Active Carbon-impregnated Silica Gel

Applicable to pretreatment (cleanup) in dioxin analysis!

Active Carbon-impregnated Silica Gel is a column clean-up filler developed for microanalysis of polychlorodibenzo-p-dioxin (PCDDs) and polychlorodibenzofuran (PCDFs).Attaining high microanalysis precision requires excellent clean-up method. As dioxins are particularly high in toxicity, the very cause of social concern, it is a must to secure high reliability in its analysis value.Active carbon has a characteristic of specifically adsorbing compounds with flat board structures, such as dioxin. It is gaining a global-wide recognition that active carbon clean-up process is an essential requirement in refining dioxins. However, conventional active carbon had such weaknesses as low penetrability when used as fine particles and poor tailing at elution when the particle is large.

This new type of column chromatography filler, made by impregnating fine-grain active carbon into silica gel, not only has the excellent characteristics of active carbon but also has good penetrability.

[Operating procedure]

1. Lay glass wool at the bottom of chromatography tube attached with a stop cock and place in anhydrous sodium sulphate at the height of about 1 cm. Then place in 1g of active carbon impregnated silica gel and lightly shake the column to fix its thickness. Again place in another layer of anhydrous sodium sulphate on top at a height of about 0.5 cm. (Refer to the equipment drawing.)
2. When column setting is complete, immediately let the specimen flow down gently (hexane solution concentrated to about 0.3 mL is desirable) onto the anhydrous sodium sulphate layer, using a pipette. Then wash off the tube wall and anhydrous sodium sulphate layer a few times with 0.1 mL of hexane.
3. After leaving at rest for a few minutes, connect a separatory funnel containing 200 mL of 25% dichloromethane/hexane [v/v] mixture to the upper part of chromatography tube and gently let the mixture flow down so spreading starts at the flow rate of 1 drop per second. (This effluent does not contain dioxin.)
4. When the dichloromethane/hexane mixture is exhausted, continue performing elution using 200 mL of toluene at the flow rate of 1 drop per second. (This effluent contains dioxin.)
5. Concentrate the toluene effluent to the target volume using pressure reducing KD concentrator.

[Note]

• PCBs are completely eluted in the 25% dichloromethane/hexane effluent ready to be supplied for quantitative analysis.
• Due to the dry type column chromatography, bubbles remain in the column during the elution process. However no adverse effect is seen in the recovery percentage and reproducibility.
• The recovery percentage is more than 90% with loads of 1 ng for each 1,2,3,4-T₄CDD and O₈CDD.T₄CDD : Tetrachlorodibenzo-p-dioxin O₈CDD : Octachlorodibenzo-p-dioxin1)

• Ono, M., Wakimoto, T., Tatsukawa, R. and Masuda, Y.: Chemosphere, 15, 1629 (1986).