Wavelength selectors, types

The atomization cell is the site were the sample is introduced the type of atomization cell can vary (flame or graphite-furnace) but essentially it causes the metal-containing sample to be dissociated, such that metal atoms are liberated from a hot environment. Such an environment of the atomization cell is sufficient to cause a broadening of the absorption line of the metal. By utilizing the narrowness of the emission line from the radiation source, together with the broad absorption line, means that the wavelength selector only has to isolate the line of interest from other lines emitted by the radiation source (Figure 11.9). This... 

Instrumentation capable of acquiring data in a multidimensional format using parallel detectors is similar to that of conventional spectrofluorimeters. The major differences are the type of detector, light source, and wavelength selectors used. In a conventional fluorimeter, a photomultiplier tube is used as... 

A schematic block diagram of the instrumentation used for AAS is shown in Figure 6.3. The components are similar to those used in other spectroscopic absorption methods as discussed in Chapters 2 and 5. Light from a snitable source is directed through the atomizer, which serves as the sample cell, into a wavelength selector and then to a detector. The detector measnres how much light is absorbed by the sample. The sample, usually in solution form, is introdnced into the atomizer by some type of introduction device. The atomizer converts the sample to gas-phase ground-state atoms that can absorb the incident radiation. 

In the classic AAS instruments, the radiation source usually consisted of a lamp with a filament (or hollow cathode) made of, or coated with, the same element that is to be determined so that there is a resonant absorption of the emitted photons. The detector used in this system can be a simple photomultiplier and an optical filter is often used to improve specificity. There are other types of photon sources, especially in modem instruments, where several wavelengths can be simultaneously anitted and detected. A wavelength selector is positioned in front of the detector in order to distinguish the absorption of the different elements (wavelengths). 

A General Designs of Optical Instruments 164 7B Sources of Radiation 166 7C Wavelength Selectors 175 7D Sample Containers 190 7E Radiation Transducers 191 7F Signal Processors and Readouts 202 7G Fiber Optics 202 7H Types of Optical Instruments 203 71 Principles of Fourier Transform Optical Measurements 204 Questions and Problems 212... 

Normally, the chiral pollutants in the environment occur at low concentrations and therefore a sensitive detection method is essential and is required in chiral CE. The most commonly used detectors in the chiral CE are UV, electrochemical, fluorescence, and mass spectrometry. Mostly, the detection of the chiral resolution of drugs and pharmaceutical in CE has been achieved by a UV mode and therefore the detection of the chiral pollutants may be achieved by the same method. The selection of the UV wavelength depends on the type of buffer, chiral selector, and the nature of the environmental pollutants. The concentration and sensitivity of UV detection are restricted insofar as the capillary diameter limits the optical path length. It has been observed that some pollutants, especially organochloro pesticides, are... 

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