Comparative study of lactic acid and polylactides using static headspace, gas chromatography and high-performance liquid chromatography

This work investigates the use of analytical methodology to determine lacti c acids and/or polylactides. This paper reports three methods that have bee n successfully developed. Firstly, static headspace gas chromatography (GC) was investigated. The results show precision values of 4-5% RSD and linear ity correlation coefficients of between 0.990 and 0.999 in the concentratio n range 300-700 mu g/ml lactic acid. The method is specific for lactic acid . Secondly, an on-column GC method is presented which minimises sample prep aration and separation of lactic acid from the polylactides. Finally, an io n-exclusion high-performance liquid chromatography (HPLC) method was develo ped. The instrumental precision was 0.1%, and linearity correlation coeffic ients >0.9999 were obtained in the concentration range between 50 and 200 m u g/ml lactic acid. A basic hydrolysis is used to convert the polylactides to lactic acid. Collectively, these methods form a successful approach for the determination of lactic acid in consumer healthcare products. (C) 1999 Elsevier Science B.V. All rights reserved.