Online temperature detection

Another important application of hyphenated NMR methods is to provide insights into processes that affect the separation. Eor example, online NMR detection of the water chemical shift was used to noninvasively probe intracapillary temperatures in CE separations with subsecond temporal resolution and spatial resolution on the order of 1 mm [111]. Lacey et al. [112] followed up this report with a second NMR study using a novel 2-turn vertical solenoidal coil to measure temperature increases of more than 50 C in a chromatographic frit of the type used in CEC. Insights into the mechanisms underlying cITP have also been investigated utilizing online NMR... 

New electronics and improved computer data acquisition capabilities have permitted the development of SEC with online triple detection using LS, VISC, and refracto-metry. Online triple detection is known as size-exclusion chromatography cubed (SEC ) with the three dimensions being defined by the three detectors.The use of eliminates the requirement for column calibration, unlike conventional and universal calibration, where a premium is put on control of variables such as flow rate, temperature, and column resolution. SEC can offer advantages in polymer production quality control as well as in research and development of new polymers. 

The most reliable method of detecting a runaway is online analysis of a product formed in the runaway reaction. For example, CO2 can be monitored in the offgas during the runaway-sensitive synthesis of ethylene oxide. If its concentration increases above a specified limit, the reactor must be shut down, purged with nitrogen, and for a certain period cooled to a lower temperature before operation is recommenced. 

Bruckner (2001) combined UV-vis with EPR spectroscopy, using online gas chromatography for product analysis. For many transition metal ions, EPR and optical spectra are complementary, in that some states are detectable or distinguishable with only one of the methods. The UV-vis facility was added to a previously described flow reactor system for EPR spectroscopy (Bruckner et al., 1996). A fiber optical probe (Avantes, AVS-PC-2000 plug-in spectrometer) was inserted directly into the reactor via a Teflon -sealed feedthrough and placed in the catalyst bed. UV-vis spectra were reported for temperatures up to 810 K. The design was later expanded to include a third method, Raman spectroscopy (Bruckner, 2005 Bruckner and Kondratenko, 2006). A hole in the... 

In further work (Jiang et al., 2007), the conversion of methanol on HSAPO-34 was investigated at temperatures up to 673 K, with simultaneous NMR and UV-vis spectroscopy and online GC analysis. In this experiment, the differing sensitivities of the two spectroscopies become apparent dienes are indicated by the UV-vis spectra at 473 K but are not detected with NMR spectroscopy. 

The second major environmental application of FFF has been the use of an element-specific detector, usually in series with a UV detector, to provide elemental composition data along with the PSD. Graphite-furnace atomic absorption spectrometry has been used off-line on fractions collected from the FFF run. However, the multi-element detection, low detection limits and capability to function as an online detector have made inductively coupled plasma mass spectrometry (ICP-MS) the ideal detector for FFE85-86 The sample introduction system of the ICP-MS is able to efficiently transport micron-sized particles into the high-temperature plasma,... 

The measurements on the research facility were carried out at stationary or quasi stationary conditions. The measurements of air flows, gas temperatures, gas composition, and heat output were analysed continously and monitored online. The gas composition was analyzed in the flue gas after the boiler exit with industrial gas analyzers. For the analysis of the hot gas in the reduction zone a suction pyrometer combined with a probe for detection was used. With this probe also short fluctuations could be monitored with extremely short delay. Besides, a hot gas sampling line with different analyzers for measuring the gas in the reburn zone was installed. Table 2 gives on overview over the gas analysis equipment. 

Polycyclic aromatic hydrocarbons (PAHs) have been separated by MEKC using a double alkyl chain di(2-ethylhexyl) phosphate as anionic micellar pseudostationary phase. Phospholipids have been separated from soya lecithins by MEKC, deoxycholic acid being used for micelle formation. Separation was tested according to solvent polarity and column temperature, with a high n-propanol concentration and a column temperature of 15 °C being ideal. Online MEKC/MS with electrospray ionisation, and atmospheric-pressure Cl, interfaces have been used in the separation and detection of standard compounds, including tetraphenylphosphonium chloride. ... 

Polymerization process control can benefit significantly from using online state estimation techniques. In general, online control of polymer properties such as molecular weight, MWD, copolymer composition, MI, density, etc. is difficult, mainly because of the lack of adequate online or in-process sensors. Therefore, many of these polymer property parameters are controlled indirectly by controlling first-level process variables such as temperature, pressure, and the flow rates of various reactants, solvents, and catalysts. When some deviations in polymer properties are detected through laboratory sample analysis, certain reactor variables need to be adjusted. Extensive plant experience might be required to make such process adjustments, or model-based online state estimator can be used. 

In one studyOPPs were extracted with SPME (85 /rm of polyacrylate coating) by the immersion technique at 75°C for 60 min. Desorption was done in a desorption device by supercritical fluid carbon dioxide (temperature 50°C pressure 306 atm) prior to online introduction into LC. The detection limits were 300 /rg/l for diazinon, 40 /rg/l for EPN, and 60 /rg/1 for chlorpyrifos, with recoveries ranging from 62 to 64%. 

Brossa et al. developed an automated SPE-GC-MS method for the determination of endocrine disrupting compounds including six phthalate esters. The interface device was a programmed temperature vaporizer (PTV), whose liner was packed with Tenax. The samples were spiked with 50% of methanol and 15 ml of this mixture were preconcentrated. Before elution, the precolumn was dried with nitrogen. The analytes were desorbed in the backflush mode with three ethyl acetate fractions of 100 /rl and online transferred to the GC system. The performance of the method was tested with several environmental water samples. The recoveries achieved were satisfactory and the detection limits were between 1 to 36 ng/1. 

---