Figure 3.

Using MFP to search for sulfated species in gasoline engine deposits. In each case, the raw 3D OrbiSIMS depth profile accumulation spectrum is shown above the spectrum of sulfated ions and the lowest is the filtered DBE plot of these species. (a) Deposit on injector tip 1, showing benzyl sulfonates present up to high masses (C₇₅). (b) Injector tip deposit 2, showing benzyl sulfonates <C₄₀ and a unique distribution of alkyl sulfonates with a DBE value <2. (c) Results from the injector needle, showing only benzyl sulfonates but to a lower maximum mass than other samples.