Spectrophotometric detection of trace copper levels in jet fuel

To sensitively and selectively monitor jet fuel for trace levels of copper, two spirobenzopyran dyes, quinolinospiropyranindoline (QSP) and nitrospiropyranindoline (NQSP), have been investigated for their application in a spectrophotometric method that is amenable to rapid, on-site detection of mug/L levels of copper in jet fuel. Both NQSP and QSP respond sensitively to various metal ions in jet fuel, including copper, nickel, and zinc, with NQSP demonstrating the best performance in terms of selectivity of spectral response and sensitivity. Principal component analysis (PCA) was applied to the spectral data, and the individual contributions to the absorption spectra by copper, nickel, and zinc in JP-5 fuel can be readily separated using this technique. The effect of metal deactivating additives (MDA) in jet fuel on the sensitivity of NQSP for copper was investigated. Silica-bound diethylenetriamine was investigated as an effective solid-phase extraction agent for defining the baseline absorbance of NQSP in jet fuel samples being analyzed by standard addition methodologies.