Alcian Blue Periodic Acid Schiff (AB-PAS) stain kit 

Alcian blue and PAS staining method can be used together to identify neutral mucin and acidic mucin in the same tissue section. This technique is also commonly used as a means of extensive detection of mucin. This technique is negatively stained, and it can be clearly determined that the substance is not mucin. In most methods, the sections are first stained with standard Alcian blue (pH 2.5). Alcian blue is a copper-titanium cyanine dye. This cationic dye combines with acidic groups, that is, Alcian blue forms an insoluble complex with anionic groups such as carboxyl and sulfate groups contained in the tissue. The positively charged salt bond in the molecule combines with the negatively charged acidic groups in the acidic mucin polysaccharide substance to form an insoluble complex and appear blue. Then, the PAS technique can be used to display three different mucin components. PAS technology can stain neutral mucins into deep red/reddish purple, and also stain tissues and cells containing both neutral mucins and acidic mucins into different shades of purple, due to the combination and reaction of Alcian blue with Schiff reagent. The above staining often occurs in intestinal goblet cells containing neutral mucins and salivary mucins.