Method of marking a hydrocarbon liquid includes: adding thereto, a tracer compound of Formula I: wherein, each A is independently selected from the group consisting of (i) a phenyl group, (ii) a phenyl group substituted with one or more halogen atoms, an aliphatic group or a halogenated aliphatic group, (iii) a partially or fully halogenated alkyl group or (iv) a linear branched or cyclic C1-C20 alkyl group, and each B is independently selected from the group consisting of a (i) phenyl, (ii) phenylmethyl group, (iii) a cyclohexyl group, (iv) a cyclohexylmethyl group, (v) a substituted phenyl or phenylmethyl group in which the benzene ring is substituted by at least one substituent selected from the group consisting of a fluorine atom, a partially or fully halogenated alkyl group and a linear, branched or cyclic C1-C20 alkyl group or (vi) a linear, branched or cyclic C1-C20 alkyl group.