Glycolic acid neutralization

PIH after a peel with 70% unbuffered glycolic acid neutralization with a sodium bicarbonate solution as soon as erythema appeared. There is no visible frosting. Postoperative developments were normal. On the 8th day, the patient consulted the doctor about the appearance of PIH 3 days before (a). Treatment consisted of tyrosinase inhibitors, topical antioxidants, sun avoidance and protection, (b) The patient after 5 weeks, (c) After 8 weeks. The hyperpigmentation has improved significantly. A telephone call revealed that the problem has cleared up completely after 3 months. 

The temperature must be controlled to avoid formation of glycolic acid. One-half of the alkali is sufficient to neutralize the acid, and the remainder may be added rapidly without danger of raising the temperature. 

If the reactants are added in this order, with the glycolic acid being introduced over a 5-10 minute period, there is no violent heating because the heat of neutralization is used to melt the indole. An equivalent amount of anhydrous glycolic acid may be used, but this offers no special advantage. 

ESR spectra, 511 Uranium(VI) complexes dioxoneocupferron, 512 Uranium hexaalkoxides physical properties, 347 Uranyl complexes cupferron, 512 formamide, 491 glycolic acid, 472 hexafluoroacetylacetone, 373, 377 photochemistry, 385 rearrangement, 384 maleic acid conformation, 467 neutral 1,3-diketones, 402 poly ketones, 399 Urea... 

CH2OHCOONH4 (aq.). de Forcrand3 measured the heat of neutralization of aqueous glycollic acid with aqueous ammonia. 

Applying large quantities of pure acid to the skin (during a glycolic acid peel with a non-neutralized solution) saturates its natural buffer capacity, and the excess acid must be neutralized to avoid burning the skin. 

AHAs may also limit or prevent the cross-linking of proteins in the extracellular matrix. Unlike TCA or phenol, AHAs do not bind with proteins and so are not neutralized by them. The type of action they produce depends on their concentration, the pH of the solution, the pK of the acids and the contact time with the skin before neutralization with a base solution. For example, a 70% glycolic acid solution (pH 0.5 for pK 3.83) in contact with the skin for 5 minutes will be more aggressive than a partially buffered (pH 3.5) 50% solution left in contact with the skin for 2 minutes before neutralization with a base solution (a saturated solution of sodium bicarbonate, for example). 

Not all glycolic acid peels are the same as far as the skin is concerned. The peels that are the most difficult to use are glycolic acid in simple aqueous solution and glycolic acid masks (because it is difficult to monitor how the skin is reacting). The most effective peel would be one that does not need neutralizing, in spite of having a pH of 0.5 for a solution with a pK, between 3 and 4. 

The effectiveness of a peel with glycolic acid in aqueous solution depends on the amount of time for which the acid is contact with the skin and therefore on how soon it is neutralized. Neutralizing too soon only allows a small proportion of the acid to act. 

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