This procedure is used to block acid groups, particularly carboxyl groups. As a consequence basophilic staining materials cease to be basophilic. Extended treatment destroys PAS positivity of some carbohydrates. This may be used as a means of identifying them, particularly if done in conjunction with other blocking procedures.
Solution
| Material | Amount | |
|---|---|---|
| Methanol | 99.17 | mL |
| Hydrochloric acid, conc. | 0.83 | mL |
Note: This is 0.1N hydrochloric acid.
Procedure
- Place dewaxed sections into the solution in a sealed container at the temperature specified for the time given.
| Tissue | Temperature | Time | State |
|---|---|---|---|
| Glycogen | 58°C | 3 days | Complete |
| Epithelial mucin | 58°C | 3 days | Complete |
| Glycogen | 37°C | 7 days | Not complete |
| Epithelial mucin | 37°C | 7 days | Not complete |
It should be noted that methylation is more commonly used to abolish metachromasia or cytoplasmic basophilia. Treatment of sections at 37°C with 1% hydrochloric acid in methanol for 2 days will usually accomplish this, while not affecting PAS reactivity.
References
- Lillie, R.D., (1954)
Histopathologic technique and practical histochemistry Ed.2
Blakiston, New York, USA
