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Talanta. 2009 Feb 15;77(4):1322-7. doi: 10.1016/j.talanta.2008.09.010. Epub 2008 Sep 17.

Biosensor based on laccase and an ionic liquid for determination of rosmarinic acid in plant extracts.

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Departamento de Química, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.


Novel biosensors based on laccase from Aspergillus oryzae and the ionic liquids (ILs) 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMIPF(6)) and 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIBF(4)) were constructed for determination of rosmarinic acid by square-wave voltammetry. The laccase catalyzes the oxidation of rosmarinic acid to the corresponding o-quinone, which is electrochemically reduced back to rosmarinic acid at +0.2V vs. Ag/AgCl. The biosensor based on BMIPF(6) showed a better performance than that based on BMIBF(4). The best performance was obtained with 50:20:15:15% (w/w/w/w) of the graphite powder:laccase:Nujol:BMIPF(6) composition in 0.1mol L(-1) acetate buffer solution (pH 5.0). The rosmarinic acid concentration was linear in the range of 9.99 x 10(-7) to 6.54 x 10(-5)mol L(-1) (r=0.9996) with a detection limit of 1.88 x 10(-7)mol L(-1). The recovery study for rosmarinic acid in plant extract samples gave values from 96.1 to 105.0% and the concentrations determined were in agreement with those obtained using capillary electrophoresis at the 95% confidence level. The BMIPF(6)-biosensor demonstrated long-term stability (300 days; 920 determinations) and reproducibility, with a relative standard deviation of 0.56%.

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