Digital chromatography

One of the techniques that has become increasingly used and replaced more of the traditional methods of sample preparation is SPE. SPE introduced in the early 1970s offered the possibility of, if not eliminating, at least reducing the tedium in sample preparation. SPE has been called digital chromatography, where samples can be introduced onto a device, interferences removed, and the analyte of interest eluted in a small amount of solvent. Conversely, the SPE device can be used as a flow-through cleanup device. SPE can be used on many occasions as a substitute for LEE. 

Solid-phase extraction has been called digital chromatography because its chief use is to retain and then remove analytes of interest in an on-off fashion. Outside of conducting breakthrough studies, the purely frontal chromatographic form has little practical value in TEQA. The elution step, in which an eluent whose polarity is near to that of the analyte, removes all analytes and can be viewed in a manner similar to that done for the sorption step ... 

Section I of this book includes chapters on the principles and practice of PLC. After this introductory Chapter 1, Chapter 2 provides information on efforts undertaken to date in order to establish the theoretical foundations of PLC. With growing availability and popularity of modem computer-aided densitometers, separation results can be obtained in digital form as a series of concentration profiles that can be relatively easily assessed and processed. From these, relevant conclusions can be drawn in exactly the same manner as in automated column chromatographic techniques. Efforts undertaken to build a theoretical foundation of PLC largely consist of adaptation of known strategies (with their validity confirmed in preparative column liquid chromatography) to the working conditions of PLC systems. 

Klebovich, 1., Application of planar chromatography and digital autoradiography in metabolism research, in Planar Chromatography, Nyiredy, Sz., Ed., Springer Scientific, Budapest, Hungary, 2001, pp. 293-311. 

B. Van de Wijdeven, J. Lakeman, J. Klaessens, B. Vandeginste and G. Kateman, Digital simulation as an aid to sample scheduling in a routine laboratory for liquid chromatography. Anal. Chim. Acta, 184 (1986) 151-164. 

Over the years, many instruments have been developed for and used in the scientific laboratory. Today, the computer is used as a major tool in the scientific laboratory for the capture, manipulation, transfer, and storage of data. Consequently, the concern for data quality has shifted from the instruments that are used in the generation of the data to these electronic systems, often neglecting the fact that the data are only as accurate as the instrument measurements. For instance, many electronic systems can be used in chromatography analysis, from the electronic log book where the test substance inventory is kept, throughout data capture in the instrument, to the digitized electronic signal that is the raw data on the computer network. For crop residue samples, the... 

The use of conventional photographic systems for data acquisition, printing and archiving results of planar chromatography [401] has now largely been superseded by video documentation systems. A sample method for documentation of TLC plates has been described by a combination of computer, scanner, and digital colour thermal printer resulting in a very... 

Link, J.C. (2004). Development and application of gradient ultrahigh pressure liquid chromatography for separations of complex biological mixtures Dissertation, University of North Carolina, Chapel Hill. Available from UMI ProQuest Digital Dissertations, Ann Arbor, MI, AAT 3156171. 

FIGURE 11.20 An illustration of how the area of an instrumental chromatography peak is determined by integration. The series of digital values acquired by the data system, represented by the vertical lines, are summed. 

Like chromatography, the FFF instrument consists of a pump to deliver the carrier fluid, a separation medium (FFF channel), a detector responding to the eluting species, and a computer to control the operative parameters (e.g., field, flow) and to acquire the digitized fractogram (see Figure 12.1). 

II III were not published at the time of writing this Section 25) Anon, "Computers Analytical Role Extended , C EN, March 18, 1968, pp 44, 48, 52 54 [At the exhibit of the "1968 Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy , held in Cleveland, Ohio (See C EN, March 11, 1968, plO) were shown the computers of DEC (Digital Equipment Corp) and of IBM (International Business Machine Corporation). The DEC exhibited "Gas Chrom-8 Computer system for gas chromatography and IBM-Model 1800 and 1130. There were also exhibited other systems, among them smaller inexpensive computers. There were also shown slides on results of work with computers done by S. Sasaki H. Abe of Japan s Tohoku University and by T. Kato of Japan Electron Optics Laboratory Co, Ltd 26) Jack Alster, Picatinny Arsenal private communication,... 

Alkylation of 1. To a mixture of the ester 1 (5 g, 25 mmol) and 6% of Aliquat 336 (715 mg, 1.5 mmol) was added t-BuOK (3.3 g, 25 mmol, 1 equiv.) under magnetic stilling over 15 min alkyl bromide (25 mmol, 1 equiv.) was then added slowly. The flask was left under the experimental conditions indicated in Table 1. Finally, the mixture was diluted with ethyl acetate (50 ml) and filtered on Florisil (10 g). The crude products were analysed by GC and characterised by MS and HNMR. 2-Alkylcyclohexanones. A mixture of lithium bromide (1.73 g, 20 mmol), tetrabutylammonium bromide (323 mg, 1 mmol), water (360 mm, 0.36 mL, 20 mmol) and ethyl l-alkyl-2-oxocyclohexanecarboxylate 2 (10 mmol) was placed in a Pyrex tube. The tube was then introduced into a Maxidigest MX 350 Prolabo microwave reactor fitted with a rotational system. Microwave irradiation was carried out for a suitable power and time (Table 2). An approximate final temperature was measured by introducing a digital thermometer at the end of irradiation. The mixture was cooled to ambient temperature. After elution with ethyl acetate (50 mL) and subsequent filtration on Florisil, organic products were analyzed by GC and finally purified by chromatography on silica gel (pentane-ethyl acetate, 95 5). 

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