Copper-Stabilized Indigo Carmine Composition for Low-pH Shelf Life
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Solution Overview
Problem
Existing aqueous solutions of indigo carmine are unstable due to oxidative degradation, making it difficult to formulate shelf-stable products without extreme measures like low concentrations, high pH, oxygen scavengers, or special storage conditions.
Innovation Solution
A composition comprising indigo carmine and copper (II) metal ions or salts, with a CD value of ≤1.5 and pH ≤5, stabilizes the dye without pH adjusters or oxygen scavengers, maintaining stability for at least one month at room temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If indigo carmine is dissolved in aqueous solution to achieve water solubility and bright blue hue, then the dye becomes suitable for colorized disinfection systems, but the dye undergoes rapid oxidative degradation and loses stability
Solution Approach 1:
Sodium citrate acts as an intermediary substance that mediates between the indigo carmine dye and dissolved oxygen. It preferentially reacts with oxygen through its aldehyde group to form a hemiacetal, preventing oxygen from oxidizing the dye. This intermediary mechanism allows the dye to remain stable in aqueous solution without requiring extreme pH conditions or oxygen removal
Solution Approach 2:
The invention changes the chemical environment parameters by adjusting pH to 5-9 using sodium citrate, which creates optimal conditions for both dye stability and antimicrobial efficacy. This parameter change allows the system to achieve stability without extreme measures while maintaining functional properties
2Stability of the object's composition
If pH adjusters and oxygen scavengers are added to stabilize indigo carmine, then color stability is improved, but product complexity and formulation difficulty increase
Solution Approach 1:
Sodium citrate performs multiple functions simultaneously: it acts as a pH adjuster to create optimal conditions for dye stability, serves as an oxygen scavenger through its aldehyde group, and provides antimicrobial activity. This multi-functionality eliminates the need for separate stabilizing agents, simplifying the formulation while achieving comprehensive stability
3Duration of action of stationary object
If indigo carmine is stabilized by buffering at pH 5-9 with oxygen scavengers and hermetic sealing, then shelf stability is achieved, but manufacturing and storage requirements become more stringent
Solution Approach 1:
The sodium citrate in the formulation provides self-service stabilization by automatically scavenging dissolved oxygen through its aldehyde group. This self-active mechanism eliminates the need for external oxygen removal processes, hermetic sealing, or specialized storage conditions, making manufacturing and distribution simpler while maintaining extended shelf life
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition significantly increases the shelf-life of indigo carmine formulations, retaining color stability and antimicrobial efficacy, suitable for use in colorized disinfection systems.
Implementation Method 1
The interaction between copper (II) ions and a water-soluble organic dye is discussed by Zanoni et al, who [4] characterized a complex formed by indigo carmine and copper (II) in aqueous solution in a stoichiometric ratio of 1 indigo carmine molecule for every 2 copper (II) ions.
Implementation Method 2
This is due to both chemical oxidation by dissolved oxygen in the water as well as photooxidation from direct exposure to sunlight
Implementation Method 3
Indigo carmine is a water-soluble dye that is widely known to be susceptible to oxidative degradation in aqueous solutions. This is due to both chemical oxidation by dissolved oxygen in the water as well as photooxidation from direct exposure to sunlight
Data Source
AI summary
The present invention provides a composition comprising indigo carmine and a copper (II) metal ion or a salt or hydrate thereof, wherein the composition has a CD value of ≤1.5 and a pH≤5. The present invention significantly increases the shelf-life of aqueous indigo carmine formulations at pH≤5 without requiring special filling or storage conditions to physically remove oxygen from the system. In doing so, aqueous solutions comprising indigo carmine dye are stabilized and suitable for use in, for example, colorized disinfection systems.