Multi-channel array detectors

In US-A-4618763 a detector module is disclosed which is formed of stacked multi-channel integrated circuits, a detector array and a module header interface. The detector array and the module header interface are disposed transverse to the plane of the integrated circuits on opposite edge portions of the integrated circuits. Each integrated circuit is formed in a semiconductor material which has been deposited upon a thin sapphire wafer. 

Rapid-scanning Spectrophotometers. These en loy multi-channel detectors. The most commonly encountered detector of diis t e is tlie linear photodiode array. The reversed-optics mode is employed, so that radiation is passed throu tiie sample or reference cell, tiien dispersed by a dif action grating polychiomator integrated intensity of radiation incident on it which is determined by tiie spectial dispersion photo ode ratio. If, for example, a 200-nm txmdwidtii of radiation were dispersed across 256 photodiodes, tiie nominal resolution per photodiode woitid be 0.78 nm. 

Electrochemical detection is very sensitive for the compounds that can be oxidized or reduced at low-voltage potentials. Therefore, it could also be applied in the HPLC analysis of phenolic acids that are present in natural samples at very low concentrations. With the recent advances in electrochemical detection, multi-electrode array detection is becoming a powerful tool for detecting phenolic acids and flavonoids in a wide range of samples. The multi-channel coulometric detection system may serve as a highly sensitive way for the overall characterization of antioxidants the coulometric efficiency of each element of the array allows a complete voltametiic resolution of analytes as a function of their reaction (redox) potential. Some peaks may be resolved by the detector, even if they are unresolved when they leave the HPLC column. ... 

The crowned isoluminol 1 has been prepared by the route shown in Scheme 1 and confirmed by NMR, IR, UV-VIS spectra as well as HRMS. The chemiluminescence spectra were recorded on a multi-channel photodiode array detector (Hamamatsu Photonics). 

Complete MCP s can be stacked to provide even higher gains. For response in the vacuum ultra-violet spectral region (50-200 nm) a SSANACON, self-scanned anode array with microchannel plate electron multiplier, has been used (36). This involves photoelectron multiplication through two MOP S, collection of the electrons directly on aluminum anodes and readout with standard diode array circuitry. In cases where analyte concentrations are well above conventional detection limits, multi-element analysis with multi-channel detectors by atomic emission has been demonstrated to be quite feasible (37). Spectral source profiling has also been done with photodiode arrays (27.29.31). In molecular spectrometry, imaging type detectors have been used in spectrophotometry, spectrofluometry and chemiluminescence (23.24.26.33). These detectors are often employed to monitor the output from an HPLC or GC (13.38.39.40). 

In another configuration of instmmentation, irradiation of white light onto the electrode surface and detection of reflected light by the use of a multi-channel detector (such as CCD or photo-diode array) through a grating monochromator makes multi-channel measurement possible [21]. 

A multi-channel spectrometer has a light source with shutter, a sample and reference compartment, a grating polychromator and a diode array detector (Fig. 4.9). 

All spectral elements are recorded simultaneously by the array detector, i. e. the measuring time with the shutter in its open position is very short The short illumination time permits the sample and reference positions to be positioned immediately after the light source. Multi-channel spectrometers may also be constructed as double beam instruments. For special measurements, e. g. rapid kinetic investigations, when the chopper frequency is too low with respect to the rate of... 

Modern conventional laser-Raman systems for recording spontaneous Raman spectra comprise essentially an appropriate source, some dispersing and collection optics and a sensitive detector. The two most common approaches are either single-channel detection using a photomultiplier in combination with a multi (double or triple) monochromator set-up, or a multi channel option with an array detector coupled to a spectrograph [12, 20, 21]. The recent commercial development of FT-Raman systems, either as standalone spectrometers or as FTIR adjuncts, has added to the armoury of techniques, and without doubt offers a cost-effective, rapid, readily applicable technique for a wide range of polymer studies [22-24]. 

For detection in the UV-visible region, photomultipliers or other photoelectric devices are used. Some instruments may use a multi-channel diode array detector. An array of typically 300 silicon photodiodes detects all the wavelengths simultaneously with a resolution of about 1 nm. This provides a great saving in time and an improved signal/noise ratio. 

In flow analysis, multi-detection is generally accomplished by resorting to multichannel flow analysers, and each channel incorporates a different dedicated detector. Another possibility is to take advantage of multi-parametric techniques such as ICP-OES, anodic stripping voltammetry and UV—visible spectrophotometry with diode array detection. A deeper presentation of this aspect is outside of the scope of this monograph. 

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