Particulate filter and method of use

Abstract

A particulate filter particularly suited for analytical gravimetric weighing applications is disclosed. The particulate filter includes a polytetrafluoroethylene (PTFE) media supported by a ring and yields stable microgram and submicrogram weighing results. The support ring may be PTFE, metal foil, or another non-hygroscopic polymer such that the mass of the filter does not vary with changes in atmospheric moisture. The filter simplifies the discharge of electrostatic charge buildup such that when a conductive filter media is combined with a conductive ring device, the discharge may be accomplished by placing the filter on a grounded weighing pan or other surface. The particulate filter can simplify filter identification by including identification symbols imprinted on each side of the filter media. Due to the chemically inert qualities of its components, the particulate filter is particularly suited for extraction techniques used during the detection of polycyclic hydrocarbons as is conducted in emissions and ambient air testing.

1 - 67 . (canceled) 
   
   
       68 . A particulate filter for analytical gravimetric weighing analysis comprising: a fluoropolymer filter membrane; an identification symbol printed on first and second sides of the filter membrane, and a support ring fused to an outer rim of the filter membrane, wherein the particulate filter is substantially non-hygroscopic and moisture invariable, and substantially inert to dissolution by organic solvents. 
   
   
       69 . The particulate filter of  claim 68 , wherein the filter membrane comprises a polytetrafluoroethylene (PTFE) material, and wherein the support ring is welded to the filter membrane. 
   
   
       70 . The particulate filter of  claim 69 , wherein the support ring comprises a material selected from the group consisting of PTFE; polymers of tetrafluoroethylene, perfluorovinylether, and perfluoroalkoxy; polymers of tetrafluoroethylene and ethylene; polyvinylidine fluoride; polymers of tetrafluorothylene and hexafluoropropylene; ethylene-chlorotrifluoroethylene copolymer; polymethylpentene; polyester, polypropylene; polyethylene; a metal foil; and a moldable thermoplastic. 
   
   
       71 . The particulate filter of  claim 69 , wherein the filter membrane comprises a PTFE material and a material selected from the group consisting of a carbon filler, a I carbon powder, a carbon fiber, and a ceramic material, to vary an electrical conductivity characteristic of the particulate filter. 
   
   
       72 . A method of analytical gravimetric weighing using the particulate filter of  claim 68  comprising the steps of: equilibrating the particulate filter to an ambient pre-test environment; identifying the particulate filter by an identification symbol printed on a first and a second side of the particulate filter; dissipating electrostatic charge buildup on the particulate filter; pre-weighing the particulate filter; conducting a testing application using the particulate filter; equilibrating the particulate filter to an ambient post-test environment; identifying the particulate filter by the identification symbol printed on a clean side of the particulate filter; post-weighing the particulate filter; and determining a net load of particulate collected by the particulate filter in the testing application based upon the pre-weighing and the post-weighing. 
   
   
       73 . A method of analytical gravimetric weighing using a particulate filter comprising the steps of: equilibrating a particulate filter comprising a fluoropolymer filter membrane and a perfluoroalkoxy polymer support ring to an ambient pre-test environment; identifying the particulate filter by an identification symbol printed on a first and a second side of the particulate filter; dissipating electrostatic charge buildup on the particulate filter; pre-weighing the particulate filter; conducting a testing application using the particulate filter; equilibrating the particulate filter to an ambient post-test environment; identifying the particulate filter by the identification symbol printed on a clean side of the particulate filter; post-weighing the particulate filter; and determining a net load of particulate collected by the particulate filter in the testing application based upon the pre-weighing and the post-weighing. 
   
   
       74 . The method of  claim 73 , further comprising the step of selecting polytetrafluoroethylene as the fluoropolymer a material. 
   
   
       75 . The method of  claim 73 , further comprising the steps of: exposing the particulate filter to a volume of air in the testing application; and calculating a load of particulate within the volume of air from the net load of particulate collected. 
   
   
       76 . The method of  claim 73 , wherein the step of dissipating electrostatic charge buildup on the particulate filter comprises placing the particulate filter on a grounded surface. 
   
   
       77 . The method of  claim 73 , wherein the step of dissipating electrostatic charge buildup on the particulate filter comprises using a Polonium 210 and an alpha emitter radioactive element. 
   
   
       78 . The method of  claim 73 , wherein the steps of identifying the particulate filter by an identification symbol further comprise scanning the identification symbol. 
   
   
       79 . The method of  claim 73 , wherein the step of conducting a testing application using the particulate filter comprises conducting an engine test to detect a polycyclic aromatic hydrocarbon. 
   
   
       80 . A method of detecting polycyclic aromatic hydrocarbons (PAHs) using a particulate filter comprising the steps of:
 identifying a particulate filter comprising a polytetrafluoroethylene filter membrane and a perfluoroalkoxy polymer support ring by an identification symbol printed on a first and a second side of the filter membrane; collecting a particulate sample by the filter; identifying the filter by the identification symbol printed on at least one of the first and second side of the filter membrane; extracting the particulate sample from the filter; and analyzing the extracted sample for PAHs.