Surrogate QC mixture?

[thohry]

In some analytical methods, besides QC mix , Internal Std mix.. there are QC surrogate mixture. What is really its purpose?

Thanks for any help.

[bluejay]

In my experience the purpose and terminology of surrogates/internal standards seem to vary method to method.

I used to run some EPA GC methods that involved a lengthy extraction procedure prior to analysis (551 and 552). In these, there was a surrogate standard that was added at the beginning of the extraction process. It's purpose was to monitor variations in the extraction and the analysis. There was also an internal standard that was added to the final extract immediately before analysis. This was used to monitor just the instrument analysis, and was also used for in the internal standard calibration.

I hope this helps.

[thohry]

In my experience the purpose and terminology of surrogates/internal standards seem to vary method to method.

I used to run some EPA GC methods that involved a lengthy extraction procedure prior to analysis (551 and 552). In these, there was a surrogate standard that was added at the beginning of the extraction process. It's purpose was to monitor variations in the extraction and the analysis. There was also an internal standard that was added to the final extract immediately before analysis. This was used to monitor just the instrument analysis, and was also used for in the internal standard calibration.

I hope this helps.

Thank you. It really helps me.