Detection on-line

Figure 8.19 illustrates another example of the versatility of multidimensional OPLC, namely the use of different stationary phases and multiple development ("D) modes in combination with circular and anticircular development and both off-line and on-line detection (37). Two different stationary phases are used in this configuration. The lower plate is square (e.g. 20 cm X 20 cm), while the upper plate (grey in Figure 8.19) is circular with a diameter of, e.g. 10 cm. The sample must be applied on-line to the middle of the upper plate. In the OPLC chamber the plates are covered with a Teflon sheet and pressed together under an overpressure of 5 MPa. As the mobile phase transporting a particular compound reaches the edge of the first plate it must-because of the forced-flow technique-flow over to the second (lower) stationary phase, which is of lower polarity. 

Stopping excursions from normal operation conditions before they become hazardous, by correction of process control variables when dangerous situations are detected on-line detection of process deviations associated with trip systems for corrective actions. 

Figure 7.19 Chronpes 25 overpressure development chamber for forced-flow TLC. The configuration shown is for on-line detection. 

Hub, L., and J. D. Jones, "Early On-Line Detection of Exothermic Reactions,"... 

For all CE instruments that use on-line detection at a fixed point along the capillary, CIEF must include a means of transporting the focused zones past the... 

Gong, Z. L., Zhang, Y., Zhang, H., and Cheng, J. K. (1999). Capillary electrophoresis separation and permanganate chemiluminescence on-line detection of some alkaloids with beta-cyclodextrin as an additive.. Chromatogr. A 855, 329—335. 

Mealiness in apples results from a breakdown in adhesion between cells so that chewing the apple tissue results in cell separation rather than cell rupture. Eating a mealy apple is therefore associated with the unpleasant sensory perception of a lack of juiciness, loss of crispness and hardness. A number of studies have succeeded in correlating the degree of mealiness with destructive reference tests such as the Magness-Taylor firmness and confined compression juiciness, but clearly there is a need for non-destructive, on-line detection of mealiness in apples. 

Ti, or PEEK (polyether ether ketone) to allow measurements under very corrosive conditions. The separated phases pass AMX gadgets for on-line detection (radiometric, spectrophotometric, etc.) or phase sampling for external measurements (atomic absorption, spectrometric, etc.), depending on the system studied. The aqueous phase is also provided with cells for pH measurement, redox control (e.g., by reduction cells using platinum black and hydrogen, metal ion determination, etc.) and temperature control (thermocouples). 

Morgan NY, Wellner E, Talbot T, Smith PD, Phillips TM. Development of a two-color laser finorescence detector—On-line detection of internal standards and nnknowns by capillary electrophoresis within the same sample. Journal of Chromatography A 1105, 213-219, 2006. 

On-line anion exchange LC/ICP-MS methods for selenium and chromium speciation have been published [30], In studies of selenium speciation in environmental samples LC/ICP-MS and LC/ ESI-MS methods have been used for the determination of both inorganic and organic selenium species [43]. For the determination of methyl selenide, strong anion exchange and RP chromatography have been employed [43], while for the determination of seleno-aminoacids, IP RP chromatography with on-line detection based on ICP-MS has been successfully employed [44],... 

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