Author Archive

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 […]

Quechers dSPE selection- which one is best?

Method development for Quechers sample cleanup can be a complicated task. Not only does the analyst need to make sure their analytes of interest can be recovered, but the matrix interferences must be removed enough to make the quantitation possible and reliable. It makes sense that selecting the best dSPE products is highly dependent on […]

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 […]

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 […]

Have there been any new applications developed for Diquat and Paraquat?

I am happy to answer “yes” to this question. Those of you who have been doing this analysis might have been using our Ultra Quat column that I talked about in an earlier blog post here, “I have an Ultra Quat column and I know how to use it…”   This updated method uses the […]

How do I Replace my LC Tubing?

For those that are experienced with LC, you probably have this all figured out.  If that is the case, this might serve as a good introduction to Restek products that you can use for this.  For those that are newbies to liquid chromatography, welcome and I hope you find this useful! The best way to […]

Can I use a 100% aqueous mobile phase with my LC column?

You might be asking this because you have read that not all columns are OK to use with highly aqueous content (>95%) in the mobile phase.  Or maybe the caption caught your eye because you have recently encountered some difficulty with using highly aqueous mobile phase. There is a phenomenon called “phase dewetting” that can […]

Which LC column should I use for my method?

We understand that with so many products on the market, choosing a column to get started can be difficult. Of course, column selection depends on what type of method you are following and what kind of LC system you have in your lab. Let’s begin by looking at our choices for the more traditional, fully […]