Process analyzers, sampling systems

The development of NeSSI is very much a collaborative result of end-users, manufacturers, researchers, and many others working together to modularize and miniaturize process analyzer sample systems. The technical and standardization concepts of NeSSI have been well documented through numerous presentations and workshops throughout the last four years, including yearly updates at ISA, PITTCON and FACSS conferences and updates at the biannual CPAC meetings. 

Sherman, R.E., Process Analyzer Sample-Conditioning System Technology John WiJey 8t Sons New York, 2002. 

This means for improvement concerns the experimental procedures that are used to collect and analyze the calibration samples. In PAC, sample collection can involve either a highly automated sampling system, or a manual sampling process that requires manual sample extraction, preparation, and introduction. Even for an automated data collection system, errors due to fast process dynamics, analyzer sampling system dynamics, non-representative sample extraction, or sample instability can contribute large errors to the calibration data. For manual data collection, there are even more error sources to be considered, such as non-reproducibility of sample preparation and sample introduction to the analyzer. 

There are many different ways in which the calibration strategy can be moved toward the favorable upper right comer of the relevance vs. accuracy plot. In most cases, these rely heavily on prior knowledge of the specific process and measurement system involved in the problem. Such prior knowledge can involve the process dynamics, process chemistry, process physics, analytical objectives, analyzer hardware, analyzer sampling system, and other factors. 

R. E. Sherman, Process Analyzer Sample-Conditioning System Techrwlogy, Wiley, New York, 2001. 

Determination of Na " and Na" ions in raw cosmetic materials was conducted with the developed method of flame photometry. A necessity of development of method of samples preparation arose up in the work process, as this spicily-aromatic raw material contained pectin in amount 0.1-0.5% and that prevented preparation of samples by standard method of extracts dilution and required incineration of analyzed sample, time of analysis was increased in 60 times. It was established that CaCl, solution with the concentration 0,4 % caused destmctions of the carbopol gel. It was established that the addition of 0,1% CaCl, and 0,1% NaCl salts solutions into the system intensified the effect of negative action of these salts onto the gel stmcture and the gel destmcted completely. 

In several chapters we discussed how the quality of the analytical result defines the amount of information which is obtained on a sampled system. Obvious quality criteria are accuracy and precision. An equally important criterion is the analysis time. This is particularly true when dynamic systems are analyzed. For instance a relationship exists between the measurability and the sampling rate, analysis time and precision (see Chapter 20). The monitoring of environmental and chemical processes are typical examples where the management of the analysis time is... 

For the purposes of instrument qualification, the PQ involves testing the equipment for overall system functionality. For dissolution equipment, these tests verify that the equipment can perform the entire dissolution process. A sample method should be observed to run properly. This can include running actual chemistry and analyzing the data results. 

First we will look at the question of stability in the z plane. Then root locus and frequency response methods will be used to analyze sampled-data systems. Various types of processes and controllers will be studied. 

In the last two chapters we have developed the tools to analyze sampled-data systems, both openloop and closedloop. The controllers we have considered have been mostly proportional and the processes have been openloop stable. 

Process analytics systems eonsist of the following components the sampling systems, the analyzer(s), automation as well as a data management system. These components must be carefully selected and tested during the design phase because each part profoundly affects all others. When designing an analyzer system, the following considerations should be addressed ... 

In this application, the process analyzer is used in the vis-NIR spectral region to measure the clear top layer on a co-extruded polymer film. The bottom layer is pigmented to an opaque white color and its thickness cannot be determined by this method. Prior to the installation of the fiber-optic spectroscopy system, film samples were measured manually in the laboratory by a subtractive scheme. First, the total thickness of a sample was measured on a manual profilometer. The top layer of the polymer was removed with methylene chloride. The sample was then repositioned on the profilometer as closely as possible to the originally measured spot and the thickness of the second white layer was determined. The thickness of the top layer was then determined by difference. 

This is based on a sample fast loop with a sample take-off probe in the main process line, and a retnm to either a pnmp-snction or ambient pressnre sample recovery system (Fignre 5.22). The fast loop provides a filtered slip-stream to the analyzer, along with flow control and monitoring (low-flow alarm), and freqnently some form of sample antograb facility for sample capture. The slipstream flow to the internal analyzer sample flow cell is relatively low volnme and allows for a very high degree of sample temperature control (typically... 

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