LCGC Europe-07-01-2006

An isocratic HPLC method for the determination of phenol and nitrophenols (4-nitrophenol, 2-nitrophenol, 4,6-dinitro-o-cresol and 2,4-dinitrophenol) has been developed and validated using 2-chlorophenol as internal standard (IS) and a monolithic column in tap water samples. Prior to HPLC, the method requires solid-phase extraction (SPE) using polymeric Lichrolut EN cartridges. The method development involved the study of methanol and acetonitrile as organic modifiers, pH and flow-rate using a Chromolith RP-18e (150 mm × 4.6 mm I.D.) column. After comparing the performance of the separations obtained with both organic modifiers, the optimum separation of these compounds was achieved using 50 mM acetate buffer (pH 5.0)-acetonitrile (80:20, v/v) as mobile phase, 3 mL min-¹ flow-rate and UV detection at maximum absorbance wavelength. Under these conditions, all analytes were separated (Rs > 2.0) in an analysis time of less than 3.5 min and the most important validation parameters were evaluated. The recoveries obtained in the accuracy test for all phenols studied were in the 90–112% range using a preconcentration factor of 40, and the intraday and interday precisions [expressed as coefficient of variation (CV)] were smaller than 15%. Finally, the proposed method was applied to wastewater samples from several industries.

Lasers that can produce coherent infrared light in the 1–2 ?m wavelength range are essential in telecommunications, biomedical diagnosis and optical sensing.

NEXUS Biosystems has announced that it has renewed its worldwide marketing agreement with Bruker AXS to continue to globally market, sell and support the NEXUS Crystal Farm line of products. The range of products is an expanding line of automated instrumentation focused on protein crystallography research.

The robustness/ruggedness of an analytical procedure is a measure of its capacity to remain unaffected by small but deliberate variations in method parameters.

Liquid chromatography–mass spectrometry (LC–MS) has been increasingly indispensable in most analytical pursuits. Such acceptance would not have occurred without encouraging, early academic efforts and also the efforts of early practitioners who pressed manufacturers to improve and extend electrospray's capabilities. I briefly described the commercialization of LC in its halcyon period of the early 1990s in a 1998 article.¹

Commercialization of the passive sampler is very important because it reflects acceptance by the wider community.

After you have worked with liquid chromatography (LC) for several years, adjustment of the mobile phase to move peaks around comes almost as second nature. To the newcomer, however, such changes border on magic. One of the rules of thumb that I teach in my short courses is "nothing's magic". This is meant to remind us that chromatography is a very systematic process - study it carefully and you will minimize your surprises. In this month's instalment of "LC Troubleshooting," we'll look at solvent strength and see how we can use it to make predictable changes in the peak movement for reversed-phase LC separations. Hopefully, you will be able to make some practical use out of the principles presented here the next time you need to develop or adjust a method.