On‐Line Monitoring of Chemical Reactions

Abstract

The article contains sections titled: 1. Introduction 2. Reaction Calorimetry 2.1. Introduction 2.2. Heat Flow Balance and Principles of Measurement 2.2.1. Heat Flow Balance 2.2.2. Basic Modes of Operation 2.3. Applications and Instrumentation 3. Ultrasonic Methods 3.1. Introduction 3.2. Theory 3.3. Applications 4. Dielectric Spectroscopy 4.1. Theory and Mechanisms 4.2. Instrumentation and Applications 5. Optical Spectroscopy 5.1. Introduction 5.2. Instrumentation for Reaction Monitoring 5.3. Applications of Optical Spectroscopy 5.3.1. UV – VIS Spectroscopy 5.3.2. NIR Spectroscopy 5.3.3. IR Spectroscopy 5.3.4. Raman Spectroscopy 5.3.5. Fluorescence 5.3.6. Other Spectroscopic Techniques 6. Particle Size Analysis 6.1. Scattering Techniques 6.1.1. Turbidimetry 6.1.2. Angular Static Light Scattering 6.1.3. Dynamic Light Scattering 6.1.4. Other Optical Techniques 6.2. Separation Techniques 7. Chromatography 7.1. Introduction 7.2. GC Hardware Components 7.3. Applications of Gas Chromatography 7.4. Other Chromatographic Techniques 8. Electroanalytical Methods 8.1. Introduction 8.2. Conductometry 8.3. Potentiometry 8.4. Amperometry, Voltammetry, and Coulometry 9. Miscellaneous Methods 9.1. Mass Spectrometry 9.2. Densimetry and Dilatometry 9.3. Rheometry 9.4. NMR Spectroscopy

Coaxial Dielectric Spectroscopy as an In-Line Process Analytical Technique for Reaction Monitoring

“…Because DS often provides insight only into the composition of the whole mixture, its use in reaction monitoring will likely be sensitive to the presence of impurities and parallel processes (e.g., side-reactions, crystallization events, etc.). In this way, it is similar to established ‘integral’ methods including reaction calorimetry and measurements of physico-chemical properties (e.g., density, conductivity, and refractive index , ). Furthermore, as noted above, dielectric property measurements can also be very sensitive to temperature .…”

“…DS measures complex relative dielectric permittivity (ε r *) as a function of frequency (eq and Figure A). , The complex relative dielectric permittivity (ε r *) is composed of the dielectric constant (ε′) and the dielectric loss (ε″), which are respectively the ease with which a sample polarizes, and how easily that polarization energy is converted into heat. Of the many molecular mechanisms that can contribute to the observed dielectric properties of a sample, those that are most likely to change during a chemical reactionand which are therefore most relevant to monitoring reaction progressare listed in Figure B. It is important to note here that both the reorientation of permanent dipoles and the mobility of charge carriers are very sensitive to the viscosity of the medium, and hence to temperature. ε normalr * prefix= ε ′ prefix− j · ε ″ where ε r * = complex relative dielectric permittivity; ε′ = dielectric constant; j = √(−1); ε″ = dielectric loss.…”

“…In this way, it is similar to established ‘integral’ methods including reaction calorimetry and measurements of physico-chemical properties (e.g., density, conductivity, and refractive index , ). Furthermore, as noted above, dielectric property measurements can also be very sensitive to temperature . Given the number of intimately linked factors contributing to the dielectric properties of a sample (Figure B), it is not straightforward to predict how sensitive a single measurement will be to temperature, or whether the degree of sensitivity changes as a function of composition (e.g., as a reaction progresses).…”

Polymerization Online Monitoring

“…Chemical reactions are accessible to reaction monitoring by DS if they lead to changes in the rate of motion and polarization of molecules contributing to the dielectric response of the mixture [100].…”

Novel Benchtop Magnetic Particle Spectrometer for Process Monitoring of Magnetic Nanoparticle Synthesis

“…Although several methods for monitoring the synthesis of nanoparticles have already been developed and applied [ 10 , 11 ], there is no detector available capable to monitor the essential magnetic functionality of MNP in line with a micromixer setup. The basic utility of inline monitoring of micromixer MNP synthesis has been demonstrated by Bemetz et al, who used a nuclear magnetic resonance (NMR) device to determine the transversal and longitudinal relaxation times of MNP [ 11 ].…”