Slurry packed columns

A calcium hydroxide column slurry packed in the laboratory was used to evaluate the distribution of all-trans-, l3-cis-, and 9-cis- isomers of P-carotene in fresh and processed vegetables and fruits. Elution order was reported to be l5-cis-, 3-cis-, sil-trans-, and 9-cw-P-carotene, using 2% p-methylanisole or 2% acetone in hexane as mobile phase, in a 35-min run. However, a column packed with calcium hydroxide as the stationary phase is not commercially available. 

Three column sets were used in this study. All consisted of 0.95 X 122 cm stainless steel columns slurry packed with Control-led-Pore Glass from Electronucleonics. The configurations were ... 

Retention times of molecules separated over mesoporous silica are much longer than those obtained by using commercially available silica, this is due to the increased surface area of mesoporous silica, which in turn increases molecular capacity factors. Differences between capacity factors are also enhanced Thus, molecules which elute with similar retention times on commercial HPLC columns, with overlapping peaks, can be successfully separated by using HPLC columns slurry packed with mesoporous silica. The long retention times are somewhat of a drawback in that large amounts of solvent must be used and the peak shapes of molecules with long retention times can be broad. Mesoporous silica may not be ideal for routine analytical separations but provides an excellent and cost-effective preparative separation medium. 

Phenol can be detected electrochemically by oxidation at a carbon paste electrode (Wehmeyer et al., 1983). A convenient means of determining a low concentration of phenol in a small volume of sample is by liquid chromatography with electrochemical detection (LCEC). A diagram of the LCEC system is shown in Fig. 2. The sample is injected by means of 20-pl sample loop into a 5-cm column slurry-packed with lO-pm Cjg stationary phase. The column serves to separate the peak for phenol from other assay constituents in order to achieve a better detection limit. The phenol is detected by oxidation in a thin-layer electrochemical cell with a carbon paste working electrode. 

A solution of 300 mL isopropyl alcohol/f-butyl alcohol containing 3.83 g N-phenylbenzylamine was irradiated under nitrogen gas for 30 h. The concentrated reaction mixture was chromatographed on a 15 x 300-mm column, slurry packed in benzene/3% acetone with 100-mesh silica gel, using benzene/3% acetone as the eluent. Three components... 

Packing the open channels with functionalized particles, as in conventional liquid chromatography, is challenging due to reproducibihty issues and difficult immobilization of the particles. However, at present, there are excellent commercially available chromatography on a chip devices with columns slurry-packed with a great variety of stationary phases. 

The mass-transfer rates obtainable across the gas-liquid interface are of nearly the same magnitude in the different operations. Bubble-column slurries exhibit rather higher transfer rates than conventional packed columns... 

Slurry packing techniques are required for the preparation of efficient columns with rigid particles of less than 20 micrometers in diameter. The same general packing apparatus. Figure 4.8, can be used to pack columns by the balanced-density slurry, liquid slurry, or the viscous slurry techniques. Down-fill slurry packing is the method of choice for small bore columns and packed capillary columns. 

Fig. 5.1a shows the slurry packing system that 1 use. This operates at a fairly low pressure, as I am not especially interested in producing columns with very high efficiencies, but rather in saving on the cost of commercial columns. The pump and high pressure valve are rated for pressures of 500 bar (7500 psi) and 400 bar (6000 psi) respectively. The slurry reservoir is a stainless steel tube 85 cm long, with a capacity of about 50 cm3. The method is not hazardous unless there is air trapped in the high pressure line nevertheless it is advisable to use a safety screen. 

Patel, K.D., Jerkovich, A.D., Link, J.C., Jorgenson, J.W. (2004). In-depth characterization of slurry packed capillary columns with l.O-pm nonporous particles using reversed-phase isocratic ultrahigh-pressure liquid chromatography. Anal. Chem. 76, 5777-5786. 

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