System Suitability - LC/MS Requirement

[AThompson]

I was wondering what value is generally used for % RSD requirement for system suitability? For LC-UV, it seems most people use a requirement of 1-2% RSD across 5-6 replicate injections of the assay standard. Where do most labs set the % RSD requirement for LC-MS system suitability? Thanks for any suggestions.

[tom jupille]

There is no single answer to that: it depends on the purpose of the analysis.

For QC, the uncertainty in the measurement must be substantially less than the variability of the process or product being measured. You can use the Wheeler "Discrimination Ratio" as a guide for how much uncertainty you can tolerate (D. J. Wheeler and R. W. Lyday (1989). Evaluating the Measurement Process, Second Edition. SPC Press, Inc.).

The same concept applies if you are simply trying to measure something without controlling a process or product (e.g., bioanalytical or environmental analysis): what is the purpose of generating the information, and how precise does it have to be to be suitable for that purpose?

[AThompson]

Thanks for the response... How about this question: What % RSD of peak area do most users here obtain across 6 replicate injections of an analytical standard when using ESI LC-MS? At least compared to LC-UV, I don't seem to get anywhere close to 2% RSD. I'm often seeing results more in the range of 3-8% RSD. Wondering what the experience of others is - thanks so much!