Gelman filter

The chlorpyrifos reference standard was used in conjunction with the analysis of coverall dosimeter sections (arms, legs, torso), air tubes, Gelman filters, head patches, and handwashes, while the 3,5,6-TCP was used as the reference standard during urine analysis. 

Determine total chlorpyrifos (mg) on the air tube and Gelman filter. 

Determine the volume of air passing through the air pumps during the test period. Divide the total pg chlorpyrifos on the air tube and Gelman filter by the total volume of air passing through the pumps. Correct for the active ventilation rate of 1.5 m3/hr. 

Respiratory Chromosorb air tubes and Gelman filters, air pump... 

Table 4 presents the amounts of chlorpyrifos used to fortify the various substrates in this study. Chlorpyrifos "low" spike levels for coverall sections (arms, legs, and torso) as well as t-shirts and briefs, handwashes, and head patches ranged from 5.1 pg to 1198 pg. "High" spike levels of these substrates ranged form 1456 pg to 191,720 pg. Air tubes and Gelman filters were fortified with only "low" amounts of chlorpyrifos which ranged from 0.1 pg to 36 pg. 

The filters used to determine inhalation exposure could not be desorbed with acetone because the Gelman filters used in the cassette to determine inhalation exposure would not dissolve, so they were treated with methanol as above. One ml of this solution was concentrated to dryness and the residue was dissolved in I ml acetone. 

Freeing a solution from extremely small particles [e.g. for optical rotatory dispersion (ORD) or circular dichroism (CD) measurements] requires filters with very small pore size. Commercially available (Millipore, Gelman, Nucleopore) filters other than cellulose or glass include nylon, Teflon, and polyvinyl chloride, and the pore diameter may be as small as 0.01 micron (see Table 6). Special containers are used to hold the filters, through which the solution is pressed by applying pressure, e.g. from a syringe. Some of these filters can be used to clear strong sulfuric acid solutions. 

Figure 4-72. Ctirtridge-type filter-pleated membrane. Courtesy of Gelman Instrument Co.

Filter cartridges, Acrodisc nylon, 25-mm (Gelman Sciences, Ann Arbor, MI, USA) or equivalent Filter paper, GF/A, 9-cm... 

Round, flint glass with polymer-lined lids, 120-mL Square, flint glass with polymer-lined lids, 0.5-oz Filter cartridges, Acrodisc nylon, 25-mm (Gelman Sciences, Ann Arbor, MI, USA) or equivalent Filter, GF/A, 9-cm Florisil, 2.5% deactivated Glass wool... 

The analytical sensitivity is limited by uncertainties in the response to blank filters. For glass fiber filters (Gelman A/E) the blank values are 2.811.4 pgC/cm for organic carbon and 0.2 pgC/cm for elemental carbon. For Pallflex QAST the respective values are 1.010.5 and 0.310.2 pgC/cm. ... 

Use a solvent resistant filter disc made from such materials as Millipore LSWP 04700, (Mitex-Teflon), Millipore URWP 04700, (Solvinert), or Gelman VF-6, (Fluoride-Metricel), plain, white, 1 Ot3 microns, 47mm diameter instead of the filter specified in Method 2276-65T... 

Materials. Gelman 37 mm, type A/E glass fiber, GN-4 0.8 metricel, and DM-800 0.8 membrane filters were used in this study. Spectral quality, pyrolytic coated, graphite furnaces and rods were used in the study. The furnace capacity was 5 yL of solution. Manual sample injections were made with a 5 yL Eppen-dorf pipet 4700 using disposable tips. 

Sampling. Samples of PAH were collected from an aluminum plant. Particulate matter was collected on a Gelman glass fiber filter. Vapors were collected in two impingers filled with ethanol and cooled with dry ice. The sampling device is reported elsewhere... 

Collection. Formic acid in diluted (1 10) diesel exhaust or mine air was collected by drawing the sample atmosphere through two fritted bubblers (10) in series, each containing 15 mL of 10 3 M Na2C03. A flow rate of 1.0 liter per minute and collection time of 60 minutes for diluted diesel exhaust or 240 minutes for mine air was used. A 37 mm glass fiber filter (Gelman Type A/E) was placed before the bubblers to remove particulates. 

The nylon filter currently sold as l- xm pore size Nylasorb (Gelman Sciences), probably the most widely used filter for HN03 sampling in the United States, was initially marketed by Ghia Corporation. Until 1985, these filters were fabricated from nylon 6, a polyamide formed from the homopolymerization of e-caprolactam. More recently, Gelman, Sartorius, and other vendors have supplied filters fabricated from nylon 6,6, made by polymerization of adipic acid and hexamethylenediamine. 

The retention of N02 on nylon 6 Nylasorb filters (Gelman Sciences), nylon 6 filters from Sartorius Filters, Inc., and nylon 6,6 filters from Schleicher Schuell (S S) was assessed 0.5 ppm NO was sampled at 75-80% RH and 21 °C for 6 h at 20 L/min with 47-mm filters. The results showed no more than 0.1% retention (19). Similarly, Perrino et al. observed with 47-mm Gelman Nylasorb filters (nylon type unstated) 0.4% retention, sampling 0.6 ppm NO for 15 h at 1.5 L/min and 60-80% RH (20). 

The degree of retention of SO on these nylon filters was also assessed 0.14 ppm S02 was sampled at 20 °C, 80% RH, and 20 L/min (total dosages for each filter, 2600 xg of SO (19). At saturation, the artifact SO values with the S S filter, 56 1 xg, was lower than that for the Sartorius and Gelman nylon 6 filters, which ranged from 65 to 70 xg. 

Other Interferent Studies with Nylon Filters. Retention of HONO on Gelman Nylasorb (nylon 6) filters was tested 0.3 to 1 xg/m3 HONO was sampled in air (—50% RH) at 20 L/min with 47-mm filters for 16-23 h. At saturation, the filters contained 1.8 xg/cm2 N02 this result indicates less than 50% efficiency for HONO retention (19). Sampling 440 xg/m3 HONO at 20 L/min with 47-mm Gelman Nylasorb filters (nylon type unstated), Sickles and Hodson reported about 25% retention efficiency, with a similar saturation value, and noted that such retention was reversible. Substantial oxidation of HONO to N03 on the filter surface by 03 was demonstrated in laboratory and atmospheric trials (21). Perrino et al. (20) observed with 47-mm Gelman Nylasorb (nylon type unstated) filters an efficiency for HONO that increased from about 25 to about 90% as the flow rate decreased from 12 to 2 L/min, with saturation at —50 xg/filter. Nitrite to nitrate conversion on the nylon filter surface increased from 13% at 45 ppb 03 to 93% at 200 ppb 03. 

Methodology. Teflon filters exhibit the lowest HN03 retention of those in common use (12). Fluoropore (Millipore Corporation) and Zefluor PTFE filters (Gelman Sciences) of 0.5- to 2- xm pore size, are frequently used as prefilters in the filter pack method (FPM). With 47-mm-diameter filters, flow rates with the FPM from 10 to 20 L/min are typical. The 2- xm pore size Zefluor filter exhibited 97% efficiency for 0.035- xm particles at a face velocity of 33 cm/s, with a pressure drop of 1.0 cm Hg (1.3 kPa) (33). 

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