Is there any variable in UV detectors, which give equal or better scanning speed than PDA detectors? What is the scanning speed of the different systems?
I recommend u this article
http://www.hwe.oita-u.ac.jp/kiki/ronnbunn/paper_choi.pdf
Advantages of Photodiode Array
Hun Choi
SCINCO. Co., Ltd.
74-27 Nonhyun-dong, Kangnam-ku, Seoul, Korea, 135-010
You cannot scan/acquire the whole absorption spectrum of the molecule with the conventional UV detector during the chromatographic run. Did you mean acquisition rate of the two detectors? As far as I know both detectors can have very fast acquisition rates of up to 80Hz, which is more than enough for 99.9 % of applications.
To acquire the full spectra you need a DAD or a PDA - which are both doing essentially the same thing, but the manufacturing companies decided to call them differently. Both detectors emply an array of diodes - a given number for a given wavelength interval. So the detector will measure the absoption per wavelength (therefore per diode). The speed can be set up from the software (as previosly mentioned in an aswer, the acquisition rate), with certain limitations - related to the software and to the capability of your processor. Also some softwares have the option of acquiring spectra for the entire length of the run, only for peaks, only every other spectra, etc. Make sure also that this specific setting is marked according to your specific needs.
Also, keep in mind that acquiring entire spectra at 80Hz througout the entire chromatographic run may produce very, very large data files.
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