It is a bit more complicated than that. There are two classes of problems in spectroscopy: qualitative (trying to identify what the sample is) and quantitative

It is a bit more complicated than that. There are two classes of problems in spectroscopy: qualitative (trying to identify what the sample is) and quantitative (deciding concentrations of one or more analyte in sample). Qualitative is quite simple: each material have quite unique fingerprint and you match it against dataset. Quantitative is very very tricky. You have to pick good region of spectra and you have to pick good features (say peak areas or peak high). For complex solutions you will get a lot of peak overlaps and then you have problem with matrix effects for most samples (non-linearities caused by combinations of various compounds and so forth). Good news is that a lot of interesting things can be found in near infrared region, so you don't really need expensive diffraction gratings and delicate optics.