The @E02040@ from the column is fed into a hydrogen-rich flame and produces light emission. Optical filters are used to select the @W06659@ range of the emission which is characteristic of specific atoms (usually sulfur or phosphorus). The detector is very specific, depending on the choice of optical filters. It can detect the S- and P-containing compounds down to \(10^{-3}\ \text{ppmv}\), but the detector is non-linear.