On-line monitoring, of chemical

Mizrotsky, N. and Grushka, E., Use of system peaks in liquid chromatography for continuous on-line monitoring of chemical reactions, Anal. Chem., 67,1737,... 

A common method for on-line monitoring of chemical compositions is the use of FIA. This approach is in essence a miniaturised wet chemical laboratory analysis. The approach was developed in the 1970s to adapt existing measurement methods to the task of rapid measurements. Typically, small pumps, tubes and mixing chambers combine to produce a flowing solution that is subjected to analysis by optical or electrochemical means using essentially the same reagents as in a normal-scale analytical determination. The key to sensitivity with these systems is to prevent dispersion in the stream. There are opportunities for imprinted polymers in both the sample purification and the detection of analytes. 

High gas pressure NMR investigations in homogeneous catalysis have focused mainly on both on-line monitoring of chemical reactions and stabilization and identification of intermediates involved in a catalytic cycle. The following sections address these high gas pressure studies according to the gas used. 

On-line monitoring of chemical reactions encompasses on-stream and on-reactor applications of analytical methods to... 

W.-D. Hergelh, On-line monitoring of chemical reactions, in UUmanris Encyclopedia of Industrial Chemistry, 7th electronic ed Wiley-VCH Verlag GmbH, Weinsheim, 2006, http //mrw,interscience, wiley,com/emrw/9783527306732/ueic/ article/cl8 cOl/current/abstract. 

Postdoctorate Fellow at the TotalFinaElf and a year and a half as an associate researcher at the National Research Council of France at the Blaise Pascal University of Clermont-Ferrand, France, with J.P. Grolier. His research interests focus on anionic polymerization of lactams in organic media, electroactivated stimuli responsive polymer gels, combined techniques for on-line monitoring of chemical processes, with an emphasis on the use of reaction calorimetry. Dan has authored more than 30 research papers, two invited book chapters, and holds one patent. 

Topnir Not a chemical process but an instrumental process for on-line monitoring of hydrocarbon process streams by infrared spectroscopy. Developed by BP and offered for license in 1997. 

Automatic on-line monitoring of inhibitor reserve. This involves sampling a bypass stream of cooling water and is usually achieved by the measurement of a specific chemical inhibitor component, such as molybdenum. Other monitoring methods include azole fluorescence (as in the well-established Nalco TRASAR system) or... 

Sensors for the detection of enantiomers are of great interest, as so far the on-line monitoring of production processes and medical diagnostics using standard chemical analytical methods is not possible. Quite often only one enantiomer of a chiral compound is actually a bioactive therapeutic. Therefore a proper analysis of the final product is essential. Currently, this involves separation techniques like liquid chromatography, GC and capillary electrophoresis, and determination of enantiomeric purity with circular dichro-ism and specific rotation. These are all off-line procedures and therefore no real-time analysis can be performed. Sensing devices for the distinction of different enantiomers would be a much cheaper, faster and easier-to-use alternative for this task, amenable to automation. 

Areas of application of reaction calorimetry include determination of calorimetric data for reactions and process design, for the kinetic characterization of chemical reactions and of physical changes, for on-line monitoring of heat release and other analytical parameters needed in subsequent process development as well as for the development and optimization of chemical processes with the objective, for instance, to increase yield or profitability, control the morphology or degree of polymerization and/or index of polydispersity, etc. 

Munson and Field reported in 1966 on a technique of ionizing molecules by gas phase ion-molecule reactions, which they called chemical ionization (Cl). In this way, break-up of the molecules can be greatly reduced or even avoided. Thus, measured ion currents can be correlated with the densities of the respective parent neutral compounds, allowing for on-line monitoring of rather complex gas mixtures. The fundamental principles of gas phase ion chemistry on which Cl is based, as well as the instrumentation for Cl, have been reviewed in great detail by Harrison." The wide variety of Cl methods that has been developed includes Medium Pressure Mass Spectrometry, Fourier Transform Mass Spectrometry, Quadrupole Ion Trap Mass Spectrometry, Pulsed Positive Ion-Negative Ion Chemical Ionization, and Atmospheric Pressure Ionization Mass Spectrometry (API-MS). Of these, API-MS has developed into a very reliable and widely used technique for analysis of VOCs in flavor release studies and human breath. A variety of API-MS applications in these fields of research has been described in a recent volume by Roberts and Taylor. ... 

The first of the separation techniques to be used in process measurement was gas chromatography (GC) in 1954. The GC has always been a robust instrument and this aided its transfer to the process environment. The differences between laboratory GC and process GC instruments are important. With process GC, the sample is transferred directly from the process stream to the instrument. Instead of an inlet septum, process GC has a valve, which is critical for repetitively and reproducibly transferring a precise volume of sample into the volatiliser and thence into the carrier gas. This valve is also used to intermittently introduce a reference sample for calibration purposes. Instead of one column and a temperature ramp, the set up involves many columns under isothermal conditions. The more usual column types are open tubular, as these are efficient and analysis is more rapid than with packed columns. A pre-column is often used to trap unwanted contaminants, e.g. water, and it is backflushed while the rest of the sample is sent on to the analysis column. The universal detector - thermal conductivity detector (TCD)-is most often used in process GC but also popular are the FID, PID, ECD, FPD and of course MS. Process GC is used extensively in the petroleum industry, in environmental analysis of air and water samples" and in the chemical industry with the incorporation of sample extraction or preparation on-line. It is also applied for on-line monitoring of volatile products during fermentation processes" ... 

In this chapter, only brief descriptions of traditional probes of the physical and chemical environments will be presented. Instead, our focus will be on the on-line (and quasi on-line) monitoring of bioprocesses. This type of measurement is required for bioprocess development, control, and optimization and places special demands on the types of sensors involved. In addition, special attention will be given to biosensors. These new probes provide on-line measurements of compounds that would otherwise require off-line analysis and have greatly increased the power of automated bioprocess monitoring and control. 

In cultivation processes, the chemical environment (normally called the fermentation broth) is one of the main foci in biotechnological analysis [36]. Substrates, products, and several metabolites can usually be found in the fermentation broth. Substrates are consumed by the microorganisms and products or metabolites are released by the cells into the medium. Thus, detailed on-line monitoring of these components can reflect not only the progress of the bioprocess but can also give an insight into the state and metabolism of the microorganisms. 

We have briefly mentioned the use of data on IMR in plasma modeling and for the understanding of interstellar molecular synthesis as well as of ionospheric chemistry, and we also want to point out the applications of IMR in various methods of chemical ionization. The most recent one, developed in our laboratory, namely proton-transfer reaction mass spectrometry (PTR-MS), allows for on-line monitoring of volatile organic compounds at levels as low as a few parts per trillion and is therefore applicable for environmental, food, and medical research involving investigations of fast metabolic and enzymatic processes. 

The need to understand metal extraction with ScFs, particularly uranium SFE, motivated the development of an on-line measurement technique for uranyl complexes in ScF CO2. In SFE processes, the extracted material is usually collected by depressurizing the ScF, followed by chemical or spectroscopic analysis. On-line monitoring of SFE can be preferable because it is fast, free of collection loss, and allows monitoring of process dynamics. However, depending on the specific analyte and the measurement matrix, the desired levels of sensitivity and selectivity can be difficult to achieve with on-line methods, particularly with detectors that can be coupled with pressurized ScF systems. 

In the field of chemical analysis, biosensors have undergone rapid development over the last few years. This is due to the combination of new bioreceptors with the ever-growing number of transducers [1]. The characteristics of these biosensors have been improved, and their increased reliability has yielded new applications. Recently, a new technique of enzyme immobilization has been developed to obtain biosensors for the determination of enzyme substrates [2]. It is based on the enzyme adsorption followed by a crosslinking procedure. Therefore, a penicillin biosensor can be obtained and associated with a flow injection analysis (FIA) system for the on-line monitoring of penicillin during its production by fermentation [3-4]. This real-time monitoring of bioprocess would lead to optimization of the procedure, the yield of which could then be increased and the material cost decreased. 

Zhu, L., Gamez, G., Chen, H.W, Huang, H.X., Chingin, K., Zenobi, R. (2008) Real-Time, On-line Monitoring of Organic Chemical Reactions Using Extractive Electrospray Ionization Tandem Mass Spectrometry. Rapid Commun. Mass Spectrom. 22 2993-2998. 

Proton transfer reaction mass spectrometry (PTR-MS) was first developed at the Institute of Ion Physics of Innsbruck University in the 1990s. Nowadays, PTR-MS is a well-developed and commercially available technique for the on-line monitoring of trace volatile organic compounds (VOCs) down to parts per trillion by volume (ppt) level. PTR-MS has some advantages such as rapid response, soft chemical ionization (Cl), absolute quantification, and high sensitivity. In general, a standard PTR-MS instrument consists of external ion source, drift tube, and mass analysis detection system. Figure... 

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