Investigation of potential-sensitive fluorescent dyes for application in nitrate sensitive polymer membranes

The applicability of various potential-sensitive dyes (PSD) for optical sensing of anions is reported. Specifically, nitrate-responsive polymer membranes have been developed which are composed of a plasticized polymer, an anion exchange catalyst, and a fluorescent dye. On exposure to nitrate, the fluorescence intensity of such membranes increases, while the wavelengths of the excitation and emission maxima remain virtually unchanged. The membranes typically are 2–4 μm thick and exhibit highest sensitivity to nitrate in the 2 to 200 mgl⁻¹ range. Signal changes on exposure to 100 mmol/1 nitrate can be as high as +300%. The detection limit is 0.2 mgl⁻¹. The cationic PSD octadecyl acridine organe was tested in combination with a tin-organic and an indium-organic anion carrier rather than with tridodecylmethylammonium chloride, but both carriers were found to display no improved selectivity

Influence of polymer composition on the sensitivity towards nitrite and nitric oxide of colorimetric disposable test strips

The influence of polymer composition on the sensitivity towards nitrite (NO 2 − ) and nitric oxide (NO) of a series of 19 polymeric hydrogel films has been stud- ied. The polymers, based on the hydrophilic monomer 2- hydroxyethylmethacrylate (HEMA), are able to encapsu- late the colorimetric indicator 1,2-diaminoanthraquinone (DAQ) and to respond to NO 2 − and NO by visual chang- es. In the case of nitrite, the calculated limits of detection (LOD) for two of the polymeric sensors (10 μ M) are very close to the sensitivity estimated for free DAQ in solution (LOD 5 μ M), but with the advantage of a solid supported sensor with the format of a disposable test- strip made with affordable starting chemicals. The re- sults are interpreted taking into account the nature and proportions of monomers and cross-linkers used for the synthesis of polymers. Key factors for obtaining sensi- tive materials are the hydro philic character of the film along with the utilization of low levels of cross-linker and the use of an acidic monomer, like acrylic acid, as a building block.Financial support from the Spanish MINECO (CTQ2015-68429-R) and Fundació Caixa Castelló-UJI (P1·1B2015-76) is acknowledged. V. F. thanks the financial support from UJI (predoctoral fellowship). We thank SCIC/UJI for technical assistance