In situ monitoring technique

L.O. Rodrigues, L. Vieira, J.P. Cardoso and J.C. Menezes, The use of NIR as a multi-parametric in situ monitoring technique in filamentous fermentation systems, Talanta, 75, 1356-1361 (2008). 

The main problem with pressure-driven membrane processes is the flux decline as a function of filtration time (Fig. 3.6-3) due, most importantly, to concentration polarization (remaining constant once estabhshed) and membrane fouling (worsening as a function of time). These cause extra resistances on top of the membrane resistance and thus slow down the transport This reduction can be as severe as 99% of the initial flux value in M F. Reviews are available on these matters [7], some focusing in more detail on in situ monitoring techniques [8], some only on concentration polarization [9] others only on fouling [10-12]. 

J.C. Chen, Q. Li, and M. Elimelech, In situ monitoring techniques for concentration polarization and fouling phenomena in membrane filtration, Adv. Coll. Int. Sci., 107 (2004) 83-108. 

Part V (2014) Developments in Ellipsometric Real-Time/In-situ Monitoring Techniques. In Hinrichs K, Eichhom K-J. (eds) Ellipsometry of Functional Organic Surfaces and Films Springer Berlin Heidelberg, pp 249-301... 

The in situ monitoring of high temperature reactions by hpl29Xe magnetic resonance is still in its infancy. Although the previous work on gas phase dynamics in porous media has shown the feasibility of dynamic microscopy and M RI and the first in situ combustion NMR spectra have been collected, much more development remains to be done. To date, hpl29Xe NMR and MRI are currently the only techniques available to study gas dynamics in porous and opaque systems. 

Kazarian et al. [281-283] have used various spectroscopic techniques (including FUR, time-resolved ATR-FHR, Raman, UV/VIS and fluorescence spectroscopy) to characterise polymers processed with scC02. FTIR and ATR-FTIR spectroscopy have played an important role in developing the understanding and in situ monitoring of many SCF processes, such as drying, extraction and impregnation of polymeric materials. 

Prior to the introduction of ion-selective electrode techniques, in situ monitoring of free copper (II) in seawater was not possible due to the practical limitations of existing techniques (e.g., ligand competition and bacterial reactions). Ex situ analysis of free copper (II) is prone to experimental error, as the removal of seawater from the ocean can lead to speciation of copper (II). Potentially, a copper (II) ion electrode is capable of rapid in situ monitoring of environmental free copper (II). Unfortunately, copper (II) has not been used widely for the analysis of seawater due to chloride interference that is alleged to render the copper nonfunctional in this matrix [288]. 

In addition to the above-mentioned possibilities for the in-situ monitoring of hydrogenations, there are, of course, also techniques involving calorimetry and IR spectroscopy [34, 35c, 39, 41, 53, 54]. 

The results of this preliminary study have shown that anthracene and Re(CO)3ClL (L = 4,7-diphenyl-l,10-phenanthroline) could be used as in situ monitors of the microviscosity changes that occur as a bone cement sample cured. In addition, the results identified a novel technique—the impedance of quenching—for monitoring local viscosity. 

Dell Orco, P. Diederich, A.M. Rydzak, J.W., Designing for crystalline form and crystalline physical properties The roles of in-situ and ex-situ monitoring techniques Am. Pharm. Rev. 

Wamken, K.W., H. Zhang, and W. Davison. 2007. In situ monitoring and dynamic speciation measurement in solution using DGT. In R. Greenwood, G.A. Mills, and B. Vrana (eds), Passive Sampling Techniques in Environmental Monitoring, pp. 251-278. Amsterdam Elsevier. 

Time-Resolved Laser-Induced Incandescence (by Prof. Alfred Leipertz et al.) introduces an online characterization technique (time-resolved laser-induced incandescence, TIRE-LII) for nano-scaled particles, including measurements of particle size and size distribution, particle mass concentration and specific surface area, with emphasis on carbonaceous particles. Measurements are based on the time-resolved thermal radiation signals from nanoparticles after they have been heated by high-energetic laser pulse up to incandescence or sublimation. The technique has been applied in in situ monitoring soot formation and oxidation in combustion, diesel raw exhaust, carbon black formation, and in metal and metal oxide process control. 

Polymer properties are very often dependent on the polymer preparation. So, a good monitoring of the polymerization process is the key step to obtaining good and reproducible materials. The extent of the polymerization can be controlled in different ways. IR is the most usual [27,30] but is not very accurate and requires the extraction of samples to analyze. Recently, an in situ monitoring of PMR-15 processing has been provided by means of frequency-dependent dielectric measurements [33,34]. This non-destructive technique allows the characterization of all the steps of the curing process and thus they can be optimized. 

In-situ IR measurements overcome the problems mentioned for in situ NMR spectroscopy. The information that we obtain from vibrational spectroscopy is far less detailed, however, than that from NMR. The concentration of the catalyst may be equal to the one used in practical catalytic systems. Secondly, autoclaves have been equipped with IR cells, either as flow cells or via real in-situ monitoring in the Moser cell (see below), which allows one to work with gaseous reactants. In the following we will mention a (very) few examples of complexes that may be intermediates in the hydroformylation reaction observed with these two techniques. 

The chemical structure of the polyimide polymers (named PI-1 and PI-2) studied by Sekkat et al. is shown in Figure 12.12. They prepared the polymer samples by spin-casting onto glass substrates. PTl was cast from a cyclohexanone solution and PI-2 from 1,1,2,2- tetrachloroethane. The Tg values of PI-1 and PI-2 were determined to be 350°C and 252 C, respectively, by scanning calorimetry method. The thicknesses of the PI-1 and PI-2 films were, respectively, approximately 0.72 im and 0.14 im, and their respective optical densities were approximately 0.79 and 0.3 at 543.5 nm. Details of the preparation and characterization of the samples can be found in References 3 and 20. In their EFISH experiment, a typical corona poling technique was used to pole the samples, with a dc electric field about 2-3 MV/cm across a 1-2 lm thick polymer film. They used the SHG output from the EFISH experiment to in situ monitor the photochemical change in the third-order susceptibility of the PI-1 and PI-2 polymers. 

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