HPLC

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.

To obtain a better understanding of the challenges faced during method development and validation, the authors - in cooperation with LCGC - conducted a survey earlier this year. This column summarizes the results.

This article demystifies the qualification procedures and proposes a well designed, easy and simple set of experiments upon which to establish internal standard operating proceduresfor the complete qualification of HPLC instruments.

A simple and inexpensive sample preparation method followed by reversed-phase high performance liquid chromatography (RP-HPLC) was developed to quantify oxytetracycline (OTC), chlortetracycline (CTC), and tetracycline (TC) residues in prawns. The total analytical time, including sample preparation, was 15 min for each sample and no organic solvents were used in the sample preparation or chromatography stages.

To characterize complex samples such as natural products or peptide digests, a single chromatographic dimension cannot completely separate and identify every single compound. For such cases, comprehensive two-dimensional liquid chromatography (LC x LC) is under rapid development.

In the last decade, research on the detection of all groups of doping agents has been investigated by LC-MS, and routine LC-MS screening applications are now available for almost all classes of doping agents.

This month's installment of "Column Watch" is the second part of a two-part series in which columnist Ron Majors examines the trends and highlights in columns and consumables at Pittcon 2008.

After taking a course on learning that stated most people only remember three main points from an eight-hour training class, John Dolan decided to use three points to form the core of a preventive maintenance program for your LC system.

If the problem source cannot be found or if found, cannot be corrected, an adjustment in flow-rate is justified.

This month's installment of "Column Watch" is the first of a two-part series in which columnist Ron Majors examines the trends and highlights in columns and consumables at Pittcon 2008.

A very efficient way to start an isocratic method development project is to make the first run as a scouting gradient run.

This article explores the progress that atmospheric pressure photoionization (APPI) has made in its relatively short history for LC–MS analysis. Specifically, the authors examine the combination of APPI and electrospray ionization (ESI).

After teaching a training class in China, John Dolan was reminded of how chromatographers worldwide encounter the same types of problems, such as method transfer. This month's column is dedicated to method transfer problems.

This study evaluates the use of HPLC to estimate the log P (the octanol–water partition coefficient) of two compounds, apocynin and diapocynin. The paper will discuss the effects of an unexpected reversal of retention that occurred when these compounds were chromatographed with various amounts of methanol–water mobile phases.

Trade extra resolution for speed.

The use of dual polarization interferometry (DPI) to measure the behaviour of alkyl-modified surfaces under different solvent regimes is described. The empirically observed and modelled behaviour of grafted long alkyl chain adlayers on a silica surface were in good agreement. The empirical data was also compared with data using analogous systems and these also matched well. This approach has the potential to gain much greater insight into the behaviour of reversed-phase (RP) columns and could help to design column surfaces that are resistant to phase collapse.