Patent ID: 9541502
Date: 2017-01-10
CPC Classifications: G01N

Claim:
1. A method of determining the suitability of a fuel, which is liquid under ambient conditions, for use in an engine, said method comprising the following sequential steps: i) obtaining a test sample of a fuel from a larger quantity of fuel that may contain solid particles of a known contaminant in an unknown amount; ii) providing a compound that is soluble in said fuel and provides a fluorophore when absorbed by, reacted with or coordinated with said contaminant in said fuel; iii) forming a mixture of said compound and said test sample; iv) exposing said mixture to electromagnetic radiation of such a wavelength that would cause said fluorophore to undergo fluorescence if said fluorophore was present in said mixture; v) measuring the amount of fluorescence that occurs in said mixture when said mixture is exposed to said electromagnetic radiation; vi) comparing the amount of fluorescence measured in step v) with the amount of fluorescence measured in a similarly tested fuel that contained a known amount of particles of said contaminant; vii) and rejecting or accepting the fuel from which the test sample was obtained as being suitable for use in said engine depending upon whether the amount of fluorescence measured in said mixture is above or below the amount of fluorescence measured for the fuel that contained the known amount of particles of said contaminant; wherein step iii) comprises forming a mixture of said compound, said test sample and at least one surfactant that is both a) miscible or soluble with said fuel and with water, and b) capable of distributing water into said fuel to provide a stable clear water-in-fuel microemulsion wherein the droplet size of the dispersed water phase is no greater than 0.25 μm; and wherein the amount of said at least one surfactant in said mixture is sufficient to distribute any water in said mixture as a water-in-fuel microemulsion having a water-phase droplet size no greater than 0.25 μm.