Tony Taylor

Peak tailing is a problem that is regularly encountered in capillary gas chromatography (GC). It can cause issues with resolution and peak integration, affecting both qualitative and quantitative analysis. In this first of a series on GC diagnostic and troubleshooting, discover how best to identify the source of the issue, and find suggestions on how to prevent or fix the problems that underly the issue.

To avoid producing data not fit for purpose, chromatographers need to know how to identify worrying symptoms from HLPC instrument output.

The selectivity (α) of an analytical system describes the ability to discriminate between sample components based on differences in chemical and physical-chemical properties.

The improved performance of chromatographic detectors, most notably mass spectrometers (MS), has enabled many advances in analytical science, however, one such advance may be given less prominence than perhaps it should.

I’m frustrated with static headspace sampling!

I’ve been dealing recently with issues in the laboratory when using ammonium acetate buffers, including surprising rises in HPLC–MS back pressures when starting the instrument after overnight storage, as well as difficulties with MS sensitivity.

In HPLC Diagnostics Skills Part I we looked at baseline issues, and we continue here with HPLC peaks and in particular the skills required to identify tailing peaks, the causes of peak tailing, and most importantly, how to fix the issues that give rise to this peak deformation.

I wanted to produce a checklist for preparation of a GC or GC–MS system prior to analysis, referencing the actions, checks, tools, and consumable items that might be required.

As I receive reports from clients in Europe and the United States that helium prices are once again increasing, and warnings are being given regarding yet another laboratory-grade helium shortage, my thoughts turn once again to the use of hydrogen as an alternative carrier-gas for gas chromatography (GC).

The improved performance of chromatographic detectors, most notably mass spectrometers, has enabled many advances in analytical science, however, one such advance may be given less prominence than perhaps it should.

Our recent discussion on the use of hydrogen as a carrier for gas chromatography applications elicited many questions and comments, however one common question was “what are the considerations for using hydrogen carrier with MS detectors?”

As I receive reports from clients in Europe and the United States that helium prices are once again increasing, and warnings are being given regarding yet another laboratory-grade helium shortage, my thoughts turn once again to the use of hydrogen as an alternative carrier-gas for gas chromatography.

In this instalment of the LCGC Blog, Tony Taylor discusses noisy baselines in high performance liquid chromatography (HPLC).

Modern HPLC method development is dominated by a small number of pH adjusting reagents and buffers that are prevalent even when the method uses UV detection. This is driven primarily by the requirements of mass spectrometry.

Sometimes, the conditions specified in legacy liquid chromatography (LC) methods seem like they come from a different planet. This month, we look at which conditions to keep, and which ones to let go of.

To answer the question "Is there a good flow diagram I can use for GC method development?" please see below for our first attempt at something suitable, in the form of stepwise decision trees and flow diagrams.

In the late “noughties” we couldn’t avoid the webinars, seminars and online calculators which were being released by HPLC column manufacturers to extol the virtues of the “new” core-shell particle morphology that promised high performance at lower back pressures.

Just as medical practitioners are able to discern worrying features from a variety of medical physics devices (electrocardiogram, electroencephalogram, ultrasound, for example), we need to develop the skill to identify worrying symptoms from our HPLC instrument output.

I’ve written several times on the operational principles and variables used in UV detection, but I also get asked questions on the basic theory of UV detection, and this time I’m going to address some of those FAQs to give a little more background theory as well as some operational tips and tricks.

You may be one of the many analytical scientists who look with envy at those laboratories who are equipped with sophisticated automated HPLC method development systems. These systems are indeed very nice and can be very efficient in narrowing down choices, however, they aren’t a universal panacea and one can achieve a lot with a simple, paired down approach.

UV detectors are undoubtedly the most frequently used type of detector with HPLC systems, and I predict this will continue for many years, despite the rise of the modular mass spectrometric detector.

In this instalment of the LCGC Blog, solutions for carryover problem in gas chromatography (GC) are considered.

I think its fair to say that there has been a paradigm change in the way we approach mobile-phase design for HPLC in recent years.

In my previous blog, I discussed the possibility of backflash in splitless GC injection and its effect on quantitative reproducibility and carry-over.While much is written in the literature on optimization of splitless injection conditions, little is available on the implementation and optimization of increased head pressure (pressure pulsed) injection, so we will concentrate on this aspect of injection optimization.

Let’s first properly define carry-over in the context that I’d like to discuss here. An injection is made and a chromatogram obtained. On injecting a “blank” as the next injection, one or more of the components of the previous injection appear in the “blank” chromatogram.

Why the technique is a handy component of any analyst’s arsenal.

Chromatographic methods often require that the analyte response is calibrated (and validated) over a wide concentration range when the analyte concentration in the sample is either unknown or is expected to vary widely. Bioanalysis, environmental, and clinical applications are just a few examples of where this may be the case.

It is often possible to achieve better sensitivity and lower limits of detection and quantitation using standard gas chromatography (GC) equipment-here I’m referring to a standard split/splitless injection port and a Flame Ionization Detector (FID). Paying attention to some of the fundamental variables as well as some of the more esoteric considerations can lead to much improved method performance.

HILIC is not straightforward and there may be a number of mechanisms in play which need to be considered.

It’s excellent to see that compendial authorities are considering updating “allowable change” regulations, and the updates to allow changes to gradient profiles certainly open up a whole new world, but there are some reservations around the new restrictions on allowable changes to stationary-phase chemistry.