Archive for the ‘Tips & Tricks’ Category

Not Every Matrix-Matched Calibration Is Made Equal – Case of Spinach

Matrix-matched calibrations are a popular option for complex matrices, such as food commodities. When it is employed, one can assume that the majority of matrix effects will be accounted for and there won’t be much difference between calibration standards and the tested samples. But are all matrix-matched calibrations equal? In the case of QuEChERS extraction, […]

Short Webinar on Calculating Column Length Using EZGC Flow Calculator

Determining the length of your GC capillary column is essential for accurate control of carrier gas flow rate.  Just because you purchased a 30 m column, does not mean that your column is exactly 30 meters long; in fact, columns will typically have a little extra tubing.  But ultimately, it is not the physical length […]

Derivatization techniques for free fatty acids by GC

Anyone who has tried to analyze free fatty acids by GC realizes they have to derivatize these compounds. The inherently low volatility of free fatty acids and the carboxylic acid (-COOH) interaction with the siloxanes in the stationary phase. If not addressed, the first problem leads to late-eluting peaks and the latter results in peak […]

Getting Your LC Up and Running Again

Welcome Back!  You and your lab have been through a lot these last few months and now it’s time to get your LC back up and running.  After it has been down for a few months, it likely needs a little TLC before it’s performing optimally again.  Just like a car that sits around for […]

Modifying QuEChERS for complicated matrices- High Sugar & Starch Samples

In previous blog posts for this series on QuEChERS, we discussed QuECHERS dSPE Selection, Modifying QuECHERS..-Dry Samples and Modifying QuEChERS..-High Fat Samples Once again, I suggest to use the following from the official QuEChERS website (, maintained by CVUA Stuttgart, these specific documents: For Extraction (Stage 1): For dSPE Cleanup (Stage 2): References […]

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 […]

How I clean a GC injection port

Recently I have been asked by several customers how to clean an injection port.  My initial answer is always the same, you should clean the injection port according to the manufacturer’s recommendations.  But what instructions do I provide when the injection port was manufactured by Restek?  I usually provide the same response but then I […]

Accounting for Atmospheric Pressure When Using EZGC Method Translator and Flow Calculator and the ProEZGC Chromatogram Modeler

Modern GC’s are equipped with advanced pneumatics controls, which allow for accurate control of flow rates and pressures.  In order to accurately control or calculate flow rates, atmospheric pressure must be measured by the GC, since this determines the outlet pressure of non-vacuum detectors. Restek’s free tool, the EZGC Method Translator and Flow Calculator, has […]