Modified Laccase-Gold Nanoparticles-Tetrathiafulvalene-SPCEs Based Biosensor to Determine W(VI) in Water

Abstract

It was developed an amperometric biosensor to determine tungsten in water, based on the inhibition of laccase enzyme, by tungsten ions using pyrocathecol as a substrate. The enzyme was immobilized with a proper mixture containing, bovine serum albumin, and glutaraldehyde, for a cross-linking process over screen-printed carbon electrodes, previously modified with tetrathiafulvalen and gold nanoparticles. Optimized experimental conditions are: pyrocatechol in cell 0.040 mM in a phosphate buffer pH 6.5 and applied potential +350 mV. The repeatability and reproducibility, in terms of relative standard deviation values, of de developed biosensor were 3.3 % (n=3), and 2.2 % (n = 5) respectively, and detection limit was 1.8 × 10-7 mol L-1. Additionally it was determined the kinetics of the systems by means of Michaelis-Menten Km apparent constants, calculated using Lineweaver-Burk plots, with and without tungsten. Kinetic study resembles to be competitive inhibition. A recovery study was performed with spiked blanks with a tungsten certified reference standard, traceable to NIST, giving as a result 102.3 ± 6.7 %; tap water samples analyzed presented a mean concentration of 1.75 µM, and recovery of the tungsten certified reference standard on the tap water samples gave 98.8 ± 3.1 %.