficiency In terms of number of plates/meter Is possible with HFLC. 

The phase ratio, l.e. the ration of the volumes occupied by the gas phase and the stationary phase. Is given the symbol H. For wall coated capillary columns, Is approximated by ... 

For packed columns the efficiency is given by the quality and particle size of the column packing. For wall coated capillaries the efficiency is a matter of the coating film properties. Furthermore, the efficiency depends on the injection mode, solvent effects, flow rate and column dimensions. 

Table III. Efficiency of Wall Coated Capillary Columns...

For gas chromatographic analysis a 50 m PONA fused silica wall coated capillary column (BP-1) was applied in temperature-programmed mode (-50 to 220 °C) with flame ionisation detection (FID) of hydrocarbons. 

Wall-coated capillary columns are therefore increasingly used in SFC [30]. These have the great advantage of high efficiency because of greater length consequent on the permeability of capillaries to the flow of low-viscosity supercritical fluids. The low volume flow rates of capillary columns facilitate the use of toxic, corrosive, inflammable, or expensive fluids. Capillary columns are also compatible with a variety of detectors (section 9.3), permit maximum... 

Chen-Ying Liu Cho-Chum Hu Cheng-Lung Yang Synthesis and characterization of the novel wall coated capillary column for the separation of polycyclic aromatic hydrocarbons. J. Chromatogr. A, 1997, 773, 199-208. 

Classical El and Cl sources can be readily coupled to GC and much less readily to liquid flows using particle beam (PB) interfaces. Packed column GCs require the used of a jet separator for successful coupling, while wall-coated capillary GC columns operating with helium flow rates in the range 1-2 mL.min can be introduced directly into a mass spectrometer without overloading the vacuum pumps. 

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