Rapid determination of oligomeric hindered amine light stabilizers in polymeric materials.

Hindered amine light stabilizers are essential for the stabilization of synthetic polymers, particularly for materials used for outdoor applications. Although up to now a considerable number of studies dealing with the analytics of this class of stabilizers had been published, especially the determination of oligomeric hindered amine light stabilizers is still an analytical challenge. In the current work, a fast and simple liquid chromatographic method for the quantitative determination of oligomeric hindered amine light stabilizers is presented. A key aspect of this method is their completely different retention behavior depending on the pH, enabling a single peak elution approach by a pH gradient run. This allows a quantitation with simple UV detection independent of the actual oligomeric composition. Calibration curves within the concentration range relevant for the analysis of real polymer samples (LOQ = 70 mg/L) were constructed with R2 values above 0.99. Spiked extracts from polyolefin samples showed recovery rates between 97.3 and 102.9% for five different commercial hindered amine light stabilizers. Relative standard deviations were between 2.0 and 3.9%. Furthermore, it was demonstrated that the employed approach can be easily adapted for mass spectrometry detection.

Identification and semi-quantitative determination of anti-oxidants in lubricants employing thin-layer chromatography-spray mass spectrometry.

A quick and simple method for identification and semi-quantitative determination of nine antioxidants commonly used in lubricants is presented. A dual step thin-layer chromatography (TLC) separation, removes in a first step the oil matrix whereas in a second step the antioxidants are separated. Cutting the spots out of the TLC-plate in the form of triangles allows direct-spray mass spectrometric (MS) measurements, providing MS and MS(n) spectra (if an appropriate MS instrument is employed) of the antioxidants, allowing their identification but also giving information about potential oxidation or degradation of these additives. Calibration curves within the concentration range relevant for the analysis of real oil samples (0.2-1.2gL(-1)) were constructed with R(2) values above 0.98 (when using an appropriate internal standard). This allowed the semi-quantitative determination of the selected antioxidants in real oils samples. Comparison with results from HPLC-UV measurement showed acceptable agreement for all analytes.