Med-Tech Innovation Testing


Summary


Material analysis is part of the understanding of the performance, lifecycle and structure of any medical device. It is an important aid to development and essential to quality control of production. With tight costing and the increasing competitiveness within the


Table I: Test methods described in ISO 10993-18 Analytical method


Dynamic mechanical thermal analysis (DMTA)


industry, material analysis helps to avoid additional costs being incurred, for example, from the lost production due to the use of unsuitable materials delivered either by mistake or due to a process change that has not been documented. This could lead to the possibility of adverse reactions and/or rejection of the device by the patient


Description Dynamic measurement of stress–strain properties over a range of temperatures


Application


Characterisation of elastic, rubber and polymeric materials; of particular interest for devices that behave differently in different phases of use such as a polymeric splint, which is heated to conform to patient anatomy and then sets at body temperature


Differential scanning calorimetry (DSC)


Measurement of the heat capacity of a sample by comparing the energy required to change temperature, compared with a reference sample


Electron dispersal – X-ray analysis scanning electron microscopy (EDX-SEM)


Gas chromatography Mass spectroscopy


Electron microscopy combined with elemental and compound analysis using energetic electrons to liberate X-rays for analysis


Separation and identification of volatile compounds


Identification of compounds by measuring mass charge ratio of ions


Characterisation of polymers, measurement of transitions and phase changes; characterisation of naturally occurring macro molecules


Identification of materials in surfaces and contaminants present; particularly useful for metals and ceramics; verification of deposition of coatings


Identification and quantification of organic impurities, monomers, plasticisers, other polymer modifiers


Identification of chemical structure; quantification of residual monomers and volatile additives in polymers; identification of contaminants; analysis of deposits on explants; analysis of coatings


Gel permeation chromatography (GPC)


High performance liquid chromatography (HPLC) Inductively charge plasma (ICP)


Infrared spectroscopy Nuclear magnetic resonance (NMR)


Separation of polymers by transit time through a gel.


Liquid phase separation by solubility


Detection of elements by excitation in a plasma


Measurement of infra red transmission through a thin film, or reflectance from a surface


Detailed analysis of complex molecules by energy measurement of nuclear environment


Ultraviolet spectroscopy


X-ray photoelectron spectroscopy (XPS)


X-ray fluorescence (XRF) Gel electrophoresis


Absorption of ultraviolet light


Surface analysis by measuring energy of electrons released by incident radiation


Similar to XPS but delivered energy results in secondary fluorescence


Separation of biological compounds by size and polarity in gel media


Characterisation of raw materials


Analysis of extractions and leachates, for additives*


Detection of trace metals in extractions particularly for USP testing


Polymer identification and verification


Material identification particularly contaminants or controlled release compounds. Polymer and other chemical structure analysis


Analysis of extractions and leachates, for additives*; characterisation of intra ocular lens material


Examination of surfaces for cleanliness, contaminants and coatings


Examination of surfaces for cleanliness, contaminants and coatings


Analysis of explants and biofilms


*Additives that may be found on medical devices or found by extraction include, lubricants, accelerators, monomers, higher molecular weight oligomers (from incomplete polymerisation), residual solvents, degradation products (temperature, absorption, hydrolysis, oxidation, corrosion or dissolution) contaminants (mould release agents, anti-static, anti-stick agents, cleaning chemicals)


28 ¦ April 2011 www.med-techinnovation.com


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