The demand on labs throughout the world to run their triple quadrupole mass spectrometers to maximum capacity is ever increasing. Instruments are often operated continuously to ensure regulatory screening requirements are satisfied for targeted pesticides, mycotoxins, and veterinary drugs. Whether you are a commercial lab or a food manufacturer, the quality of the data you acquire is vital to your business. You must be certain that the last batch of strawberries you tested conform to pesticides regulations—your targeted list of usual suspects. However, what if a farming practice is using alternative pesticides or others not within your analytical suite? Unless you are informed, you are left in the dark and have to trust the data from your targeted list. With this inherent uncertainty, is the data you are reporting to your customer at risk? Does a contaminated batch go out into supply?
Targeted analysis has been the benchmark for GC-MS and LC-MS methods for years. Samples are extracted using robust and efficient practices, such as QuEChERS. LC gradients provide excellent reproducibility regarding retention time drift. Therefore, sample prep and LC conditions are rock solid. Pesticides, mycotoxins, and veterinary drugs are easily seen by the mass spec if you use these parameters. However, triple quad mass spectrometers will only see what they are setup to see. The MRM’s you have entered into the acquisition software will only search for that particular transition. Running the mass spec in full scan mode will not suffice, as you won’t have the desired sensitivity to detect nor will you be able to satisfy regulatory compliance with ion ratio measurements (IRM).
There is a solution to overcome this tunnel vision limitation. SWATH Acquisition is an advanced workflow born from the world of genome mapping where the technique has led to breakthroughs in precision medicine for the treatment of cancers. SWATH has evolved to address small molecule compounds making it ideal for routine pesticide, mycotoxin, and veterinary drug analysis. SWATH sees almost all—quite literally. This intuitive scan type is unique to SCIEX and is a key feature of the X500R QTOF system and SCIEX OS (data acquisition, data processing, and data reporting software).
So What Does SWATH Do?
SWATH Acquisition acquires MS/MS of all detectable compounds in your sample. Therefore, it is looking for everything all the time. It will detect the required pesticides, antibiotic veterinary drugs or mycotoxins in your targeted list, plus you can scan for other contaminants that may be in your sample. Using this approach enables you to attain a comprehensive profile of your food sample.
The MS/MS data you acquire using SWATH acquisition allows you to see those compounds in your targeted list which you can still process and quantify with SCIEX OS, and you can also cross reference any detected unknowns against a reference library. What if the detected compound is not in your library? You can cross reference the acquired spectra from your data with ChemSpider which is integrated into SCIEX OS and interpret your acquired spectra using that database.
You can still do all the targeted quantitation you require and need, plus in the same injection, you are also building a complete profile of what else is hiding in your sample.
One of the unique features for the SWATH screening workflow on the X500R is the ability to measure the ion ratios of the detected unknowns. The ion ratio is crucial for regulatory compliance in the identification of analytes. For example, in the Europe Union - Guidance Document on Analytical Quality Control and Method Validation Procedures for Pesticides Residues Analysis in Food and Feed (SANTE/11945/2015) states in Section D, Table 4 Identification requirements for different MS techniques, the SWATH workflow conforms to the “requirements of identification.”
The accumulation of SWATH-MS/MS data is extremely fast and reduces the significance of missed peaks. Therefore the excellent quality of the MS/MS data you get along with confident ID using ion ratio and quantitation, are not a problem. Having variable windows in a SWATH workflow enables a greater selectivity factor in a wider m/z detection range. You now have the power to build a comprehensive profile of what is in your sample.
There is no need to alter existing sample preparation or LC conditions to run SWATH. However, only with a SCIEX X500R QTOF can you get this ultra-comprehensive study of what is present in your sample.
- Guidance document on analytical quality control and method validation procedures for pesticides residues analysis in food and feed. SANTE/11945/2015