Commonly Abused Drug Screen Analysis
February 2nd 2009Many businesses have recently adopted the federal government guidelines for drug testing of employees created by NIDA (The National Institute on Drug Abuse) and SAMSHA (The Substance Abuse and Mental Health Services Administration) as a result of federal legislation or drug related accidents and deteriorating work performance.
Scientists Attempt to Source Sea Salt
February 2nd 2009There are a host of volatile organic compounds (VOC) in sea salt that originate from several sources such as the surrounding plants, algae, bacteria and environmental pollution. A team of scientists from the University of Aveiro, one region where sea salt is produced, reasoned that the combination of VOC from the different local sources could be sufficient to create a unique fingerprint of the salt.
Practical Aspects of Solvent Extraction
February 1st 2009Columnist Ron Majors discusses some of the practical considerations in the successful application of the popular yet age-old technique of solvent extraction (also known as liquid–liquid extraction, or LLE). After a brief review of the basics, guidelines on the selection of the appropriate extraction solvents and how to use acid–base equilibria to ensure efficient extractions of ionic and ionizable compounds are provided. Problems in LLE and the solutions to these problems are highlighted. A newer technique called dispersive liquid–liquid microextraction is introduced.
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.