Contamination Teflon

Chem. Descrip. PTFE fluoroadditive CAS 9002-84-0 EINECS/ELINCS 204-126-9 Uses Modifier for inks, coatings, lubricants, and sealants lubricant for thermoplastics, thermosets, elastomers Properties Wh. powd., odorless 1.8-4 p avg. particle size 90% > 0.3 p insol. in water sp.gr. 2.1-2.3 bulk dens. 200-425 g/L surf, area 5-10 mV g m.p. 342 C flash pt. none > 99% assay Toxicohgy OSHA PEL 15 mg/m (8 h TW/, total dust), 5 mg/m (8 h TWA, respirable dust) nonirritating to skin TSCA listed Envronmental Aquatic toxicity expected to be low Precaution Nonflamm. in air, but will bum if or en cone, exceeds 95% heating or burning may evolve fumes which cause polymer fume fever and small amts, of carbonyl fluoride and hydrogen fluoride incompat. with finely divided metal pc s. and oxidizers Storage Keep containers closed to avoid contamination Teflon MP 1200 [DuPont DuPont Canada]... 

TWA, respirable dust) nonirritating to skin TSCA listed Environmentai Aquatic toxicity expected to be low Precaution Nonflamm. in air, but will bum if oxygen cone, exceeds 95% heating or burning may evolve fumes which cause polymer fume fever and small amts, of carbonyl fluoride and hydrogen fluoride incompat. with finely divided metal powds. and oxidizers Storage Keep containers closed to avoid contamination Teflon MP 1300 [DuPont DuPont Canada]... 

Although chloroform is an analyte, it also can be interferent. Due to its volatility, chloroform present in the laboratory air may diffuse through the sample vial s Teflon septum, contaminating the samples. How can we determine whether samples have been contaminated in this manner ... 

It is often important to quantify the contamination of pore fluid in the unsaturated soil 2one, where monitoring wells are ineffective. In this region, suction cup lysimeters are useful (7). These samplers consist of a porous cup, typically ceramic, having two access tubes which are usually Teflon. One access tube provides a pressure-vacuum, the other discharges the sampled fluid to the surface. The porous cup, typically between 2 and 5 cm in diameter, is attached to a PVC sample accumulation chamber. 

Chlorosulfuric acid attacks brass, bronze, lead, and most other nonferrous metals. From a corrosion standpoint, carbon steel and cast Hon are acceptable below 35°C provided color and Hon content is not a concern. Stainless steels (300-series) and certain aluminum alloys are acceptable materials of constmction, as is HasteUoy. Glass, glass-lined steel, or Teflon-lined piping and equipment are the preferred materials at elevated temperatures and/or high velocities or where trace Hon contamination is a problem, such as in the synthetic detergent industry. 

The fluorine concentration in hydrofluorides of tantalum and niobium is an extremely important issue. Fluorine that separates into the gaseous phase interacts with the construction elements of the furnaces, leading to additional contamination of the final product by silicon, aluminum, etc. Thus, it is recommended to perform diying in crucibles made of Teflon or polypropylene with appropriate temperature limitations. Use of crucibles made of carbon-glass ensures high quality and a broad working temperature range, at least up to 300-350°C. 

The sample water container should be made of appropriate materials to avoid adsorption of the chemical of interest on the vessel surfaces. In most cases, a glass bottle may be better than a plastic bottle. The bottle is washed with an organic solvent in advance and also washed with sample water just before sampling. The bottle should be tilled to the limit with water and capped tightly with a Teflon seal to prevent contamination. The top 1-cm of water is not taken to prevent the mixing of floating materials such as oil. 

Once machined, all the copper and teflon pieces will undergo a surface cleaning procedure that will guarantee the required low level of surface radioactive contamination for those parts that directly face the detectors. 

The mercury values obtained by the Teflon-piston sampler were high at 0.21 0.2 nmol/kg due to malfunction with incomplete filling and previous contamination, as indicated by the very low salinity in this set. The values inside the bag were higher than those outside, measured about one month after intercomparison to be 0.02,0.03, and 0.04 nmol/kg. There was a subsampling problem. The first and second draw of the sampling bottle usually showed a very wide spread of values, as much as 0.07 nmol/kg, e.g., between 0.05 and... 

Close inspection of USP Apparatus 1 and 2 before use can help identify sources of error. Obviously, dimensions should be as specified. In cases of both baskets and paddles, shafts must be straight and true. The paddles are sometimes partially coated with Teflon. This coating can peel and partially shed from the paddle, causing flow disturbance of hydrodynamics within the vessel. Paddles can rust and become nicked or dented this can adversely affect dissolution hydrodynamics and be a source of contamination. Thorough cleaning of the paddles is also important, to preclude carry over of drug or medium. 

The design and construction of an electrochemical cell derives from consideration of the system being examined. Potential sources of contamination must be carefully evaluated. Cell components are typically made of inert materials such as Teflon or Kel-F. Alternatively, electrolyte contact with confining materials may be avoided altogether by letting the cell be defined by the geometry of a hanging meniscus. The latter method has been incor-... 

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