calculation in HPLC

[lotussss]

Hello,
Can one use the artifact of injection at the beginning of chromatogram to calculate k' or is it necessary absolutely a chemical substance (so yes which)?
Where can one find the data following: porosity of a column.
Thanks

[amaryl]

Hello,
Can one use the artifact of injection at the beginning of chromatogram to calculate k' or is it necessary absolutely a chemical substance (so yes which)?
Where can one find the data following: porosity of a column.
Thanks

What do you mean by artifact of injection? The solvent peak at the begining of chromatgram is used to calculate K' for your analyte retention.

For porosity of column you need to check it with the manufacturer for the same.

Regards,

Amaryl.

[Uwe Neue]

It depends on what you are doing. The artifact peak is undefined. If this is not an important issue for your work, you can do that. If you want to do thermodynamics on peak retention, it is not good enough, and you need to define an unretained peak.

[lotussss]

If I want do thermodynamics on retention peak, what kind of chemical substance can I use?

[wxmwqr]

Yuo can use sodium nitrate (NaNO3)and detect at 210nm.

[Srinivas SK]

Hello:

By "artifact of injection", I'm assuming you mean one of two things : the small dip in the baseline that sometimes occurs on injection, or the so-called "solvent peak" that occurs if the sample is not dissolved in mobile phase, but another solvent instead. Both these peaks can't be used for system suitability calculations, since (a) they may not be reproducible and (b) they may be distorted in shape.

What you need is a reproducible clean peak of an unretained solute for validatable calculations.

If validation is an issue, then you would definitely need to use an unretained solute for K' calculation. For a C18 column, uracil is commonly used.

The best thing to do would be to check the test chromatogram and certificate of analysis that should accompany every column on purchase. These documents would tell you all need to know about the column and its validation protocols.

If you don't have these for your column, the original vendor would provide them, if you tell him the column's serial number.

Rgds

[HW Mueller]

This was all discussed not too long ago. I use tritiated water for reverse phase columns. Uracyl can have considerable retention in esp. "aqu" type columns, NO3- may do an ion exclusion, organic modifyer could be retarded. I can imagine that even T2O could show an interference with some stat. phases, nothing seems perfect. It doesn´t harm to compare these measurements with empirical-mathematical estimations of "dead time".