An acoustic wave sensor for the hydrophilic fluoride

✍ Scribed by Nuno I.P. Valente; Paulino V. Muteto; Andreia S.F. Farinha; Augusto C. Tomé; João A.B.P. Oliveira; M. Teresa S.R. Gomes

• Publisher: Elsevier Science
• Year: 2011
• Tongue: English
• Weight: 498 KB
• Volume: 157
• Category: Article
• ISSN: 0925-4005
• DOI: 10.1016/j.snb.2011.05.028

✦ Synopsis

A new acoustic wave sensor to detect and quantify fluoride, one of the most hydrophilic anions, is proposed. Meso-octamethylcalix[4]pyrrole (OMCP) and seven of its derivatives were evaluated as piezoelectric quartz crystal coatings. Some of these sensors experienced appreciable coating leaching under a water flow, while others did show a very small sensitivity to fluoride. As the OMCP-naphthoquinone sensor was very sensitive to fluoride and did not lose a significant amount (˛ = 0.05) of coating during eight weeks, it was selected among all the others. A piezoelectric crystal coated with an amount of OMCPnaphthoquinone that produced a frequency decrease of 22 kHz showed a linear calibration range that extended up to 80 mg L -1 , within which sensitivity to fluoride was 0.45 Hz L mg -1

, and was able to detect fluoride at the concentration of 3.66 mg L -1 . This sensor was used to determine fluoride in commercial fluoride tablets, and the result found was not statistically different (˛ = 0.05) from the value provided by the manufacturer.