Author Archive

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, […]

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 […]

How can analyte protectants and matrix help improve peak shapes?

In my last blog, I presented a new technique called low pressure gas chromatography (LPGC, Figure 1). Just to recap, the LPGC system consists of a relatively short analytical column (10 – 15 m) with large ID and thick film (e.g. 0.53 mm and 1.0 µm, respectively) which is restricted with a narrow guard column […]

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 […]

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 […]

Pesticides are like Siblings, They Don’t Always Get Along part 2 – now with the GC mix!

Last year my colleague Landon publish his blog about pesticide multiresidue LC mix stability in a celery matrix and in a solvent. Today, I’d like to show you what happens when you do this with the GC multiresidue pesticide kit. On day 0, I prepared stock solutions from all 9 ampules of the GC multiresidue […]

One Stop Shop for Essential Oils Chromatograms

In the past few months, we have collected a variety of chromatograms using two different column phases, and three different column dimension formats. The peak identifications were performed using some standards but mostly from the NIST MS EI spectra library, 2005 edition. Let us know what you think in the comments below. Citronella Java GC_FF1296 […]

Analyzing avocado: How to deal with lack of water and keep the fats out

Avocados are a popular produce item. In fact, the consumption of avocados rose by 450% since 2000! Avocado may be delicious, but it is difficult to deal with in the lab. The good news – avocados are ranked number 1 on the clean 15 list, meaning they have the least amount of pesticide residues. With […]

Are Wax columns always used for essential oils?

My last blog examined the analysis of essential oils using GC columns with wax phases. While these columns are commonly used for natural oils, they are not the only option. Another choice that falls on the other end of the selectivity spectrum, in this case, a non or low polar; dimethyl diphenyl polysiloxane stationary phase. […]

A closer look at selectivity and tailing: Essential oils and Wax phases

The most common way to analyze essential oils is to use GC with either a FID or MS. The wax-based columns are the number one choice for many users and following up on an excellent blog post by Corby, I wanted to evaluate two wax in Restek inventory: Stabilwax and Rtx-Wax. The essential oil we chose was […]