Asparagus-based amperometric sensor for fluoride determination Original Research Article

A plant tissue-based bioelectrode obtained by incorporating asparagus (Asparagus officinalis) tissue into a ferrocene-mediated carbon paste electrode for the determination of fluoride was developed. It is based on the amperometric determination of the inhibitory effect of fluoride on the asparagus peroxidase activity. The measurements were performed in non-de-aerated 0.05 M NaH2PO4–NaOH buffer (pH 5.0) containing 0.1 mM H2O2 at −0.05 V (versus Ag/AgCl). The bioelectrode consisted of 7% (w/w) of asparagus tissue and 6% (w/w) of ferrocene. The bioelectrode exhibits a linear response up to a fluoride concentration of 14 mg l−1 with a detection limit (S/N=3) of 0.5 mg l−1. A response time (t90) of 60 s and a relative standard deviation (R.S.D.) of 2.1% (n=15) were achieved. The bioelectrode sensitivity decreased to 50% of the original value within 12 days. This bioelectrode was tested by assaying fluoride in tablet formulation and the result compared favorably with potentiometric measurement.