Computer-assisted separation

In the development of the CAMEO system (Computer-Assisted Mechanistic Evaluation of Organic reactions) [8 it was decided to treat large classes of mechanistically related reaction types by separate modules. 

Ishino, S., Nakanishi, H., Norisuye, T., Awatsuji, Y. and Tran-Cong-Miyata, Q. (2006) Designing a polymer blend with phase separation tunable by visible light for computer-assisted irradiation experiments. Macromol. Rapid. Commun., 27, 758-762. 

The experimental results obtained in the laboratory by the researchers can be monitored using computer programs with help of empirical equations or models. Most of the computer-assisted procedures have been developed for HPLC separations and mainly for RPLC, and some of them are commercially available. 

Computer-assisted techniques for optimizing HPTLC have been available for a number years and are well presented in the hterature [20,77-82]. The strategy of integrating these techniques is to solve each separation problem in the simplest way possible. 

Procedures used vary from trial-and-error methods to more sophisticated approaches including the window diagram, the simplex method, the PRISMA method, chemometric method, or computer-assisted methods. Many of these procedures were originally developed for HPLC and were apphed to TLC with appropriate changes in methodology. In the majority of the procedures, a set of solvents is selected as components of the mobile phase and one of the mentioned procedures is then used to optimize their relative proportions. Chemometric methods make possible to choose the minimum number of chromatographic systems needed to perform the best separation. 

Xianren, Q., Chong-yu, X., and Baeyens, W., Computer-assisted predictions of resolution, peak height and retention time for the separation of inorganic anions by ion chromatography, ]. Chromatogr., 640, 3, 1993. 

Infrared spectroscopy is often used for qualitative analysis, and its powerful selectivity means that it can be used as a detector. However, the absorption of the eluent molecules, particularly in reversed-phase separations, often interferes with the detection of analytes. The infrared absorption detector therefore requires mechanical assistance to eliminate the solvent or needs powerful computer assistance to eliminate the background signal. 

Modem tables of thermod5mamic data are made self-consistent either by methods of iteration or by computer-assisted simultaneous solutions [1]. The value of AH for any chemical reaction that can be obtained from two or more thermodynamic cycles should have the same value from each of those cycles if the data are obtained from the same tables. Any thermodynamic calculation, therefore, should be carried out using data from a single database whenever possible. Thus, in listing some values of enthalpies of formation below, we provide values from different databases in separate tables. 

Fig. 5.10 Computer-assisted extraction kinetics-measuring apparatus for highly stirred phases (A) high-speed stirrer (B) stirrer shaft (C) sample inlet (D) Teflon stirring har (E) Teflon phase separator (F) water hath (G) flow-cell (H) spectrophotometer (I) peristaltic pump (J) chart recorder (K) A/D converter (L) clock (M) minicomputer (N) dual-floppy disk drive (O) printer, (P) plotter. (From Ref. 16.)...

Two-dimensional electrophoresis [86] is a well established technique for the separation of intact proteins. In the first dimension the proteins are separated based on their isolectric point while the second dimension separates them based on their size. The presence on the gel of the proteins is revealed by Coomassie blue or silver staining. Under favorable conditions several thousand spots can be differentiated. The gel is digitized and computer-assisted analysis of the protein spot is performed. The spots of interest are excised either manually or automatically and then digested with trypsin. Trypsin cleaves proteins at the C-terminal side of lysine and arginine. In general one spot represents one protein and the peptides are analyzed by MALDI-TOF to obtain a peptide mass fingerprint. A peptide mass fingerprint involves the determination of the masses of all pep-... 

The experiment is used to separate chemical shifts and J-couplings for homo- and heteronudear systems. In simple cases the chemical shifts and J-couplings may be directly obtained from the 2D spectrum by inspection. For severely overlapped first-order spectra or strongly coupled spin systems the estimated parameters obtained from the spectrum may be used as starting values in a computer assisted spectral analysis as outlined in Modern Spectral Analysis (Volume 3). 

By marrying molecular dynamics to transition state theory, these questionable assumptions can be dispensed with, and one can simulate a relaxation process involving bottlenecks rigorously, assuming only 1) classical mechanics, and 2) local equilibrium within the reactant and product zones separately. For simplicity we will first treat a situation in which there is only one bottleneck, whose location is known. Later, we will consider processes involving many bottlenecks, and will discuss computer-assisted heuristic methods for finding bottlenecks when their locations are not known a priori. 

The racemate of 1,3,2-benzodithiazole 1-oxide 42 was separated by supercritical fluid chromatography on the (A j )-Whelk-( )l column with supercritical carbon dioxide containing 20% methanol as a mobile phase. Peak areas of enantiomers prior to and after the separation, used for the calculation of the enantiomerization barrier, were detected by computer-assisted peak deconvolution of peak clusters registered on chromatograms using computer software <2002CH1334>. 

Occasionally, a binary mixture will not enable the separation to be attained. In this case a ternary mixture may be helpful. There is much in the literature about using more than one organic solvent in the mobile phase for attaining selectivity. Not only do chromatographers share insights about how and why solvents contribute to a separation, but there are also available software routines for computer-assisted development of mobile phases using... 

Hinshaw J.V. 2004. Optimization of separations and computer assistance. In Modem Practice of Gas Chromatography (Barry, E.F., Ed.). Wiley-Interscienee, Hohoken, N.J., pp. 193-228. 

Precise and rugged quantitative analysis generally requires that be greater than 1.5. Further, the time of analysis should be short (preferably within 5-10 min) and the consumption of the mobile phase per run should be minimal, such as in the example in Fig. 1.18A. This is rarely obtained in the first one or two runs with a new sample. However, the results of the initial test runs can provide useful information for improving the separation either empirically or by using a computer-assisted optimisation approach. 

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