Indirect determination of fluoride in waters with lanthanum alizarin complexone and inductively-coupled plasma emission spectrometry

Fluoride is determined indirectly by measurement of the La II 333.75-nm line in the lanthanum/alizarin complexone/fluoride complex. The ternary complex is extracted into hexanol containing N,N-diethylaniline and the extract is introduced directly into the plasma. Related to water samples, the detection limit (3σ, concentration factor 5) is 0.59 ng ml^?1 fluoride, calibration is linear up to 1.2 μg ml^?1 and the relative standard deviation for 0.04 μg ml^?1 is 2.6%. Alkali, alkali elements and most anions do not interfere. The method is applied in the analysis of river water, coastal seawater and drinking water.