Bar coating

This connection allows the combination of the high extraction efficiency of the stir bar (coated as a thick film of PDMS) with the high selectivity of the en-antio-MDGC-MS system [44]. 

Nonporous polyethylene or silicone materials Silicone rods or bars coated with silicone Glass fibers coated with a thin layer of various sorbent materials... 

To date, the only sorbent used reportedly for coating the stir bar is poly-dimethylsiloxane (PDMS), although the use of stir bars coated with polar sorbents is predicted for the future [141]. Using this sorbent, the primary mechanism of interaction with organic solutes is via absorption or partitioning into the PDMS coating such that the distribution constant [equation (2.37)] between PDMS and water (APDMs/w) is proposed to be proportional... 

The reaction is carried out at room temperature in a hood. A 500-mL filter flask is equipped with a stirring bar coated with Teflon, and a slow stream of... 

The reaction is carried out under an inert atmosphere, using standard techniques.5 A 125-mL flask equipped with a magnetic stirring bar coated with Teflon is charged with 50 mL of methanol and di-p-chloro-tetrakis(ethylene)-dirhodium(0)6 (1.16 g 3.6 mmole). Trimethyl phosphite (5.00 g,40 mmole)is added dropwise over a period of 5 minutes. Upon completion of the addition, stirring is continued for 30 minutes until all the starting material is in solution. 

It is worthy of note that the thickness of the H-dip-coated film is much less than the gap height. This is characteristic of the main way in which the premetered H-dipping process differs from the conventional metered doctor-blade (or wire-bar) coating (Kuo et al., 2004). In the conventional approach, the doctor-blade (or wire-bar) coating process produces a film thickness of the order of the gap size whose thickness is independent of the carrying sp>eed of the substrate. In the H-dipping method, the premetered process allows the critical control of the thickness and can produce superior quality and extremely thin films at line speeds of the order of a few meters per minute. 

A 250-mL two-necked, round-bottomed flask fitted with an argon-inlet tube and a reflux condenser with a silicone oil bubbler is charged with Mo(CO)6 (S.3 g, 0.02 mole), dithiobisfdiethylphosphine sulfide)5 (18.4 g, 0.06 mole), 70 mL of toluene (dried by distillation from P4OI0), and a magnetic stirring bar coated with Teflon. 

SBSE is a novel sample preparation method introduced by Baltussen et al. ° based on the same mechanisms as SPME. In SBSE, a magnetic stirring bar coated with PDMS is added to water samples of 10 to 200 ml to promote the transport of analytes into the coating polymer. After a predetermined extraction period, the analytes are thermally desorbed in the GC injector or solvent extracted for HPLC analysis. The main advantage of SBSE is that 25 to 100 jA PDMS polymer is used instead of 0.5 /rl as in SPME. The applications developed with SBSE have shown low detection limits (sub-ng to ng 1 levels) and good repeatability, confirming to the great potential... 

Since only PDMS coating is available as an extraction phase, SBSE has been used predominantly for low-polarity analytes, but the problems of extraction of polar compounds may be solved by in situ derivatiziation. It is clear that further developments in stir bar coatings and designs could extend the applicability of the method. The main drawback of this method is the duration of extraction, typically 30-150 min. For this reason SBSE may be impractical for routine high-throughput laboratories. 

Clifton, J.R., Beaghley, H.F. and Mathey R.G. Non-metallic coatings for concrete reinforcing bars, Coating materials. US National Bureau of Standards, Technical Note 768, August 1975. 

SBSE Adsorption of analytes from liquid samples (solutions) on a coated stir bar followed by their thermal desorption for GC analysis Glass-linked magnetic stir bar coated with a sorbent thermodesorption unit... 

A weighed quantity of polymer (1-10 g) is added to 50 ml of a methanol/water solution (80 20 v/v) in a glass bottle. A magnetic stirring bar coated with Teflon is added and the solution is stirred to extract the acrylamide monomer for at least 3 honrs, preferably overnight. 

Steel bars, coated with tantalum by the FLINAK process, have been borided under low pressure and the properties evaluated. The process (Fig. 1) is conducted by consecutive coating procedures. To define the boride processing data for the diffusion treatment of refractory metals preliminary investigations have been carried out, such i.e. 

Fig. 4 Steel bars, coated with tantalum and borided...

Mass loss tests are a common means of testing many metals in atmospheric and submerged exposure. For steel in concrete they are destructive to the concrete and difficult to perform. Laboratory specimens typically have a portion of the embedded bar coated or taped to define a specific test area. These materials are often hard to remove and could gain or lose mass. Furthermore, at the initial stages of corrosion most of the damage is in pits which have relatively low mass loss relative to that lost in the formation of the passive film [12], and thus mass loss is not necessarily a good indicator of corrosion activity. 

After an appropriate length of time, 25 cm of the methanolic extraction solution are removed and added to a bottle containing 5 g of mixed resin and a magnetic stirring bar coated with Teflon resin and stirred for 20 min. This mixed resin treatment removes interfering cationic and anionic species. However, impurities extracted from the resin do increase the polarographic residual current and, therefore, it is necessary that a blank be run using the same resin treatment time (viz about 20 min). 

Soluble LCP (sLCP) was supplied by Sumitomo Chemical Co., Ltd. (Tokyo, Japan) (Okamoto et al. 2005, 2006). The sLCP was dissolved in n-methylpyrrolidone. A LCP film was obtained from sLCP by a solvent casting method described as follows The sLCP was applied to a substrate such as copper foil by bar coating and subjected to heat treatment at 100 °C for 1 h. The sLCP film was in an amorphous (non-crystalline) state and therefore transparent. The film was heated to 300 °C for 3 h under nitrogen atmosphere, and then the liquid crystal phase in the film was reached. After that, the film turned semitransparent or opaque. 

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