Analytical Sciences

Naked-eye and Colorimetric Detection of Arsenic(III) Using Difluoroboron-curcumin in Aqueous and Resin Bead Support Systems

Sirinya SIRAWATCHARIN,* Amornrat SAITHONGDEE,** Anusak CHAICHAM,* Boosayarat TOMAPATANAGET,* Apichat IMYIM,* and Narong PRAPHAIRAKSIT*

*Department of Chemistry, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Pathumwan, Bangkok 10330, Thailand
**Program of Petrochemistry and Polymer Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand

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 (BF₂-curcumin), prepared by the reaction of borontrifluoride diethyletherate ((C₂H₅)₂OBF₃) and curcumin. The BF₂-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 BF₂-curcumin solution changed from orange to blue and the absorbance was measured by UV-visible spectrometry at 632 nm. The BF₂-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 BF₂-curcumin solution and naked-eye detection with BF₂-curcumin-coated resin were found to be 0.26, 25 and 30 μM, respectively.

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