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Interview with an Expert: Lukasz Rajski from EURL-FV Discusses Pesticide Analysis Utilizing HRAM Orbitrap Technology

publication date: Oct 25, 2016
author/source: Thermo Fisher Scientific

Lukasz Rajski works in EURL-FV, an EU reference lab, while finalizing his Ph.D. thesis.

ŇĀukasz RajskiHis focus is pesticide analysis of fruits and vegetables using high resolution accurate mass spectrometry (HRAM). Today we’ll be discussing his experiences with HRAM Orbitrap technology.

What type of work are you involved in and what is your expertise?

Currently my work is focused on the application of HRAM for analysis of pesticides in fruits and vegetables. Initially, I was involved in the development of pesticide extraction methods utilizing triple quadrupoles. Then, I began utilizing high resolution mass spectrometers and have been dedicated to this technique ever since.

How does HRAM Orbitrap technology compare to QTOF?

Orbitrap-based instruments offer an unsurpassable balance of sensitivity and selectivity. The very high resolution offered is the most obvious, which assures very high selectivity. It’s easier to distinguish pesticides from matrix ions, and the number of false positives and negatives is considerably minimized. Orbitrap technology is ideal for pesticides and other small molecule analysis, as the resolution is higher for a lower m/z, which accounts for the great majority of pesticides which have an m/z of below 500. Another feature I like about Orbitrap technology is the sensitivity gain in Single Ion Monitoring mode (SIM) which can increase sensitivity 5-10 times when compared to full scan MS. By combining good chromatographic separation and spectra multiplexing, we can analyze fractions of compounds in SIM mode in one chromatographic run, making it a perfect solution when extremely low LOQs are needed. An advantage of Orbitrap I would also like to mention is the small size of the mass analyzer.

What is your experience with high resolution mass spectrometry as a quantitative tool?

The Q Exactive Focus is definitely a quantitative instrument. Triple quadrupoles have long been the gold standard for quantitation, so we analyzed hundreds of real samples using various instruments and compared concentration values. The differences between concentrations obtained with a triple quadrupole and the Q Exactive Focus were not higher than the differences between two triple quadrupoles.

Is the Q Exactive Focus living up to your expectations?

Absolutely! It is a very powerful and flexible instrument that provides very good sensitivity and excellent selectivity. It’s perfect for both qualitative and quantitative analysis. This instrument is robust and maintenance is easy and fast. What more could you want?

What is your experience with using Compound Discoverer data analysis software?

Compound Discoverer is a very powerful piece of software. It includes chemometric tools like PCA that can be used for food authentication, for example. Dealing specifically with pesticides, I think that the most interesting feature is the in silica MS2 fragmentation. Let’s say we are looking for an uncommon pesticide residue, or a metabolite, for which we don’t have a standard. Compound Discoverer allows us to predict the masses and structures of MS2 fragments for any compound. We just import the mol file (information about molecules: atoms, bonds, structure, etc.) or draw the structure of the compound in the software. Compound Discoverer automatically predicts the fragment ions and searches for them in the data file. Another interesting feature is the metabolite structure prediction. We can use Compound Discoverer to search for pesticide metabolites, even if we don’t know their formulas. The software contains a database of metabolic degradation. We introduce the pesticide formula and the software automatically generates formulas of possible metabolites and searches for them in data file.

How do you see the future of LC-MS analysis in food safety labs?

LC-MS will be predominant technique, however due to the nature of electro-spray ionization we will need GC-MS for a certain group of pesticides.

Regarding LC-MS specifically, I expect that in the near future HRAM MS will become the new gold standard in pesticide analysis. Currently, the sensitivity of HRAM and triple quadrupoles is comparable and the quantitation capabilities and software are the same. The differences between HRAM and triple quadrupoles are obvious when it comes to selectivity, method development and the information obtained from each sample: HRAM is simply better.   Manufacturers are now designing HRAM instruments specifically for routine laboratories and prices are becoming much more competitive. The Q Exactive Focus is a perfect example of this. In my opinion, the future belongs to HRAM. Utilizing HRAM means you gain reliability of your results and time, which is typically wasted on method optimization.

As a young scientist yourself how would you convince other young scientists to consider a career in mass spectrometry?

Mass spectrometry offers a lot of possibilities. This is a very versatile and widespread analytical technique that can analyze food and beverage contaminants, environmental contamination, and you can focus on proteomics, metabolomics, and more. What is fascinating for me is the fact that MS (especially high resolution) is being developed very fast. Every few years new systems are launched, so mass spectrometry isn’t just a tool, but can also be the object of investigation. You can focus on creating new applications for MS and pushing the limits of new instruments.

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