A LOW-COST DEVICE FOR THE ESTIMATION OF FLUORIDE IN DRINKING-WATER

Fluorosis is endemic in many regions of the world due to high (>1.5 mg I-1) levels of fluoride in groundwater. This problem is aggravated by the lack of a simple and inexpensive test for fluoride in drinking wa ter. We discuss the design and testing of a low-cost LED-based colorim eter for estimating the fluoride concentration in water. The device wa s calibrated with the use of the cerium-alizarin complexone (Ce-AC) an d the sodium (parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulf onate (SPADNS) methods, which show color changes in the visible region on addition of water containing fluoride. Raw water samples collected from different parts of India were analyzed for fluoride. The fluorid e concentration, as estimated by using a fluoride electrode, was in th e range 0.7-1.20 mg I-1. The results obtained by the colorimeter showe d good agreement with the electrode method for most of the samples. Th e cost of chemicals per test was $0.14 for the Ce-AC method and $0.018 for the SPADNS method. The cost of the colorimeter was about $14. (C) 1998 John Wiley & Sons, Inc.