Design of dual Beam multi-wavelength UV-visible absorbance detectors based on CCD

Abstract

Because the general multi-wavelength UV-Visible absorbance detector cannot avoid the noise and drift resulting from the intensity fluctuation of the light source, a dual beam multi-wavelength UV-Visible detector based on CCD was designed. The ray of light source is divided into a signal ray and a reference ray by the beam splitter after it passes through the chopper. The signal ray shines into the sample cell. The signal ray passing through the sample cell fails onto a concave mirror which focuses it onto a slot that is imaged on one portion of CCD by a concave grating. The reference ray is imaged on the other portion of CCD by the concave grating after the slot. The signal spectrum, the reference spectrum and the dark current of CCD can be measured on the same CCD under the cooperation of the optical system and accessorial circuits. The real-time compensation for the signal spectrum by using the reference spectrum and the dark current of CCD can effectively depress the noise and drift of the detector. The short-term noise is 10−5 AU and the drift is 10−4 AU/h.