Nanoliter Titration Based on Piezoelectric Drop-on-Demand Technology and Laser-Induced Fluorescence Detection

An automated technique for fast acid−base titration of 9-nL sample volumes has been developed, based on the use of piezoelectrically driven pipets and laser-induced waveguide fluorescence detection. As an example, a standard titration of a H 2 SO 4 solution with NaOH was examined by utilizing fluorescein as an indicator. The technique had reproducibility in quantitative determination on the order of 1%. The technique allows hundreds of individually executed unattended titrations to be performed in a few hours on an area less than 3 cm 2 . The lowest amount of acid titrated was ∼670 fmol.