Diode array detector spectral resolution

If needed, spectral analysis of light from the output beam can be achieved using a simple monochromator with a multiwavelength detector (CCD or diode array). The spectral resolution is determined by the size of the monochromator, the width of the entrance slit, the density and order of the grating, and the distance between individual elements in the detector array. Fast temporal analysis may be achieved using a fast detector such as a streak camera with picosecond or subpicosecond temporal resolution. 

The most advanced UV-vis detector that is used in HPLC is the diode array. Compared to its predecessors, the diode array generates a large amount of spectral information without compromising sensitivity or wavelength resolution. In order to discuss the properties of the diode-array detector, a brief historical description of its technological development is presented. 

The SERS measurements in the visible spectral range were obtained using a triple monochromator unit MOLE S 3000 (Instruments S.A./Jobin Yvon). The spectrometer consists of a double monochromator DHR 320 (600 grooves/mm), a main monochromator HR 640 (600 or 1800 grooves/mm), a diode array detector (E-IRY 1024), and a microscope (Olympus BH 2) with CCD camera and monitor. The microscope focuses the radiation of the laser (488 and 514 nm model 2020-03 Ar ion laser 633 nm model 127 HeNe laser, both Spectra-Physics) onto the sample giving a spatial resolution of 1 /im. The spectral solution is 8 1/cm. 

In contrast, diode array based instruments, popular as relatively low cost spectrometers, have a reverse arrangement by having the dispersion of wavelengths post-sample by a dispersive optic (e.g. a diffraction grating) which irradiates the diode array detector with the spectrum across its elements. Whilst commercially available diode array instruments are invariably of lower optical quality than the best scanning instruments, and are limited by their spectral resolution through the number of elements in their array, they do offer the advantage of rapid spectral acquisition as the complete... 

A modern spectrophotometer (UV/VIS, NIR, mid-IR) consists of a number of essential components source optical bench (mirror, filter, grating, Fourier transform, diode array, IRED, AOTF) sample holder detector (PDA, CCD) amplifier computer control. Important experimental parameters are the optical resolution (the minimum difference in wavelength that can be separated by the spectrometer) and the width of the light beam entering the spectrometer (the fixed entrance slit or fibre core). Modern echelle spectral analysers record simultaneously from UV to NIR. 

Diode resolution is an important consideration in a PDAD detector. It is calculated by dividing the wavelength range by the number of diodes in the array. This, in combination with the optical resolution, will affect the spectral resolution of the instrument (i.e., the wavelength in nm, between data points in an acquired spectrum). (Operation and Maintenance of the ZQ with MassLynx, Waters Corporation.)... 

Spectral resolution is a measure of the separation between two adjacent wavelengths. The two adjacent peaks are said to be resolved when the minimum absorbance between the two peaks is 80%i or lower of the maximum absorbance. Most double-beam spectrophotometers have resolution below 0.5, typically 0.1. However, many diode array and rapid scan spectrophoto-metric detectors have resolution between 1 and 2 nm. 

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