Abstract: The use of a pH-responsive polymer, based on tridodecylamine incorporated in a PVC matrix, was studied for the fabrication of low-cost NH3- and CO2-sensing electrodes for, e.g., detection in biochemical analysis. Miniature static gas sensors were constructed either (i) with or (ii) without internal reference solution In (i) an earlier design (cf. Meyerhoff et al., Anal. Abstr., 1983, 44, 3D29) was used, and in (ii) the membrane was coated directly on to a graphite rod. Under optimum conditions such static sensors exhibited rectilinear responses with slopes of 48 to 62 mV per decade, and potentials were reproducible to within ±1.5 mV at gas concentration. >1 mM. For automated continuous-flow systems, tubular forms of the polymer-membrane electrodes and a simple flow-through gas-dialysis arrangement were used (cf. Anal. Chem., 1981, 53, 992). The polymer-based sensors provide an attractive alternative to gas-sensing devices based on conventional glass pH electrodes.

Abstract: The use of liquid drop-based systems are examined for the following: truly renewable gas sampling interfaces, windowless optical cells, reaction vessels for flow injection turbidimetry and solvent extraction systems with nested drop arrangements. The drop minimizes sample and reagent consumption and allows a fresh reaction surface for every sample. Drops are applicable to biphasic systems.