Archive for 2019

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.  […]

What impurities are hiding in your monocyclic aromatic solvents?

As we approach the end of the year we are indulging in a bit of nostalgia and most experts agree that reminiscing about the past is a good thing1. It makes us more optimistic and generous. Researchers also noticed that in cold rooms we are more inclined to nostalgize than if we are in a […]

Two for the Price of One? Using CPP to Simultaneously Clean Pesticide and PCB Extracts

In a recently published blog, we introduced the advantages of cleaning EPA Method 8081 extracts using CarboPrep Plus (CPP) as a replacement.  The sample preparation for PCBs by EPA Method 8082 is commonly combined with the pesticides EPA Method 8081 for the extraction step then split into two portions for sample cleanup.  The logical question […]

Determining Optimal LC-MS/MS MRMs: Sensitivity is NOT Everything!

LC-MS/MS using electrospray ionization (ESI) is a widely used platform for routine target analysis and quantitation. However, one big challenge faced through the use of ESI is the presence of matrix effects. So, what are matrix effects and why are they important? Simply put, when matrix components coelute with the target analytes, they have the […]

GC Inlet Liner Selection, Part III: Inertness

The inlet liner is the first surface analytes will interact with after introduction into a GC.  It is critical that liners are deactivated, as a number of adverse interactions can occur between analytes and the glass surface.  Deactivations typically involve some type of silanization of the surface to cover active sites inherent in glass, such […]

Terpene Analysis Approaches – Part II

Welcome back my fragrance fanatics! Today, we continue exploring approaches for analyzing terpenes. If you missed part one, you can get caught up here! Last time, we discussed two HS approaches that just flat out stunk! So, it’s time to make some adjusts. The first thing to check was the way our samples were prepared. […]

Amines: Topaz or Base Deactivated Liners?

Amines can be difficult to analyze by GC, since they are active and adsorb to surfaces within the chromatographic system, including the inlet liner and the column.  This leads to loss of compound response, and peak tailing.  While deactivations can help to mitigate these effects, the quality of deactivations varies.  Primary amines are especially difficult, […]

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 […]

Using Raptor ARC-18 for a Rapid Analysis of Vitamin E Acetate

We recently took a look at combining Vitamin E Acetate and cannabinoids into one method https://blog.restek.com/?p=65679.  This route allows labs to diversify their testing services with a few simple modifications, if using our potency method.  We wanted to give labs another option as well.  Therefore, Justin Steimling went back into the lab and developed a […]

Tetrachlorobenzene isomers added to ProEZGC!

Tetrachlorobenzenes are manufactured as intermediates for the production of fungicides, herbicides, defoliants, insecticides as well as dielectric fluids for transformers (1). There are three isomers with the following chlorine substitutions; 1,2,3,4 / 1,2,3,5 / 1,2,4,5. While the chemical industry measures these compounds for purity they are also found in the environment as the result of […]