The structure and purity of a reference dye standard used for quantification of C.I. Solvent Red 164 in fuels

This study characterizes a primary reference dye standard, certified as being 99% C.I. Solvent Red 26, that is used in the United States to identify tax-free fuel, using nuclear magnetic resonance spectroscopy, thin-layer chromatography, gas chromatography/mass spectrometry and high-performance liquid chromatography/mass spectrometry. It was found that 72% of the primary reference dye is equivalent to National Institute of Standards and Technology Standard Reference Material 2037 (C.I. Solvent Red 24). Several of the impurities were tentatively identified and a number of additional impurities were partially characterized. Possible explanations and implications are briefly discussed.