Electrospray ionization collision induced dissociation of thiocarbocyanine and selenocarbocyanine dyes

Abstract

The effect of the properties of sulphur and selenium atoms, the composition and location of substituents (―CH3, ―OCH3, ―C2H5, and ―C3H6―((N+Br−)C5H5)), and the charge state on the collision induced dissociation (CID) behaviour of ions generated by electrospray ionization (ESI) of thiocarbocyanine and selenocarbocyanine dyes have been investigated. The results show that, for of all the examined singly charged ions, the main dissociation channel was related to the formation of distonic ions, generated as a result of cleavages within the dimethine bridge. In the case of doubly charged ions (with propyl‐pyridinium substituents), competition between fragmentation processes related to charges located at different nitrogen atoms has been observed. The S/Se replacement also has an impact on the CID behaviour of the examined carbocyanine dyes. On the basis of the performed CID MS/MS experiments, general rules for the CID of thiocarbocyanine and selenocarbocyanine dyes have been proposed.

Tautomeric equilibrium, proton affinity and mass spectrometry fragmentation of flexible hydrogen-bonded precursors and rigid $$\hbox {N}\longrightarrow \hbox {BF}_2$$ fluorescent dyes

“…Tandem mass spectrometry methods (MS/MS), such as Collision Induced Dissociation (CID, based on inelastic collisions of ions with inert gases) 21 or Higher Energy Collisional Dissociation, also called a beam type CID 22 provide detailed information on the structure of the analyzed compounds. They have been used for the structural elucidation of different classes of dyes, including: cyanine dyes 23 – 25 , xanthenes 26 , water soluble azo-dyes 27 and BODIPYs and their derivatives 17 , 28 . However, because of the dependence of the MS/MS fragmentation behavior of dyes on all structural motifs of the analyzed ions (the presence of specific functional groups, occurrence of heteroatoms, the charge of the examined species) 24 , 26 , 29 , the application of HCD technique as the essential analytical tool on a larger scale requires the establishing of general rules for the fragmentation of specific classes of dyes.…”