Chromatography Forum

We are being asked to have PQLs of 0.08 ug/l for most VOCs by EPA 624. Any suggestions?

Thank you.

Just say no.
Realistically, while some targets may achieve an MDL of 0.08 ug/l on a clean system, unless your samples are very clean and something close to magic happens you won't see a PQL that low especially across the board. This is a wastewater method after all. Drinking water maximum contaminant levels are higher than that, at least in the US.

Just say no.
Realistically, while some targets may achieve an MDL of 0.08 ug/l on a clean system, unless your samples are very clean and something close to magic happens you won't see a PQL that low especially across the board. This is a wastewater method after all. Drinking water maximum contaminant levels are higher than that, at least in the US.

I'm working with VOCs on water recently and i couldn't say it better. He's right, even if you can go that low on concentration there is too much contamination risk to obtain good performances, at that level.

Who's asking and to what end. I'm running 524 and could not get down to 0.08!

The industry would need to move to a more expensive approach to achieve these limits. The current approach is limited where we strip the VOAs out of 5 to 25 ml of water, then discard 90 to 99 percent of the analyte in order to introduce them to the detector. Things have really gone backwards in this respect.

The approach used for air cans retains all the sample, but uses relatively expensive and balky techniques to remove the water and carbon dioxide. Of course, at lower levels, absorbtion and carry-over are bigger problems than detector sensitivity. There is a lot of crappy data out there for some of the heavier analytes.

Better techniques exist, but they are more expensive and cannot compete with the lab that justifies reporting the latest lower limits with an unrealistic MDL study. It all gets a bit frustrating.