By Vlase Laurian on Friday, May 7, 2004 - 09:15 am:

Hello,
for LC/MS analysis, when the precipitation of plasma proteins with acetonitrile is not suitable (very low plasma levels of drug due 1:3 dilution), is possible to make a precipitation with perchloric acid (!non-volatile), but to "tell" MS system to divert the flow (first 2 minutes) from detector? I think that in the first 2 minutes the non-volatile percholic acid will be totaly removed from column to waste and after the MS process can occur normally.
What is your opinion about that? Have you experience whith that??
Thank you,
Vlase Laurian

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By Brent on Monday, May 10, 2004 - 07:48 am:

Depending on how much you add in your sample, it may not be a problem with a small injection volume. Setting the stream to divert should work too.

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By Anonymous on Monday, May 10, 2004 - 08:51 am:

how about using rotary evaporation after MeCN extraction to concentrate the drug?

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By Uwe Neue on Monday, May 10, 2004 - 04:08 pm:

A better and faster approach might be SPE. It allows enrichment and sample cleanup. Standard, simple, universally applicable procedures are around. Contact me if you want a procedure!

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By MG on Tuesday, May 11, 2004 - 10:33 am:

I have used the divert-valve trick for other nasty things (such as high salt concentrations), but not specifically for perchloric acid. I think it should work for perchloric acid.

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By jean-paul on Friday, May 28, 2004 - 10:12 am:

You can use different acids (triclhoracetic, perclhoric, sulfo salicilic or metaphosphoric). A comparative study of their precipitating properties appeared in Ther Drug Monitor 23 (2001) 542 Stempack et al and I confirm that a diverting valve between the column and the spectrometer is efficient to protect the detector.We work for four years like that without any problem.

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By walid on Friday, June 11, 2004 - 08:20 am:

Dear sir
how are you.Iwant to use perchoric acid as proteint preciptant to extract cyclosporin A from plasma.Is perchoric acid suitable this type of drug.

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By Patrick B. Kyle on Wednesday, June 23, 2004 - 11:43 am:

Try precipitating proteins with Seraprep reagent (Pickering Laboratories) followed by the addition of Seraprep Lithium Diluent to adjust the pH. I have used this successfully in my LC/MS/MS work.

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By Constantin Sychov on Wednesday, June 30, 2004 - 08:12 am:

You can possibly use SPE to easily remove perchloric acid, and in addition to make your sample cleaner.