Emerging technologies in process NIR analyzers

In Sections 5.3.1 to 5.3.4 we have reviewed the main NIR technologies in successful current widespread use for process analytical technology applications. NIR is an evolving technology, however, and there are a number of recent developments which may in time prove significant. This is not the place for a detailed review of such technologies, but a brief overview for orientation will be provided. 

Section 5.3 described a number of alternative design and implementation strategies for near-infrared analyzers, suitable for operation in a process analytical environment. However, none of these analyzers can operate without a robust, maintainable and repeatable sampling interface with the process sample under consideration. In addition to this question of the optical interface to the sample, there is a whole wider area of concern, which is how far the particular sample interface is representative of the sample in the process as a whole. This complex issue is not addressed here, and is dealt with separately in Chapter 3. 

In terms of practicality the optical interface to the sample is certainly the most demanding aspect of all. It requires a number of issues to be addressed and clearly understood for each specific application to be attempted. These include  

The physical nature of the process stream. Is it single-phase or two-phase Is it liquid, solid, vapor or slurry What is its temperature and pressure at the sampling point, and how far can these be allowed to change during sampling What is its viscosity at the appropriate sample measurement temperature The chemical nature of the process stream. Is it at equilibrium (a final product) or is it to be measured mid-reaction Is sample transport possible, or must the sample be measured in situ Is it corrosive, and what material and metallurgical constraints exist  

The optical nature of the process stream. Is it a clear fluid or scattering, highly absorbing, diffusely transmitting or reflecting  

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