Method of mass spectrometry for the detection of perfluoroalkyl or polyfluoroalkyl substances (pfas)

A method of determining the presence of a perfluoroalkyl or polyfluoroalkyl substance (PFAS) in a sample, the method comprising:

• generating sample ions from a sample either:
• (i) by using electron impact (EI) ionisation, direct laser ionisation, or field desorption ionisation;
• or (ii) by using electrospray ionisation (ESI) or chemical ionisation (CI), and electron induced dissociation (EID);
• mass analysing the sample ions using a mass analyser so as to produce mass spectral data, wherein the mass analyser has a mass accuracy ≤about 100 ppm and a resolving power ≥about 10,000;
• determining whether, in the mass spectral data, an ion peak is present that has an accurate mass to charge ratio within ±100 ppm of a first accurate mass to charge ratio m/z, wherein the first accurate mass to charge ratio m/z is the accurate mass to charge ratio of an ion indicative of the presence of a PFAS in the sample;
• and
• when it is determined that an ion peak is present that has an accurate mass to charge ratio within ±100 ppm of the first accurate mass to charge ratio m/z:
• determining that a PFAS is present in the sample;
• wherein:
• the ion indicative of the presence of a PFAS is a CF3 cation having a nominal mass to charge ratio of 69, and the first accurate mass to charge ratio m/z=68.99466;
• and/or
• the ion indicative of the presence of a PFAS is a CF3CF2 cation having a nominal mass to charge ratio of 119, and the first accurate mass to charge ratio m/z=118.99147;
• and/or
• the ion indicative of the presence of a PFAS is a CF3CF cation having a nominal mass to charge ratio of 131, and the first accurate mass to charge ratio m/z=130.99147.