Rapid and Accurate Determination of Stern—Volmer Quenching Constants

Abstract

In this work, a novel system has been designed, characterized, and validated for the determination of fluorescence quenching constants. Capillary flow injection methods are used to automate the preparation and mixing of the fluorophore and quencher solutions. Because of the small diameter of the capillary (75–200 μm), fluorescence measurements can be made without corrections for primary and secondary absorbance effects. The fluorescence spectrometer is equipped with a charge-coupled device (CCD) that has a detection limit of 3.0 × 10−9 M (2.3 ppb) and a linear dynamic range of 105 for integration times of 0.01–10 s. This spectrometer has a 300 nm spectral range with 1 nm resolution, allowing the fluorescence quenching constants to be calculated at single wavelengths or over integrated wavelength ranges. This system was validated by comparison to traditional methods for the determination of Stern–Volmer constants for alternant and nonalternant polycyclic aromatic hydrocarbons with nitromethane and triethylamine.