Column packings metal impurities

Methyl vinyl dichlorosilane [124-70-9] M 141.1, 43-45.5°/ll-ll.5mm, 91 /742mm, 92.5°/743.2mm, 92.5-93°/atm, d 1.0917, n 1.444. Likely impurities are dichloromethylsilane, butadienyl-dichloromethylsilane. Fractionate through a column packed with metal filing (20 theoretical plates) at atmospheric pressure. [Isvest Akad SSSR Otd Chem 1474 1957 and 767 7955]. 

HPLC is performed on analytical columns packed with a commercially available solid phase containing long hydrocarbon chains (e.g. Cg, Cig) chemically bound onto silica. Chemicals injected onto such a column move along at different rates because of the different degrees of partitioning between the mobile aqueous phase and the stationary hydrocarbon phase. The HPLC method is not applicable to strong acids and bases, metals complexes, surface-active materials, or substances that react with the eluent. The HPLC method is applicable when the log Kow value falls within the range 0 to 6 (OECD 117, 1989). The HPLC method is less sensitive to the presence of impurities in the test compound compared to the shake-flask method. 

Likely impurities are dichloromethylsUane, butadienyl-dichloromethylsilane. Fractionate the silane through a column packed with metal filings (20 theoretical plates) at atmospheric or reduced pressure. [Izy Akad Nauk SSSR Ser Khim 1474 1957 and 767 1958, Beilstein 4 III 1894,4 IV 4184.]... 

An alternative method for oxygen removal is catalytic reduction over a platinum-on-alumina catalyst in the presence of methanol [22,23]. A short column packed with the catalyst is inserted between the pump and injector. Provided that the mobile phase contains about 1% methanol (or more) oxygen is very efficiently reduced producing formaldehyde and formic acid. It is necessary to ensure that these products do not react with or degrade the sample. An in-line chelation column placed between the pump and injection valve was suitable for the removal of metal impurities from the mobile phase [24]. 

Silani/cd surfaces of column packings may still show a residual adsorption, which apparently occurs with metal oxide impurities in the diatomaecous earth. Acid wa.shing prior to silaniTtaliun removes these impurities. Fused siliea used for manufacturing open tubular columns is largely free of this type of impurity. Beeausc of this, fewer problems with adsorption arise with fuscd-silica columns. 

Materials. Cyclohexene, obtained by dehydration of reagent grade cyclohexanol (3), was heated at reflux over sodium metal, fractionated on a 60-cm. Helix packed column, stored over sodium, and filtered just before use. No impurity was found by gas chromatography (column, TCP and Si-550 carrier gas, helium). Propylene (Neriki Research Grade) used showed no impurity by gas chromatography (column, active carbon and acetonylacetone). 

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