On-line identification

LC-NMR plays a central role in the on-line identification of the constituents of crude plant extracts (Wolfender and others 2003). This technique alone, however, will not provide sufficient spectroscopic information for a complete identification of natural products, and other hyphenated methods, such as LC-UV-DAD and LC-MS/MS, are needed for providing complementary information. Added to this, LC-NMR experiments are time-consuming and have to be performed on the LC peak of interest, identified by prescreening with LC-UV-MS. NMR applied to phenolic compounds includes H NMR,13 C NMR, correlation spectroscopy (COSY), heteronuclear chemical shift correlation NMR (C-H HECTOR), nuclear Overhauser effect in the... 

Adaptive control has been an active area of research for many years. The fullblown ideal adaptive controller continuously identifies (on-line) the parameters of the process as they change, and retunes the controller appropriately. Unfortunately, this on-line adaptation is fairly complex and has some pitfalls that can lead to poor performance. Also, it takes considerable time for the on-line identification to be achieved, which means that the plant may have already changed to a different condition. These are some of the reasons why on-line adaptive controllers are mot widely used in the chemical industry. 

However, the main reason for the lack of wide application of on-line adaptive control is the lack of economic incentive. On-line identification is rarely required because it is usually possible to predict with off-line tests how the controller must be retuned as conditions vary. The dynamics of the process are determined at different operating conditions, and appropriate controller settings are determined for all the different conditions. Then, when the process moves from one operating region to another, the controller settings are automatically changed. This is called openloop-adaptive control or atn scheduling. 

He, X.-G., On-line identification of phytochemical constituents in botanical extracts by combined high-performance liquid chromatographic-diode array detection-mass spectrometric techniques, J. Chromatogr. A, 880, 203, 2000. 

Queiroz, E.F. et al., On-line identification of the antifungal constituents of Erythrina vogelii by liquid chromatography with tandem mass spectrometry, ultraviolet absorbance detection and nuclear magnetic resonance spectrometry combined with liquid chromatographic micro-fractionation, J. Chromatogr. A, 972, 123, 2002. 

Santos-Buelga, C., Garcia-Viguera, C., and Tomas-Barberan, F.A., On-line identification of flavonoids by HPLC coupled to diode array detection, in Methods in Polyphenol Analysis, Santos-Buelga, C. and Williamson, G., Eds., Royal Society of Chemistry, Cambridge, Chap. 5, 2003. 

An interpretation of the absorption spectrum in the low-excitation phase has been made by Williams (1987), based on line identifications of scandium, strontium,... 

Traditional methods of pharmaceutical analysis involve a series of multiple steps. For example, the identification of natural products traditionally involves the scale-up of fermentation broths, solvent extraction, liquid/liquid or column fractionation, chromatographic fraction collection, and spectroscopic analysis (usually NMR) of the individual components. Figure 5.2 illustrates the integration of these bench-scale steps into a dedicated LC/MS/MS system (Lee et al., 1997). Integration provides unique and powerful advantages for the on-line identification of natural products (Kerns et al., 1994 Ackermann et al., 1996a). Experiments that once required 2 weeks to perform with traditional approaches are now performed in half a... 

Frassanito, R., Cantonati, M., Tardio, M., Mancini, I., and Guella, G. 2005. On-line identification of secondary metabolites in fresh water microalgae and cyanobacteria by combined liquid chromatography-photodiode array detection-mass spectromet-ric techniques. J. Chromatogr. A, 1082,33-42. 

Similarly, screening of 12 different species and their varieties belonging to the tribe Datureae has been reported [70], GC-MS investigation permitted on-line identification of 66 tropane alkaloids from crude leaf and root extracts using no more than 300 mg of plant material. Many of the alkaloids were described for the first time in the corresponding species, and their identification was based on their fragmentation pathways. One new tropane alkaloid was reported as well however, its stereochemistry could obviously not be assigned. 

Fu, L. C.,and Sastry, S., Frequency domain synthesis of optimal inputs for on-line identification and adaptive control, IEEE Trans, on Autom. Control 36, 353 (1991). 

Stephanopoulos, G. Application of macroscopic balances and bioenergetics of growth to the on-line identification of biological reactors. Ann. N. Y. Acad. Sci. 1986, 469 (Biochem. Eng. 4), 332-349. 

TOF (time-of-fiight) mass spectrometers are also increasing in popularity and have been successfully coupled with gas chromatographs. In fact, the first successful on-line identification of GG eflBiuents by MS was with a TOF (29). TOF spectrometers are sensitive instruments. They are by far the fastest scanning of the three major spectrometer types— 50,000 lines per second. This feature makes it the only mass analyzer available for fast reaction research. The TOF also has a stable mass scale and can be computerized readily. However, resolution and mass range of the TOF instrument are low—about 500 amu. This may limit its application for pesticide residue analysis however, mass spectra of organophos-... 

N. Eisenreich, J. Herz, H. Kull, and W. Mayer, Fast On-Line Identification of Plastics Materials by Near Infrared Sprectoscopy in proceedings of R 95, Geneva, Switzerland, 3, pp. 230-235 (1995). 

Applied Spectroscopy 51, No.6, June 1997, p.856-65 APPLICATION OF A SPECTROSCOPIC INFRARED FOCAL PLANE ARRAY(FPA) SENSOR FOR ON-LINE IDENTIFICATION OF PLASTIC WASTE... 

Antec 96. Volume III. Conference proceedings. Indianapolis, 5th-10th May 1996, p.3131-5 FAST ON-LINE IDENTIFICATION OF PLASTICS BY NEAR-INFRARED SPECTROSCOPY FOR USE EV RECYCLING PROCESSES Eisenreich N Herz J Kull H Mayer W Rhoe T Fraunhofer-Institut fuer Chemische Technologie (SPE)... 

Cui LJ, Abliz Z, Xia M, Zhao LY, Gao S, He WY, Xiang Y, Liang F, Yu SS. On-line identification of phenanthroindolizidine alkaloids in a crude extract from Tylophora... 

Chromophores can also be synthetically attached to specific protein groups, either to assist identification or incidental to blocking reactive fiinctionalities. One common chromophore is the pyridylethyl group added to cysteine using 4-vinylpyridine after disulfide bond reduction but prior to enzymatic digestion. The pyridylethyl cysteine has a strong absorbance maximum near 254 nm that permits easy on-line identification of Cys-containing peptides [16]. 

Yang, J.N. Lin, S. 2004. On-line identification of non-linear hysteretic structures using an adaptive tracking technique, International Journal of Non-Linear Mechanics. 39,1481-1491. 

Wang FY, Cameron IT. Multi-level optimal control of particulate process with on-line identification, to be presented at The 7 World Congress of Chemical Engineering (WCCE 7), Glasgow, Scotland 10-14 July (2005). 

Polasek, J., Queiroz, E.F. Hostettmann, K. (2007). On-line identification of phenolic compounds of Trifolium species using HPLC-UV-MS and post-column derivatisation. Phytochemical Analysis, 18, 13-23. 

Lijie, C., Zeper, A., Min, X., Liyan, Z., Song, G., Wenyi, H., Yun, X., Feng, L., and Shishan, Y. 2004. On-line identification of phenanthroindolizidine alkaloids in a crude extract from Tylophora atrofolliculata by liquid chromatography combined with tandem mass spectrometry. Rapid Communications in Mass Spectrometry, 18, (2), 184-190. 

M D Orazio. On-line identification of gas chromatographic fractions by a Raman multichannel spectrometer. Appl Spectrosc 33 278-283, 1979. 

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