Liquid Chromatography (LC/HPLC)

Liquid chromatography (LC) separations performed at elevated temperatures offer the following advantages.

This month's Technology Forum looks at the topic of HPLC/Ion Chromatography Focus and the trends and issues surrounding it. Joining us for this discussion is Chris Pohl, VP and Chief Science Officer at Dionex Corporation, Larry Tucker from Metrohm-Peak, and Yuichi Fusho of Shodex.

Chiral Technologies Inc., a provider of chiral chromatography columns, has announced that it will expand Latin American sales efforts by partnering with exclusive distributors.

Waters is acquiring Calorimetry Sciences, a manufacturer of high-performance calorimeters.

In an article recently published in Public Health Nutrition that discusses medicinal herbs? growing popularity, researchers report that While Western medicine currently employs pure, single compounds, CM has long used multiple combinations of compounds in the form of processed natural products, primarily medicinal herbs, to treat and relieve the symptoms of many different human diseases.

In an article recently published in Analytica Chimica Acta, researchers describe the simultaneous determination of sulfamonomethoxine, sulfadimethoxine, and their N4-acetyl metabolites in eggs using restricted-access media high performance liquid chromatography (RAM-HPLC) with a photo-diode array detector.

In an article recently published in the Journal of Nutrition, researchers reported that a mixture of anthocyanins from bilberries and blackcurrants reduced levels of transcription factor NF-kB - responsible for orchestrating a wide range of inflammatory responses.

In an article recently published in Analytica Chimica Acta, researchers developed a procedure for the determination of artemisinin in A. annua using high performance liquid chromatography (HPLC) with evaporative light scattering detection (ELSD) in couple with microwave-assisted extraction (MAE) as an efficient sample preparation technique. Afterwards, method validation system for HPLC?ELSD analysis was developed.

In an article published in Microchemical Journal, researchers used HPLC to determine the linuron preconcentrated on octadecyl silanized (ODS) magnetite.

In this installment of "Column Watch" columnist Ron Majors revisits expert predictions from a survey conducted in 1987. A cross section of column experts of the time were asked a series of questions on the future directions in high performance liquid chromatography (HPLC) column technology. Now, 20 years later, these predictions are contrasted against current column technology. In many cases, the experts were entirely correct, while in other cases, they were dead wrong. Some current trends were not even considered 20 years ago. The author backs up his analysis with current survey information.

Flash chromatography was first introduced by W.C. Still in 1978. The following report published in the June 2006 issue of LCGC North America provided a good overview of the technique.

Faster isn't always better

Modern gas chromatography (GC) capillary columns are rugged and forgiving but some care should be taken when handling and using these high-efficiency columns. In this instalment of "Column Watch", the authors discuss the issues surrounding avoiding column breakage, stationary phase damage and column contamination. Prolonging the life of a column by keeping an oxygen-free system, providing a cleaner sample and not exceeding the upper temperature limit of the stationary phase are highlighted in this practical discussion.

An evaporative light scattering (ELS) detector is a powerful detection tool if the solutes are less volatile than the eluent. Three main processes occur successively: nebulization, evaporation of the liquid chromatographic (LC) effluent and measurement of the light scattering by the residual particles. This leads to a non-linear calibration curve such as, A= a.m b where A is the peak area,m the sample mass and b the response coefficient measured as the slope of Log A = b>Log m + Log a.

Column temperature plays an important role in controlling peak spacing (selectivity) in reversed-phase liquid chromatography (LC) separations. Temperature has long been known to affect retention time, and more recently, its use in adjusting selectivity has gained popularity (see reference 1 for a review of temperature selectivity). In preparation of a paper for the most recent Pittsburgh Conference, I had an opportunity to reexamine some data that compare temperature selectivity with other variables used to control selectivity in LC separation. This month's instalment of "LC Troubleshooting" examines temperature selectivity and its relationship to pH selectivity.

This article describes the use of ultrahigh-pressure liquid chromatography (UHPLC) in pharmaceutical analysis of drug substances and drug products with UV absorption detection.

Getting started on the right foot is important for efficient method development.

The laboratory life science and analytical instrument industry is comprised of a large, diverse group of organizations that manufacture and distribute their products worldwide. However, overall industry sales are concentrated among a small set of companies. Approximately 950 firms are included in the industry, but only about 100 companies have sales above $50 million.

This month's Technology Forum looks at the topic of HPLC/Chiral and the trends and issues surrounding it. Joining us for this discussion is Magali Curiel of Thar Technologies, Inc., Rich Cowman of JASCO, and Geoffrey Cox of Chiral Technologies.

In early 2007, a web-based HPLC columns survey was conducted. Current usage was compared to a 1997 survey.

The concept of membrane-controlled processes is widespread in nature. Nearly all biological mechanisms concerning mass transport and exchange are regulated by membrane barriers and a variety of technical and biotechnological applications have been devised based on this mechanism. Membrane applications in analytical chemistry are geared towards the enrichment of target substances from an aqueous solution or the separation of compounds from a complex matrix. This article describes membrane-assisted extraction processes to separate traces of polar pharmaceutical substances the so called emerging micropollutants from aqueous samples. Basic prospects and examples of membrane-supported extractions are presented.

High-performance liquid chromatography (HPLC) is a powerful tool for the enantioselective separation of chiral drugs. However, the selection of an appropriate chiral stationary phase (CSP) and suitable operating conditions is a bottleneck in method development and a time- and resource-consuming task. Multimodal screening of a small number of CSPs with broad enantiorecognition abilities has been recognized as the best strategy to achieve rapid and reliable separations of chiral compounds. This paper describes the generic screening strategy developed at Johnson & Johnson Pharmaceutical Research and Development (J&J PRD) to successfully develop enantioselective HPLC methods for chiral molecules of pharmaceutical interest.

lthough liquid chromatography (LC) is most commonly associated with analytical techniques that are found inside the laboratory, LC also has been used in industrial applications for separation of a wide range of products for decades. The technique recently has been applied to requirements in the pharmaceutical and biotechnology industries, both inside the laboratory and in industrial settings. With global sales of over $1.7 billion, the market for preparative LC has encountered a stellar growth over the past few years.

The topic of this month's instalment of "LC Troubleshooting" was prompted by a manuscript I recently reviewed and a question I received from a reader of this column. Both inputs related to the variability of retention times observed in liquid chromatography (LC) methods. Variable retention is a topic that has been touched on many times over the history of this column, sometimes just in passing and other times in depth. Yet, it seems to be a problem that keeps recurring, so I think it is worth considering again.

Different methods require different strategies.