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: A marking apparatus (1) for marking an item (12). The apparatus comprises: means to receive the item; a nucleic acid marker; means to release a marking fluid (8); and a distribution mechanism (11) coupled to the nucleic acid marker and the means to release the marking fluid. The means to release the marking fluid can be activated to release the marking fluid such that the distribution mechanism disperses a mixture of the nucleic acid marker and the marking fluid onto the item.

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 for detecting the presence of a hydrocarbon deposit (2) in a geographical location (1). The method comprises the steps of: detecting the presence, at the location, of a target polynucleotide encoding a protein capable of metabolising a hydrocarbon, wherein the presence of the target polynucleotide is indicative of the presence of the hydrocarbon deposit; determining the concentration of the target polynucleotide at the location; and determining a value related to the concentration of bacteria at the location and calculating the ratio of the concentration of the target polynucleotide to the value.

Abstract: A particle (1) for tagging a liquid. The particle comprises a nucleic acid tag; a carrier nucleic acid; and a linear polymer. The linear polymer has a backbone comprising amido and tertiary amino groups arranged regularly on the backbone. The nucleic acid tag and the carrier nucleic acid have different sequences. The particle comprises at least ten times more carrier nucleic acid than nucleic acid tag. Use of particles for marking materials in which the particles comprise the said linear polymer and a nucleic acid.

Abstract: A marking apparatus (1) for marking an item (12). The apparatus comprises: means to receive the item; a nucleic acid marker, means to release a marking fluid (8); and a distribution mechanism (11) coupled to the nucleic acid marker and the means to release the marking fluid. The means to release the marking fluid can be activated to release the marking fluid such that the distribution mechanism disperses a mixture of the nucleic acid marker and the marking fluid onto the item.