Separation Science

The Case of the Unintentional Ion-Pairing Reagent

Shifting retention times within a sample batch can be a real source of headaches in the routine HPLC laboratory. Previously we talked about the kind of retention drift experienced by some HPLC methods for the first few injections. This often is...

Why do retention times drift for the first few injections of an HPLC method?

How many of you have experienced this? You think you’ve fully equilibrated the HPLC column by running mobile phase through it for 30 min, but for the first 3 or 4 injections, the retention times drift a little, finally settling down after half a...

Does a Guard Column Make Sense?

My short answer: Yes!... and No!... and Maybe. 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. Let’s look at some of the different aspects of guard column use to see...

Internal Standards #2: What Makes a Good Internal Standard?

In a previous blog we took a brief look at why we might decide to use an internal standard and how a calibration plot is constructed and used in HPLC analysis. This time, we’ll consider some properties that are necessary when choosing a compound...

Internal Standards #1: How Does It Work?

In the next few blogs in this HPLC Solutions serieswe’ll look at several aspects of the use of internal standards (IS) in HPLC and LC-MS applications. The topic of this discussion is how an internal standard is used in quantitative analysis.

Column Protection #1: Filtration or Centrifugation?

It is easy to take knowledge for granted, especially when you’ve been involved in a field for a long time, as I have with HPLC. One of those areas is about how to protect the column. In the training courses we teach, Tom Jupille and I jokingly...

Column Protection #2: In-Line Filter

In an earlier blog, we looked at the processes of sample filtration or centrifugation as a means of reducing or eliminating particulate matter from the injected sample. As I mentioned, I prefer centrifugation, because it is easy, inexpensive and...

LC-MS: Be Prepared

In previous blog posts we've talked about various aspects of buffers. We saw that some buffers were better than others and that there were certain buffer-preparation practices that should be avoided. This prompted one reader (I.M.) to remind me...

Genetic Drift

Sometimes I don’t know whether to be amused or dismayed when I am presented with an HPLC method. Whether it is a method question from one of the readers or a paper to review for the 'Journal of Chromatography', it is a bit surprising to me how...

My Favourite Things, #1: “Introduction to Modern Liquid Chromatography” 3rd Edition

My first “real” job was working for Technicon Instruments Corp. in Tarrytown, New York, USA. My boss was Lloyd Snyder, who was to become a close friend and who has been my business partner for almost 26 years. Little did I know what my future had...

MS Column Switching

Save 50% on the cost of your LC-MS! Now that I have your attention, perhaps I shouldn’t make such a grand claim – maybe only 40%. Of course I’m talking about operating costs, not the purchase price, but if it means that you can do the work of two...

THF vs ACN injection

Q: I have observed peak splitting in my chromatograms when I inject the sample in tetrahydrofuran (THF) as the injection solvent, but I don’t see any problems when acetonitrile (ACN) is used. I am using a C18 column with a mobile phase of...