What value is "acceptable" for a carry over?

[crlar]

I know that the question looks too "general" and depending on the analysis, concentrations, etc but I am very interested in knowing the "real" values that the users of analytical HPLC with autosampler (specially, Gilson 233XL) have and accept for carryover (the % of signal of the compound of interest you have injecting a blank after a sample).



Thanks in advance

[syx]

Carryover is accepted when it is not occurred.

[AA]

Several things to think about. All autosamplers carryover at some level, sometimes you just can not measure the carryover. So what is acceptable? It really depends on the nature of your assay. Example: If you analyse for content uniformity and the specification for the final product is plus or minus 10% then a carryover of 0.01% really would never impact that assay. On the other hand, ifyou are interested in a yes or no answer (is my compound there or not) then a very low carry over (0.001%) would be of benifit. As many things in LC, there in no single answer.

AA

[crlar]

As you say, AA, all depends on the nature of the assay. But at the present moment I have a problem with my injector and I have not any reference value to compare with in order to ask for a corrective maintenance...
I began to check for carryover about one year ago, and my instruments have values between 0.5%-5%, depending on the analysis and instruments (two HPLC-MS/MS with the same model of injector: Gilson 233XL)...I suspected this was a really high value, but we could continue working due to the caracteristics of the assays.
But now I need more clean blanks, and I am trying to get a "reference" or "normal" value and I thought of collecting values of other users of these injectors...

[tom jupille]

That's high. Based on my experience, you should be well under 0.1%

[AA]

0.5-5%, ouch, that is way high. Often, something is broken with the LC or wrong with the assay (wrong wash solvents, or sample binding to ports, stuff like that. Check the specs of your system, see if you can duplicate the vendors method to determine if the hardware is broken, and then go from there.

AA

[marc]

Yeah... that is way too high. Like Tom, I also used to work for Rheodyne. Some of the Gilson autosamplers had some issues and it is rarely the valve. There may have been a problem with a large dead volume in the connection from syringe to valve. Gilson came out with some newer schemes and you might check on it. If you reduce the system volume to a several microliters and rinse with at least 100 uLiters of strong solvent (~80%+ ACN) you should be getting less than 0.01% carryover.