Reactive Gases in Collision Cells

Reactive collision gases have also been used in organic MS. Pioneering experiments involved the study of the formation of an adduct ion between protonated esters and ammonia in the collision cell of a TQ instrument [50]. Since then, numerous examples have been reported such as the study of gas-phase reactions of dilactones, psorospermin, and quabalactone diterpenes [51], different phospholipid classes [52], ethyl vinyl ether, the transacetalization with gaseous caiboxonium and carbosulfonium ions by colhsion cell reactions with cyclic acetals and ketals [53], and ketalization of phosphonimn ions using 1,4-dioxane [54]. 

Data acquisition in the neutral in analysis mode, where both quadmpole mass analyzers are operated in scanning mode but with a fixed m/z offset depending on the reaction performed, has been apphed to efficiently monitor these type of gas-phase reactions in complex mixtures of, e.g., phospholipids [52] and phosphonium ions in relation to chemical warfare agents [54]. The ethyl vinyl ether reaction with phospholipids yields a neutral gain of 26 Da for phosphatidylglycerols and of 57 Da for phosphatidylinositols [52], whereas the reaction of the phophonium ion with 1,4-dioxane yields a neutral gain of 44 Da [54]. 

A pentaquadrupole (PQ-MS) instrument, thus featuring Q-qjoii-C -q.oii has been developed and extensively used for the study of gas-phase ion-molecule reactions [58, 59]. The PQ-MS instruments obviously allow sequential product-ion analysis, i.e., MS experiments, but other types of experiments are possible as well. The PQ-MS instrument can be used to perform reactive colhsion of selected ions either in the first or the second collision cell, as illustrated with a wide variety of examples [59]. 

---