Abstract: A handheld sensor device is provided for measuring an ion concentration in a solution. The solution is in an electrochemical cell that includes a counter electrode, a working electrode, and a reference electrode. The sensor includes a control amplifier configured to provide a current through the counter electrode and the working electrode so as to maintain a predetermined voltage between the working electrode and the reference electrode. The sensor also includes a current amplifier configured to measure the current provided through the counter electrode and the working electrode. In one embodiment, the sensor also includes a direct digital frequency synthesizer (DDFS) including a phase accumulator. The DDFS is configured to selectively generate a waveform specified by an electrochemical technique such as square wave voltammetry, cyclic voltammetry, linear sweep voltammetry, differential-pulse polarography, normal-pulse polarography, or other known electrochemical techniques.

Abstract: A handheld sensor device is provided for measuring an ion concentration in a solution. The solution is in an electrochemical cell that includes a counter electrode, a working electrode, and a reference electrode. The sensor includes a control amplifier configured to provide a current through the counter electrode and the working electrode so as to maintain a predetermined voltage between the working electrode and the reference electrode. The sensor also includes a current amplifier configured to measure the current provided through the counter electrode and the working electrode. In one embodiment, the sensor also includes a direct digital frequency synthesizer (DDFS) including a phase accumulator. The DDFS is configured to selectively generate a waveform specified by an electrochemical technique such as square wave voltammetry, cyclic voltammetry, linear sweep voltammetry, differential-pulse polarography, normal-pulse polarography, or other known electrochemical techniques.

Abstract: A handheld sensor device is provided for measuring an ion concentration in a solution. The solution is in an electrochemical cell that includes a counter electrode, a working electrode, and a reference electrode. The sensor includes a control amplifier configured to provide a current through the counter electrode and the working electrode so as to maintain a predetermined voltage between the working electrode and the reference electrode. The sensor also includes a current amplifier configured to measure the current provided through the counter electrode and the working electrode. In one embodiment, the sensor also includes a direct digital frequency synthesizer (DDFS) including a phase accumulator. The DDFS is configured to selectively generate a waveform specified by an electrochemical technique such as square wave voltammetry, cyclic voltammetry, linear sweep voltammetry, differential-pulse polarography, normal-pulse polarography, or other known electrochemical techniques.

Abstract: A handheld sensor device is provided for measuring an ion concentration in a solution. The solution is in an electrochemical cell that includes a counter electrode, a working electrode, and a reference electrode. The sensor includes a control amplifier configured to provide a current through the counter electrode and the working electrode so as to maintain a predetermined voltage between the working electrode and the reference electrode. The sensor also includes a current amplifier configured to measure the current provided through the counter electrode and the working electrode. In one embodiment, the sensor also includes a direct digital frequency synthesizer (DDFS) including a phase accumulator. The DDFS is configured to selectively generate a waveform specified by an electrochemical technique such as square wave voltammetry, cyclic voltammetry, linear sweep voltammetry, differential-pulse polarography, normal-pulse polarography, or other known electrochemical techniques.

Abstract: Acoustic impedance immunosensors are disclosed that are capable of real-time measurement of GABA in a buffer solution. Several embodiments include a bio-specific recognition layer on a quartz crystal surface, where the bio-recognition layer is formed by molecular self-assembly on a gold electrode surface. Various real time measurements can be made by examining the impedance parameters of the quartz crystal on which the bio-specific recognition layer is located as it interacts with GABA. In one embodiment, the invention includes an electrochemical cell that possesses a working electrode. The working electrode including a layer of piezoelectric material, at least one electrode layer fixed to the piezoelectric material and a bio-specific recognition layer formed on the electrode layer and including anti-GABA. In addition, an electrochemical workstation is connected to at least one electrode of the electrochemical cell and an impedance analyzer is connected to the working electrode.