Improving the sensitivity of electrode-separated piezoelectric quartz crystal sensor for copper(II) ions by immobilization of the N-2-aminoethyl-3-aminopropylsilane group

Abstract

Um sensor a cristal piezelétrico de quartzo com eletrodos separados e superfície quimicamente modificada foi proposto. A silanização com N-2-aminoetil-3-aminopropiltrimetoxisilano permitiu a imobilização do grupo N-2-aminoetil-3-aminopropilsilano sobre a superfície de um cristal de quartzo de 3,5 MHz. Uma cela em fluxo foi fabricada em poli(metacrilato de metila) com dois eletrodos de latão. Nesta cela, a solução entra em contato somente com um lado do cristal e o eletrodo é recoberto com um filme de poliéster, prevenindo assim a corrosão do eletrodo. Esta inovação reduz o custo da cela e proporciona o desacoplamento DC. O cristal modificado mostrouse mais sensível a íons cobre (II) do que a magnésio(II), níquel(II), zinco(II) e cobalto(II). Para injeções de 100 µL de amostra, o limite de detecção para cobre(II) foi de 6 µmol L -1 que é um resultado significativo comparado com aqueles obtidos com cristal não modificado.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 DC-coupled 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 100µL sample injections, the limit of detection for copper(II) was 6 µmol L -1 , which is an impressive result when compared with that for an unmodified crystal.

Retention of copper(II) metal ions in a silicon-glass microfluidic device

“…As reported by Jesus et al, 24 N-(β-Aminoethyl)-γ-aminopropyl group (AEAPS) presents favorable stability constant for copper(II), but also exhibit selectivity for zinc(II), cobalt(II), nickel(II) and magnesium(II). Although these ions are possible interfering species, the potential applied to the gold electrode is not enough for the reduction of these ions.…”

“…The channels surfaces were modified according to the protocol proposed by de Jesus et al 24 The channels were filled with a solution of 5 % AEAPTS in dry toluene for 30 minutes, washed with dry toluene, chloroform, and methanol, in this sequence. Finally, the microchip was left in an oven at 80 ºC for 24 hours to complete the cure of the deposited film.…”

The evaluation of copper contamination of food cooked in copper pans using a piezoelectric quartz crystal resonator

“…Piezoelectric copper sensors have been either based on copper electrodeposition on the crystal electrodes [3][4][5] or on the adsorption of the copper ion itself, or a copper complex [6][7][8][9][10][11][12]. Coated quartz crystals and electrode separated piezoelectric quartz crystals (coated [6,7] or uncoated [8][9][10]) have been used.…”

“…Coated quartz crystals and electrode separated piezoelectric quartz crystals (coated [6,7] or uncoated [8][9][10]) have been used. The electrode-coated quartz crystals were either non-selective and used as a detector after a chromatographic separation [11], or coated with polymers containing chelating ligands with some selectivity [12].…”

“…The electrode-coated quartz crystals were either non-selective and used as a detector after a chromatographic separation [11], or coated with polymers containing chelating ligands with some selectivity [12]. In addition to a lack of selectivity of some sensors, all of them, except the one used after HPLC, required metals to either to be electrochemically stripped off [4,5], removed with a 50% 2-propanol/water solution [8,9], or removed with an EDTA solution [6,7,12] during the cleaning processes.…”