Discrete automatic analysers

These analysers resemble hquid and gas chromatographs, although their background is markedly different. They differ from discrete automatic analysers (DAA) in various respects, namely the fashion in which samples are transported and mixed with diluents and reagents, the manner in which carry-over between samples and reagents is avoided and the type of detection used. 

Figure 6.5 Transparent analytical test pack (100 mm X 80 mm) for Du Pont aca analyser containing all the reagents for the assay of glucose. A wide range of test packs is available for use in the automated discrete analyser. Once the pack is loaded into the instrument, sample and diluents are automatically injected. The sealed reagent compartments are then broken open at various stages in the assay and the contents of the pouch are mixed and incubated. The transparent pouch then serves as a cuvette for absorbance measurements.

K3. Kamp, H. H., Luderer, T. K. J., Muller, H. J., and Sopjes-Kruk, A., Rapidimmunoturbidimetric assay of albumin and immunoglobuUn G in serum and cerebrospinal fluid with an automatic discrete analyser. Clin. Chirrr Acta 114,195-205 (1981). 

Since ISEs can be used in continuous flow systems or in flow systems with sample injection (flow injection analysis, FIA)21 their application is wide, not limited to discrete samples. Analysis time becomes shorter, with faster recycling. Additionally, in flow systems the experimental assembly and data analysis can be controlled automatically by microcomputer, including periodic calibration. Another development is the use of sensors for the detection of eluents of chromatographic columns in high-pressure liquid chromatography (HPLC). Miniaturization has permitted an increase in the use of sensors in foods, biological tissues, and clinical analyses in general. 

The simplest application of these multiplexing methods involves the so-called direct-reading spectrometer , which was used with some success for a short period in atomic spectroscopy [42]. This instrument consists of a dispersion system with an array of exit silts arranged at appropriate locations. Behind each silt Is a photodetector —usually a photomultiplier. These multiplexing methods have also been used In UV-vIsIble spectroscopy, although to a lesser extent they have been Implemented on automatic discrete analysers featuring an optical system of this type with 5-10 channels or wavelengths... 

We discuss in this chapter analysers that arc highly automated, such as flow injection and discrete analyzers. In addition, laboratory robotic systems that are becoming more and more commonplace for sample handling and preparation arc also described. The latest advances in automation involve the development of microlluidic systems, which are sometimes called lab-on-a-chip or micro total analysis systems. These recent developnienis are also described here. It is important to note that the same principles of automatic analysis discussed here also apply to process control systems, which analyze the current state of a process and then use feedback to alter experimental variables in such a way that the current state and the desired state are nearly identical,... 

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