Liquid Chromatography

This installment of HPLC Solutions begins a series on different measurements that we make on chromatograms. Measuring the baseline noise generated by an HPLC system may seem like a singularly boring subject. But if you think about it, noise can be a...

In HPLC Solutions #122, we looked at how to measure baseline noise from a liquid chromatogram. One practical application of such measurements is to determine the noise and drift of the detector, which we’ll consider now.

In HPLC Solutions #122, we looked at how to measure baseline noise from a liquid chromatogram. One practical application of such measurements is to determine the signal-to-noise ratio (S/N), which we’ll consider here.

In this issue of HPLC Solutions we’ll look at the first two methods, and then consider the third in #126. For additional references, you might want to look at #122 for the determination of noise and #124 for calculation of the signal-to-noise ratio...

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...