Hi all. Can anyone give me reasons why RSD would be high (For HP/Agilent systems)? I'm trying to compile a list for analysts in our lab and I want to make sure I haven't left anything out. I'd appreciate your thoughts/comments.

Steve

Some things to look for:

1. Is the RSD different for peak height versus peak area measurements? If so, that points at either detector or column overload problems, or possibly separation problems (pH?)

2. Is the RSD dependent on the mass of analyte (keeping injection volume constant); i.e., does your RSD get significantly worse as the sample load decreases? If so, that points to S/N or integration problems.

3. Assuming you have more than one peak in your separation, measure the RSD of the ratio of areas of two peaks. If the RSD of the ratio is significantly better than the RSD of the individual peaks, that points to injection volume problems.

I'm sure others will chime in with additional suggestions, but hopefully this will be a start.

Also, there is a very thorough "if . . . then" troubleshooting checklist in the Dolan and Snyder book "Troubleshooting LC Systems". You can check our web site at http://www.lcresources.com/books.htm.


--Tom Jupille / LC Resources Inc.

If the system is in good working condition, you should have no problem of obtaining %RSD of 0.5 or much better. If you are not sure whether the problem is with your methodology or the insrument, you should conduct an autosampler test, described in the operator's manual for performance verification check.