Fluoride analysis in nanoliter- and microliter-size fluid samples.

A variety of techniques is described for measuring fluoride in volumes of from 0.005 to 5 microL, including: (1) micropipette procedures for transference and dilution of samples, (2) construction of miniature and micro fluoride-selective electrodes, and (3) methods for adapting standard electrodes for micro- and semi-micro volumes. These described techniques have a number of advantages, including speed of analysis, high accuracy, and adaptability to many types of fluid samples. Recent studies involving use of these procedures include the analysis of fluoride in: (1) plaque fluid samples from single sites before and after topical fluoride administration, (2) tooth mineral samples recovered by acid-etch or microdrill biopsy of enamel, and (3) fluid recovered from the interior of the tooth during simulation of the caries process.