Sample application packed column

Packed columns are still used extensively, especially in routine analysis. They are essential when sample components have high partition coefficients and/or high concentrations. Capillary columns provide a high number of theoretical plates, hence a very high resolution, but they cannot be used in all applications because there are not many types of chemically bonded capillary columns. Combined use of packed columns of different polarities often provides better separation than with a capillary column. It sometimes happens that a capillary column is used as a supplement in the packed-column gas chromatography. It is best, therefore, to house the capillary and packed columns in the same column oven and use them selectively. In the screening of some types of samples, the packed column is used routinely and the capillary column is used when more detailed information is required. 

An SPE column is assembled by packing polymer particles (100 mg) between two Teflon frits in a 6-mL glass cartridge. The column is mounted on a BAKER spe -12G Column Processor (containing a 12-port vacuum manifold and a vacuum gauge controller) from J.TBaker (Deventer, Holland). Prior to sample application, the column is equilibrated by passing 5 mL of toluene at approximately 2 mL min flow rate, by applying an appropriate vacuum to the manifold. 

Clemo-McQuillen pycnometer, 49 color tests, 631, 649, 653 column chromatography. See also chromatography column elution, 94-95 column packing, 93-94 defined, 92 fraction collection, 95 materials, 92-93 sample application, 94 column holdup, 65 columns... 

A third parameter to consider is the column construction. Thus the sample applicator should provide optimal sample application to give the most performance possible out of the packed bed. Constructions should also allow simple, fast, and reproducible packing of the column. Because costs for repacking of columns are a substantial operating cost item in industrial chromatography, the selection of column construction from this point of view is also important. Some novel column constructions allow very simple procedures both for laboratory and for industrial scale (e.g., INdEX columns, see Section V). 

For capillary GC, the split/splitless inlet is by far the most common and provides an excellent injection device for most routine applications. For specialized applications, there are several additional inlets available. These include programmed temperature vaporization (PTV) cool on-column and, for packed columns, direct injection. PTV is essentially a split/splitless inlet that has low thermal mass and a heater allowing rapid heating and cooling. Cool injection, which can be performed in both split and splitless mode with the PTV inlet, reduces the possibility of sample degradation in the inlet. Capabilities of the commonly available inlets are summarized in Table 14.3. 

Current EPA analytical methods do not allow for the complete speciation of the various hydrocarbon compounds. EPA Methods 418.1 and 8015 provide the total amount of petroleum hydrocarbons present. However, only concentrations within a limited hydrocarbon range are applicable to those particular methods. Volatile compounds are usually lost, and samples are typically quantitated against a known hydrocarbon mixture and not the specific hydrocarbon compounds of concern or the petroleum product released. By conducting EPA Method 8015 (Modified) using a gas chromatograph fitted with a capillary column instead of the standard, hand-packed column, additional separation of various fuel-ranged hydrocarbons can be achieved. 

The high resolution power provides for a good profile analysis of the sample with a clear pattern and minor peak overlap compared to packed column GC. Furthermore, in view of the possible toxic, synergestic or antagonistic effects of the individual PAH, it is important to quantify each compound separately. The chromatograms also demonstrate the application of 0V-73 to PAH analysis, a stationary phase similar to SE-52, but with improved temperature stability. 

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