Had the chance to visit a lab today with an XRF and a GDMS. It was very interesting. Even though I’m an organikker by training, I have to say that I really dig haunting other parts of the periodic table. Organic chemists are spoiled by the splendid richness of multinuclear, multidimensional NMR. But when you stray from C,H,N, & O, composition and structure can become much more problematic.
The XRF samples were prepared as a lithium borate fusion in a Pt mold in the muffle furnace. The vitreous buttons were then placed in the instrument sample station. One of the problems with XRF, like any other kind of spectroscopy, is the occasional interfering peak. But, like the famous British philosopher M. Jagger once said, you can’t always get what you want.
The GDMS was a sight. This instrument is sensitive to sub ppm levels all over the periodic table. At this level, just about everything shows up to some extent. The concept of purity becomes muddied a bit, at least for mining samples. For most things there aren’t good standards at this level. You have to trust in the linearity of the instrument and be happy with 30 % error.