Composition, device and method for determining reducing agents

DETAILED DESCRIPTION OF THE INVENTION The indicators which comprise the heart of the present invention are known as thiazine (when X in structure [I] is S) and oxazine (when X in structure [I] is O) dyes.
The structures used in this specification show these compounds in their oxidized state, wherein they exhibit deep colors.
Upon contact with ascorbic acid or other reducing agents in aqueous solution, these oxidized dyes are converted to a colorless reduced state.
Thus, when a compound of this genre is contacted with a test sample containing a reducing agent its color is bleached to an extent dependent upon the amount of reducing agent present.
Thus, by observing the degree of bleaching of the indicator, one can accurately estimate the concentration of reducing agent present in the sample.
The Colour Index, third edition, published by the Society of Dyers and Colourists, in conjunction with the American Association of Textile Chemists and Colourists (1971) is a standard, industry-recognized dye index, which cataloques many of the indicators of the present invention.
These compounds are listed under "C.
I.
" numbers, and such notations as used herein refer to listings in the Colour Index.
Some examples of thiazine dyes useful in the present invention are Lauth's violet (C.
I.
52000), azur A (C.
I.
52005) methylene green (C.
I.
52020) and toluidine blue (C.
I.
52040).
Some oxazine dyes particularly suitable for this invention are gallocyanine (C.
I.
51030), prune pure (C.
I.
51040), gallamine blue (C.
I.
51045), celestine blue (C.
I.
51050), and Meldola's blue (C.
I.
51175).
Although the color fading phenomenon inherent in the presently claimed indicator compounds is, by itself, sufficient to provide a qualitative and semi-quantitative analytical basis, it was found that a still better detectable response can be had if the indicator compound is used in conjunction with an ancillary, or background, dye.
Such a dye is neutral red (C.
I.
50040).
Thus, for example, a carrier matrix incorporated with neutral red and methylene green is initially dark blue, changing to purple, lavender and ultimately red, depending on the presence of a reducing agent and its concentration