Alcian blue is a copper phthalocyanin basic dye that is water soluable and colored blue because of its copper content. It has an affinity for acidic tissue elements like mucin.
The pH of the alcian blue staining solution is a critical factor in the staining procedure and has a direct effect on the category of mucins that can be demonstrated with the procedure. The pH of alcian blue staining solutions should range from 0.4 to 2.5, with a pH of 1.0 and 2.5 being used most commonly.
Alcian blue solution with a pH of 1.0 is capable of staining most sulfated acid mucins. These mucins can be found in cartilage, large intestine goblet cells, and bronchial serous glands. The pH of 1.0 is accomplished by dissolving alcian blue stain in powder form into a 0.1N hydrochloric acid solution. An alcian blue pH 1.0 stain can be seen in the top image.
Alcian blue solution with a pH of 2.5 is capable of staining carboxylated mucins in connective tissues and cartilage. It is also capable of staining some weakly sulfated acid mucins like those in cervical tissue. The pH of 2.5 is accomplished by dissolving alcian blue stain in powder form into a 3% acetic acid solution. An alcian blue pH 2.5 stain is shown in the bottom image.