Teflon® bags

Gases from the furnace, metal tap, slag tap, and feed system are combined and fed to a sis-ceU pulse baghouse containing 864 high temperature Teflon bags. The dust from the electric furnace system is fed continuously back to the reverberatory furnace in a close screw conveyor. 

The facility, methods of procedure, and materials employed in this study have been discussed in detail elsewhere O9O 9 and are only briefly described here. The outdoor reaction chamber employed in this study consists of a 309000-liter FEP-type Teflon bag of triangular cross section held semi-rigidly by a framework of steel pipes. The chamber houses a set of multiple-reflection optics (capable of pathlengths in excess of 1 km) which is interfaced to a Midac interferometer and associated data system. 

Reactions that simnlate tropospheric conditions have been carried ont in Teflon bags with volumes of ca. 6 m htted with sampling ports for introduction of reactants and snbstrates, and removal of samples for analysis. Substrates can be added in the gas phase or as aerosols that form a surface him. The primary reactants are the hydroxyl and nitrate radicals, and ozone. These mnst be prepared before use by reactions (a) to (c). 

The Netherlands Organization of Applied Scientific Research (TNO) carried out a comparative study with Teflon-FEP-bags. Ratios between the dynamic and static method ranged from 0.7 to 1.1 after a storage time of 24 hours (7). These Teflon-bags can be used several times. Normally the sample size is 50 to 100 litres but for ambient air samples of 1600 litres are sometimes necessary. 

During some of the weeks, in Hoogvliet air samples were collected in order to make a direct comparison between immission concentration and experienced annoyance. The sampling was done by the Division for Nutrition and Food Research TNO Zeist. The samples were collected by a mobile unit of this institute during the same hour in which the panels made their measurements. Fourty teflon bags of 40 liters each were filled at three locations in such a way that all bags contained equal amounts from all three... 

Photolytic. A -nitrosodimethylamine absorbs UV at 228 nm. An enhanced oxidation process equipped with UV lamps (195 to 240 nm), mineralized >99.9 % of Amitrosodimethylamine in water to concentrations <0.25 pg/L (Smith, 1992). A Teflon bag containing air and A-nitrosodimethylamine was subjected to sunlight on two different days. On a cloudy day, half of the A-nitrosodimethylamine was photolyzed in 60 min. On a sunny day, half of the A-nitrosodimethylamine was photolyzed in 30 min. Photolysis products include nitric oxide, carbon monoxide, formaldehyde, and an unidentified compound (Hanst et al, 1977). 

Third type of culture is stroma-non contact . In this system primitive progenitor cells are sustained when cells are co-cultured with irradiated allogeneic stroma but separated from it by the 0,4 micron membrane in transwell inserts (Costar, Cambridge, MA). These cultures are maintained by daily supplementation of stromal feeder conditioned media (Roller et al. 1998, Verfaillie, 2001) successfiilly expanded umbilical cord blood cells in a novel automated perfusion culture system. Development these approaches followed in the studies of investigators who incorporated the stromal components into the expansion culture. Recently published trials by McNiece et al. 2000 are more encouraging where cells were expanded in static culture for 10 days in Teflon bags (American Fluoroseal, USA). 

In static method a known amount of contaminant is introduced into a fixed volume of air in devices such as teflon bags, gas sampling bulbs and gas cylinders, etc. Dynamic methods involve continuous introduction of contaminant (at a controlled rate) into a stream of air. Static methods are generally much simpler to construct and use, however, these suffer from a number of problems. Dynamic methods, while more elaborate and relatively more expensive, offer greater flexibility in concentration range, sample volume and are also less affected by adsorption losses. 

Table 3 - Measurements of CH4 and CO2 in a teflon bag enclosure air above a Trinervitermes species nest... 

Table 4 - Concentrations of Methane and Carbon Dioxide in a Teflon bag enclosure air sample of an Amitermes unidentatus in ppmv.

Samples of the exit gas were withdrawn through 3.2-mm quartz tubing at about 0.8 cm /sec. The gas passed through a condenser, a water trap, a tube containing Drierite, and a vacuum pump and was collected in a Teflon bag for analysis. CO and CO2 were determined by non-dispersive infrared, O2 by paramagnetic analysis, NO, by chemiluminescence, and hydrocarbons by flame ionization. N2 and H2O were calculated from stoichiometry. 

Generating Aerosols by Dark Phase Ozone Reaction. Reactants, various hydrocarbons and O3, were brought together in low ppm or tenths of a ppm concentration in 150-liter Teflon bags. The organic reactants used were a-pinene, cyclohexene, 1,5-hexadiene, cyclohexane, and 2-hexene. In all but one series of experiments, relative humidity was virtually zero (dew point <—48°C). In experiments using cyclohexene and O3, the water vapor pressure was varied relative humidities of -. 0%, — 50%, and 95-100% were used at 21°C. a-Pinene and other hydrocarbons alone in clean air in Teflon bags do not deteriorate detectably in 24 hours ozone deteriorates less than 5% in 18 hours. 

Hydrogen peroxide concentrations in FEP Teflon bags were determined by the titanium IV-8-quinolinol and the catalyzed 1% potassium iodide colorimetric method (10). 

Pressure The chamber is designed to investigate boundary layer processes and will flierefore operate at ambient atmospheric pressure. That the chamber does not require pressurisation allows the use of a flexible FEP Teflon bag. Teflon film is gas permeable, but with advantages that generally compensate for die drawbacks. It is broadly transparent to radiation at boundary layer wavelengths with well characterised transmission characteristics (Cocker et al., 2001). In addition, despite documented wall losses and re-emission of reactive... 

Chambers were also used in the research on heterogeneous reactions of isoprene and of other atmospheric trace compounds. As already discussed, Czoschke et al. (2003) studied the formation of SOA from products of isoprene oxidation in 500 dm Teflon-bag chambers at UNC. FoUcers et al. (2003a,b,c) studied the partitioning and influence of dicarboxylic acids on aerosol formation in Aerosol Chamber in Julich. Shantz et al. (2003) investigated the growth of aqueous organic particles and cloud condensation nuclei in the CALSPAN chamber, linuma et al. (2004 paper submitted to this book) studied the reaction of a-pinene with ozone on acidic particles in the Leipzig tent-chamber (9 m ). 

The EUPHORE chambers in Valencia, Spain, are described in detail elsewhere (Becker, 1996). Briefly, there are two chambers, each consisting of a half-spherical Teflon bag with a volume of about 204 m (see Figure 1). The chambers are protected against atmospheric influences by two half spherically shaped protective housings. The inlet and... 

Food and plant CRMs H B C N Na Cl K S Seal in Teflon bag [N/MT] Irradiate in thermal neutron fadlity, 24-h coimt times while irradiated [PGAA] [N/MT-PGAA] Anderson (2000)... 

In hydrophobic teflon bags, the test compound and blood monocytes isolated from pooled buffycoats at a density of 2 x 10 -cells/mL McCoy s medium supplemented with 20% fetal calf serum are cultured for 2 days. The monocytes are washed with... 

When pyrolysis temperatures are reached, the six-port Valeo valve is switched and the 34-port Valeo valve automatically takes 15 samples of the gas stream for later analysis in the Hewlett-Packard 5834a Gas Chromatograph (HPGC). Unsampled gas is collected in a Teflon bag for later analysis. 

When used in the integral mode, total gas production by species is measured using teflon bags to collect all the reactor effluent. The dependence of total gas production on gas-phase residence time in the gas-phase zone of the reactor is determined using the combined data of many experiments. This data can be used to infer rates of gas production within the gas-phase reactor. Kinetic models of gaseous species formation can be obtained through a study of the effects of both temperature and residence time on species production. 

Laboratory kinetic studies of gas-phase elementary reactions of importance to tropospheric chemistry were initiated as part of the LACTOZ programme at the Swiss Federal Institute of Environmental Science and Technology (EAWAG) in October 1989. Two types of experiments have been carried out (i) studies of the kinetics of competitive OH radical reactions with VOC in an atmospheric flow reactor and (ii) detailed end-product analyses of the OH radical initiated photooxidations of VOCs carried out in a static Teflon bag reactor. 

In the second series of experiments, the products from the photo-oxidation of diethyl ether, carried out in a Teflon bag reactor at ppm and ppb levels, have been determined by withdrawing vapour samples and monitoring by gas chromatography, HPLC and by chemiluminescence analysis. The major reaction products which have been measured are ethyl formate, ethyl acetate, acetaldehyde, formaldehyde, PAN, methyl nitrate and ethyl nitrate. The products observed arise from the decomposition reactions of the 1-ethoxyethoxy radical and from its reaction with oxygen. The data enable the establishment of a quantitative mechanism for the photo-oxidative reaction. In addition the rate of conversion of NO to NO2, determined by chemiluminescence analysis, shows that for each molecule of ether reacted only one molecule of NO is converted to NO2. In further end-product analyses experiments, the OH radical initiated photo-oxidation of n-hexane or the photolyses of 2- or 3-hexyl nitrites were studied to examine the... 

The experiments were carried out in 200 dm Teflon bag reactors at room temperature (297 3 K) and at atmospheric pressure (725 5 Torr). The decay of the VOC concentration and build up of the product concentrations were monitored during the course of the experiment. The concentration of VOC was measured by GC-FID. The formation of organic nitrates and carbonyls were measured by GC with sample preconcentration using adsorption tubes filled with Tenax TA. Detection was performed with FID and BCD coupled in series. The carbonyl... 

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