Photodiode Array detector, or PDA (Photo - Array) detector or DAD
A new uv Detector developed in the 1980s, the
Its working principle is as follows: light flow through a series of optical reflector in pool, came out from the liquid pool of light, then through spectroscopic system slit exposure to a group of photoelectric diode, real-time data collection system to record component of spectral absorption, 3 d three-dimensional spectra.
With a group of photoelectric diode detection at the same time through the sample all wavelengths of ultraviolet light, rather than one or several wavelengths, and ordinary ultraviolet-visible spectroscopic detector is different in the light of the flow cell is no longer a monochromatic light.It has the following advantages: (1) it is very convenient to have a chromatographic map of any wavelength.(2) a spectrogram of any time is equivalent to uv;(3) the function of chromatographic peak purity identification and spectral image retrieval can provide qualitative information of components.
Basic principle:
the complex color components selective absorption by sample pool and then enter the monochromator, illuminate in the diode array device, make each wavelength of light intensity into corresponding electrical signal intensity, component for absorption spectra of the component of the structure to obtain specific information, help to unknown components or determined the structure of the complex components.
A number of chromatographic workstations can draw two maps on a three-dimensional map and obtain a three-dimensional spectrogram, or a peak purity check.The purity of a certain chromatographic peak is indicated by the peak purity, and the higher the value is, the greater the possibility of a single peak is.The lower the number, the higher the probability of the peak of overlap, and the exploration of the separation conditions of the chromatographic method.With the development of stoichiometry, the combination of the chromatographic information and the corresponding spectral information can be processed by a certain mathematical model to solve the identification and quantitative problems of overlapping peaks.But the DAD detector is an order of magnitude less sensitive than the usual UA detector.Therefore, it is better to use UA detector when it is used for content determination or impurity inspection.