It's called PMI; psoitive material identification.
There pretty expensive devices (in the EU they can easily cost 35k euro's), and are not 100% accurate/reliable, but I believe theyre accurate enough to determine if a Chinese stainless steel pipe really complies with the certificate ...
Ive seen them in action once and it's pretty impressive.
ARC-MET8000 from Dynatech will also "do" carbon content. It will leave a small plasma mark at the spot tested. Carbon content requires a tiny sample to be evaporated.
The Niton 'guns' use X-Ray Fluorescence, and leave no marks. But no carbon analysis.
There are also slightly bigger, but more accurate device (size in the range of a compact GTAW device). They're more accurate than PMI, and I believe they also do carbon content,