Liquid chromatographic determination of levodopa, levodopa-carbidopa, and related impurities in solid dosage forms.
A rapid reverse phase liquid chromatographic method was developed for the determination of levodopa and levodopa-carbidopa in tablets and capsules. The method also separates these drugs from 3-(3,4,6-trihydroxyphenyl)alanine and methoxytyrosine, impurities of levodopa, and from methyldopa and 3-O-methylcarbidopa, impurities of carbidopa. The mobile phase was 3% acetic acid and the detection wavelength was 280 nm. The method was linear over the concentration range 0.05-0.40 mg levodopa/mL, 0.01-0.06 mg carbidopa/mL, 0.9-12.8 micrograms 3-(3,4,6-trihydroxyphenyl)alanine/mL, 0.7-3.1 micrograms methyldopa/mL, 5-20 micrograms methoxytyrosine/mL, and 0.5-3.3 micrograms 3-O-methylcarbidopa/mL. Mean recoveries (%) for spiked commercial tablets were: levodopa 100.3, carbidopa 100.4, 3-(3,4,6-trihydroxyphenyl)alanine 99.1, methoxytyrosine 100.0, methyldopa 100.0, and 3-O-methylcarbidopa 99.4.
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D000082:Acetaminophen / Q000032:analysis; D002214:Capsules; D002230:Carbidopa / Q000032:analysis*; D002853:Chromatography, Liquid; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives / Q000032:analysis; D004340:Drug Contamination / Q000032:analysis; D007980:Levodopa / Q000032:analysis*; D008750:Methyldopa / Q000032:analysis; D012997:Solvents; D013607:Tablets; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
D002214:Capsules; D012997:Solvents; D013607:Tablets; C001388:6-hydroxydopa; D000082:Acetaminophen; D014443:Tyrosine; D007980:Levodopa; D008750:Methyldopa; D004295:Dihydroxyphenylalanine; D002230:Carbidopa; C008404:3-methoxytyrosine