[rulba]

Hello,

I am sorry if this is asked in the wrong forum.

I am confused how People judge how their HETP tests fails by just looking at the test chromatography plot. I know about broadning and assymetry, but I heard that "cracks" often are observed before the chromatogram as a little shoulder and if the shoulder is observed after the spike, Then it is most often something Else.

Today I did a couple of HETP tests on commercial columns. It was done ising conductivity and low and high molar salt solutions. They Both failed and did not raise to the conductivity of the High molar salt when eluted. After the spike there was a shoulder on one of Them and a broadning after the spike of the other one.

Is it possible to find the reason from this?

I calculated h and As and their were around 6 and 2 respectively. So their were too broad and perhaps a "mixing champer" is formed due to bad storage of the columns.

But how Can our scientist judge if it should be repacked, cip'ed and retested from this chromatogram. Is it judged by being close to a normal spike or if the shoulder is placed in front of the spike or after?

Normally I would do a HETP test in the same direction as the chromatography to make it as realistic as possible, but we do it in the opposite direction (downflow). Is this normal?

Sorry for the Many questions, but I have trouble estimating what to when I receive my chromatogram. I know it has failed from my calculations, but what the consequence should be from this is difficult. It is expensive to unpack these columns and it could maybe amount in the same Price by just using it and possibly loose a little yield. But it depends of course also of the type of comumn used i.e affinity, cation etc.

Any thoughts explanations are very welcome.

Thanks alot.