An instrument for measuring circular dichroism simultaneously at all wavelengths in a limited spectral range

An instrument is described for the simultaneous measurement of circular dichroism at all wavelengths in a limited spectral range. A polychromator and a charge‐coupled device (CCD), serving as multichannel sensor, are arranged behind the sample cell, which is located close to the entrance slit, in contrast to the arrangement of a monochromator before the cell and using a photomultiplier as radiation detector, as usual until now. The CCD with low‐noise electronics is driven by the system clock of a microprocessing unit controlled by a quartz oscillator and works fully synchronously with modulation and acquisition cycles. This leads to a high suppression of noise and systematic deviations. An electro‐optic modulator with approximately rectangular excitation voltage is used. Partial CD spectra over the range of 80 nm each down to 200 nm have been recorded. The detection of a smaller amount of substance is possible than with other modern commercial instruments such as a JASCO J‐600, with the same signal‐to‐noise ratio.