Dr. KnowIntroduction
In Packed Gas Chromatography liquid phases need a support material as carrier. This support is mainly diatomaceous earth, i. e. fossilized shells of very small sea life from millions of years ago. It is a natural product coming out of mines nowadays. It is possible to also make it synthetically, but normally the natural product is used.
Chromosorb Properties
| → Increasing Inertness → | Chromosorb P |
Chromosorb G |
Chromosorb W |
Chromosorb 750 |
Chromosorb T |
| P NAW | G NAW | W NAW | |||
| P AW | G AW | W AW | |||
| P AW-DCMS | G AW-DCMS | W AW-DCMS | |||
| G HP | W HP | 750 | T | ||
| Max. Efficient Load | 30 % | 5 % | 15 % | 12 % | 5 % |
|---|---|---|---|---|---|
| Abs. Max. Load | 40 % | 10 % | 30 % | 25 % | 15 % |
| pH | 6.5 | 8.5 | 8.5 | 8.0 | - |
| Max. Temperature | > 350 °C | > 350 °C | > 350 °C | > 350 °C | 250 °C |
| Free Fall Density | 0.38 g/ml | 0.47 g/ml | 0.18 g/ml | 0.33 g/ml | 0.42 g/ml |
| Packed Density | 0.47 g/ml | 0.58 g/ml | 0.24 g/ml | 0.38 g/ml | 0.49 g/ml |
| Surface Area | 4.00 m²/g | 0.50 m²/g | 1.00 m²/g | 0.75 m²/g | 7.50 m²/g |
| 1.88 m²/mL | 0.29 m²/mL | 0.29 m²/mL | 0.24 m²/mL |
Descriptions
GC Support |
Support treatments |
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Chromosorb P This is a pink diatomite support prepared from firebrick. It is used primarily for hydrocarbons and moderately polar compounds on analytical as well as preparative scale. The surface of Chromosorb P is more adsorbent than the surfaces of the other Chromosorb supports. Owing to the large surface area, Chromosorb P provides high column efficiencies. However, Chromosorb P exhibits a high reactivity towards polar compounds. This effect can be decreased by masking the support surface with a liquid phase or by deactivating the support surface (for example by AW-DMCS treating). |
Non Acid Washed (NAW) All Chromosorb supports prepared from diatomite (Chromosorb grades G, P and W) are available in an untreated form, referred to as non-acid washed (NAW). |
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Chromosorb W A flux calcinated diatomite, used for the separation of polar compounds. The surface of Chromosorb W is relatively low in adsorption. Chromosorb W is fairly fragile and if it is not handled carefully, it will produce active areas which may reduce efficiency and inertness. |
Acid Washed (AW) Chromosorb grades G, P and W are available having undergone the acid washed treatment. The acid washing procedure removes mineral impurities from the support surface and reduces surface activity. |
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Chromosorb G A flux calcinated support especially developed for the separation of polar compounds. Its low surface area, hardness and excellent handling characteristics make it a good replacement for light friable supports such as-Chromosorb W. Because of its smaller surface area and higher density, Chromosorb G is employed with a lower liquid phase coating. A 5% coating on Chromosorb G corresponds approximately to a 12% coating on Chromosorb W. |
Acid Washed Dimethyl dichlorosilane Treated (AW-DMCS) Chromosorb grades G, P and W are available with the combined acid washed and DMCS treatment. It should be recognized that the untreated diatomaceous supports are not inert and vary significantly in adsorption and catalytic activity. Surface interaction may be recognized by the tailing. |
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Chromosorb T Made from a PTFE resin, Chromosorb T has a highly inert surface and is extremely useful for analysis of highly polar compounds. Recommended maximum temperature is 250°C; higher temperatures will cause clogging and decomposition of the support. Handling may be difficult because of the static charge which causes the support to clog and stick to its container. If force is applied, Chromosorb T tends to compress and become a compact solid rather than remain porous, and its chromatographic properties will be destroyed. Chromosorb T is specifically suitable for the analysis of very polar compounds such as water, hydrazine or sulfur dioxide which will show severe tailing on other supports. |
High Performance (HP) The 'HP' grade has been developed for use with steroids, bile acids, alkaloids and for the other analyses of pharmaceutical, medical and toxicological compounds. Chromosorb HP is a high quality, carefully acid washed and silanized, flux-calcinated diatomite. Its features include superior inertness and column efficiency, no catalytic surface activity and short column conditioning time. Each batch of supports is quality controlled and checked using gas chromatography to insure product uniformity. Chromosorb W and Chromosorb G are available in the 'HP' grade. |
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Chromosorb 750 The manufacturer proclaims this support to be the most inert and highly efficient support available. It is produced from highly pure diatomite crude, is acid washed, and effectively silane treated. Chromosorb 750 is especially designed for biomedical and pesticides analyses. The mechanical strength is similar to Chromosorb G. |