pH-sensor
The present invention relates to an optical H + -sensor, comprising an H + -indicator material, wherein the H + -indicator material is present between a support material and a H+-permeable layered structure, the layered structure comprising an H + -permeable hydrophilic layer and an H + -permeable cation exchange layer. Further, the invention relates to a method for determining the H + -concentration, e.g. expressed as pH, in a product or sample thereof, the method comprising contacting the product or sample with an optical H + -sensor according to the invention, measuring an optical property of the indicator material, and determining the H + -concentration of the product or sample based on said optical property.
1. Optical H + -sensor, comprising an H + -indicator material, wherein:
the H + -indicator material comprises a H + -indicator dye covalently coupled to a hydrophilic polymer,
the H + -indicator material being situated between a support material and an H + -permeable layered structure,
the H + -permeable layered structure comprising an H + -permeable hydrophilic layer and an H + -permeable cation exchange layer, and
the H + -permeable cation exchange layer being situated between the H + -indicator material and the H + -permeable hydrophilic layer.
2. Optical H + -sensor according to claim 1 , wherein the support material is a waveguide, in particular a polymeric waveguide.
3. Optical H + -sensor according to claim 2 , wherein the waveguide is an optical fibre.
4. Optical H + -sensor according to claim 1 , wherein the H + -permeable hydrophilic layer is selected from the group consisting of hydro-gels and ionomers.
5. Optical H + -sensor according to claim 1 , wherein the H + -permeable hydrophilic layer comprises a polymer selected from the group consisting of poly(meth)acrylates, polyvinylalcohols, polysugars, polysugar alcohols and polylactates, including copolymers and derivatives thereof.
6. Optical H + -sensor according to claim 1 , wherein the H + -permeable cation exchange layer is selected from the group consisting of sulphonated cation exchange materials.
7. Optical H + -sensor according to claim 1 , wherein the H + -indicator material comprises an H + -indicator dye selected from the group consisting of fluorescent H + -indicators.
8. Optical H + -sensor according to claim 1 , wherein the H + -indicator material comprises reflecting particles.
9. Optical H + -sensor according to claim 1 , wherein the sensor comprises a light-source and a photo-detector which light-source and photodetector are—at least during use—in optical communication with the H + -indicator material.
10. Method for determining the H + -concentration, in a product or sample thereof, the method comprising contacting the product or sample with an optical H + -sensor according to claim 1 , measuring an optical property of the H + -indicator material, and determining the H + -concentration of the product or sample based on said optical property.
11. Method according to claim 10 , wherein the H + -concentration is determined in-line in a process for manufacturing or further processing the product.
12. Method according to claim 10 , wherein the product is a food product.
13. Method according to claim 10 , wherein the product or sample thereof has a pH in the range of 3-10.
14. A method for determining the H + -concentration in water or an aqueous liquid, comprising contacting a sample of water or an aqueous liquid with an optical H − -sensor comprising an H + -indicator material, wherein:
the H + -indicator material comprises a H + -indicator dye covalently coupled to a hydrophilic polymer,
the H + -indicator material being situated between a support material and an H + -permeable layered structure,
the H + -permeable layered structure comprising an H + -permeable hydrophilic layer and an H + -permeable cation exchange layer, and
the H + -permeable cation exchange layer being situated between the H + -indicator material and the H + -permeable hydrophilic layer.
15. Optical H + sensor according to claim 1 , wherein the H − -permeable cation exchange material is a sulphonated fluoropolymer.
16. Optical H + sensor according to claim 15 , wherein the sulphonated fluoropolymer is a nafion.
17. Optical H + -sensor according to claim 7 , wherein the fluorescent H + -indicator is selected from the group consisting of porphyrines, porphynes, carboxy-fluoresceins, pyranines and xanthenes.
18. Optical H + -sensor according to claim 8 , wherein the reflecting particles are selected from the group consisting of glass particles and silicagels.
19. Method according to claim 12 , wherein the food product is selected from the group of sauces, soups, dairy products, and dairy substitute products.
20. Method according to claim 10 , wherein the product is a nutrient substrate for growing a plant.
21. Method according to claim 20 , wherein the nutrient substrate is used in a greenhouse wherein plants are grown.
22. Method according to claim 10 , wherein the product is a chemical product.
23. Method according to claim 13 , wherein the product or sample thereof has a pH in the range of 3-6.
24. Method according to claim 13 , wherein the product or sample thereof has a pH in the range of 5-10.
25. Optical H + -sensor according to claim 1 , wherein the H + -indicator dye is covalently coupled to the H + -permeable hydrophilic polymer via an ester linkage or a peptide linkage.