Liquid Chromatography

QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) is a sample preparation technique used primarily in the food industry to extract and clean up samples for instrumental analysis. Originally, the QuEChERS approach was developed for multi-residue...

A reader wrote to ask why he was seeing such a difference in the appearance of a gradient chromatogram when all he did was change the flow rate. He’d been making similar changes with isocratic methods for years – an increase in the flow rate...

In the last instalment of HPLC Solutions (#74), we looked at the gradient proportioning valve (GPV) test as a tool to check for proper operation of the proportioning valves used to blend solvents in low-pressure-mixing HPLC systems. The test...

If you have a low-pressure-mixing system on your HPLC, the solvents are blended using a proportioning valve. Usually this mixes up to 4 different mobile phase components. The pump delivers at a constant flow rate, for example, 1 mL/min, and the...

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.

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.

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.

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.

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 percentage...

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...