Techniques in Using an Asbestos Microscope

Asbestos microscope is the primary tool used to identify asbestos fibers. It is also referred to as a polarized light microscope. It examines different minerals and rock sections. It is also capable of identifying asbestos, a known carcinogen. Also, it contains a reticle used for counting the fibers.

If you have already collected a sample of a rock specimen or asbestos for instance, place it in a glass vial. Collection of specimen should be done by light microscopy. This specimen will be analyzed by way of gross examination and phase polar assessment as well as dispersion microscopy. Now check on the presence of fibrous components. If a pre-preparation is felt to be necessary, perform one to determine the amount of phases that are present.

After doing the pre-preparation, slides have to be prepared for each phase. There should be two preparations in similar phase. Examine the asbestos microscope and estimate the amount of asbestos in percent by basing on the birefringent fiber that is present. Observe the slides on the microscope at 10x magnification ans 400x magnification. Take note of the presentation of the fibers. Make an estimate of the asbestos percentage. Fibers that appear smaller than 1.0 um based on thickness have to be identified. This will only result to a tentative identification. If a more accurate identification is to be done, a dispersion microscopy is required.

Once these fibers are determined, adjust the asbestos microscope for dispersion manner and again, perform an observation of the fibers. This type of microscope has one rotating stage, a polarizing component and a method of generating dark field images. Consequently, align the fiber with all the length in parallel form. Rotate the stage so that every fiber is examined. Go on with the analysis until all of the asbestos species are identified. Small quantity of asbestos would need slower way of scanning.

Dark field method is employed as it allows refraction of light by the particle. Establish your objective in a way that the circular stop is equal to the objective opening located at the back plane of the microscope.

When using an asbestos microscope, the microscope user should carefully calibrate and select the reticle for the definite eyepiece and objective to be used. The reason underlying this is the optics has tolerance. Other parts of this microscope have tolerance too. The optics’ magnification varies from one device to another therefore it has to be compounded if additional lens are being used. In the case of asbestos microscope, it possesses a 40x objective, which is a phase contrast one as well as an eyepiece ranging 10x totalling to a 40x magnification. Although the actual magnification has the possibility to vary at this point, it still produces a great magnification.

To ensure that the reticle will result to a considerable diameter, a stage micrometer is used. This stage micrometer has a certified fixed distance. If you have an asbestos fiber as your specimen, it can easily be counted within 100micron diameter field. This proves that asbestos microscope depends on a microscopy which employs polarized light and phase contrast. In the polarized light microscopy, the properties of plane polarized light are utilized.

The asbestos microscope’s polarizing filters are classified into two namely plane and circular. As mentioned above, this type of microscope uses properties of plane polarized light and this is created starting from a normal light. We all know that light’s waves scatters in many different ways. It is much difficult to achieve a consistent alignment. The filter allows only those light waves with aligned directions. These light waves that pass through the circular polarized filters are somewhat in a rotating form.

The passing light in this instance is plane polarized and will be reflected on a surface and differing quantity of plane polarized light will be in line with the vibration axis. If you rotate the filter, lesser light will pass through it. As the filter approaches 90 degrees from the vibration axis, all of the plane polarized light will be blocked. This procedure is used to examine various structures of specimens. Structural stress is then determined.

Detection limit is another consideration for the examination of specimen using asbestos microscope. At times, detection limit can be very low and most often depend on the number of particles being examined. For samples which are finely divided and homogenous in nature, the detection limit can be below a percent provided that there are no complicated interferences of fibers. In the cases of non-homogenous samples, detection limit is more undefined. A lot of experts have conducted tests of proficiency. But still, there were difficulty in establishing accuracy more specifically in the lower concentration status.