Gradient liquid chromatography methods

All above homopolymers are used also for the identification of suitable conditions for the coupled polymer HPLC techniques. Typical examples are liquid chromatography under critical (LC CC) and limiting (LC LC) conditions, and eluent gradient liquid chromatography (EG LC). For the development of latter methods, several defined statistical and block copolymers are available. 

Ayrton, J., Plumb, R., Leavens, W. J., Mallett, D., Dickins, M., and Dear, G. J. (1998c). Application of a generic fast gradient liquid chromatography tandem mass spectrometry method for the analysis of cytochrome P450 probe substrates. Rapid Commun. Mass Spectrom. 12 217-224. 

K. Stella, M. Stella, A. Pandora, A. Morfis, B. Antonios, K. Maria, New gradient high-performance liquid chromatography method for determination of donepezil hydrochloride assay and impurities content in oral pharmaceutical formulation, J. Chromatogr. A 1189 (2008) 392-397. 

A particularly attractive feature of GC, one that distinguishes it from liquid chromatography methods, is the lack of a sensitive dependence on solvents, modifiers, and gradient elution systems. Prerequisites for the use of GC, however, are volatility, thermostability, and resolvability of the chiral analyte. Obviously, this restricts the utility of the method. 

Dolan, J.W. Snyder, L.R. Saunders, D.L. Van-Heukelem, L. Simultaneous variation of temperature and gradient steepness for reversed-phase high-performance liquid chromatography method development, n. The use of further changes in conditions. J. Chromatogr. A, 1998, 803 (1-2), 33 50. 

Despite these difficulties (discussed in Section 5.3.3a) API sources are currently used widely in combination with a wide range of liquid chromatography methods, i.e. normal and reverse phase, isocratic and gradient, normal bore (4.6 mm i.d.) and capillary columns, as well as ESI with capillary electrophoresis and APCI with GC. In the context of trace level quantitation, API techniques are most often used in combination with reverse phase HPLC, and it is this combination that will be the main focus of discussions of matrix effects (Sections 5.1.1 and 5.3.6a) and of the more practical aspects in Sections 9.6 and 10.10.4.1d. In this regard it is worth noting here that in reverse phase chromatography using e.g., a Cjg-derivatized silica... 

Others have examined the necessary parameters that should be optimized to make the two-dimensional separation operate within the context of the columns that are chosen for the unique separation applications that are being developed. This is true for most of the applications shown in this book. However, one of the common themes here is that it is often necessary to slow down the first-dimension separation system in a 2DLC system. If one does not slow down the first dimension, another approach is to speed up the second dimension so that the whole analysis is not gated by the time of the second dimension. Recently, this has been the motivation behind the very fast second-dimension systems, such as Carr and coworker s fast gradient reversed-phase liquid chromatography (RPLC) second dimension systems, which operate at elevated temperatures (Stoll et al., 2006, 2007). Having a fast second dimension makes CE an attractive technique, especially with fast gating methods, which are discussed in Chapter 5. However, these are specialized for specific applications and may require method development techniques specific to CE. 

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