Fast separation

Prepacked columns with cross-linked high-resolution (HR) agarose gels provide a high number of theoretical plates and fast separations (29,30).The Superose gel material of Pharmacia Biotech is a highly epichloro-hydrine cross-linked... 

Z. Liu, S. R. Siiimanne, D. G. Patterson-Jr, L. L. Needham and J. B. Phillips, Comprehensive two-dimensional gas cliromatography for the fast separation and determination of pesticides exrtacted from human serum . Anal. Chem. 66 3086-3092 (1994). 

Another way to improve the analysis of complex matrices can be the combination of a multidimensional system with information-rich spectral detection (31). The analysis of eucalyptus and cascarilla bark essential oils has been carried out with an MDGC instrument, coupling a fast second chromatograph with a matrix isolation infrared spectrometer. Eluents from the first column were heart-cut and transferred to a cryogenically cooled trap. The trap is then heated to re-inject the components into an analytical column of different selectivity for separation and subsequent detection. The problem of the mismatch between the speed of fast separation and the... 

Figure 15.13 Comprehensive two-dimensional GC chromatogram of a supercritical fluid exti act of spiked human semm. Peak identification is as follows 1, dicamha 2, tiifluralin 3, dicliloran 4, phorate 5, pentachlorophenol 6, atrazine 7, fonofos 8, diazinon 9, cWorothalonil 10, terhufos 11, alachlor 12, matalaxyl 13, malathion 14, metalochlor 15, DCPA 16, captan 17, folpet 18, heptadecanoic acid. Adapted imm Analytical Chemistry, 66, Z. Liu et al., Comprehensive two-dimensional gas chromatography for the fast separation and determination of pesticides exuacted from human senim , pp. 3086-3092, copyright 1994, with pemiission from the American Chemical Society.

Studies of ligands which might provide specificity in binding to various oxidation states of plutonium seems a particularly promising area for futher research. If specific ion electrodes could be developed for the other oxidation states, study of redox reactions would be much facilitated. Fast separation schemes which do not change the redox equilibria and function at neutral pH values would be helpful in studies of behavior of tracer levels of plutonium in environmental conditions. A particularly important question in this area is the role of PuOj which has been reported to be the dominant soluble form of plutonium in some studies of natural waters (3,14). 

Van Nederkassel, A. M., Aerts, A., Dierick, A., Massart, D. L, Vander Heyden, Y. Fast separations on monolithic silica columns method transfer, robusmess and column ageing for some case smdies. /. Pharm. Biomed. Anal. 2003, 32, 233-249. 

When the object is to perform fast separations equation (1.57) indicates that we should not demand an overly large value for the... 

Upon substitution of the reduced parameters given above the separation time for a packed column and an open tubular column would be Identical if d 1.73 dp given the current limitations of open tubular column technology the column diameter cannot be reduced to the point %diere these columns can compete with packed columns for fast separations. This is illustrated by the practical txanple in Figure 6.3 (57). Ihe separation speed cannot be Increased for an open tubular column by increasing the reduced velocity since the reduced plate height is increased... 

Reversed TosoHaas SuperODS C-18 on silica 2p Fast separations... 

Li, J., Hu, Y. and Carr, P.W., Fast separations at elevated temperatures on polybutadiene-coated zirconia reversed-phase material, Anal. Chem., 69(19), 3884, 1997. 

The main characteristic features of HPTLC (use of fine particle layers for fast separations, sorbents with a wide range of sorption properties, high degree of automation for sample application, development and detection) are the exact opposite of conventional TLC. Expectations in terms of performance, ease of use and quantitative information from the two approaches to TLC are truly opposite [419], Modern TLC faces an uncertain future while conventional TLC is likely to survive as a general laboratory tool. 

Capillary electrophoresis offers several useful methods for (i) fast, highly efficient separations of ionic species (ii) fast separations of macromolecules (biopolymers) and (iii) development of small volume separations-based sensors. The very low-solvent flow (l-10nL min-1) CE technique, which is capable of providing exceptional separation efficiencies, places great demands on injection, detection and the other processes involved. The total volume of the capillaries typically used in CE is a few microlitres. CE instrumentation must deliver nL volumes reproducibly every time. The peak width of an analyte obtained from an electropherogram depends not only on the bandwidth of the analyte in the capillary but also on the migration rate of the analyte. 

Fast separations without the need to employ gradient elution... 

Instrumental developments concern micro ion traps (sub-mm i.d.) [193], extension of the mass range, mass resolution and capture efficiency for ions generated externally. Fast separations at very low detection levels are possible by means of hybrid QIT/reToF mass spectrometry [194]. 

In practice, because of the slow diffusion rates in liquids, dispersion due to longitudinal diffusion becomes important only at very low velocities. Because the dispersion increases only slowly with increasing mobile phase velocity, flow rates used in hplc are considerably higher than the value corresponding to minimum dispersion. This gives us fast separations without too much loss of efficiency. 

UHPLC (600 to 1000 bar) Significant runtime reduction for ultra-fast separation minimal solvent consumption Five-fold increase in speed for SIM Significantly higher efficiency for most complex separations Higher mass sensitivity Rapid method development... 

Length 10 m Fast separations Use with thin films, small inside diameter Pneumatics and flows most critical... 

Inside diameter 0.1mm High pressure drop required Lowest sample capacity Fast separations Most efficient but usually short column... 

The key to attractive solutions to high-throughput compatible GC-analytical technologies will require the development of fast separations. There are again several ways to shorten the analysis time required for a GC separation. The choice of the GC column is essential but will not be discussed in this context as this would go far beyond the framework of this chapter. 

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