Chromatography Forum

Hi Chromatography community. I am requesting some help in deciding a debate we are having at work regarding calibration curves and standards for standard Anions (F, Cl, NO2, NO3, Br, PO4, and SO4).

The debate is whether a blank or Zero point should be run as calibration standard one. The way things have always been is to run a blank as calibration standard 1 and then follow with our normal standards. With the purchase of some new instrumentation, the company has said a zero point is not necessary, and not a good practice to do. The methods we run are EPA 9056 and 300.0. The way the methods are written leaves the argument open for debate. I am wondering what the community here thinks.

Hi Akurth,

I'm not sure that including a true blank in the calibration is a "poor practice," as your management indicates (it depends on exactly what you're doing), but I can't see that it's necessary to put a true blank in the calibration, either. Seems to make sense to show that the water (a reagent blank) you're using is free of interference(s) or anions you're interested in measuring, but you don't need to include such an injection in your calibration.

Let's see what others think...Best Wishes!!

By the way, there's a good discussion about this very same issue...as well as "forcing zero," in the Student Projects section right now. It's worth a look--many comments.

Hello,

In our lab we run a blank before the calibration, but it is labeled as an unknown, not as a calibration standard. I don't believe it is necessary to run the blank as an actual standard, but it's good practice to include a blank before your calibration.