Novel optical pH sensor for high and low pH values

Fluorescence based fibre optic pH sensor for the pH 10–13 range suitable for corrosion monitoring in concrete structures

“…The signal leveled off after equilibrium and no drift in response was observed under the experimental conditions employed. This response time, which is long in comparison with those of previously developed pH sensor systems [38,39,61], could be due to diffusion in the rather thick polymer layer. However, this is not a problem for concrete monitoring as pH changes in concrete structures occur over much longer periods of time.…”

“…The pK a value calculation for the polymer-bound dye was performed using the Boltzmann model -Equation (4) where dpH is the slope of the curve within its linear zone. [8,18,[32][33][34], trinitrobenzensulfonic acid [14], thymol blue [20,21,35,36], cresol red [20], phenolphthalein [19], aniline blue [37], rhodamine 19 [38], Victoria blue [39] etc. as well as reported in the literature such as fluorescent Schiff bases [40], porpholactones [41] or a benzo [de]anthracen-7-one derivative [23] , that are known to be useful for the spectroscopic determination of high pHs, the majority of them are absorptive dyes rather than fluorescent dyes and only a few meet the requirements of being stable for a long period of time in highly alkaline media, possessing a pK a in the range between 11-12.5, having reasonable fluorescence quantum yield and good photostability, being fully compatible with LED light sources and bearing one or more functional chemical groups suitable for covalent immobilization of the indicator.…”

Simultaneous high-resolution pH and spectrophotometric recordings of oxygen binding in native blood microvolumes

“…The non-linear dynamic range of pH optodes restricts accurate recordings to pH values between 5.5 and 8.5, which, however, suffices in most of the blood-physiological experiments. Optical pH sensors that cover the extreme and even the full pH range may soon remove this limitation (Safavi and Bagheri, 2003). Further, the 150 μm sensor tip breaks easily and requires careful handling.…”

Transmitted light pH optode for small sample volumes

“…Moreover, optical sensors seem to have very good properties in terms of stability to electrical interference stability, measurement stability and quality in extreme pH regions. They offer the possibility of remote sensing and real-time analysis (Safavi and Bagheri, 2003). Further advantages are the lack of a need for a reference element and the possibility of low-cost, autoclavable and precalibrated sensor patches (Capel-Cuevas et al, 2010).…”