Liquid Chromatography

A reader wrote me recently asking what would happen if he injected his sample, which came dissolved in hexane, into a reversed-phase mobile phase of methanol-buffer. The first answer is that this is not a good habit, but is it possible? We’ll see.

I recently had an inquiry from a reader of 'HPLC Solutions' that comes up with some regularity in the HPLC troubleshooting classes that I teach: “Will I damage the column by getting air in it?” Let’s consider the possibilities for a moment. One...

A reader asked me if she was in danger of shortening the lifetime of an HPLC column by removing it after each batch of samples and storing it. This also raised the related question about expectations of shorter column lifetimes if the same...

What happens if your favourite HPLC column accidentally rolls off the bench and lands on the concrete floor of the lab? Is it ruined?

After I wrote an article on in-line Degasser (HPLC solutions #72), I immediately received some reader feedback on a specific failure, which was published in 'Failed Degasser' (HPLC solutions #73). Since that time I have been collecting occasional...

A reader reported a problem blockage of a column packed with one of the newer shell-type packings. The mobile phase A comprises a mixture of 0.1 M KH₂PO₄, 0.05% triethylamine (TEA), and 150 mg/L EDTA adjusted to pH 7.5 with NaOH. The B-solvent is a...

A reader recently emailed me a question that went something like this: “I’m using LC-MS/MS to analyse a biomolecule that I have isolated from tissue by LC-MS/MS. The lowest point on the calibration curve that I prepared is 0.1 µM. All the samples...

A reader recently asked a question about the use of the peak-purity function of his diode-array UV detector (DAD). The question related to whether or not he could detect the presence of enantiomers, stereoisomers, diastereoisomers, or epimers with...

The dwell volume comprises all the HPLC system volume between the point the solvents are mixed to the head of the column. For high-pressure-mixing systems, this includes the mixer, connecting tubing, and sample loop. For low-pressure-mixing systems,...

In a previous article (Dwell Differences, HPLC Solutions #85) we saw an example of how the appearance of a chromatogram could change when a gradient method was run on two HPLC systems of differing dwell volume. In this article we’ll look at a simple...

In a previous article (Measuring Dwell, HPLC SOlutions #86) we looked at a simple technique to measure the dwell volume of an HPLC system. In a prior discussion (Dwell Differences, HPLC Solutions #85), it was seen that differences in dwell volume...

Recently a reader sent me a question regarding a problem he was having with recovery of a vitamin he was measuring in pet foods. He found that the precision, measured as repeatability of peak area for a given sample, was adequate for multiple...

In an earlier article (#88) we looked at the need to use a matrix-based calibration curve so as to correct for low recovery when extracting an analyte from a sample matrix. To do this, we used a blank matrix and spiked in known concentrations of...

I recently had an email from a reader who wondered how it was possible to use an evaporative light scattering detector (ELSD) with an HPLC for quantitative analysis when instead of a linear response, the concentration vs response relationship...

I recently had a reader send me an email complaining that the peaks in his chromatogram were too narrow. At first, this seems a bit odd – after all, most people complain because peaks are too wide, so narrow peaks usually are preferred over broader...