Active pharmaceutical peak purity

PLATE I Determination of the enantiomeric purity of active pharmaceutical ingredient (main compound = MC, peak I is the enantiomeric impurity). Conditions lOOmM sodium phosphate buffer pH = 3.0, lOmM trimethyl -cyclodextrin, 60 cm fused silica capillary (effective length 50 cm) X 75 pm I.D., injection 10 s at 35 mbar, 25°C, 20 kV (positive polarity) resulting in a current of approximately lOOpA, detection UV 230 nm. The sample solution is dissolved in a mixture of 55% (v/v) ethanol in water. (A) Typical electropherogram of an API batch spiked with all chiral impurities, (B) overlay electropherograms showing the selectivity of method toward chiral and achiral impurities, a = blank, b = selectivity solution mixture containing all known chiral and achiral compounds, c = API batch, d = racemic mixture of the main compound and the enantiomeric impurity. 

The addition of a chiral crown ether [(+)-(18-crown-6)-2,3,ll,12-tetracarboxylic acid] to the background electrolyte allowed Blanco and Valverde [147] to separate the enantiomers of benser-azide and determine the enantiomeric purity of Dopa (3,4-dihydroxyphenyl-alanine). Levodopa is the main active ingredient in the pharmaceutical formulation Madopar , which is used to treat Parkinson s disease, while dextradopa causes unwanted side effects. The dextradopa impurity was clearly resolved from the main peak and determined to be 0.5%. 

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