Chromatography Forum

Hi everybody

I am looking for references or anybody experience on the use of switching columns valve to extract plasma samples prior to chromatography and MS/MS analysis.

Instead of using liquid liquid or solid phase extraction, we can filter or centrifuge the sample, inject in the " column " and after a one or two step cleaning, the sample goes to the LC-MS/MS system while the valve change the positiion and clean the " column" that will be ready for the next sample.
I am looking for a " system " that could run (extract) 1000 to 2000 samples.

Hope to hear from anybody soon.....
Maristela

I do this with a Shimadzu HPLC on a Sciex 4000. One pump to carry sample from autosampler onto first column. 6 port switching valve. Binary pumps to carry sample from extraction column (backflushed) onto analytical column.

wala

It's actually a fairly standard technique. Rheodyne has a diagram of essentially that approach on their web site:
http://www.rheodyne.com/products/fluidi ... /index.asp

VICI has a number of variations:
http://www.vici.com/support/app/2p_japp.php

John Dolan did a write-up of a similar approach in one of his LC Troubleshooting columns in LC-GC a couple of years ago:
LC-GC 22(4) 338-343 (2004) I think that one is available on the LC-GC web site (via the sponsors link at the top of the forum)

Here are some publications on the subject:

C. R. Mallet, Z. Lu, J. Mazzeo, U. Neue, “Analysis of a Basic Drug by On-Line Solid Phase Extraction Liquid Chromatography/Tandem Mass Spectrometry using a Mixed-Mode Sorbentâ€

I do this with a Shimadzu HPLC on a Sciex 4000. One pump to carry sample from autosampler onto first column. 6 port switching valve. Binary pumps to carry sample from extraction column (backflushed) onto analytical column.

wala

What columns and mobile phase or cleaning solutions did you use to do the extraction procedure ? Did you published ?

What columns and mobile phase or cleaning solutions did you use to do the extraction procedure ? Did you published ?

Not published yet. It should be in the JAOAC next year though. I don't think my exact method would be applicable to your situation, as my matrix is less complex than blood/plasma/urine. However, my extraction column is a Phenomenex Onyx Monolithic column (C18 25x4.6mm). I have been using new extraction columns as I notice an increased signal in one of my ions of interest (this is about every 300-350 injections).

Edit: my mobile phases are the typical LC/MS type: 5mM Ammonium Acetate and Water/Methanol.

Check the Dionex web site. A method like this is built into their Chromeleon software.

The valve setting is qutie standard now. The key is the pre column. Currently there are two types of columns that can trap small molecules and remove proteins from blood sample. One is restricted access material column (RAM) and the other is large pore column + high flow rate (a patented technique).

Yuu may have a look on website www.promochrom.com for more application information.