The globalization of our food supply has challenged food safety scientists with several concerns. The food needing to be tested could be from any part of the world. Differences in regulatory issues between countries, unknown applications of pesticides, unknown potential environmental contamination with pesticides and other toxins, and global sourcing of raw materials and distribution of products, means that food safety testing laboratories must look for a wider and wider list of potential residues.
In fact, both Katerina Maštovská and Jana Hajšlová raised the question of whether it is even suitable anymore to do targeted analysis (in which a specific list of compounds is interrogated) or whether an untargeted approach with high-resolution accurate mass spectrometry (HRAM) is a more appropriate approach due to its ability to perform retrospective analysis of the sample for additional contaminants.
Challenges in the Analysis of Dietary Supplements
Dietary supplements pose additional special challenges for food safety scientists. Firstly, they are often extracts, which can mean any contaminants that are present may be concentrated compared to the amount a person would get from eating a typical amount of the food from which the extract came. Supplements, such as teas, extracts, oils, and herbal capsules, can also pose special sample preparation challenges.
Finally, dietary supplements can carry additional concerns about natural toxins that may be present, such as mycotoxins or pyrrolizidine alkaloids. Mycotoxins and pyrrolizidine alkaloids can be damaging to your liver as well as causing other problems.
To this end, robust multi-residue analytical methods are a must.
Multi-Residue Chromatography & Mass Spectrometry Analytical Methods
Many of the analytes included in the method are considered troublesome to analyze, such as polar compounds with poor retention in reversed-phase chromatography. The method was validated in leek, wheat, and tea, which were prepared using a QuEChERS-based method using an optimized extraction protocol with extended extraction times in both acidified water to protect base-sensitive pesticides and acetonitrile.
For the HPLC separation, one of our Thermo Scientific Accucore aQ polar-endcapped LC columns (150 mm x 2.1 mm) was evaluated. A 20-min separation gradient was employed with water and methanol buffered with 5mM ammonium acetate (for ESI(-) mode) or 5mM ammonium formate in water and methanol, both acidified with 0.1% v/v formic acid (for ESI(+) mode), followed by a 5.5 minute wash and equilibration.
In addition to demonstrating good retention, resolution, and peak shape for even the polar compounds, the authors noted that the solid-core particle HPLC column demonstrated low backpressure and excellent lifetime, withstanding about 2000 injections of the relatively dirty extracts. For the mass spectrometry, a full MS/data-dependent MS2 experiment was set up. Resolutions of 70,000 (FWHM) and 17,500 were used for MS and MS/MS measurement, respectively. A library of target analytes was created via direct infusion.
The method was assessed against SANCO/12571/2013, the European guidance document on analytical control and validation procedures for pesticide residues analysis (link to guidance document). From the 389 analytes included in the method, two fragment ions were identified for 313 (80.5%) of the analytes. All remaining analytes were confirmed by detection of at least one highly accurate (< 5 ppm) fragment ion. Demonstrated recoveries, linearity, and repeatability were all excellent.
In her talk at the Symposium, Jana Hajšlová showed some additional results from a study of herbal supplements her lab performed. They found pesticides exceeding Maximum Residue Limits (MRLs) in about half of the 23 tea samples and detected 6 of the 11 pyrrolizidine alkaloids in their method. Mycotoxins were also detected, especially in the milk thistle sample, a supplement meant to protect your liver (link to WebMD)! Milk thistle was one of the supplements I was thinking of adding to my regimen but I have to admit that seeing this data has made me give it a second thought.
Additional Resources for Pesticides Analysis
Besides downloading over 15 talks, including those by Jana Hajšlová, Katerina Maštovská, on our symposium web page linked to in the second paragraph, I also invite you to visit our Pesticides Residues web page for many on-demand webinars, application notes, and more.
What is the biggest challenge in your contaminant analysis of dietary supplements? Give us your feedback in the comments box below.