Abstract: The invention provides a composition which comprises an apolar medium and a tracer compound, which tracer compound comprises a hydrophobic group and an oligonucleotide. Various uses of the tracer compound are also described.

Abstract: The invention provides a composition which comprises an apolar medium and a tracer compound, which tracer compound comprises a hydrophobic group and an oligonucleotide. Various uses of the tracer compound are also described.

Abstract: A method of marking a material and subsequently detecting that it has been marked is disclosed, comprising adding or applying a marker comprising a nucleic acid tag to the material, sampling a portion of the material containing such marker, and detecting the presence of nucleic acid tag in the sample. The method is characterized in that the quantity of the nucleic acid tag present in the sample is determined to provide an indication of the quantity of marker present in the material. The nucleic acid tag may comprise one or more identifying sequences, and the tag is amplified by means of a nucleic acid amplification reaction.

Abstract: Methods for marking a material and subsequently detecting that it has been marked, comprising adding or applying a marker comprising a nucleic acid tag to the material, sampling a portion of the material, and detecting the presence of the tag. The quantity of the tag present in the sample provides an indication of the quantity of marker present in the material. The tag may comprise one or more identifying sequences, and the tag is amplified by means of a nucleic acid amplification reaction.

Abstract: A method of marking a solid article or item comprises applying thereto beads having nucleic acids attached thereto. A method of monitoring an interaction between any material, article or item and a person or animal comprises providing a device capable of producing an aerosol containing a nucleic acid label and means to activate the aerosol on interference by a person or animal with the material, article or item. Methods of marking a material comprise adding to the material a plurality of beads having attached thereto a plurality of nucleic acid molecules. At least two distinct primer sequences are associated with different nucleic acid molecules.

Abstract: A method of monitoring the movement of a material which comprises adding to the material, as a microtrace additive, DNA molecules, sampling the resulting material after movement thereof and detecting the presence of said microtrace additive in the sample. The method is particularly suitable for use in monitoring the movement of oil shipments and the microtrace additive is selected such that it will remain in the oil phase in the event the oil is dispersed in water e.g. sea water.

Abstract: A method of marking a liquid and subsequently detecting that the liquid has been marked, which method comprises: adding to the liquid an additive comprising a plurality of particles in an amount no greater than 1 part weight of particles per 10.sup.6 parts weight liquid, the particles comprising signal means to aid their detection and not being visible in the liquid to the naked eye; sampling a portion of the liquid containing said additive, and detecting the presence of particles in the liquid, with the proviso that said signal means does not consist solely of a nucleic acid tag.