A process for detecting oil or lubricant contamination in a manufactured product, the process comprising adding a fluorescent taggant to oils or lubricants contained in processing machinery for said product, conveying said product past an infrared detection apparatus, irradiating said product with infrared radiation from said detection apparatus as it passes the detection apparatus, and detecting infrared radiation emitted from said irradiated product.

A gas chromatographic method for detecting a marker compound in a fuel by (a) introducing a sample of fuel into a first capillary column coated with a stationary phase based on polydimethylsiloxane and allowing the sample to flow through the first column to produce a first effluent; (b) allowing the first effluent to pass through a detector and identifying a retention time range in it which includes a retention time of the marker compound; (c) introducing only a portion of the first effluent stream which is within the retention time range into a second capillary column coated with either (i) an ionic sorbent or (ii) a polyethylene glycol, and allowing said portion to flow through the second capillary column to produce a second effluent stream; and (d) allowing the second effluent to pass through a detector; wherein the marker compound has formula Ar(R.sup.2).sub.m(OR.sup.1).sub.n and is present in the fuel at a level from 0.01 ppm to 100 ppm.

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.

A method for detecting mentholated tobacco, comprising irradiating tobacco containing menthol and a fluorescent taggant with radiation and observing the tobacco for fluorescence from the taggant. A system and method for detecting and separating mentholated tobacco from non-mentholated tobacco within a product stream is also provided.

A method for marking a petroleum hydrocarbon or a liquid biologically derived fuel; said method comprising adding to said petroleum hydrocarbon or liquid biologically derived fuel at least one compound that is a R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9 and R.sup.10-substituted diaryl ether, wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9 and R.sup.10 independently are hydrogen, hydrocarbyl or hydrocarbyloxy; wherein each compound having formula (I) is present at a level from 0.01 ppm to 20 ppm.

The present disclosure provides methods for identifying a hydrocarbon fuel, such as the presence and/or amounts of marker compounds having a fluorescence intensity and, through correlation, the presence and/or amounts of additive package(s) within the hydrocarbon fuel.

The present invention is a method of making 1,4,5,8-tetrakis(R-phenylamino)anthracene-9,10-dione (where R is H or a hydrocarbyl group) comprising the step of contacting 1,4,5,8-tetrachloroanthraquinone with a mixture of R-anilines comprising at least two different R groups, under conditions to produce 1,4,5,8-tetrakis(R-phenylamino)anthracene-9,10-dione. The present disclosure also provides a reaction mixture of 1,4,5,8-tetrakis(R-phenylamino)anthracene-9,10-dione characterized by having the R groups on at least 75% of the 1,4,5,8-tetrakis(R-amino)anthracene-9,10-dione molecules in the mixture be comprised of 2 or more different R groups. The present disclosure also provides a method of improving the solubility of 1,4,5,8-tetrakis(R-phenylamino)anthracene-9,10-dione in aromatic hydrocarbons distilled from crude oil, comprising selecting a mixture of 1,4,5,8-tetrakis(R-phenylamino)anthracene-9,10-diones which are characterized by having at least 75% of the 1,4,5,8-tetrakis(R-phenylamino)anthracene-9,10-dione molecules in the mixture comprise two or more different R groups. The compounds of the present invention exhibit a suitable UV visible absorbance profile making them suitable for use as a fuel marker.

The disclosure provides dyes for marking hydrocarbon compositions. More particularly, the disclosure relates to non-mutagenic dyes for marking hydrocarbon com positions.

The present invention relates to a process for preparation of metal free, nontoxic, hydrocarbon fuel compatible fluorescent carbon quantum dots (CQD), which act as marker as well as lubricity improver. CQDs are highly stable in non-polar hydrocarbons, at ppm level exhibit distinct fluorescent color upon irradiation with light of specific wavelength and exhibit distinct spectral properties compared to non-polar base hydrocarbons.

A method of marking a hydrocarbon liquid comprising adding to said hydrocarbon liquid a tracer compound, the tracer compound being a substituted biphenol ether having a core structure of Formula I, wherein the two R groups are the same or different and selected from straight chain, branched or cyclic alkyl groups, phenyl or substituted phenyl groups, benzyl or substituted benzyl groups, or the two R groups form a single substituent linked intramolecularly to both oxygen atoms, and wherein one or both of the aromatic rings of the core structure is further substituted with at least one non-planar group.

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