Columns | The LCGC Blog

Most HPLC columns are packed with silica onto which some form of hydrophobic ligand is bonded – these columns form the vast majority of those used for modern reversed phase HPLC.

My initial inclination was to write about something other than the current status of life, given the threats of coronavirus. However, after a month extension to the shelter-in-place was ordered by the U.S. government this past weekend, and after various e-discussions with friends and colleagues throughout the world who are experiencing similar challenges, I felt I might have something to offer to make life easier.

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.

The 44th International Symposium On Capillary Chromatography (ISCC) and 17th GC×GC Symposium will be held at the Palazzo dei Congressi, in Riva del Garda, Italy, from 24–29 May 2020.

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

It was a pretty significant fight to get our most recent paper into the scientific literature. But, after five reviewers opining and four submitted revisions later, we were able to publish a very unique piece of work characterizing anecdotal claims of groundwater contamination in shale energy basins across the United States.

I’m frustrated with static headspace sampling!

Looking back, the start of my penning of blog articles matches quite well with the start of efforts to investigate the potential environmental impacts of unconventional oil and gas extraction, and the formation of the Collaborative Laboratories for Environmental Analysis and Remediation (CLEAR; http://clear.uta.edu) at the University of Texas Arlington. It also well coincided with my effort to begin some outside consulting activities, predominantly the review of forensics evidence for blood alcohol determination. Both of these activities have blossomed considerably in the past seven years, and it has become interesting to contemplate the most rewarding way to spend my time going forward.

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.

I run into scientists all the time who have never heard the term exposome. Most are not intimately connected in the analytical world; these days, analytical scientists seemingly expect “ome” and “omics” to be tacked onto pretty much anything.

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.

Theoretical computations can contribute input into experimental determinations.

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.

Traveling to interesting places for conferences and hearing new ideas is certainly one of the most enjoyable aspects of a faculty position. Recently, I attended the 16th International Interdisciplinary Meeting on Bioanalysis (CECE 2019) in Gdansk, Poland. I was absolutely delighted both by the city and the scientific quality of the meeting.

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.

In an effort to better understand the current application potential of microscale liquid chromatography (micro-LC), I picked up a few recent review articles from the literature. What one immediately appreciates from glancing through the literature for such information, is that there are a lot of different configurations and alternative formats, which can be placed under the micro-LC umbrella.

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?”

Recently, I was honored to attend the 2019 Shimadzu Global Innovation Summit, hosted by Shimadzu Corporation in Kyoto, Japan. The focus of this meeting was to highlight innovation at the interface between analytical chemistry and medicine.

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.

As someone who has been associated very closely with poster presentations, I have to say, it is time for a change.

Exosomes are small lipid membrane-bound extracellular vesicles, on the order 30 – 150 nm in diameter, which are shed by normal and tumor cells in the body. They are circulating within your body and can be isolated from virtually any biological fluid. Exosomes released from tumor cells have been shown to be enriched in certain proteins. These nanobodies hold significant promise for the discovery of cancer biomarkers, for cancer diagnosis and prognosis, and for biomarker quantitation.

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.

We have been working to develop the use of liquid chromatography–triple quadrupole–mass spectrometry (LC–MS/MS) for quantification of intact proteins from biological fluids.

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.

As we close in on a little more than a month to go before the 43rd International Symposium on Capillary Chromatography and the 16th GCxGC Symposium (ISCC & GCxGC 2019; www.isccgcxgc.com), May 12 – 17 in Ft. Worth, Texas, my excitement burgeons. All of the groundwork has been laid to provide forums for presenting and discussing the latest advances in capillary and comprehensive separations science.

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.

Virtually exclusively, liquid chromatography–mass spectrometry (LC–MS)-based assays for protein quantitation rely on bottom-up strategies, where the protein is initially digested into constituent peptides during sample preparation. Top-down intact protein quantitation, especially using affordable, low resolution triple quadrupole (QQQ) mass spectrometers, has been largely unexplored.

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.

If you have a method or process that involves a number of different variables, multivariate optimization approaches can provide a faster route to optimum conditions and can lead to a more reliable outcome than using a one-factor-at-a-time approach. With a little study and practice, students and researchers can apply these optimization techniques, even if a complete understanding of the underlying statistical treatments is not immediately apparent.

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.