Fluoropore filter

Materials. Unless otherwise stated, all chemicals and solvents were analytical grade materials (Fluka and B.D.H.), and were used as received. The water used for washing and preparation of aqueous electrolyte solutions was deionized and freshly double-distilled in a fused-silica still. All liquids are filtered (0.22 pm Millipore or Fluoropore filters) prior to introduction into the glass cell. The mica used throughout was Best Quality FS/GS grade 2 Muscovite Ruby mica, mined in Kenya (Mica and Micanite Ltd., U.K.). 

Refractive Index Detector (Knauer). The KMX-6 scattering intensity was measured with the 6-7 degree forward-scattering annulus. A series of Zorbax PSM columns (DuPont) was used PSM 60, PSM 1000, PSM 1000, PSM 60, PSM 1000. Tetrahydrofuran (THF) from Baker was filtered through a 0.22 micrometer Fluoropore filter (Millipore Corp.) before use in chromatography, and a flow rate of 0.7 ml/min was used. 

Stock solutions of samples were prepared with a known concentration (w/v) in THF in the range of x 10 to 5 x 10gm/ml. These stock solutions were filtered through a 0.22 micrometer Fluoropore filter prior to injection, and an injection size of 50 microliters was used. Of all the input... 

It has been observed in this laboratory, as in many others, that compounds, which volatilize from the mass spectrometer direct insertion probe at a certain temperature under electron impact conditions, will often volatilize at a lower temperature (50°C or more) if the analysis is carried out under chemical ionization conditions with reagent gas sweeping around the probe tip and then into the source. For sulfuric acid deposited on a Fluoropore filter, a decrease in volatilization temperature of approximately 70°C has been observed for sulfuric acid when the analysis is carried out in the chemical ionization mode. The elution profile is sharper and better defined than that obtained under electron impact conditions. 

Aqueous solutions of ammonium sulfate and ammonium bisulfate were deposited on Fluoropore filters, placed in the direct insertion probe, and analyzed in the chemical ionization mode (H2O reagent) gas. The samples were heated from 100°C to 330 C at 15 C/minute. No sample ions were observed under these anlaysis conditions, even when several micrograms of ammonium salts were analyzed. The thermal decomposition of ammonium salts of sulfate has been the subject of many studies. (29,30) Some pathways include sulfuric acid production at one stage of the decomposition while others suggest ammonia, SO2 and SO3 are the products. None of these accurately simulate the conditions (temperature, pressure, gas flow) present in our chemical ionization source. However, no sulfuric acid ions (H3SO4+, etc.) were ob-served... 

Analyses of ambient air samples have thus far failed to detect the presence of sulfuric acid. However, considerable quantities of ammonium sulfate salts have been detected. One possible explanation is that sulfuric acid aerosol trapped on a filter is converted to ammonium salts by reaction with ammonia in the air pulled through the filter. A laboratory generated sulfuric acid aerosol collected on a Fluoropore filter was placed in a filter holder. Arbitrarily selected suburban and urban air was passed through the filter at a rate or 30 liters/minute for approximately one hour. In every case > 95% of the sulfuric acid was apparently converted to ammonium salts of sulfate. A strict material balance was not performed. A blank sample of laboratory generated sulfuric acid aerosols was transported to and from the field with proper precautions. Less than 5% conversion of the sulfuric acid to ammonium sulfate was observed for this sample. 

Sampling. Four aerosol samples were collected isokinetically on July 26, 1979, at ports on the inlet duct of the ESP at Plant A two were taken with 62-mm fluoropore filters and two were taken with the University of Washington MKV Cascade impactor (1 ). At plant D, samples were collected over a 6-day period at ports both in the outlet duct of the ESP (i.e., upstream of the FGD system) and at the 91-m level of the stack. Eleven fluoropore filter, 1 MKV, and 4 MKIII impactor samples at each location, giving a total of 22 filter, and 8 MKIII samples. A single MKV sample was also collected in-stack at reduced pressure at plant D during the 6-day period. Polycarbonate material coated with apiezon L vacuum grease and 62 or 47-mm-diam, l-pm pore Fluoropore filters were used as back-up filters in the MKV impactor. 

Three filtering media commercially available from Millipore Corporation were evaluated for the collection of airborne particulates of the organoarsenical compounds. These were (l) cellulose ester membranes (2) Fluoropore and (3) Mitex. The cellulose ester membrane filters (0.8 ym pore size) are the standard Millipore filters used for aerosol sampling and consist of a mixture of cellulose nitrate and cellulose acetate. The Fluoropore filters are made of Teflon (PTFE) and are bonded to a polyethylene net. Fluoropore filters with a pore size of 1.0 ym were selected for this study. 

On the basis of these results, it is clear that a more inert filter material, Mitex or Fluoropore, should be used. As will be discussed below, the collection efficiency of the Fluoropore filters is better than that of the Mitex filters, and for this reason it was finally decided to use Fluoropore filters for the combined sampling and analytical procedure. 

The collection efficiency of the Mitex and Fluoropore filters was tested by generating and collecting mixed aerosols containing MMA, DMA and p-APA under controlled conditions and analyzing the resulting filter extracts by the developed analytical technique. 

Table VII. Effect of temperature (50°C) and humidity (95% BH) on particulate organoarsenicals collected on Fluoropore filters...

Table IX. Precision of combined sampling and analytical method using Fluoropore filters loaded in the aerosol generation/sampling system (N = 7)...

Soot from an 02-propane flame was produced in a 5 cm diameter 1-meter flow tube, with a total flow rate (N2 carrier gas) of 3.5 liter min. 1 0.2 pm pore size Fluoropore filters (Millipore Corp.) were used for mass evaluation. 

When examining dirty garments, a number of Deldrin units may be required to cover the entire surface as a result of the fluoropore filter... 

Briefly, the analysis comprises dissolution of the coal liquid in DMF/ xylene (2 1) and filtration through a Fluoropore filter. The... 

Analytical GPC. Size measurements were made on an analytical GPC system using %-in. o.d. /x-Styragel columns (Waters Associates) with 1 ft 104 A porosity, 2 ft 500 A porosity, and 1 ft 100 A porosity. The samples were run as 0.1% tetrahydrofuran solutions prefiltered through a 0.5-/1 Fluoropore filter (Millipore Corporation) with THF at 2 mL/min as the mobile phase. 

Briefly, the analysis comprises dissolution of the coal liquid in DMF/ xylene (2 1) and filtration through a 0.2-fim Fluoropore filter. The filtrate is analyzed for metals (Fe, Ti, Al, Ca, Mg, Na, and Si) by atomic absorption spectroscopy (AAS) to give soluble metals. The filter cake is... 

Sierra Radial Slit Jet Millipore Fluoropore filters 10.2... 

The use of piezoelectric crystals for measuring dissolved CO2 was investigated (22). Crystals were coated with didodecylamine (DDDA) or dioctadecylamine (DODA) and placed in a chamber separated from the sample solution by a Teflon membrane, a Polyvinyl chloride membrane, or a Fluoropore filter with polyethylene web backing. The DDDA was 33 times more sensitive to H2O vapor than to CO2. The membranes were not sufficient for a selective measurement of CO2, and a differential mode of measurement was used to circumvent H2O vapor interference. 

All samples were filtered through 0.5y m Fluoropore filters before being introduced into the viscometer. 

Figure 4. Chromatograms obtained for sample A in THF after filtration through a 1.0 pm fluoropore filter.

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