Analysis of linear and cyclic oligomers in polyamide-6 without sample preparation by liquid chromatography using the sandwich injection method II. Methods of detection and quantification and overall long-term performance

By separating the first six linear and cyclic oligomers of polyamide-6 on a reversed-phase high-performance liquid chromatographic system after sandwi ch injection, quantitative determination of these oligomers becomes feasibl e. Low-wavelength UV detection of the different oligomers and selective pos t-column reaction detection of the linear oligomers with o-phthalic dicarbo xaldehyde (OPA) and 3-mercaptopropionic acid (3-MPA) are discussed. A gener al methodology for quantification of oligomers in polymers was developed. I t is demonstrated that the empirically determined group-equivalent absorpti on coefficients and quench factors are a convenient way of quantifying line ar and cyclic oligomers of nylon-6. The overall long-term. performance of t he method was studied by monitoring a reference sample and the calibration factors of the linear and cyclic oligomers. (C) 2000 Elsevier Science B.V. All rights reserved.