Noise in atomic absorption flame spectrometry—a comparison between single beam and double beam instruments

Noise levels have been measured under a variety of conditions using comparable single and double beam instruments. At low absorbance, in the vicinity of the detection limit, the major types of noise are photon noise, flame transmission noise and lamp flicker noise. The precision at low absorbance is slightly better with single than double beam providing a blank correction is made before and after each sample measurement. At higher absorbances, analyte absorption noise is dominant and there is no difference in precision between single and double beam.