Archive for the ‘Optimizing Applications’ Category

FDA Issues Second Warning on Methanol Based Hand Sanitizers

The U.S. Food and Drug Administration has placed methanol containing hand sanitizers on an import alert (1). These products do not list this ingredient and some are incorrectly labeled “FDA approved.” Currently, 87 hand sanitizers have been found to contain methanol (2). Methanol (methyl alcohol Cas# 67-56-1), known as wood alcohol, is commonly found in […]

Thermo Trace 1310 Inlet Temperature Profile vs Agilent 7890 for Split/Splitless Injectors

Several years ago, my colleague Scott Grossman wrote an excellent article entitled “It’s a Matter of Degrees, but Do Degrees Really Matter?”  He measured the temperature profile across various Agilent inlets, demonstrating different gradients in temperature exist across inlets, depending on the type of inlet and even among the same inlet type.  One consistent finding […]

Hydrocarbon Ranges of Natural Gas and Petroleum Products

Sometimes customers need to analyze natural gas and petroleum products, whether it is to confirm the purity of the product by looking for the impurities which may be present, or for an environmental reason such as a spill or leak.  In order to choose the correct GC column and reference standards, one needs to know […]

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 […]

Optimizing Splitless Injections: Initial Oven Temperature and Solvent Polarity

Beyond optimizing the inlet parameters of temperature and splitless valve time, initial oven temperature also plays an important role for splitless injections. When a liquid sample is injected into a GC, the first goal is to vaporize the sample within the inlet and transfer it to the column. As you know, this sample volatilization and […]

Optimizing Splitless Injections: Splitless Purge Valve Time

In my previous blog, I discussed optimizing inlet temperature for splitless injections.  Today I would like to discuss another critical parameter for splitless injections: splitless purge valve time.  The key feature of a splitless injection is that all the carrier gas flow is directed to the column and the splitless valve is closed during injection.  […]

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 […]

ProEZGC Chromatogram Modeler – there is much more to the program than just the Welcome Screen

When you log into the ProEZGC Chromatogram Modeler software, you will see the screen below, which is what I refer to as the Welcome Screen. This is the starting point for all, and unfortunately all some customers will think there is to the ProEZGC software.   For those of you who have used ProEZGC, you […]

Optimizing Splitless Injections: Introduction

Split and splitless are the two most common modes of injection for GC.  Each has its own set of pros and cons, with the required method sensitivity vs the sample concentration ultimately dictating which one to use.  For trace level analyses, a splitless injection is often the best choice, as the goal is to recover […]

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 […]