1) A dual beam system provides the correct answer, obviating the need for calibration against a standard.
2) The Olis DSM 1000 CD (based on the DeSa RSM monochromator) uses two matched 50 mm² gratings. These gratings can be any available gratings. That is, one might choose a pair blazed at 200 nm with 2400 lines/nm, or one might choose a pair blazed at 800 nm with 300 lines/nm. The choice of gratings determines current spectral range, spectral resolution, and bandpass. All Olis CDs use two matched photomultiplier tubes; these PMTs can be UV/Vis or red-sensitive, as the situation requires. For NIR work, InGaAs detectors are used.
3) There is no CD which can provide subsecond spectra other than those built around the DeSa monochromator.
4) Since all Olis systems can acquire spectral scans as a function of time, they are ideally suited for use in kinetic analyses. The 3D global fitting software provided with these systems is the fastest and most accurate and robust available in the world. This software uses the simplex method and matrix exponentiation to solve the rate equations describing the reaction being studied; these new (but in the literature) methods have no connection to outmoded methods such as Levenberg-Marquardt and numerical integration techniques. The Global approach can be applied also to situations wherein the spectral changes are induced by non-kinetic means, such as temperature and titration.
5) DSM 20 CD: Mechanical characteristics of its grating mount include 4 steps/nm; therefore, the 1200 line grating results in a spectral range of 170-700 nm and a resettability of 0.25 nm/step below 300 nm and 0.5 nm/step from 300-500 nm.
DSM 17 CD: Optimized for high resolution work and including a double prism grating design, the DSM 17 has an available range of 185-1700 nm resulting in a resettability of 0.05 nm/step to 800 nm and ~0.1 nm/step into the NIR.
DSM 1000 CD: Mechanical characteristics of our grating mount include 8 steps/nm; therefore, the 2400 line grating results in a spectral range of 170-450 nm and a resettability of 0.125 nm/step.
* Every CD spectrophotometer by every CD manufacturer is a single beam instrument, other than the three models by Olis, Inc. Thus, Them is every non-Olis CD.