Zusammenfassung
An improved pH indicator derived from a new design concept for luminescent europium complexes and its favourable properties in wide-range pH sensors are introduced. By decorating Eu3+ with ligands that display widespread pK(a) values and an antenna ligand, this probe covers a dynamic range up to 8 pH units. Unlike widerange pH sensors that employ multiple organic dyes with multiple pK(a) values, ...
Zusammenfassung
An improved pH indicator derived from a new design concept for luminescent europium complexes and its favourable properties in wide-range pH sensors are introduced. By decorating Eu3+ with ligands that display widespread pK(a) values and an antenna ligand, this probe covers a dynamic range up to 8 pH units. Unlike widerange pH sensors that employ multiple organic dyes with multiple pK(a) values, our concept requires almost no synthetic effort and only one excitation and emission wavelength which simplifies the instrumental requirements. The improved indicator only uses the chelators theonyl trifluoroacetone (TTA) as antenna ligand and pyridine dicarboxylic acid (PDA). The luminescence emission of the Eu3+-TTA-PDA complex in a 1:3:2 feed ratio in aqueous buffer is dependent of pH from pH 2-10. Sensor membranes containing Eu3+-TTA-PDA respond continuously and reversibly from pH 2-8 over 6 pH units in few minutes. This range is one order of magnitude wider than that of a previous lanthanide indicator. Additionally, we fabricated a high-throughput pH sensor microtiterplate with a dynamic range from pH 2-8 over 6 pH units. It constantly works up to 24 h. Finally, we demonstrate that the pH of some real samples taken with the sensor microtiterplate agrees well with the pH obtained by a pH glass electrode.
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