Liquid Chromatography

As we saw in HPLC Solutions #125, the International Committee on Harmonization (ICH, 1) lists three ways to determine the limit of detection (LOD) or limit of quantification (LOQ):

With today’s data systems for HPLC, we tend to take peak measurement for granted. Much of the time we’re pretty safe if we use the default integration conditions, but this is not always the case. In this HPLC Solutions series on integration, we’ll...

In HPLC Solutions #127 we took a brief look at how HPLC integrators detect and measure a peak’s height or area. Much of the time the default settings for the data system are sufficient for reliable operation, but you may find that the integration...

In the first two parts of this series (HPLC Solutions #127 and #128), we looked at how HPLC data systems integrate chromatograms and some of the adjustments that can be made if you don’t like the way the default settings perform. Even with proper...

I’m sure you’ve all heard the proverb that says if you give a person a fish, you’ll feed them for a day, but if you teach a person to fish, you’ll enable them to feed themselves. There are lots of on-line options for “fishing lessons” through LC...

This is the third instalment of HPLC Solutions related to resources you should have at your fingertips when you are working in an HPLC laboratory (see also #130 and #131). If you work in a regulated industry, such as pharmaceuticals, your HPLC...

In this instalment of HPLC solutions , I’d like to share a few of the places that I look when confronted with a new separation problem.

This is the fourth instalment of HPLC Solutions related to resources you should have at your fingertips when you are working in an HPLC laboratory (see also #130,131,132). In the last discussion (#132) we looked at online resources from the...

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.