This paper describes a method and instrumentation for electrical pH control in aqueous solutions. It is targeted to environmental and industrial on-line chemical and optic fibre sensors measurement, calibration and process control. The method is an alternative to the existing automatic pH controllers based on correction chemical addition 2The on-line measurement of dissolved gaseous species which produce acidic and basic waters is of great concern for environmental monitoring applications. Such measurements are maintained by using preconditioned water samples and ion-selective electrodes or absorption spectrometry. A gas-permeable membrane can be used to allow only the transport of the molecular form of the measured species where the solution pH is controlled to ensure the reversible transition of the species of interest from ionic to molecular form and to allow their permeation through the membrane.An electrochemical instrument for electrolysis-based feedback controlled pH regulation has been attempted. The choice of galvanostatic, potentiostatic and combined methods of modulation electrodes biasing with their speed, settling time and accuracy are discussed. Different feedback control approaches, involving electrochemical and optical sensors, are compared.
A new combination of silica fibres, highly transparent in the ultraviolet (UV) and showing long term stability, combined with a teflon-coated liquid-core waveguide (LCW) is presented for remote sensing in the deep UV, for monitoring one of the major pollutants, nitrates, in water, but with potentially wider applicability. The arrangement exhibits low spectral loss in the range between wavelengths of 200 nm and 400 nm and can be used for analytical investigations to determine small concentrations of such impurities in water. The operation of the optical system to achieve guidance of UV light below a wavelength of 250 nm for fibre optic sensors is discussed. With an optical pathlength of 203 mm, nitrate concentrations as low as 22 μg/l could be detected.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.