An electrode-separated piezoelectric quartz crystal sensor with a chemically modified surface was proposed. The modification was carried out by a silanization procedure with N-2-aminoethyl-3-aminopropyltrimethoxysilane, yielding the immobilised N-2-aminoethyl-3-aminopropylsilane group over the surface of a 3.5 MHz piezoelectric quartz crystal. A flow cell was manufactured with poly(methyl methacrylate) and brass, instead of noble metals, for the electrodes. In this cell, the solution touches only one side of the crystal and the related electrode is coated with a polyester film, which prevents corrosion and does not disturb the oscillation process. This innovation reduces the cost of the cell and renders an electronics non DCcoupled to the solution. The modified crystal proved to be more sensitive to copper(II) ions than magnesium(II), nickel(II), zinc(II), and cobalt(II). For 100muL sample injections, the limit of detection for copper(II) was 6 mumol L-1, which is an impressive result when compared with that for an unmodified crystal.
electrode-separated piezoelectric sensor; silanization; flow injection analysis; QCM; N-2-aminoethyl-3-aminopropyltrimethoxysilane
