Archive for the ‘GC/MS’ 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 […]

LPGC – Fast way to your pesticide analysis!

Throughput is one of the most important parameters in the lab. The more samples we can analyze in a day, the sooner we can get home. Enter Low Pressure GC (LPGC) – this is an invention from our brilliant Jaap de Zeeuw [1-2], where a relatively short analytical column (10 – 15 m) with large […]

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 […]

Did you know you can manage jagged bleed with a controlled cooling program?

GC column bleed sounds like one of those old problems people used to have. The XLB was developed to lower detection limits by minimizing bleed. Now, virtually all polysiloxane GC columns are low bleed, with thick film and high polarity phases being the exception. Modern GC-MS instruments are so sensitive that I’m rarely concerned about […]

The New U.S. EPA Method TO-15A Blog Series-Part4: Clean Lines for Clean Air

In previous blogs (Part 1, Part 2, Part 3) we’ve covered the need to use air instead of nitrogen as a fill gas, the new lower blank requirements, and how these increase the importance for very clean lab air for canister filling. We’ve shown that using high quality gas filters or generators will get you […]

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 […]

QuEChERS approach optimization for low-moisture matrices – case of honey and brown rice flour

Last month, Nancy published a blog summarizing how to approach samples with less than 80% water. Today, I want to go into more detail on how to deal with different commodities with less than 20%. As Nancy said, QuEChERS was first developed for high-moisture matrices such as strawberries and spinach. However, the method is very […]

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 […]