A method of marking a hydrocarbon liquid includes the step of adding to the liquid, as a tracer compound, a compound of Formula I: wherein at least one of R1-R4 is selected from: i. a bromine or fluorine atom; ii. a partially or fully halogenated alkyl group; iii. a branched or cyclic C4-C20 alkyl group; iv. an aliphatic substituent linking two positions selected from R1-R4 in Formula I to one another; or v. a phenyl group substituted with a halogen atom, an aliphatic group or halogenated aliphatic group. The tracer compounds are resistant to removal from the fuel by chemical laundering or by contact with absorbents such as charcoal.