This work presents a new colorimetric method that is simple, rapid and cost effective for the determination of arsenic(III) in water samples. The method is based on changes in the absorbance of difluoroboron-curcumin (BF
2-curcumin), prepared by the reaction of borontrifluoride diethyletherate ((C
2H
5)
2OBF
3) and curcumin. The BF
2-curcumin was dissolved in 60% ethanol, which yielded an orange solution with the maximum absorbance at 509 nm. Upon the addition of arsenic(III), the color of the BF
2-curcumin solution changed from orange to blue and the absorbance was measured by UV-visible spectrometry at 632 nm. The BF
2-curcumin was applicable in both solution and coated resin. Under the optimal conditions, the detection limits achieved by means of UV-visible spectrometry, naked-eye detection with BF
2-curcumin solution and naked-eye detection with BF
2-curcumin-coated resin were found to be 0.26, 25 and 30 μM, respectively.
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