Defects in molded silicone medical part identified.This provider of independent chemical analysis, physical testing, and research and development received a molded silicone medical part that contained a small discoloration dis·col·or·a·tion n. 1. a. The act of discoloring. b. The condition of being discolored. 2. A discolored spot, smudge, or area; a stain. Noun 1. on the tip. Testing showed that the defect was composed of an alloy of cobalt, chromium and molybdenum molybdenum (məlĭb`dənəm) [Gr.,=leadlike], metallic chemical element; symbol Mo; at. no. 42; at. wt. 95.94; m.p. about 2,617°C;; b.p. about 4,612°C;; sp. gr. 10.22 at 20°C;; valence +2, +3, +4, +5, or +6. , embedded in a silicone matrix. This alloy was present in another process in the same manufacturing facility and contaminated contaminated, v 1. made radioactive by the addition of small quantities of radioactive material. 2. made contaminated by adding infective or radiographic materials. 3. an infective surface or object. the silicone part. In order to arrive at this conclusion, the company used two main analytical techniques to examine the defect region, including optical microscopy and scanning electron microscopy electron microscopy Technique that allows examination of samples too small to be seen with a light microscope. Electron beams have much smaller wavelengths than visible light and hence higher resolving power. , coupled with energy dispersive dispersive /dis·per·sive/ (-per´siv) 1. tending to become dispersed. 2. promoting dispersion. spectroscopy. Initially, the defect was viewed and documented using an optical microscope optical microscope See under microscope. at 32x magnification. In order to characterize the defect region, scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS (Electronic Data Systems, Plano, TX, www.eds.com) Founded in 1962 by H. Ross Perot (independent candidate for the President of the U.S. in 1992), EDS is the largest outsourcing and data processing services organization in the country. ) was utilized. This analytical technique is said to be ideal for determining the presence of inorganic species, especially in very small spot sizes. SEM magnifies the region of interest, while EDS acquires spectra of the chemical elements present in the magnified section. One can also map the spatial location of the chemical elements that are detected. The sample was analyzed using the SEM. A reference spectrum was acquired of a silicone region where there were no defects. Silicon, oxygen and aluminum were detected. The presence of silicon and oxygen was generated from the silicone medical part, and aluminum may have derived from interference from the SEM vacuum chamber components or the sample mount. The defect region was then located under the SEM. Many small particles were embedded in the surface of the silicone. EDS analysis of a wide area of the defect region indicated the presence of silicon, oxygen, aluminum, cobalt, chromium and molybdenum. Next, one of the particles in the defect region was isolated for spot mode analysis. Spot mode EDS analysis allowed a spectrum to be obtained from a very specific location on a defect particle. High concentrations of cobalt, chromium and molybdenum were detected compared to the wide scan. In order to illustrate the spatial distribution of the elements in the defect region, elemental maps were acquired in the defect region. The elemental maps illustrate the spatial position of the chemical elements that were detected and relate directly to the SEM micrograph micrograph /mi·cro·graph/ (-graf) 1. an instrument used to record very minute movements by making a greatly magnified photograph of the minute motions of a diaphragm. 2. that was obtained prior to mapping. The maps show that the particle is composed of cobalt, chromium and molybdenum, and is embedded in a silicone matrix. The distribution of these three metals in the particle was consistent with an alloy of cobalt, chromium and molybdenum. Polymer Solutions Circle 8 on card |
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