Spectrography

Spectrography is a form of sensor technology used to detect chemical elements by means of comparing scans to the visual spectrum.

This form of technology was used by the geological lab aboard the USS Enterprise (NCC-1701) in 2254 to determine what elements would be encountered on the surface of Talos IV. Spectrography scans determined in the preliminary lab survey that Talos had an oxygen-nitrogen atmosphere, with a surface heavy with inert elements. 

In 2265, Doctor Leonard McCoy had the lab run a bio-analysis Enterprise crewmembers who had become infected with polywater intoxication. The lab's spectrography readings showed no contamination, nor any unusual elements.