Impurity profiling of l-methionine by HPLC on a mixed mode column

•Impurities of methionine have been synthesized.•HPLC method for impurity profiling in methionine has been developed and validated.•Application of mixed mode chromatography.•The content of impurities in batches was found to be very low.

Methionine is mostly produced synthetically. Thus, impurities are synthesis by-products in addition to oxidation and dimerization products. Here, a sensitive HPLC method for the determination of impurities in l-methionine was developed and validated using a SIELC® Primesep 100 column. Impurities were separated on the mixed mode column by reversed phase and cationic exchange mechanism. The limit of detection was in the range of 0.06–0.30 μg/ml (0.0004–0.002%), limit of quantification in the range of 0.30–0.75 μg/ml (0.002–0.005%) and linearity was shown in the range of 0.3–30.0 μg/ml (0.002–0.200%). The method was found to be precise (intermediate precision RS <5%; n = 2) and accurate (recovery 96.0–121.4%, n = 3). The method is also suitable for the purity assessment of dl-methionine and d-methionine. The amount of impurities found in batches was very low. Only l-methionine-sulfoxide and N-acetyl-dl-methionine could be detected in levels less than 0.05%.

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