New Analytical Methods for Silicone Elastomers Used in Drug Delivery Systems

• Main Author: Karlsson, Anders
• Format: Doctoral Thesis
• Language: English
• Published: KTH, Fiber- och polymerteknologi 2003
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3533; http://nbn-resolving.de/urn:isbn:91-7283-505-2

The modern pharmaceutical industry requires high qualityperformance and documentation in all the manufacturing steps tomeet continually increasing economic and regulatory demands.This includes the need for new advanced analytical methods toensure high consistency of the incoming raw materials, and ofthe intermediate and final products. This thesis describes the development of new analyticalmethods or the refinement of established methods for siliconeelastomers with a focus on high selectivity, accuracy andprecision. Spectroscopy (NMR, IR MS), chromatography (GC, LC)and thermoanalytical techniques (TGA, DSC, DMTA) have been usedto analyse the consistency of the silicone materialcomposition. These methods have also been used to improve theproduction processes for a controlled drug release product andto ensure that the regulatory demands of the final product aremet. The dimethyl silicone elastomer used was cured by ahydrosilylation mechanism where vinyl and hydride siloxanegroups add and form an ethylene crosslinking bond. Thisreaction is catalysed by platinum in the presence of aninhibitor to prevent the material from curing at roomtemperature. The low amounts of vinyl and hydride groups were quantifiedby a new NMR method. As a complement, a large number of sampleswere analysed with respect of their hydride content with arapid IR method. The low molecular weight inhibitor was determined with a newheadspace GC method. We also found that the inhibitor contentwas of great importance in the manufacture of the controlleddrug delivery device. If the inhibitor content was too low, thepre-curing made the material practically impossible tohandle. After curing, we found residues of hydride groups in theelastomer that had a negative impact on the product properties.Using NMR and IR for hydride quantification, we developed acontrolled procedure by storing the material in a room atconstant temperature and humidity in order to decompose thesehydride groups. Several other methods which were developed are alsodescribed in this thesis. The methods are essential both duringthe development phase and in the quality control phase in themanufacture of a silicone elastomer drug delivery device.