Tracer and method of identifying tracer in product
A method of detecting a tracer compound dissolved in a liquid composition via surface-enhanced spectroscopy includes the steps of: a. optionally, diluting the liquid composition or the separated liquid by mixing with a diluent liquid; b. bringing a sample of the separated liquid into contact with, a spectroscopy-enhancing surface including gold, silver or copper; c. obtaining a Raman spectrum from the sample; and d. calculating, from the spectrum, the concentration of the tracer in the sample relative to the concentration of a second component of the composition.
1. A method of identifying a liquid composition comprising at least one original liquid ingredient, said method comprising the steps of:
a. adding a tracer compound to a known liquid composition containing said at least one original liquid ingredient so as to dissolve the tracer in the known liquid composition and form a tagged known liquid composition;
b. obtaining a sample of an unidentified liquid composition,
c. contacting said sample of the unidentified liquid composition with a spectroscopy-enhancing surface comprising gold, silver or copper;
d. obtaining at least one Raman spectrum from the sample of the unidentified liquid composition; and
e. calculating, from said spectrum, the concentration of the dissolved tracer relative to the concentration of said original liquid ingredient in the sample of the unidentified liquid composition; and
f. comparing the relative concentration calculated in step e with the corresponding relative concentration of the dissolved tracer and original liquid ingredient of the tagged known liquid composition,
wherein the original liquid ingredient comprises a functional ingredient of the composition and the original liquid ingredient is not the dissolved tracer compound.
2. The method according to claim 1 , wherein the at least one Raman spectrum is a resonance Raman spectrum.
3. The method according to claim 1 , wherein the concentration of said original liquid ingredient is estimated by a spectroscopic method.
4. The method according to claim 3 , wherein said calculation comprises the step of comparing at least one characteristic of a first peak in a spectrum attributed to the tracer compound with at least one characteristic of a second peak in a spectrum attributed to said original liquid ingredient.
5. The method according to claim 4 , wherein the first and second peaks occur in the same spectrum.
6. The method according to claim 4 , wherein the first and second peaks occur in first and second spectra which are different spectra.
7. The method according to claim 6 , wherein said first and second spectra are obtained using the same spectroscopy method.
8. The method according to claim 6 , wherein said first and second spectra are obtained using different spectroscopy methods.
9. The method according to claim 1 , wherein the liquid composition to be identified comprises a fuel, fuel additive, lubricant, biologically derived product, diesel exhaust fluid, pesticide, paint, ink or medicine.
10. The method according to claim 1 , wherein the sample of an unidentified liquid composition is separated into a solids portion and a liquid portion prior to step c.
11. The method according to claim 1 , wherein an
aggregating agent is added to the sample of unidentified liquid composition prior to, during or immediately after step c.
12. The method according to claim 2 , wherein the concentration of said original liquid ingredient is estimated by a spectroscopic method.
13. The method according to claim 1 , wherein the sample of an unidentified liquid composition obtained in step b is diluted by mixing with a liquid to provide a diluted sample of an unidentified liquid composition and said diluted sample of an unidentified liquid composition is contacted with a spectroscopy-enhancing surface comprising gold, silver or copper in step c.