Chemical control, automation continuous analysis

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). 

Since 1970, new analytical techniques, eg, ion chromatography, have been developed, and others, eg, atomic absorption and emission, have been improved (1—5). Detection limits for many chemicals have been dramatically lowered. Many wet chemical methods have been automated and are controlled by microprocessors which allow greater data output in a shorter time. Perhaps the best known continuous-flow analy2er for water analysis is the Autoanaly2er system manufactured by Technicon Instmments Corp. (Tarrytown, N.Y.) (6). Isolation of samples is maintained by pumping air bubbles into the flow line. Recently, flow-injection analysis has also become popular, and a theoretical comparison of it with the segmented flow analy2er has been made (7—9). 

Integrated Raman systems can be classified as instruments designed for the research laboratory, for routine analysis, for process control, and for portable, field-deployable applications. Research laboratory instruments offer new and state-of-the-art capabilities in exchange for compromised reliability and frequent need for support from a Raman expert. Research laboratory instruments are extremely adaptable to address unanticipated measurement needs. Routine analysis instruments provide limited flexibility with good reliability. They are operationally simple and contain enough Raman expertise built in for technicians to carry out repetitive assays efficiently and reliably. Process control instruments are typically fiber optic Raman systems that have been hardened to perform in the more challenging environmental conditions typical of a chemical production facility. A process control instrument usually runs continuously in a fully automated mode. There... 

Titrimetry is one of the oldest analytical techniques, originating in the middle of the eighteenth century as a rapid means of quality control of industrial processes, such as acid manufacture. Since that time, the equipment has been refined, the procedures have been automated, and the number of chemical reactions utilized greatly increased, but the basic principles are unchanged. Its continued popularity stems from the simplicity of equipment and execution, wide applicability, and high accuracy and precision (greater than most instrumental techniques), all of which make it particularly applicable to the determination of major and minor components of samples. Skilled titrimetric analysis should give results with a precision of <0.2% at the 1 X 10 moll level. 

---