Characterisation of polyacetylenes isolated from carrot ( Daucus carota ) extracts by negative ion tandem mass spectrometry

The potential use of negative electrospray ionisation mass spectrometry (ESI‐MS) in the characterisation of the three polyacetylenes common in carrots ( Daucus carota ) has been assessed. The MS scans have demonstrated that the polyacetylenes undergo a modest degree of in‐source decomposition in the negative ionisation mode while the positive ionisation mode has shown predominantly sodiated ions and no [M+H] + ions. Tandem mass spectrometric (MS/MS) studies have shown that the polyacetylenes follow two distinct fragmentation pathways: one that involves cleavage of the C3–C4 bond and the other with cleavage of the C7–C8 bond. The cleavage of the C7–C8 bond generated product ions m/z 105.0 for falcarinol, m/z 105/107.0 for falcarindiol, m/z 147.0/149.1 for falcarindiol‐3‐acetate. In addition to these product ions, the transitions m/z 243.2 → 187.1 (falcarinol), m/z 259.2 → 203.1 (falcarindiol), m/z 301.2 → 255.2/203.1 (falcarindiol‐3‐acetate), mostly from the C3–C4 bond cleavage, can form the basis of multiple reaction monitoring (MRM)‐quantitative methods which are poorly represented in the literature. The 'MS 3 ' experimental data confirmed a less pronounced homolytic cleavage site between the C11–C12 bond in the falcarinol‐type polacetylenes. The optimised liquid chromatography (LC)/MS conditions have achieved a baseline chromatographic separation of the three polyacetylenes investigated within 40 min total run‐time. Copyright © 2011 John Wiley & Sons, Ltd.