TEM (Transmission Electron Microscopy) Asbestos Analysis

Air filter samples tested for asbestos are collapsed with acetone, mounted on slides, partially ashed in a low temperature plasma, carbon-coated, mounted on copper specimen grids, and dissolved.

Prepared grids are examined by Analytical Transmission Electron Microscopy (TEM). TEM is used to count and characterize suspect asbestos fibers by morphology and internal structure, the latter by selected area electron diffraction, or (SAED). The microscopes are interfaced with Energy Dispersive X-ray (EDX) Spectrometers, which help to confirm chemical compositions of the fibers.

Water, dust and bulk samples are also analyzed by TEM. For such samples, vacuum filtration of aqueous suspensions derived from the samples is conducted prior to preparation of the filters. Quantitative matrix reduction (ashing and/or acid dissolution) is also necessary for most bulk building material samples.

TEM is very useful for confirming problematic samples (floor tiles, roofing, etc.) that actually contain many small or organically bound asbestos fibers which cannot be detected by PLM. It can also be used to quantify very low levels of asbestos (0.1% by weight or less) on some types of bulk samples.