Miniaturised method for the quantitation of stabilisers in microtome cuts of polymer materials by HPLC with UV, MS or MS² detection

Abstract

A method for quantitative depth profiling of polymer stabilisers in polypropylene materials is presented. Microtome cuts down to 10 μm thickness were prepared and an amount of as low as 10 mg was used for subsequent analysis. The sample preparation procedure included dissolution in toluene, followed by precipitation of the polymer by addition of methanol or acetonitrile, and subsequent analysis of the solution by reversed phase HPLC coupled with UV, MS and MS² detection. A comparison of the different detection techniques is given and their particular advantages are discussed. Depending on the stabiliser type, the presented method with MS detection can quantify stabiliser concentrations down to 0.007 mg L⁻¹ (this corresponds to 0.0007 mg g⁻¹ in the polymer sample) with repeatabilities better than 5 % relative standard deviation (n = 3). This equals a quantitation of absolute stabiliser amounts at the 0.1-μg level and concentrations down to 0.1 mg L⁻¹ in the corresponding polymer extracts. The developed method shows high sensitivity by the use of MS detection as well as good repeatabilities. Mainly due to the use of an appropriate internal standard, improved repeatability during sample extraction could be obtained. Furthermore, the applicability to real samples has been demonstrated.