Liquid Chromatography

Last week (HPLC Solutions #72) we looked at how in-line degassers work. This week I’d like to look at an interesting case study related to the degasser that was contributed by a reader (WLT). The story goes like this: I am running a gradient from 0...

For the first part of my HPLC troubleshooting career, it was very easy to name the number one HPLC problem – degassing. Air bubbles in the pump were a headache for nearly every user. Helium sparging was the gold standard in degassing, but was...

In this article the selection of appropriate robustness factors and factor levels relating to the mobile phase will be discussed and in particular, the volume fraction of the organic solvent in the mobile phase for reversed phase HPLC.

One question we regularly receive is regarding porous-layer bead packing materials. Are these for real or are they just hype? Let’s take a look at some of the characteristics of these column packings and see what lies between the frits of the column.

In this technical article you'll learn about the roles of pore size and particle size for an HPLC packing material.

This article explains how a guard column is one of those HPLC accessories that is a bit of a mixed grill – it can be a good thing or a not-so-good thing. Different aspects of guard column use will be assessed to see if they make sense for you.

Covers the essentials that every scientist needs in order to make effective use of liquid chromatography instrumentation. You should take this course if you are new to HPLC, or do you supervise new users of HPLC.

I had a follow-up enquiry about one of the recent articles. In 'Why Acid?', I discussed some of the reasons why acids such as formic or trifluoroacetic (TFA) are added to mobile phases for LC-MS work. The reader noted that in Figure 1 of that...

Q: I am running an isocratic method with a 250 x 4.6 mm, 10 µm particle column at 1 mL/min with a 20% acetonitrile (ACN)/buffer mobile phase. I dissolve my sample in ACN and inject. Normally my compound of interest comes out at 7.7 min. I switched...

This technical article looks at the best way to clean the frits used in the HPLC system. In this example, the reader had been sonicating them in nitric acid, but wasn’t sure if that was the best way to approach the problem.

A reader complained about retention times that changed in an overnight HPLC run and wondered how to diagnose the problem source. The question left too many possibilities, and because there was no complaint about changing resolution, I’ll assume that...

Recently, a reader sent a question about how to get started with a method that required separation of enantiomers by reversed-phase HPLC. Unfortunately, the problem is a non-starter in this context. Enantiomers cannot be separated by reversed-phase...

A reader recently sent in this e-mail: “I am trying to find information that I can put in an SOP regarding how long a mobile phase can be used before it must be discarded. I’ve heard 1-2 weeks from some sources, whereas others say a month, and some...

This technical article addresses why formic acid would be specified as an additive for the mobile phase in an HPLC method. Formic or trifluoroacetic acid at 0.1% concentrations are common, especially for LC-MS work. There are a number of reasons for...

PEEK (poly-ether-ether-ketone) tubing and fittings have become a standard part of most HPLC systems today. The flexibility and ease of cutting the tubing, coupled with the convenience of finger-tightened fittings make a combination that is hard to...