A Study of Qunizarin (Orange Dye 2) in Hexane as a Model Fuel Dye

A study was performed using Quinizarin 1,4-Dihydroxyanthraquinone (Direct Orange 26) in hexane to model the behavior of a fuel dye. A stock of the dye solution was made and diluted before measuring the full visible spectrum (400-700 nm). The peak Absorption wavelength, found at 460 nm, had a good correlation with the Beer-Lambert Law. Additionally, the area under the Absorption profile, from 400 nm to 550 nm, was measured and also yielded an excellent correlation to the Direct Orange 26 dye concentration. Using both of the methods, the Beer-Lambert Law for the peak Absorption, and the area under the profile, one can obtain exceptional correlations of concentration and identification of the specific dye.

General
Dyes have been used to “tag” fuels for identification, concentration, environmental, and taxation purposes1-9. Most applications include marine, aviation, heating, and automobile fuels including gasoline, diesel, and kerosene. The color may vary from red, green, blue, orange, and yellow, and can be identified by the user. An example7 is the dyeing of diesel fuel, started in the United States in 1993 under Environmental Protection Agency (EPA) regulations and expanded for tax enforcement
purposes on January 1, 1994. The diesel fuel dyeing programs served two distinct purposes: to identify fuel that did not meet the sulfur content for use in highway vehicles, and to identify Federal excise tax-exempt fuel. Taxation also plays a large role in the dyeing of fuels, with billions of dollars being evaded in taxes.9 Another example is quinizarin (Direct Orange 26) used in red diesel, along with Solvent Red 26 dye in the United Kingdom.