# US 2019/0376904 A1 · Test for Determining the Phosphate Concentration > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0376904 A1 - Document ID: US20190376904A1 - Status: Published application - Kind: A1 - Application number: 16/430,829 - Filed: 2019-06-04 - Published: 2019-12-12 - Earliest claimed: 2018-06-07 - Assignees: Axagarius GmbH & Co. KG - Applicants: Axagarius GmbH & Co. KG - Inventors: Ralph Husmann; Lucas Mertens - Web page: https://patentgrep.com/patent/US20190376904A1 ## CPC - G01N 21/78: producing a change of colour - G01N 33/84: involving inorganic compounds or pH - G01N 33/18: Water - G01N 31/22: using chemical indicators (G01N31/02 takes precedence) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract The present invention relates to a device for determining the concentration of inorganic phosphate, especially orthophosphate, where said device is a test matrix including a molybdate salt, a solid acid, a PVP derivative, and a mixture of at least two different chromogenic reducing agents. In addition, the invention relates to a process for increasing the sensitivity of a test device. ## Claims ### Claim 1 A test device for determining the concentration of inorganic phosphate in a liquid sample, wherein said test device contains a support matrix serving as a support for the liquid sample, the detection reagents and the detection reaction, wherein said support matrix comprises: a) at least one molybdate salt; b) at least one acid that is solid at room temperature; c) a polyvinyl pyrrolidone derivative; and d) a combination of at least two different chromogenic reducing agents. ### Claim 2 (depends on 1) The test device according to claim 1, wherein said molybdate salt is selected from the group consisting of ammonium molybdate, sodium molybdate, calcium molybdate, and potassium molybdate. ### Claim 3 (depends on 1) The test device according to claim 1, wherein said at least one solid acid is selected from the group consisting of methylamidosulfonic acid, amidosulfonic acid, and cyclamic acid. ### Claim 4 (depends on 1) The test device according to claim 1, wherein said polyvinyl pyrrolidone (PVP) derivative has a K value of from 25 to 90. ### Claim 5 (depends on 1) The test device according to claim 1, wherein the chromogenic reducing agents occurring in the combination are selected from the group consisting of leuko Bindschedler's green (LBG), leuko malachite green (LMG), leuko crystal violet (LKV), 3,3′,5,5′-tetramethylbenzidine (TMB), benzoyl-leuko-methylene blue, 4,4′-methylene-N,N-bis(dimethylaniline) (MDA), 1,2-phenylenediamine, 1,3-phenylenediamine, and 1,4-phenylenediamine. ### Claim 6 (depends on 5) The test device according to claim 5, wherein said test device has a combination of exactly two chromogenic reducing agents being one of the following combinations: a) LBG and TMB b) LBG and benzoyl-leuko-methylene blue c) LBG and 1,3-phenylenediamine d) LBG and MDA e) LBG and LMG f) LBG and LKV g) LMG and TMB, or h) LKV and TMB. ### Claim 7 (depends on 1) The test device according to claim 1, wherein said support matrix is a liquid-absorbing material selected from the group containing filter paper, non-woven, glass fiber, porous polymer material made of polysulfone, polyester, nylon, nitrocellulose, PVDF, polycarbonate. ### Claim 8 (depends on 7) The test device according to claim 7, wherein said non-woven consists of polyester (PES) and/or viscose (CV). ### Claim 9 (depends on 7) The test device according to claim 7, wherein said non-woven is a mechanically and/or thermally bonded non-woven fabric. ### Claim 10 (depends on 1) The test device according to claim 1, wherein the test device comprises a test strip with a support matrix that includes: a) cyclamic acid b) PVP K40 c) ammonium molybdate d) leuko Bindschedler's green e) 3,3′,5,5′-tetramethylbenzidine. ### Claim 11 (depends on 1) The test device according to claim 1, wherein the test device is designed as a test strip, test rod or test tape, and/or can be included in an integrated test system. ### Claim 12 (depends on 1) A test method for determining the concentration of orthophosphate in a liquid sample using the test device according to claim 1, comprising: soaking the support matrix with the liquid sample; removing any excess sample material from the support matrix; and visually detecting the color value of the support matrix. ### Claim 13 (depends on 1) A method for enhancing the sensitivity of a test device comprising: providing a test device according to claim 1. ### Claim 14 (depends on 9) The test device according to claim 9, wherein said non-woven fabric has a water absorption coefficient of from 500 to 1000 kg/m2√h. ### Claim 15 (depends on 12) The test method according to claim 12, wherein soaking the support matrix with the liquid sample comprises dipping the support matrix in the liquid sample. ### Claim 16 (depends on 12) The test method according to claim 12, further comprising shaking off or stripping off excess liquid sample. ### Claim 17 (depends on 12) The test method according to claim 12, further comprising incubating the test strip for at least 5 seconds. ### Claim 18 (depends on 17) The test method according to claim 17, wherein the test strip is incubated at room temperature. ### Claim 19 (depends on 12) The test method according to claim 12, wherein visually detecting the color value of the support matrix comprises comparing the support matrix with a color standard. ### Claim 20 (depends on 13) The method according to claim 13, wherein said test device has a combination of exactly two chromogenic reducing agents being one of the following combinations: a) LBG and TMB b) LBG and benzoyl-leuko-methylene blue c) LBG and 1,3-phenylenediamine d) LBG and MDA e) LBG and LMG f) LBG and LKV g) LMG and TMB, or h) LKV and TMB.