|
Author
Pineda Puig, Laura
|
Abstract
Mass spectrometry (MS) is an analytical technique that allows the obtention of mass-to-charge ratios (m/z), isotopic profiles and characteristic fragmentation patterns of each molecule. Mass spectrometry can be coupled to other analytical techniques. One of the most widely used current combinations is high performance liquid chromatography (UHPLC) combined with hybrid quadru-pole time-of-flight (QTOF) mass spectrometers. This is a very versatile technology, with application in different fields of analysis, from the pharmaceutical field to the application in metabolomics among many others. For this reason, the Institut Químic de Sarrià (IQS) acquired a UHPLC-QTOF that allows to support the different research groups and at the same time to create a new line in the application of mass spectrometry. Being the first UHPLC-QTOF instrument to be installed at IQS, the need to explore all the options of the instrument arises and to reflect them into a document so that any user can consult them. For this reason, the ExionLC™ AD System (UHPLC) - SCIEX X500B QTOF System (MSMS) equipment User's Manual is elaborated, following the UNE-EN ISO 9001:2015 standard.
The UHPLC-QTOF instrument has two different modes of operation that allow quantitative and qualitative analysis. These modes are mass spectrometry (MS) and mass spectrometry/mass spectrometry (MSMS). In the first mode, only the precursor ion of the analyte of interest is tracked and an isotopic profile, an exact mass and a chemical formula are obtained. In contrast, with MSMS spectrometry, the fragmentation profile of the precursor ion is studied and mass/mass spectra characteristic of the molecular formula of the compound are acquired. The recorded MSMS spectra can be compared with bibliographic spectra, which help to identify the compound. Mass/mass spectra can be generated following different acquisition modes: TOF MSMS, Multiple Reaction Monitoring (MRM), Information Dependent Acquisition (IDA) and Sequential Window Acquisition of all Theoretical Mass Spectra (SWATH).
In order to know the UHPLC-QTOF equipment and its different working modes, it is necessary to study specific analytes. In this case, polyphenols present in tea samples and infusions are chosen. These compounds have benefits for human health, such as antioxidant and anticarcinogenic prop-erties. Hence, using all available modes (MS and MSMS), eight polyphenols (benzoic acid, cate-chin, cinnamic acid, gallic acid, rosmarinic acid, salicylic acid, vanillic acid and vanillin) are quanti-fied by calibration curve interpolation in 23 tea samples and infusions. In addition, by applying targeted and non-targeted analysis, 88 polyphenolic compounds are identified with different levels of confidence without the use of standards. Finally, chemometric tools (PCA-DA) are applied to classify the analyzed samples into 4 different groups and to identify characteristic markers for each group.
Thus, by means of the identification and characterization of polyphenolic compounds, it has been possible to evaluate all the analysis modalities of the UHPLC-QTOF instrument. Likewise, a written record of the different workflows has been included in the User's Manual for any user to consult.
|
|
