HPLC

Microemulsion liquid chromatography (MELC) is a recent development offering reduced sample preparation times for complex samples and generic separation conditions applicable to a wide range of solutes. This article introduces the concepts of MELC and discusses the possible benefits and future applications.

A number of commercial in-solution, and in-gel IEF fractionation systems are described in this month's column.

Ron Majors continues his summary of the technical highlights of HPLC 2008, discussing more hot topics from the show.

John Dolan regularly receive e-mails from readers with a wide variety of questions. As he cleans out his inbox, he chooses a few of these to share.

Micellar liquid chromatography (MLC) is a reversed-phase liquid chromatographic mode with a solution of surfactant forming micelles as the mobile phase. The interaction of solutes with the stationary phase coated with surfactant monomers, combined with the increased solubilization capability of micelles, have profound implications with regard to retention, selectivity and efficiency. Practical steps that a chromatographer involved in MLC should consider when developing an analytical procedure are described, including mobile phase preparation, column conditioning and cleaning.

The move from conventional particle sizes (5 μm or higher) to smaller diameter packing materials is one of the most attractive approaches to achieve higher separating efficiency. Recently developed 3 μm polysaccharide-derived chiral stationary phases demonstrate characteristics of favourable mass transfer kinetics, high column efficiency and good column permeability. This allows the fast analysis of enantiomers using conventional HPLC instruments.

HPLC 2008 was held in Baltimore in May. Columnist Ron Majors covers the highlights of this major symposium, held in the U.S. every two years.

After returning from Israel, John Dolan dedicates this month's column discussion to three problems that know no international boundaries: how to condition a new column, the effect of washing a column with water, and ...

Nanostream, Inc. (Pasadena, California), a developer of microfluidics-based parallel HPLC technology and a provider of assay development has closed all business operations.

The authors meet the need for a method for the determination of cytosine purity by developing a hydrophilic interaction chromatography (HILIC) method with demonstrated advantages in comparison to other separation techniques.

This month's column will consider two problem areas; peaks that have severely tailing peaks, or split or doubled peaks, and the peaks that front badly.

Guest Editor Peter Schoenmakers provides an introduction to LCxLC, and then goes on to talk about peak capacity, sample dimensionality, phase orthogonality, and some of the successes of the technique and the obstacles yet to be overcome.

In gradient mode, the quality of the analysis will be influenced by the performance of the proportioning and mixing of the eluents at any time during a given chromatogram.

I remember reading a study on learning in the all-day short-course format. Because teaching liquid chromatography (LC) classes is a significant part of my work, my attention was captured. The writers claimed that in a 6–8 h class, only three points would be remembered. One of my LC troubleshooting classes has approximately 200 slides - what does this say about how effective a short course is at conveying critical knowledge? As the saying goes, I have tried to make lemonade out of these lemons, and use the "only three things" concept to help reinforce what I think are the key points. So, this month's "LC Troubleshooting" instalment will use these points to form the core of a preventive maintenance programme for your LC system.

Only a generation ago, HPLC was considered an exclusive, futuristic technique that only a select few laboratories could afford to use. Today, HPLC and its various related techniques continue to dominate the world of chromatography. From HILIC to Chiral technology to hyphenated techniques such as HPLC-MS, it is without a doubt the most widespread technique currently used in the field of analytical chemistry. This month E-Separations Solutions' Technology Forum looks at the topic of HPLC-Chiral and the trends and issues surrounding it. Joining us for this discussion is Elena Eksteen, Ph.D., of Chiral Technologies, Inc., Todd Palcic of Thar Instruments, Inc., and Bill Ciccone of Microsolv.

This article investigates the different methods that can be used to compare the performance of liquid chromatography (LC) columns to assess the advantage of using them at high pressures and/or high temperatures. The main focus is on the kinetic plot method. This method, which is based on two simple equations, allows the user to transform the more common Van Deemter curve into a curve describing the ultimate separation speed as a function of the required plate number, or the required peak capacity or the required resolution.

What do you do when the method can't be reproduced?

Many HPLC analyses could be performed at lower expenditure. This could involve a combination of reducing the analysis time, reducing the resolution between critical peaks, and lowering the consumption of mobile phase. Successfully optimizing the method in such instances - as well as in situations where it is necessary to transfer the method to another laboratory that lacks the same selection of columns - can save the analyst time and money.

This article investigates the different methods that can be used to compare the performance of liquid chromatography (LC) columns to assess the advantage of using them at high pressures and/or high temperatures. The main focus is on the kinetic plot method. This method, which is based on two simple equations, allows the user to transform the more common Van Deemter curve into a curve describing the ultimate separation speed as a function of the required plate number, or the required peak capacity or the required resolution.

John Dolan has discovered that check-value problems have jumped to the top of the list with LC users. He takes a look at them in this month's installment of "LC Troubleshooting."

Guest columnsist and LCGC Emerging Leader award recipient Gert Desmet considers the different methods that can be used to compare the performance of LC columns.

Advion Biosciences Inc. (Ithaca, New York), a developer of microfluidic sampling technology for mass spectrometry (MS) has bought almost all assets of its production supplier, Washburn Manufacturing Technologies Inc. (Trumansburg, New York) for an undisclosed amount.

In this instalment of "Column Watch", columnist Ron Majors examines the role of pressure in high performance liquid chromatography (HPLC) from two viewpoints: the impact of the ultrahigh pressures encountered in ultrahigh-pressure liquid chromatography (UHPLC) on chromatographic parameters and increases in column pressure encountered in normal daily use. The latter is of more practical consequence to HPLC users because increased back pressure usually implies that something has gone wrong with the column. Pressure increases as a result of physical and chemical contamination are explored and practical approaches to solve these problems are suggested.

Ion-pair chromatography can be your best friend or your worst enemy.

For this month's discussion, John Dolan shares some of the key resources that he recommends using when you have one of those "How do I?" questions.