Quantifying both ammonium and proline in wines and beer by using a PDMS composite for sensoring

Two of the reagents involved in the Berthelot's reaction, thymol and nitroprusside, were embedded in a PDMS composite in order to apply this assay to determine ammonium and proline, in wine and beers. Safety, portability, rapidity, cost-effectiveness and simplicity of the assay were improved. For the proline determination, a modified Berthelot's reaction, which included a ring cleavage of proline, was optimized. The accuracy of the assay was tested. The limits of detection for ammonium was 0.12 µg mL^-1 and for proline was in the range from 0.7 to 4.1 µg mL^-1, depending on the kind of wine (white, red, or sweet), for beer the LOD was 6 µg mL^-1. The precision achieved was slower than 10%. The accuracy of the assay was tested by means of a confirmatory validation study. Good results were obtained for real samples.