By now, you’ve likely heard of Roundup. Roundup is the trade name for the broad spectrum herbicide developed by Monsanto in 1974 and it’s one of the world’s most widely used agricultural weed killers. Roundup and other herbicides like it contain a polar organophosphorus compound called glyphosate. Glyphosate is degraded predominantly by bacteria into aminomethylphosaphonic acid (AMPA). Another broad-spectrum herbicide that is very similar in structure and global use is glufosinate. The consumption of these compounds have been linked to severe health concerns including but not limited to cancer ..read more

Calibration curves are an essential part to potency testing. A question often brought up by customers is “how many calibration points are needed for a calibration curve?” The answer to this question isn’t the same for everyone, as it depends on your laboratory’s objectives and accreditation body guidelines. Since the answer could potentially be different between labs, let’s do some statistics with different numbers of calibration points to gain insight on the effects of choosing more or less points. Confidence intervals can be calculated for calibration curves and can give us an indication of ..read more

Screening for volatile inhalants of abuse, as well as analyzing for blood alcohol content, is commonly performed in forensic toxicology laboratories using headspace gas chromatography with flame ionization detection (HS-GC-FID). Because these analyses are typically performed using FID detection, they generally use a dual column set-up, allowing for the use of a confirmation column with different selectivity than the primary column. Restek offers two unique column sets catered to these analyses: the Rtx-BAC1/Rtx-BAC2 and the Rtx-BAC Plus 1/Rtx-BAC Plus 2. All four of these columns have been add ..read more

In previous blogs (https://blog.restek.com/cyrogenic-cooling-for-air-analysis-interferences-from-n2-co2-and-o2/ and https://blog.restek.com/cyrogenic-cooling-for-air-analysis-part-2-combining-to-15a-and-ethylene-oxide/) I’ve talked about a combined ethylene oxide (EtO) and TO-15A method, focusing mainly on the chromatography and the use of cryogenic cooling to achieve separation of EtO from the several possible critical coelutions. However, it doesn’t matter how good the chromatography is if you can’t get your sample to the instrument, and I’ve been finding that EtO has some surprising complic ..read more

As we learn more about the chemical constituents of cannabis, more cannabinoids are being discovered and with it more THC isomers. You are probably very familiar with the two most commonly tested: Delta-9-THC and Delta-8-THC https://www.restek.com/Technical-Resources/Technical-Library/Video-Library/Did-You-Know-THC-Has-Isomers. There have been a total of 30 different isomeric forms of THC discovered thus far including different conformations. These isomers all share the molecular formula C21H30O2. In this blog, we will be focusing on isomers of THC that vary by the location of the double bond ..read more

We have had several blog posts and articles that discuss high backpressure observed in LC systems. Much of this discussion involves how to determine if the problem is in the column and what to do about it. Here are links to several of these: The Clog Blog Building up pressure on HPLC? Technical Service Red Flags- LC BUT, wait – what if the problem is not the column? Where is it coming from? Our Technical article here does a great job of discussing all of the possibilities: Diagnosing and Preventing High Back Pressure in LC Systems. One common source of high backpressure mentioned in the above ..read more

One of the tools we can’t live without when modifying/developing a GC method is the EZGC method translator. Changes made to GC method parameters like; inlet/outlet pressure, flow/carrier gas type or even capillary column dimensions will result in different retention times for our analytes and will affect resolution. Method translators calculate new analysis conditions by keeping the analytes’ elution temperatures the same, thus preserving the elution order. Using this tool, the analysis method can be translated to a different column dimension, carrier gas type, linear velocity, for example, wi ..read more

Several years ago, my colleague, Alan Sensue wrote Chemical Reference Standards; don’t just snap and pour. In it, he described a personal experience where he mixed several expensive reference standards together assuming the vials contained exactly 1 mL. It was a mistake he has remembered for some time. Here are a few other examples as to why you don’t want to just snap and pour your reference standards: Before opening the vial, it is a good practice to examine it and its contents. During shipment, vials can get bounced around on the delivery truck. As a result, a portion of the solvent can adh ..read more

Every once in a while, I meet a customer who is interested in analyzing cannabinoids by GC. Before Pro EZGC, these requests were difficult since we could only guess on the resolution and conditions.  Through the power of Pro EZGC and some previously published blogs, I was able to come up with a column and conditions. So, without further ado, I would like to welcome the neutral cannabinoids to the family of modeled compounds! Currently, this class of compounds is available on the Rxi-35Sil MS. The list includes: delta-9-THC delta-8-THC CBD CBC CBG CBN CBL For those looking to save time i ..read more

Every GC analyst experiences baseline issues at some point in their career, whether the baseline is higher than normal, or it contains additional peaks/spikes, or becomes erratic and drifts up and down.  In order to fix the baseline issues you will need to determine the cause.   I hope that the information contained in this post, and within the links it contains, will help you troubleshoot and remedy your GC baseline issues.   High Bleed Symptoms: Abnormally elevated baseline compared to previously obtained/expected baseline for the same (or equivalent) GC column for the ..read more