Oxidized multiwalled carbon nanotubes for quantitative determination of cationic surfactants in water samples using atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry

A new biosensor for detection of phenols, based on tyrosinase immobilization with alumina sol-gel on Sonogel-Carbon transducer, has been developed. The electrode was prepared using high energy ultrasounds directly applied to the precursors. The alumina sol-gel provided a microenvironment for retaining the native structure and activity of the entrapped enzyme and a very low mass transport barrier to the enzyme substrates. Phenols are oxidized by tyrosinase biosensor to form a detectable product, which was determined at −300 mV vs. Ag/AgCl reference electrode. For phenol, the sensor exhibited a fast response which resulted from the porous structure and high enzyme loading of the sol-gel matrix. The linear range was from 5 × 10⁻⁷ M to 3 × 10⁻⁵ M, with a detection limit of 3 × 10⁻⁷ M. The stability of the biosensor was also evaluated.