# US 5,710,372 A · Method of analysis for aqueous fluids > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,710,372 A - Document ID: US5710372A - Status: Granted - Kind: A - Application number: 08/768,190 - Filed: 1996-12-17 - Granted: 1998-01-20 - Earliest claimed: 1996-12-17 - Assignees: Cincinnati Milacron Inc. - Inventors: Giles J. P. Becket - Web page: https://patentgrep.com/patent/US5710372A ## CPC - G01N 31/22: using chemical indicators (G01N31/02 takes precedence) - G01N 31/221: {for investigating pH value} - 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 A simple, convenient method is provided for measuring the concentration of a constituent of an aqueous fluid composition (e.g. aqueous machining fluid composition) and for measuring total alkalinity thereof. The method comprises the steps of a) contacting a solid state test device with the aqueous fluid wherein the solid state test device comprises a plurality of individual spaced apart test regions on an inert support, each test region comprising an inert matrix impregnated with a reagent selectively interactive with the constituent and a color indicator that produces a change in color in response to changes in the test region resulting from interaction between the reagent and the constituent and wherein the amount of reagent in each test region differs in a predetermined manner from the amount of reagent in adjacent test regions, and b) comparing the solid state test device after contact with the aqueous fluid to a constituent concentration color calibration scale for the same reagent, color indicator and constituent. ## Claims ### Claim 1 In a method of measuring the concentration of a constituent of an aqueous fluid composition the steps comprising a) contacting a solid state test device with the aqueous fluid composition, the solid state test device comprising an inert support and a plurality of individual spaced apart test regions on the support, wherein each test region comprises an inert matrix impregnated with a reagent selectively interactive with the constituent and a color indicator that produces a change in color in response to changes in the test region resulting from interaction between the reagent and the constituent and wherein the amount of the reagent in each test region differs in a predetermined manner from the amount of reagent in adjacent test regions, and b) comparing the solid state test device after contact with the aqueous fluid to a constituent concentration color calibration scale, whereby correspondence is determined between a pattern of resultant colors of the test regions and a constituent concentration represented by the constituent concentration color calibration scale. ### Claim 2 (depends on 1) The method of claim 1 wherein the constituent color calibration scale is specific to the reagent, the color indicator and the constituent. ### Claim 3 (depends on 1) The method of claim 1 wherein the constituent concentration is such that after contact with the aqueous fluid, a color change is produced in at least one but not all of the test regions. ### Claim 4 (depends on 1) The method of claim 1 wherein the reagent is a solid. ### Claim 5 (depends on 1) The method of claim 1 wherein the contacting of the solid state test device with the aqueous fluid composition is by immersing the solid state test device in the aqueous fluid composition. ### Claim 6 (depends on 1) The method of claim 1 wherein the reagent is also the color indicator. ### Claim 7 (depends on 1) The method of claim 1 wherein the interaction between reagent and constituent alters the pH in the test region and the color indicator is a pH color indicator. ### Claim 8 (depends on 7) The method of claim 7 wherein the reagent is chosen such that relatively large changes of pH are effected by relatively small changes in the proportions of reagent and constituent and the pH color indicator is chosen such that the band of pH over which its color changes is relatively narrow. ### Claim 9 (depends on 1) The method of claim 1 wherein the step of comparing the solid state test device after contact with the aqueous fluid composition to a constituent concentration color calibration scale is a step of visually comparing the solid state test device to a constituent concentration color calibration scale. ### Claim 10 In a method of measuring the concentration of a constituent of an aqueous machining fluid composition, the steps comprising a) contacting a solid state test device with the aqueous machining fluid composition, the solid state test device comprising an inert support and a plurality of individual spaced apart test regions on the support, wherein each test region comprises an inert matrix impregnated with a reagent selectively interactive with the constituent and a color indicator that produces a color change in response to the changes in the test region resulting from interaction between the reagent and the constituent and wherein the amount of reagent in each test region differs in a predetermined manner from the amount of reagent in adjacent test regions and b) comparing the solid state test device after contact with the aqueous machining fluid to a constituent concentration color calibration scale, whereby correspondence is determined between a pattern of the resultant colors of the test regions and a constituent concentration represented by the constituent concentration color calibration scale. ### Claim 11 (depends on 10) The method of claim 10 wherein the interaction between reagent and constituent alters the pH in the test region and the color indicator is a pH color indicator. ### Claim 12 (depends on 11) The method of claim 11 wherein the reagent is chosen such that relatively large changes of pH are effected by relatively small changes in the proportions of reagent and constituent and the pH color indicator is chosen such that the band of pH over which its color changes is relatively narrow. ### Claim 13 (depends on 10) The method of claim 10 wherein the constituent concentration color calibration scale is specific to the reagent, the color indicator and the constituent. ### Claim 14 (depends on 10) The method of claim 10 wherein the constituent concentration is such that after contact with the aqueous machining fluid, a color change is produced in at least one but not all of the test regions. ### Claim 15 (depends on 10) The method of claim 10 wherein the step of comparing the solid state test device after contact with the aqueous machining fluid composition to a constituent concentration color calibration scale is a step of visually comparing the solid state test device to a constituent concentration color calibration scale. ### Claim 16 In a method of measuring the total alkalinity of an aqueous machining fluid composition the steps comprising a) contacting a solid state test device with the aqueous machining fluid composition, the solid state test device comprising an inert support and a plurality of individual spaced apart test regions on the support, wherein each test region comprises an inert matrix impregnated with an acid reagent selectively interactive with the alkaline constituents of the aqueous machining fluid and an acid-base color indicator that produces a color change in response to the changes in the test region resulting from interaction between the acid reagent and the alkaline constituents of the aqueous machining fluid and wherein the amount of the acid reagent in each test region differs in a predetermined manner from the amount of acid reagent in adjacent test regions and b) comparing the solid state test device after contact with the aqueous machining fluid to a total alkalinity color calibration scale, whereby correspondence is determined between a pattern of the resultant colors of the test regions and a total alkalinity represented by the total alkalinity color calibration scale. ### Claim 17 (depends on 16) The method of claim 16 wherein the acid reagent is chosen such that relatively large changes of pH are effected by relatively small changes in the proportions of acid reagent and alkaline constituents of the aqueous machining fluid and the acid-base color indicator is chosen such that its color changes over a relatively narrow band of pH. ### Claim 18 (depends on 16) The method of claim 16 wherein the total alkalinity color calibration scale is specific to the acid reagent, the acid-base color indicator and the total alkalinity of the aqueous machining fluid composition. ### Claim 19 (depends on 16) The method of claim 16 wherein the total alkalinity of the aqueous machining fluid composition is such that after contact, a change in color is produced in at least one but not all of the test regions. ### Claim 20 (depends on 16) The method of claim 16 wherein the step of comparing the solid state test device after contact with the aqueous machining fluid composition to a total alkalinity constituent concentration color calibration scale is a step of visually comparing the solid state test device to a total alkalinity constituent concentration color calibration scale.