Chemical control, automation

THEORY AND APPLICATIONS IN AQUEOUS AND NON-AQUEOUS MEDIA AND IN AUTOMATED CHEMICAL CONTROL... 

Electroanalysis. Theory and Applications in Aqueous and Non-Aqueous Media and in Automated Chemical Control... 

Electroanalysi3 theory and applications in aqueous and non-aqueous media and in automated chemical control. 

There may be circumstances in which an electroanalytical method, as a consequence of the additional chemicals required, has disadvantages in comparison with instrumental techniques of analysis however, the above-mentioned advantages often make electroanalysis the preferred approach for chemical control in industrial and environmental studies. Hence, in order to achieve a full understanding of what electroanalysis can do in these fields first, it will be treated more systematically in Part A second, some attention will be paid in Part B to electroanalysis in non-aqueous media in view of its growing importance and finally, the subject will be rounded off in Part C by some insight into and some examples of applications to automated chemical control. 

Continuous analysis offers another very useful possibility of completely automated chemical control, especially in manufacturing processes, but also in analytical processes such as separational flow techniques where the analytical measurement proper acts as a sensor, usually called the detector. As long as a physical or physico-chemical constant yields a sufficiently accurate and specific... 

The character and the degree of automation in chemical control may have been covered in the above treatment of semi-automatic or completely automatic, and of discontinuous or continuous analysis, but something more should be said about the means by which automation proper has been performed in recent times. Whereas in the past automated analysis involved the use of merely, mechanical robots, to-day s automation is preferably based on computerization in a way which can best be explained with a few specific examples. Adjustment knobs have been increasingly replaced with push-buttons that activate an enclosed fully dedicated microcomputer or microprocessor in line with the measuring instrument the term microcomputer is applicable if, apart from the microprocessor as the central processing unit (CPU), it contains additional, albeit limited, memory (e.g., 4K), control logics and input and output lines, by means of which it can act as satellite of a larger computer system (e.g., in laboratory computerization) if not enclosed, the microcomputer is called on-line. 

Earlier in this chapter we considered the nature of chemical control (Section 5.1), the character and degree of automation (Section 5.2) with the choice between discontinuous and continuous analysis, the role of electroanalysis in automated chemical control (Section 5.3) and automated electroanalysis in laboratory control (Section 5.4). 

The HP 6890 series GC gas-samphng valve technology, in conjunction with programmed interval sampling, makes this type of GC-based quahty-control automation a reahty. The GC can control and sense the position of multi-position valves to make it possible to automate sample-stream selection. Each sample, which is downloaded automatically, can then be analysed by a different method. Automated analysis of multiple process streams is especially attractive and cost-effective for complex chemical and petrochemical operations in which raw materials for product streams need to be assessed at regular intervals. 

E. A. M. F. Dahmen, Electroanalysis theory and applications in aqueous and non-aqueous media and in automated chemical control, Elsevier, Amsterdam, 1986. 

Robert Fretz joined F. Hoffmann-Fa Roche more than 30 years ago as a chemical engineer. He is presently responsible for Process Automation in all chemical and galenical manufacturing sites and leads the corporate Mamrfacturing Execution systems program. Mr. Fretz has broad international experience in all levels of control/automation projects from instrumentation to the enterprise level. Many of these projects included computerized system validation. He co-authored the Hoffmann-Fa Roche corporate guideline on Process Automation Qualification. 

For routine syntheses of labelled compounds, automated procedures have been developed which enable fast, safe, reproducible and reliable production. Automation has found broad application for the synthesis of radiopharmaceuticals. All steps must be as efficient as possible. For that purpose, target positioning and cooling, irradiation, removal of the target after irradiation, addition of chemicals, temperature and reaction time, purification of the product and dispensing are remotely controlled. Automation may be aided by computers and robotics may be apphed. 

Theoretical studies (Adloff and Guillaumont, 1993 Guillaumont et al., 1989, 1991) have shown that it is valid to combine the results from many identical experiments in which only a single atom was present to obtain information about chemical behavior although it may be necessary to repeat the identical experiment hundreds of times to obtain statistically significant results. Thus, computer-controlled automated systems become especially attractive. Although they are not necessarily... 

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