Coupon design for enhanced color sensitivity for colorimetric-based chemical analysis of liquids

A system for monitoring an analyte concentration in liquid comprising:

• a coupon comprising an absorbent body, which is translucent or opaque such to transmit light, not transmit light, or to transmit light to a limited degree, with a window through said absorbent body wherein said liquid is maintained in said window by capillary action and surface tension;
• a reactant in said absorbent body wherein said reactant is capable of reacting with a designated analyte to induce a color change in proportion to the concentration of the analyte, with the reactant diffusing into said window to react with an analyte in said liquid, or with the reactant reacting with the analyte within the absorbent body itself, with the color-indicating by-product of this reaction diffusing into said window induce a color change in the contained liquid, wherein said analyte is present in said analyte concentration to form a reactant with a color wherein said color has an intensity which correlates to said analyte concentration;
• and
• a light source capable of passing light into said window wherein said light is attenuated by said color proportional to said analyte concentration to form attenuated light further comprising a system capable of measuring an intensity of said attenuated light.