Automated Impedance Measurements in Electrochemical Cells
Abstract In this paper a system is described for impedance measurements in electrochemical cells, integrated by a fast potentiostat, signal generator, digital transient recorder and a computer interface. The treatment of the signal is made by obtaining the correlation between the response cell signal with the in-phase and in-quadrature signals, as is made in the frequency response analysis systems, but the quadrature component being numerically generated. This allows one to obtain the d.c. first and second harmonic cell responses in a single experiment, as well as the a.c. phase selective response by programming the reference signal phase angle. The results obtained with a dummy cell showed the validity of the procedure since the deviation of the measured results from the theoretical data is low. The C/E curve of the interface 1 M KCI/Hg at 25°C is concordant with that previously reported in the literature. Moreover, the system has been tested with the reduction of Cd(II) ion.
Microcomputer-based instrumentation for multi-frequency Fourier transform alternating current (admittance and impedance) voltammetry
Microcomputer-based instrumentation has been developed which enables high quality Fourier transform alternating current admittance and impedance voltammograms to be obtained over a wide range of frequencies and d.c. potentials. A carefully chosen phase-optimised small amplitude alternating potential waveform containing sets of frequencies which avoid harmonic or intermodular interference are periodically superimposed onto a staircase d.c. ramped voltage. Considerable versatility is available in the choise of the excitation waveform and the d.c. ramp. Frequencies in the range of about 50 to 50 000 Hz may be applied at many potentials in any given experiment. Data are reported at both macro- and microelectrodes to illustrate the excellent signal-to-noise ratios that can be obtained under conditions commonly encountered in mechanistic or analytical applications of voltammetric techniques. In the analytical context, linear plots of peak height vs. concentration were obtained when using the admittance mode for both reduction of [Fe(CN)6)]3− at a carbon fibre microelectrode and reduction of Cd2+ at a hanging mercury drop electrode. Many mechanistic and analytical applications presently associated with single frequency linear sweep and cyclic a.c. voltammetry are expected to be enhanced when the instrumentation is used in the multi-frequency mode.
Ten Years of Public Interest Disclosure Legislation in the UK: Are Whistleblowers Adequately Protected?
Purpose The purpose of this article is to assess the operation of the UK’s Public Interest Disclosure Act 1998 (PIDA 1998) during its first 10 years and to consider its implications for the whistleblowing process. Method The article sets the legislation into context by discussing the common law background. It then gives detailed consideration to the statutory provisions and how they have been interpreted by the courts and tribunals. Results In assessing the impact of the legislation’s approach to whistleblowing both in the UK and elsewhere, the author draws upon empirical research. Conclusion The author concludes that PIDA 1998 has not adequately protected whistleblowers and makes 12 recommendations for change. Despite the European Commission’s acknowledgement that whistleblowers can play a part in the fight against corruption, the author notes that common standards for their protection still seem a long way off.