PubMed · 14840404
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W A STEPHENSON, F A GIBBS. 1951. A balanced non-cephalic reference electrode.. https://doi.org/10.1016/0013-4694(51)90017-x
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We report on a new sensor strategy that we have termed site selectively templated and tagged xerogels (SSTTX). The SSTTX platform is completely self-contained, and it achieves analyte recognition without the use of biomolecules. To illustrate the SSTTX scheme's potential, we present results for the selective detection and quantification of a model compound, 9-anthrol. The first-generation SSTTX shows the following: (i) exhibits an apparent dissociation constant of (1.8 +/- 0.3) x 10(-4) M for 9-anthrol; (ii) provides 0.3 muM detection limits for 9-anthrol; (iii) yields a 45-s response time (2-mum-thick film); (iv) is completely reversible (6% relative standard deviation after 25 cycles); (v) yields a selectivity factor for 9-anthrol over several structurally similar analogues/interferences (e.g., anthracene, 9,10-anthracenediol, benzophenone, 2-naphthol, phenol, and pyrene) of between 290 and 520; and (vi) is stable (<2% drift in performance) for at least 10 months when stored under ambient conditions in the dark. The results also suggest SSTTXs as new sensor elements for glycoside, pharmaceutical, prostaglandin, and steroid sensors.
The treatment and disposal of sewage sludge is one of the most problematical issues affecting wastewater treatment in the developed world. The traditional outlets for sewage sludge are to spread it on agricultural land, or to form a cake for deposit to landfill or incineration. In order to create a sludge cake, water must be removed. Existing dewatering technology based on pressure can only remove a very limited amount of this water because of the way in which water is bound to the sludge particles or flocs. Several researchers have shown that electrokinetic dewatering of sludge is more efficient than conventional hydraulically driven methods. This involves the application of a dc voltage across the sludge, driving water under an electrical gradient from positive (anode) electrode to negative (cathode) electrode. However, there have been several reasons why this technique has not been adopted in practice, not least because the, normally metallic, anode rapidly dissolves due to the acidic environment created by the electrolysis of water. This paper will describe experimentation using electrokinetic geosynthetics (EKG): polymer-based materials containing conducting elements. These have been used to minimise the problem of electrode corrosion and create a sludge treatment system that can produce dry solids contents in excess of 30%. It will suggest different options for the treatment of sludges both in situ in sludge lagoons and windrows, and ex situ as a treatment process.
A polystyrene-based membrane of 7,8:16,17-dibenzo-6,9,15,18-tetraoxo-1,5,10,14-tetrathiacyclooctadeca-7,16-diene [Bz2Oxo4(18)dieneS4] was fabricated using sodium tetraphenylborate (NaTPB) and dioctyl phthalate (DOP) as anion excluder and plasticizing agent. The best performance was obtained from the membrane with the composition ionophore [Bz2Oxo4(18)dieneS4]:polystyrene:DOP:NaTPB, 5:100:150:10 (w/w). The response of the electrode was linear over a wide range of concentration, 1.26 x 10(-6)-1.00 x 10(-1) mol L(-1) for silver ion with a Nernstian slope of 58.4 +/- 0.1 mV per decade and a detection limit of 1.0 x 10(-6) mol L(-1). The electrode was found to be chemically inert and of adequate stability with a response time of 10 s and could be used for a period of 3 months without change of potential. It worked satisfactorily in mixtures containing up to 35% (v/v) non-aqueous content. The proposed membrane sensor had good selectivity for Ag+ over a wide variety of metal ions in the pH range 2.2-8.5. It was successfully used as an indicator electrode in potentiometric titration of silver ion. The electrode was also useful for determination of Ag+ in waste from photographic films.