Asymmetric Flow Field Flow Fractionation: A Powerful Method for Polymer Characterization
February 1st 2009Recent development of the instrumentation for asymmetric flow field flow fractionation (FFF) brings new possibilities for the characterization of synthetic and natural polymers with several advantages over traditionally used size exclusion chromatography (SEC). The main difference of asymmetric flow FFF compared to SEC is that the polymer separation takes place in an entirely empty channel, which eliminates undesirable SEC effects such as shearing degradation of polymers with ultra high molar mass, anchoring of branched macromolecules in SEC column packing, and enthalpic interactions of polymer molecules with a stationary phase.
Are Short Columns Always The Best Option?
February 1st 2009Using a fixed length-variant of the kinetic plot method, it is illustrated how an analysis that is performed near the optimal flow-rate of a given commercial column can, in many cases, be performed between 50–200% faster by switching to a longer column and operating it at a higher pressure - at least, if the available instrument pressure admits so. The present article aims to show that short columns are not always the best choice to get the fastest separation.
The Separation of Enantiomers on Modified Cyclodextrins by Capillary Electrochromatography (CEC)
February 1st 2009Various modes of capillary electrochromatography (CEC) for the separation of enantiomers on immobilized cyclodextrin derivatives are described. The following techniques have been used: (i) open-tubular electrochromatography (o-CEC), (ii) packed electrochromatography (p-CEC) and (iii) monolithic electrochromatography (rod-CEC). Three different strategies to prepare enantioselective cyclodextrin-coated chiral monoliths are described. The advantages and disadvantages of the various methods are outlined.
Enhanced ELSD Sensitivity of Parabens using Sub-Ambient Evaporation
January 16th 2009Varian, Inc. has published an application note entitled Enhanced ELSD Sensitivity of Parabens using Sub-Ambient Evaporation. Parabens are widely used as food additives, in personal care products and pharmaceutical formulations. They are relatively volatile but can easily be detected by the Varian ELSD. By manipulating the operating conditions, the Varian ELSD detects semi-volatile parabens, thus conserving sample integrity and providing maximum sensitivity. This application note shows that the innovative design of the Varian ELSD represents the next generation of ELSD technology, providing optimum performance across a diverse range of HPLC applications.
Rapid Identification of GSH-Conjugated Metabolites Utilizing Accurate Mass Data
January 15th 2009Incorporating metabolite profiling for absorption, distribution, metabolism, and excretion (ADME) properties early in the drug discovery process has resulted in an increase in drug success in development by reducing failure rates due to poor pharmacokinetic properties (1).
Reversed-Phase HPLC-MS Analysis of Salivary Peptides for Autism Diagnosis
January 15th 2009Italian researchers in Rome (Universita Cattolica and Consiglio Nazionale delle Ricerche) and Cagliari (Universita di Cagliari) have used reversed-phase high performance liquid chromatography with electrospray ionization mass spectrometry to analyze naturally occurring salivary peptides from subjects with autism and compare the profiles with those obtained from age-matched control subjects.
Molecularly Imprinted SPME in Analysis of Beta Blockers
January 15th 2009Researchers from Sun Yat-sen University and South China Normal University (both in Guangzhou, China) developed a sample preparation method for extracting the beta-blockers propranolol, atenolol, pindolol, and alprenolol from human plasma and urine samples.
Mixed-Mode SPE Used in Analysis of Pharmaceuticals in Wastewater
January 15th 2009Researchers from Stockholm University (Stockholm, Sweden) and Nankai University (Tianjin, China) used a serial mixed-mode cation-exchange and anion-exchange solid-phase extraction (SPE) method to extract 15 basic, neutral, and acidic pharmaceutical compounds from wastewater.