Archive for the ‘Food’ Category

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

Quechers dSPE selection- which one is best?

Method development for Quechers sample cleanup can be a complicated task. Not only does the analyst need to make sure their analytes of interest can be recovered, but the matrix interferences must be removed enough to make the quantitation possible and reliable. It makes sense that selecting the best dSPE products is highly dependent on […]

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! The good news – avocados are ranked number 1 on the clean 15 list, meaning they have the least amount of pesticide residues. With so many avocados on the market, the testing is as important as ever, which […]

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. […]