Liquid Chromatography Blog

Pore Size vs Particle Size

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

Does a Guard Column Make Sense?

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.

Just Enough Sample Preparation

This technical article shows how sample preparation is an integral part to successful chromatographic analysis and how selecting the right sample preparation technique is dependent upon a number of factors.

The Basics of HILIC

How can we describe the mechanism at the basis of HILIC retention? We will answer this question and give you an insight into the main interactions that govern chromatographic separation in HILIC mode.

Do you HILIC?

Are your analytes eluting close to the void volume of a reversed-phase (RP) column? Do you have problems retaining organic molecules under conventional reversed‑phase liquid chromatography (RPLC) conditions? Have you increased the initial...

Acid in A and B

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...

Injection Problems

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...

Frit Cleaning

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.

Retention Shifts

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...

Enantiomer Separations

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...

MP Lifetimes

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...

Why Acid?

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...

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