Lactic acid [50-21-5].
»Lactic Acid is a mixture of lactic acid (C3H6O3)and lactic acid lactate (C6H10O5)equivalent to a total of not less than 88.0percent and not more than 92.0percent,by weight,of C3H6O3.It is obtained by the lactic fermentation of sugars or is prepared synthetically.Lactic Acid obtained by fermentation of sugars is levorotatory,while that prepared synthetically is racemic.[NOTELactic Acid prepared by fermentation becomes dextrorotatory on dilution,which hydrolyzes L-(-)-lactic acid lactate to L-(+)-lactic acid.]
Packaging and storage Preserve in tight containers.
Labeling Label it to indicate whether it is levorotatory or racemic.
Identification It meets the requirements of the test for Lactate á191ñ.
Specific rotation á781Añ: between -0.05and +0.05,for racemic Lactic Acid.
Readily carbonizable substances Rinse a test tube with sulfuric acid TS,and allow to drain for 10minutes.Add 5mLof sulfuric acid TSto the test tube,carefully overlay it with 5mLof Lactic Acid,and maintain the tube at a temperature of 15:no dark color develops at the interface of the two acids within 15minutes.
Residue on ignition á281ñ: not more than 3mg,from a 5-mLportion (0.05%).
Sugars To 10mLof hot alkaline cupric tartrate TSadd 5drops of Lactic Acid:no red precipitate is formed.
Chloride To 10mLof a solution (1in 100)acidified with nitric acid add a few drops of silver nitrate TS:no opalescence is produced immediately.
Sulfate To 10mLof a solution (1in 100)add 2drops of hydrochloric acid and 1mLof barium chloride TS:no turbidity is produced.
Heavy metals,Method IIá231ñ: 0.001%.
Limit of citric,oxalic,phosphoric,or tartaric acid To 10mLof a solution (1in 10)add 40mLof calcium hydroxide TS,and boil for 2minutes:no turbidity is produced.
Assay To about 2.5mLof Lactic Acid,accurately weighed in a tared 250-mLflask,add 50.0mLof 1Nsodium hydroxide VS,and boil the mixture for 20minutes.Add phenolphthalein TS,and titrate the excess alkali in the hot solution with 1Nsulfuric acid VS.Perform a blank determination (see Residual Titrationsunder Titrimetry á541ñ).Each mLof 1Nsodium hydroxide is equivalent to 90.08mg of C3H6O3.
Auxiliary Information Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist
Expert Committee:(DSN)Dietary Supplements:Non-Botanicals
USP28NF23Page 1105Pharmacopeial Forum:Volume No.28(6)Page 1817