Quartz filters are made of pure quartz fiber without fiberglass or binders and are used for sampling acid gas and air in chimneys. The pure quartz content prevents the filter from reacting with acid gases, which can occur with fiberglass filters and cause false readings. Quartz filters are also inert, durable, moisture resistant and designed for high temperature filtration applications. They have the following characteristics:
●Resistant to chemical attack
●biologically inert
●Easy sterilization
●Low trace metal content
●Low adsorption
●It can be stored indefinitely and is not affected by moisture
Applications of quartz filters:
Accurate and reliable air quality monitoring begins with selecting the appropriate filter to collect samples from and then following the workflow associated with that specific filter. High purity quartz filters offer resistance to high temperatures and low contaminant levels, making them the best choice for:
●Organic carbon/elemental carbon (OC/EC) monitoring.
●Detection of heavy metals.
Organic carbon/elemental carbon (OC/EC) monitoring.
Typical OC/EC test methods first involve gradually heating the filter to approximately 700°C in an oxygen-free atmosphere. This process breaks down most organic carbon and all carbonates, leaving some elemental carbon behind. The evaporated organic carbon is converted to CO2, which can then be measured by reduction to methane and using a hydrogen flame ionization detector (FID).
FID cannot be used to measure inorganic carbon. Therefore, to measure the remaining elemental carbon, the temperature must be low and a small amount of oxygen added to the chamber. A second heating step at 850°C burns off the remaining elemental carbon, oxidizing it to CO2 for FID analysis.
Combining the two FID values allows measurement of organic and elemental carbon on the filter and therefore in the raw air sample.
These steps require the use of carbon-free filters that are resistant to high temperatures. As a material, quartz is ideal for this task. High-purity quartz filters do not contain carbon and remain stable at temperatures up to 900°C.
Detection of heavy metals
Detection of heavy metals in air requires extensive air filtration and sampling times are typically at least 8 hours. Extended sampling times help maximize reliability and detect low concentration contaminants.
The heavy metal testing workflow involves weighing the filter before and after sampling to determine the total mass of particles captured. There are several possible analytical methods to identify and measure heavy metal contamination, including:
Energy Dispersive X-ray Fluorescence (EDXRF)
Acid digestion followed by inductively coupled plasma mass spectrometry (ICP-MS).
Choosing filters with extremely low levels of heavy metals is critical to the accuracy of these methods. Filters containing measurable amounts of critical elements such as lead (Pb) and copper (Cu) will cause inaccurate results.
Quartz is composed of pure SiO2, and high quality quartz filters contain negligible heavy metal contaminants, especially compared to fiberglass. They therefore have little impact on measurements and are ideal for testing heavy metals.
