Rapid determination of sulfonated naphthalenes and their formaldehyde condensates in aqueous environmental samples using synchronous excitation fluorimetry

Abstract

Sulfonated naphthalenes and their formaldehyde condensates (SNFC) were determined in aqueous environmental samples by spectrofluorimetry. A clean-up step using n-hexane to extract possibly interfering nonpolar compounds such as naphthalene is the only preparatory procedure. Synchronous excitation mode with a Δλ of 105 nm allows the determination of SNFC in environmental samples without additional clean-up or analyte enrichment. Interferences by humic acids and nitrate occurred only at concentrations higher than 1 mg C L⁻¹ and 10 mg NO₃⁻ L⁻¹, respectively. The limit of detection was 0.2 µg L⁻¹, the average recovery was 104% and the confidence interval (95% certainty) was 24%. The response factor for the quantitative determination of total SNFC, depending on the distribution of the different SNFC components, was validated for groundwater from two field sites using an HPLC-FD (fluorescence detection) method as a reference method.