Determination of submicromolar concentrations of fluoride in biological samples.

The fluorescence of a Morin-thorium complex provides a more sensitive fluoride reagent than has been previously used. It has immediate stability and a linear response to fluoride up to 50% reduction in fluorescence. The values for serum fluoride, as measured with this reagent after diffusion at room temperature, agree with those obtained with the fluoride electrode and with those predicted by the renal clearance of radioactive fluoride. The relative standard deviation when measuring 10(-6)M fluoride in 2 ml of serum is +/-10%.