Archive for the ‘LC’ Category

Modifying QuEChERS for complicated matrices- High Fat Samples

This post is part of a series on QuEChERS. Here are links to the previous two posts, in case you may wish to catch up before reading this one: QuEChERS dSPE selection-which one is best? Modifying QuECHERS for complicated matrices- Dry Samples (See Jana’s post here for further details on dry samples: QuECHERS approach optimization […]

Modifying QuEChERS for complicated matrices- Dry Samples

Before getting in to this discussion, I recommend reading my previous blog post first regarding classical applications for methods based on Quechers. https://blog.restek.com/quechers-dspe-selection-which-one-is-best/ QuEChERS methods were originally written to analyze pesticides in fruit and vegetable matrices, most of which have high water content and low fat content. More recently, the technique has been used for […]

Are PFAS sticking in your system?

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in our society and can be found in a wide range of consumer products; hence they are widely present in the environment, people and animals. They are persistent chemicals that have the potential to accumulate. Therefore, they are evaluated and monitored using a variety of methods and controlled […]

Shutting down your LC during a quarantine period?

It certainly does not only pertain to a quarantine period, but certainly more likely during the current Covid-19 crisis. Some of you might be needing to shut down your projects for a while. If you will not be using your LC column for more than 3 days, here are some recommendations and tips that might […]

Why is my LC Retention Time Shifting?

If you have experienced retention time shifts with LC, you know it can be complicated and can cause problems with quantitation if not resolved. Hopefully this post will help you navigate through troubleshooting this situation. For the purposes of this discussion, we will be discussing changes in retention on one individual column, not differences from […]

Falling Victim to One of LC’s Classic Blunders: Mismatching Your Diluent and Mobile Phase

An early lesson most of us learn in liquid chromatography is this: Always match your diluent to your mobile phase.  Once the exams are done, if you learned this in a college course, or your manager has walked away, you start flexing this “requirement” a little to see how matched they really need to be.  […]

Chiral separation on a C18 column? Separation of d- and l- Amphetamines, Part I

Did you know that chiral chemistry was discovered by Louis Pasteur, a French chemist and biologist in 1848? However, it took about a century to find that chirality plays a key role not only in the life of plants and animals, but also in several aspects of drug design, and both pharmaceutical and illicit drug […]

Afraid of HILIC? Watch These Videos and Overcome Your Fear!

Hydrophilic Interaction Liquid Chromatography or HILIC is a powerful tool to analyze polar compounds that have limited retention on typical reversed-phase columns. The power of HILIC can be utilized across multiple markets including environmental, food safety, and clinical diagnostics. But to be honest, it can be challenging to implement a HILIC method and more considerations […]

My fitting nut has broken off in the end of my LC column. What to do?

If excessive force is applied at an angle to a fitting or column connector, the ferrule could become stuck in the column end fitting. Likewise, a PEEK connector, column nut or plug can also break and leave part of it in the end fitting. Stainless steel nuts are much harder to break, although a stainless […]

Pesticides are like Siblings – some get along well and some don’t – No. . .Really?

My colleague, Joe Konschnik and I have been asked by many food chemists out there about how much they can trust their pesticides mixes after they combine them into one single larger mixture for calibrating their instrument, or monitoring the accuracy and precision of their method – and rightfully so.  Well, like siblings, sometimes they […]