Column packing methods supports

Chromatographic system. (Follow the method described in the general procedure <621 >.) The gas chromatograph is equipped with a flame ionization detector and a 1.2 m x 2 mm column packed with 3% phase G32 on support S1A. The injection port, detector, and column temperatures are maintained at about 250, 300, and 250 °C, respectively, and helium is used as the carrier gas, flowing at rate of about 50 mL/min. The relative retention times for cholestane and miconazole nitrate are about 0.44 and 1, respectively. Chromatograph the Standard preparation, and record the peak responses as directed for procedure The resolution, R, between cholestane and miconazole nitrate is not less than 2 and the relative standard deviation of replicate injections is not more than 3%. 

An alternative method for achieving the effect of a small diameter is to coat a thin layer of porous solid on a solid core (such as glass). Such materials were widely used in the early days of LC and are usually called pellicular supports. Typically the porous layer is 1-2 pm thick, and the solid core has a diameter of about 40 pm. Pellicular solids are easier to pack than microporous solids, but they are less stable, have smaller capacities, and are more expensive. Since good packing methods are now known for the microporous solids, the pellicular solids have become much less popular. They are commonly used in guard columns (discussed later in this chapter). 

Potassium permanganate adsorbed on either silica or alumina can also be used to cleave double bonds under mild conditions and in good yields. In one procedure the alkene, dissolved in benzene, is passed through a column packed with KMn04 on a silica gel support.The reaction occurs rapidly at room temperature and is equally effective for the cleavage of all types of double bonds, even some that are inert to other traditionid methods. ... 

The AOAC-CIPAC method (1983) adopts a 1.22m x 4 mm i.d. glass column with 5% OV-J01 or OV-1 on 80/100 mesh Chromosorb W (HP), using dicyclo-hexyl phthalate as IS. The 1993 edition of the British Pharmacopoeia lists a GLC method using a 1.0m X 4mm glass column, packed with 3% of phenyl-methyl-silicone fluid (OV-17) on an acid-washed, si 1 anized diatomaccous support (100/120 mesh), with tetraphenylelhylenc 0.2% as IS. A typical GLC chromatogram is shown in Fig. 4.6. 

A gas chromatographic method using a gas density balance detector has been described407 for the determination of chlorinated phenylchlorosilanes using a column packed with Celite 545 supporting 10% of Lukopren G 1000 (a silicone elastomer), with nitrogen as carrier gas. 

---