Chromatography Forum

Morning everyone,
I've recently developed several dilute and shoot assays for quantification of drugs in urine. Fairly straight forward procedure, 100ul urine, 300ul acetate buffer, 5ul ISTD's, centrifuge, and run on the LC. After two weeks for running 150-200 samples a day, i'm noticing that my backpressure is rising gradually. Two weeks ago my starting pressure was about 150 bar, today it's about 400 bar. I'm running on an Agilent 1290 with a 1200 bar limit, so I have plenty of overhead, but i'm looking for any advice on maintaining the lifetime of my columns. I know i'm going to be replacing them more frequently than columns that extracted samples run on, but how much more frequently? Also, i'm changing the inline filter regularly and I know that's not clogged, because were running on two columns with the automated column regeneration setup. I've got roughly the same pressure across both columns (the analytical column with the inline filter in the flow path, and the column undergoing reneration). Any advice you can offer would be much appreciated.
Thanks,
Chemboy831

We filter all samples, dilute and shoot consumer products though. We use either guard cartridges or inline frits before our columns. Many columns can be reversed and washed out with high organic to restore lower pressures, check with column manufacturer.

You still may be saving a lot of extration labor costs that even reduced column lifetimes are still economically advantageous for you.

Hello,

Have you had any trouble replacing the frit in your in-line filter for the Agilent 1290? I tried changing ours for the first time today, but the frit seems to be very tightly stuck to the frit holder and I cannot remove it. Maybe it is a result of the high pressure? Do you have any tricks for easily removing the frit? Any advice you have would be greatly appreciated.

Thank you.

we use this approach, allows you to do much more injection on the column;
http://www.sielc.com/upload/file/pdf/SI ... r_2004.pdf