LC-MS analysis of a sample consisting of the Matrix solution and H-PINS Standard mix. a, the gradient used for separation of the Matrix solution spiked with H-PINS Standard mix. b, the TIC of the Matrix solution spiked with H-PINS Standard mix acquired using an LTQ-Orbitrap mass spectrometer. c, extracted ion chromatograms of all 10 H-PINS with their respective retention time. d, mass and isotopic distributions from all H-PINS at a resolution of 50,000. NL, normalized.