Author Archive

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 […]

Two Detector Solution to Analyzing Sulfur

Dan Li, Katarina Oden, Chris English, and Jason Herrington Sulfur compounds are reactive, corrosive to pipes, and destructive to catalysts in petroleum refineries. Sulfur emission are strictly regulated globally. When released into the atmosphere sulfur dioxide converts to sulfuric acid resulting in adverse effects on human health and the environment. Sulfur detection is found useful […]

How Dirty Are You? Part 5…Micropipette Tips

Pipettes are common tools for drawing and dispensing precise volumes in chemical, biological and medical labs. Thanks to the invention of micropipettes and other techniques, we don’t do mouth pipetting anymore. Positive displacement pipettes are particularly useful because the air gap in standard micropipettes are replaced by capillary pistons, which greatly improve the accuracy for […]

Looking for a Cryogenic Valve for your Shimadzu GC-MS?

I was working on a project for volatile sulfur analysis. It took so long to cool the GC oven to 30 °C, and yet the most volatile analytes were still difficult to separate. At that time, I realized that I needed a cryogenic cooling system for my Shimadzu GC-MS QP2010 plus! However, I was not as excited as […]

Simple Analysis of Bile Acids by GC-MS

Bile acids are a group of steroidal acids with carboxyl and hydroxyl groups on the side. They are the major metabolic products of cholesterol. Bile acids play important roles as biomarkers for early diagnosis and therapeutic monitoring of many diseases, especially liver and intestinal diseases. For instance, high levels of intestinal bile acids, in particular, […]

Comparison between Different Stationary Phases for the Separation of Phthalates using Gas Chromatography-Mass Spectrometry (GC-MS)

Dan Li, Rebecca Stevens, and Chris English Phthalates are widely used as plasticizers in a variety of industry products. However, some phthalates are considered as endocrine disruptors[1] associated with a number of problems, including birth defects[2], high blood pressure in children[3], pregnancy-induced hypertensive heart diseases[4], respiratory problems[5], and obesity[6]. The European Union (EU) and United States Environmental Protection Agency (US EPA) […]

Phthalate Determination by Dual Column Set in Eight Minutes

Dan Li, Rebecca Stevens, Jason Thomas and Chris English If you don’t have a GC-MS for identification of the EPA regulated phthalates, don’t worry! Here we introduce a parallel dual column set for the analysis of regulated phthalates using µECD. As shown in my previous blog , the Rtx-440 column (cat. # 12923) is a […]

EPA Regulated Phthalates FREE?

Dan Li, Rebecca Stevens, and Chris English Phthalates are a class of compounds that have gained global notoriety. Most investigations focus on determination of phthalates in environmental matrices, baby products or demonstrate the adverse effect on human health. However, the presence of EPA regulated phthalates as impurities in technical phthalate mixtures is underestimated. Regulated phthalate […]

Minimizing Phthalate Interferences Using the Rtx-CLPesticides/Rtx-CLPesticides2 Columns

Dan Li, Chris English, Jack Cochran, Jason Thomas, and Rebecca Stevens   The alkyl and aryl esters of 1,2-benzenedicarboxylic acid, better known as phthalates, are widely used as plasticizers. Mainly added to polyvinyl chloride (PVC), phthalates make plastic products more durable and flexible. Phthalates are everywhere: plastic toys, PVC water pipes, wallpaper, artificial leather, electrical […]