SWATH acquisition on a Sciex TripleTOF system is a mass spec acquisition strategy for identification and quantitation of analytes in complex samples.
The technology enables a permanent digital record of quantitative MS/MS data for the sample and uses generic MS acquisition settings, requiring little or no method development.
It allows simultaneous identification and quantification of most detectable compounds in a sample from a single analysis.
Look for everything
The definition of SWATH is sequential window acquisition of all theoretical fragment ion spectra.
Philip Taylor, Sciex global marketing manager, food, environmental and forensic, said there is no change to run time and processing takes a couple of minutes.
“SWATH is a DIA-type method where it triggers and scans for everything in your sample, and data dependent acquisition uses a targeted traditional MRM approach. SWATH also does that so you can look for the targeted pesticides which your regulator requires but then you’re also looking for everything that is detectable in the sample,” he told FoodQualityNews.
“You can still report all the pesticides that you need for the regulation and your customers but you’re also creating a digital archive of what was in that sample. So it could be a newly synthesized pesticide or a new contaminant which is present in your sample, so if you were doing it on a targeted data approach you would never see it and it could be something of interest.”
Since commercialisation in proteomics workflows five years ago, SWATH acquisition can move into areas such as food testing as the X500 series of mass spectrometers can acquire high resolution MS/MS spectra at high acquisition rates.
Taylor said the TripleTOF 6600 is the top of the range instrument used in cancer research and biomarker discovery and that is where SWATH came from.
“Sciex is developing application software for our instruments that doesn’t require analysts to be mass spectrometry experts, while still providing laboratories with the high performance they need for advanced workflows,” said Jean-Paul Mangeolle, president of Sciex.
“We manufactured the X500R which was custom built for high throughput food testing and environmental laboratories and we’ve adapted and converted SWATH so it is now applicable to the mainstream of commercial laboratories who are running 24/7 every single day,” he said.
“When we were engineering and designing this product we went out to customers and got customers to come to our R&D facility in Toronto to tell us what they want out of a QTOF instrument.
“Software is the thing. They wanted it to be quick and easy to use because some software is complicated and there is a lot of redundant functionality across all mass spec platforms and vendors. With this package everything is together, the customer does not have to run the application on one software package, process on another and report somewhere else.”
Dr Amadeo R Fernández-Alba, head of the European Union Reference Laboratory (EURL) for fruits and vegetables, presented at ASMS his work on analysing regulated pesticides in baby food using the Sciex X500R QTOF system with SWATH acquisition.
“The most important aspect of the X500R QTOF System is the ability to work with SWATH acquisition, especially when analysing food samples with complex matrices,” said the professor of Analytical Chemistry at the University of Almeria.
“It also enables fast quantification, making it ideally suited to high-throughput applications, without compromising on sensitivity.”
SWATH instead of MRM
SWATH comes as standard with the X500R QTOF System.
“Some labs may be more familiar with using MRMs which is associated with triple quads and on the X500R you can do MRM HR (high resolution). It is a familiar workflow where staff will be used to the two transitions, the ion ratios and all the required parameters for reporting a positive food result,” said Taylor.
“However, you can still get all that data out of SWATH; you can get the transitions you require and the ion ratios and you’ll also get the spectral fingerprint of that compound which they’ll cross reference with a library.”
Taylor said SWATH data does not require much space.
“One of the concerns now in this digital age is storage of your data so customers and companies have an obligation to store that data and some data files can be big. You can say what you are looking for if you want to process your data against a target list of compounds,” he said.
“You can also scan everything in the library and there is a traffic light system where only those analytes which are positive and found will be coming up as green if it is a complete match or amber if it’s a partial match and if it is not there it will be red.”
Pesticide residues in items such as baby food are required to be under 10 µg/kg and foods such as fruits or vegetables often exhibit a high number of active components and can be difficult to analyse.
When using traditional LC-MS/MS approaches to analyse such complex matrices, there is a risk of missing an important low level residue.
Labs will still be using MRM which is the standard way of quantifying and detecting pesticides and mycotoxins.
“The message we are trying to get across is you can get better quality data with more confidence and more information using this SWATH workflow on a QTOF. Customers all over the world are starting to adopt that,” added Taylor.