Simultaneous Determination of ε-Caprolactam and ε-Aminocaproic Acid by Planar Chromatography

This paper describes the qualitative and quantitative determination of ε-caprolactam and ε-aminocaproic acid, which are potential contaminants of polyamid 6, by instrumental thin-layer chromatography (planar chromatography). A validation of the method is proposed. Detection was performed by photodensitometry in UV range at 200 nm for ε-caprolactam, and at 588 nm after derivatization by ninhydrin reagent for ε-aminocaproic acid. Correlation coefficients for calibration were found about 0.996-0.999. Repeatability results were included between 2.4% and 5.5%. Derivatization by Overpressured Derivatization (OPD) technique gave similar results as direct UV detection.