Gradient elution HPLC

An excellent and comprehensive review has covered HPLC analysis of AOs and light stabilisers up to 1990 [576]. Normal vs. reversed-phase and isocratic vs. gradient-elution HPLC separation of synthetic mixtures of additives and of solvent extracts from polymers were discussed. 

How is gradient elution HPLC similar to temperature programming in GC ... 

E. H. Larsen, J. Sloth, M. Hansen, S. Moesgaard, Selenium speciation and isotope composition in 77Se-enriched yeast using gradient elution HPLC separation and ICP-dynamic reaction cell-MS, J. Anal. Atom. Spectrom., 18 (2003), 310- 316. 

In 1997. another retention parameter for QSRR analysis was introduced based on fast gradient elution HPLC. Krass et al. [2.1] proposed the parameter A defined as follows ... 

Theoretical backgrounds of the determination of log Aw by gradient elution HPLC were elaborated recently by Snyder and Dolan [24]. The approach has been developed to determine both log Aw and p/f , of analytes by means of two gradient runs [25]. 

Holcomb, M., Thompson, Jr., H. C., and Hankins, L. J. 1993. Analysis of fumonisin B1 in Rodent feed by gradient elution HPLC using precolumn derivatization with FMOC and fluorescence detection, J. Agricul. Food Chem., 41, 764-767. 

As a consequence of the toxicity related to the presence of aristolochic acid in plant preparations, several health institutions, such as the US Food and Drug Administration, Therapeutic Goods Administration have recently published safety information to prevent further cases of intoxication (information available at web address http //www.cfsan.fda. gov/ dms/ds-bot.html) [471], So detecting aristolochic acids in plant species that could be used in herbal remedies, and also in herbal preparations of uncertain composition, has attracted great priority in recent years to help prevent future adverse reactions. Aristolochic acids present in medicinal plants or herbs are analyzed by soxhlet extraction followed by TLC in the Chinese pharmacopoeia [412]. Another report used multiple ultrasonic extraction followed by HPLC analysis [472]. Ong s laboratory reported a method using a home made pressurized liquid extraction (PLE) system in dynamic mode to extract aristolochic acid in medicinal plants, followed by gradient elution HPLC [473]. Several scientific communities described various analytical methods for... 

Figure 4 Breakthrough curve of 2-propanol in heptane on a Separon SGX silica gel column in normal-phase gradient-elution HPLC calculated using the experimental isotherm data. Gradient 0-50% 2-propanol in 30min, 1 ml min" . V- milliliters of eluate from the start of gradient elution,

FT-IR and evaporative light-scattering detection indicated decreasing PDMS macromonomer incorporation corresponding to increasing retention time for a graft copolymer. More detailed information was obtained by multidetector SEC of composition fractions from gradient elution HPLC. 

FIG. 3 Gradient elution HPLC analysis of a mixture of 400 MW polyethylene glycol and an octylphenol 10 mole ethoxylate. The column is of porous graphitic carbon and detection is by ELS. (Reprinted with permission from Ref. 100. Copyright 1998 by Elsevier Science.)... 

FIG. 5 Reversed-phase gradient elution HPLC analysis of A, sorbitan monooleate and B, sorbi-tan trioleate. Detection by post-column reaction. Peak assignment 1, oleic acid 2, monoester 3, diester 4, triester 5, pentaester. (Reprinted with permission from Ref. 118. Copyright 1991 by Elsevier Science.)... 

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