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Abstract: The use of metachromatic dye-based formulations for the preparation of inkjettable prototype indicators suitable for the detection of charged macromolecules, surfactants or other low molecular weight molecules was investigated. Such indicators were based on the use of metachromatic o-toluidine blue (OTB) that undergoes a characteristic change in color (from blue to pink) upon interaction with anionic macromolecules. When applied onto absorbing substrates such as paper and paperboard, solutions containing OTB and the same dye in the presence of potassium polyvinyl sulfate (KPVS), proved to indicate negatively charged polymers and cationic surfactants. The colorimetric responses suggest a detection limit and sensitivity both are in the order of 1mM of charged species but can be further improved. Interactions between active species in the indicators and some of the additives in inkjettable formulations (surfactant and humectants) interfered with the mechanism by which an OTB/KVPS-based system work only to a minor degree and could be overcome by priming the substrate. An OTB-based system was formulated into an inkjettable formulation that, once applied to a substrate, was showed to indicate charged polymers and surfactants. This concept has the potential for sensing/indication of other charged macromolecules, such as carboxylates and polyphosphates, which are relevant in biomedical (e.g. fouling due to microbial activity), packaging applications (e.g. migration or release of compounds, food spoilage), microfluidic devices or a simple dipstick application to indicate the presence of charged components. [Copyright &y& Elsevier]

Waste gas containing diethyldisulphide (DEDS) is generated from various industries including pulp and paper, refinery, rayon and molasses based distilleries, etc. DEDS has odour threshold detection with an average concentration of 10−9 mg/m3 at 25°C. DEDS is toxic to bacteria, fungus and also to mammals when exposed for a long period. Waste gas containing DEDS require proper treatment prior to discharge into the environment. DEDS containing waste gas was treated in a biofilter, packed with compost along with wooden chips and enriched with DEDS degrading microorganisms. The biofilter could remove DEDS to the extent of 94±5% at a loading of 1.60g/m3/h with an empty bed retention time of 150s. At optimal operating conditions, the average moisture content required by the biofilter was in the range of 60–65%. The biodegradative products of DEDS were thiosulphate and sulphate. [Copyright &y& Elsevier]