A generally applicable method is described for simultaneous measurement of reference and analyte spectral features which would not otherwise fall within the range covered by a single linear diode array detector. The method employs dual entrance slits on the spectrometer to cause two spectral windows to overlap on the detector. The method is demonstrated for fluorescence measurement of Rhodamine B in ethanol. Recovery of the spectral information from the overlapped spectra using a least-squares fitting procedure is demonstrated. The simultaneously recorded reference measurements are shown to be effective in correcting for excitation source intensity variation by comparing corrected and uncorrected excitation spectra and calibration curve data.
Jianxiong Zhu, Charles K. Mann, and Thomas J. Vickers, "Simultaneous Dual-Window Measurements with a Linear Photodiode Array Detector," Appl. Spectrosc. 42, 1567-1571 (1988)