Archive for the ‘Pesticides’ 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, […]

The Foundation of Separation is Preparation

Restek is known as a leader in the field of chromatographic column technology.  The idea is built into our very identity – resolution technology is at the heart of Restek.  We also believe that proper sample preparation sets chromatography up for success, though, by reducing the incidence of confounding results and prolonging the lifetime of […]

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 […]

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 (QuEChERS.com), maintained by CVUA Stuttgart, these specific documents: For Extraction (Stage 1): https://www.QuEChERS.com/pdf/reality.pdf For dSPE Cleanup (Stage 2): https://www.QuEChERS.com/pdf/cleanup.pdf 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 […]

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 […]

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 […]

Tips on the analysis of pesticides and mycotoxins in cannabis products: Matrix matters! (Part II)

In part I of this blog series, we learned about matrix effects, how to assess them, and how to address them (you can check the blog here). One of the main conclusions of part I was the importance of using matrix matched calibration as the means to account for possible ionization effects in LC-MS/MS, and […]

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 […]