On-slide synthesis of a schiff reagent

A kit comprising:

• (i) a dye composition comprising a compound having any one of Formulas (I)—(XII):
• wherein
• R1, R2, R3, R4, R5, and R6 are independently H, a halogen, a branched or unbranched, substituted or unsubstituted C1-C6 alkyl group or cycloalkyl group, —OH, —O—C1-C6 alkyl, or —N(Rx)(Ry), where Rx and Ry are independently H or a branched or unbranched C1-C6 alkyl group optionally substituted with one or more halogen atoms, or where either R1 and R2 together, or R3 and R4 together, or R5 or R6 together form a 5- or 6-membered cyclic ring or heterocyclic ring which may be optionally substituted with one or more C1-C6 alkyl groups or one or more —N(Rx)(Ry) groups;
• and
• A is a counterion;
• and
• wherein a concentration of the compound having any one of Formulas (I)—(XII) ranges from between about 0.05% w/v to about 8% w/v by total volume of the dye composition;
• and
• (ii) a sulfite composition comprising a sulfite or SO2 source selected from the group consisting of metabisulfite, bisulfite, dithionite, thiosulfate, sulfites, and sulfurous acid;
• wherein a concentration of the sulfite or SO2 source ranges from between about 0.1% w/v to about 18% w/v by total weight of the sulfite composition.