Browsing by Author "Myllyperkiö, Minna"

Synthetic polymer matrices are found in many materials being part of people's everyday life. Metals are utilized in the polymerization process, and added to plastic polymers as colorants and additives. Toxic metals, such as Cd, As and Pb should not exceed certain limits within polymeric materials. Various analytical techniques may be utilized for quantification of metal concentrations in polymer samples. Many analysis methods require liquid samples with low carbon concentration. Therefore, efficient sample preparation methods are needed. Different sample digestion techniques and analytical instruments employed for these tasks are reviewed in the literature part of this thesis. Because polymers are a wide group of material with very different properties, there is no single sample preparation method applicable to all of them. Even within one sample digestion technique, there are multiple optimization parameters to be considered; generally these parameters need to be studied for every polymer type separately. In addition to the variable properties of polymer classes, also the specific properties of each metal and its chemical forms affect the choice of the analytical approach. The most frequently employed sample preparation technique is closed-vessel microwave digestion, attractive because of its efficiency and its ability to retain volatile elements. Other techniques discussed in this thesis include dry and wet ashing, fusion, and microwave induced combustion (MIC). Most commonly used instrumentation for metal analysis are inductively coupled plasma optical emission and mass spectroscopy (ICP-OES and ICP-MS), atomic absorption spectroscopy (AAS) and x-ray fluorescence XRF. In the experimental part, a microwave digestion method for quantification of As, Cd, Cr, Cu, Hg and Pb in selected polymers and monomers and using ICP-MS analysis was developed. For every studied sample, suitable digestion conditions using nitric acid as reagent were identified. Water insoluble polymers were found to be more challenging to digest as compared to water soluble and solid polyethylene samples. In addition, a full evaluation of method uncertainty was performed for the method addressing the water soluble polymer. Final expanded method uncertainty was found to be approx. 15 % at 95 % confidence level at a measurement level of 2 μg l-1 for every studied metal.