Working of photodiode
How does photodiode work : A photodiode array (PDA) is a linear range of discrete photodiodes on an integrated circuit (IC). For spectroscopy it is placed at the image level of a spectrometer to allow simultaneous detection of a wavelength. In this sense, it can be considered an electronic version of the photographic film. Array detectors are particularly useful for recording total UV absorption spectra of samples that pass through a sample flow cell, such as an HPLC detector.
Diagram of a PDA (Photodiode arrays)
Photodiode array detector
DAD differs from that of the UV-VIS light detectors that the light illuminates directly on the flow cell, the light passing through the flow cell is dispersed by the diffraction grating and the amount of diffused light is estimated for each wavelength of the photodiode array.
Photodiode devices (semiconductor devices) are used in the sensing unit. A DAD detects absorption in the UV-VIS region. While a UV-VIS detector has only one section to receive light, a DAD has multiple (1024 L-2455 / 2455U) to obtain information on a wide range of wavelengths at a time, which the Father deserves.
The idea is that spectra are measured at intervals of 1 second or less during HPLC separation of the eluate with continuous delivery in photodiode arrays. If the measurement is made at a fixed wavelength, only the components are identified by the retention time; therefore, a small deviation during retention can make identification of the components difficult. In this case, the DAD can be used to identify components by comparing the spectrum.
DADs (pda detector) differ from UV-VIS detectors in the light from which light shines directly onto the flow cell, the light passing through the flow cell is dispersed by the diffraction grating and the amount of diffused light is estimated for each wavelength in the photodiode of the matrix.
How does a diode array spectrophotometer work
Diode array is particularly useful for spectrophotometer applications where light scattered by a prism is irradiated onto the array and intensity. When a light source emits electromagnetic radiation evenly in this area, the emitted light appears white. White light is a composition of many wavelengths of light.
This is easily demonstrated by separating it into its component colors (wavelengths) by refraction or diffraction. The CCD array spectrometer operates in a similar manner, except that a tungsten lamp as a light source and a linear CCD array with 2048 pixel elements serves as a detector.
Compared to a UV-VIS detector, the DAD (pda detector) has the following disadvantages:
The noise is high because the amount of light is small; The DAD is also susceptible to various modifications, such as fluctuations in the lamp, since the reference light can not be received. However, the DAD has recently been improved to reduce the performance gap with UV-VIS detectors.