INFLUENCE OF THE SPECTRAL BANDWIDTH OF THE SPECTROMETER ON THE SENSITIVITY USING CONTINUUM SOURCE AAS

The influence of the spectral bandwidth of the spectrometer on the per formance of the spectrometer is of great importance in atomic absorpti on spectrometry using continuum source (CS-AAS). For a theoretical ana lysis of the detection of small absorbances two cases have to be taken into account: as long as the limiting noise of the signal is given by the detector noise an increase in spectral bandwidth of the spectrome ter implies an improvement in the limit of detection. In contrast, if the noise of the signal is dominated by the photon shot noise the dete ction limit should become independent of the spectral bandwidth. In th is case the spectral bandwidth of the spectrometer should be chosen eq ual to the bandwidth of the absorption line to avoid spectral interfer ences. Theoretical calculations are presented for the dependence of th e characteristic mass on the spectral bandwidth in case of CS-AAS meas urements. The results are compared with experimental measurements for six different elements using continuum source as well as line sources. The investigations were done using a double echelle monochromator (DE MON) which offers a high spectral resolution lambda/Delta lambda of ab out 140,000.