Polyacrylamide sensor particles have been synthesized by using a microfluidic arrangement for generation of microdroplets containing a reaction mixture for forming gel microparticles. The droplets are formed in an inert carrier liquid immiscible with the reaction mixture based on aqueous solutions. Gel particles are formed in situ by photochemical initiation of polymerization inside droplets using an UV-sensitive photoinitiator. In result, water-swellable spheres with submillimetre size are obtained. Those spheres were loaded with N,N′-dimethyl-9,9′-biacridinium dinitrate (lucigenin) as ion selective fluorescence probe for chloride. The particles can be dried, stored and re-swollen. Upon exposure of dried particles to sodium chloride solutions they showed dynamic fluorescence quenching obeying the linear plot of Stern–Volmer-equation between 0 and 130 mM Cl−. Thus, chloride concentrations up to 50 mM could be measured with appropriate accuracy. The particles allow a fast optical determination of chloride in tiny analyte volumes down to below ten microliters.
Graphic abstract
Water Soluble Disulphonated Aromatic Ketones — Photophysical and Photochemical Properties
By the sulphonation of benzophenone, xanthone, thioxanthone, acridone, and methylacridone the disulphonated derivatives BPS, XS, TXS, AcS and MAcS are produced. Their disodium salts are well soluble in water. The absorption and the emission spectral data of these ketones are similar to those of the respective parent compounds. The S1 state of BPS alone is of n — π* type, in all the other cases it possesses mainly π — π* character. The S1 states can serve as donors in electron transfer reactions with iodonium salts. The kinetic curves of flash photolysis of these ketones in water show two decay processes, which are attributed to the triplet state and the long living ketyl radical. The triplet absorption spectra of the disulphonated ketones are very close to those of the unsubstituted ketones, but the life times of the former are much higher. The T1 are quenched through onium salts by electron transfer reactions. Acryl amide, too, acts as a quencher for the triplets.
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