TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Method: The tracer material is added to the product in an amount calculated to provide: a predetermined concentration of the or each tracer compound in the product; and a concentration of the or each tracer compound in (I) at a concentration of 5 ppb-5 ppm, preferably 50-500 ppb. The analysis is performed by chromatography (preferably liquid chromatography, gas chromatography or a combination of gas chromatography coupled with a pulsed flame photometric detector or with a mass spectrometer). In the method, at least one of the tracer compounds present in the sample is separated from the product derivatized or concentrated prior to analysis.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The tracer compound is a compound, which is listed as a permissible food additive by the US Food and Drug Administration (FDA) and/or the European Commission. The tracer compound comprises a carbonyl compound, or a ketone. The ketone is pentan-2-one, 4-methylpentan-2-one, 4-hexen-3-one, heptan-2-one, heptan-3-one, heptan-4-one, 6-methylheptan-3-one, 2,6-dimethylheptan-4-one, octan-2-one, octan-3-one, nonan-2-one, nonan-3-one, decan-2-one, undecan-2-one, undecan-6-one, pent-3-en-2-one, hex-4-en-3-one, 2-methyl-3-heptanone, 5-methyl-2-hepten-4-one, 2,6-dimethyl-4-heptanone, 6-methylhept-5-en-2-one, oct-1-en-3-one, oct-2-en-4-one, oct-3-en-2-one, dec-3-en-2-one, 4-phenyl-3-buten-2-one, ethyl vinyl ketone, cyclohexanone, cyclohex-2-en-one, acetophenone, alpha-ionone, camphor, canzone, damascenone, beta-damascone, fenchone, geranylacetone, iso-menthone, nootkatone or zingerone. The tracer compound comprises a nitrogen- and/or sulfur-containing heterocycle (preferably pyrazinyl methyl sulfide, 2,3-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine or 5-acetyl-2,4-dimethylthiazole). The tracer material comprises more than one tracer compound, the relative amounts of the tracer compounds being selected to provide an identifiable characteristic to the tagged product, and the analysis of the sample is performed in order to identify the presence of the tracer material through the identification of the characteristic relative amounts of the tracer compounds. The tracer material contains from two to twelve tracer compounds. EXAMPLE - 2-Methyl-3-heptanone, 6-undecanone, ethyl vinyl ketone, 5-methyl-2-hepten-4-one and 2,6-dimethyl-4-heptanone were dissolved in crude palm oil at a concentration of 500 ppb. The tagged oil (10 ml) was then extracted with methanol (5 ml) and stirred for 1 hour at 60 degrees C. The extract containing the tags was removed. Aqueous O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride (5 ml) was added to the extract and incubated for 2 hours at 60 degrees C. The reaction mixture was then extracted with chloroform (2.5 ml) and stirred for 20 minutes at 60 degrees C. The chloroform layer containing the derivatives was removed and dried through a cotton wool plug prior to analysis. For the derivatives of 2-methyl-3-heptanone, 6-undecanone, ethyl vinyl ketone, 5-methyl-2-hepten-4-one and 2,6-dimethyl-4-heptanone signals of m/e 303, 345, 259, 301 and 317 respectively, were monitored.