Rapid Communications in Mass Spectrometry

Hydrolysis scheme of quinalphos. (PA-Q, formula: C12H15N2O3PS, MW: 298.3 g/mol). The two hydrolysis products are 2-hydroxyquinoxaline (HQ, formula: C8H6N2O, MW: 146.1 g/mol) and O,O-diethyl phosphorothioic acid (PA-OH, formula: C4H11O3PS, MW: 170.2 g/mol).

MS/MS spectra and proposed fragmentation pathways of transition metal ion–quinalphos complexes: (A) for the observed complex [PA-Q + 107Ag+] with m/z 405 and (B) for the observed complex [PA-Q + 63Cu+] with m/z 361. The fragmentation pathways for both complexes are similar and differ only in observed fragmentation ion intensities.

Proposed structure for the Cu(II) complex with two PA-Q molecules in solution and possible reaction pathways (i–v) for the observed ion species in the MS scan after transfer to the gas phase (explanation in the text). There is no direct experimental evidence for pathway ii to occur, but CID MS/MS spectra (see Supplementary Scans 5 and 6, Supporting Information) for ion complexes [(PA-Q)2 + Cu+] with m/z 659/661 and [PA-Q + Cu2+ +NO3–] with m/z 423/425, yielding [PA-Q + Cu+] with m/z 361/363 as the main fragment, support the suggested pathways iv and v.

MS spectrum and proposed ion complex structures of species obtained by Hg(NO3)2 addition. Note, only the species with m/z 541 shows a sodiated or potassiated adduct form, since only this complex contains an easily exchangeable proton. Insert I shows a theoretical isotope model for the complex at m/z 669 and insert II reflects the zoomed-in real data. The complex at m/z 405 is most likely an in-source fragmentation product of the complex at m/z 541, as it is one of the main fragmentation products in a respective MS/MS study (see Supplementary Fig. S4). The lack of sodiated or potassiated signals for this complex indicates that the respective precursor sodiated/potassiated complexes (m/z 563 and 579) do not easily undergo in-source fragmentation. All observed complexes undergo in-source loss of ethyl groups (-C2H4).

MS/MS spectrum of the complex resulting from Hg(NO3)2 addition to quinalphos at m/z 669, proposed main fragmentation pathways, and an insert depicting a proposed structure for the fragment with m/z 411 (explanation in the text).