curiosity about phase %

[Jumpshooter]

I noticed that a column we have is supposed to be comprised of "active phase" 50% diphenyl and 50% dimethylpolysilox---yet the curious thing about it is that only ~ 3.5% of the entire packing material's mass is actually composed of the "active phase". Only 3% seems to be an awfully small amount of active phase. Is this normal or has an error been made by the manufacturer or by myself in not properly understanding the % composition phase?

[BB65]

I noticed that a column we have is supposed to be comprised of "active phase" 50% diphenyl and 50% dimethylpolysilox---yet the curious thing about it is that only ~ 3.5% of the entire packing material's mass is actually composed of the "active phase". Only 3% seems to be an awfully small amount of active phase. Is this normal or has an error been made by the manufacturer or by myself in not properly understanding the % composition phase?

3% load of phase on a support doesn't sound unreasonable. The composition of that 3% is 50% diphenyl, 50% dimethyl.

[chromatographer1]

The 'liquid' phase is a polymer composed of units of dimethyl silicone and diphenyl silicone which can be of several hundred 'mers' in length.

This oily silicone fluid is put onto a solid support as a percentage of the total weight of the packing.

3% (OV-17, or SP-2250, or HP-17 or whatever the phase is called) is 3g of phase and 97 g of diatomaceous earth support packed into a column.

Different earths can hold different amounts of phase before they become 'overloaded'. Chromosorb P can hold as much as 40% phase while Chromosorb W usually holds only 5-10 % as a maximum amount.

1% OV-17 on Chromosorb W is a common packing for di and tri saccharides and 3% OV-17 on Chrom W is a commonly used for steroids and simple sugars.

Then there is Chromosorb G, and P, and there used to be a Chromosorb A back in the day.

With capillary columns the phase is described as its thickness along the inner surface of the capillary tube, not a weight percent because there is no support and the tube is hollow.

The amount of phase per length for packed columns is dependent upon how densely the packing is packed into the column and the percentage of phase per weight in the packing.

I still think it would be worth your while to buy me a doughnut and a cup of coffee some morning while we chat over the good old days of packed column chromatography.

best wishes,

Rodney George