By zetto on Tuesday, August 10, 2004 - 05:18 am:

Hi all
What is the purpose of a surrogate in a method which there's already a internal standard added ? In other words what's the difference between the two ?
Many thanks
Z

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By Mark on Tuesday, August 10, 2004 - 09:03 am:

Zetto,
I used to work for an environmental analytical lab and we used CLP protocols for analysis. They called for a "surrogate" to be added to each sample prior to extraction. This compound was then subjected to all the same conditions that the sample went thru, extraction, clean-up, concentration, etc. Just before analysis the samples had an internal standard added to them. The surrogate was to evaluate the recovery of analytes during preparation and the internal standard was used to correct for any variation in injection volume.

Hope this brief comment help,
regards,
Mark

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By zetto on Tuesday, August 17, 2004 - 11:24 am:

Thanks Mark much appreciated !