Hydrophobic vent

Of course, the opposite phenomenon occurs with hydrophilic liquid filters where air bubbles are present in the liquid process stream it is called "air-binding". Often a hydrophobic vent-filter will be used in conjunction with the main hydrophilic membrane filter to allow escape of accumulated air without permitting liquid leakage. 

In order to provide controlled and sensorless sample positioning and immobilization of the sample into the PCR chambers, valves and hydrophobic vents were used. In addition, by using microfabricated heaters and... 

Other applications of filters include sterilization of venting or displacement air in tissue and microbiological culture (carbon filters and hydrophobic membrane filters) decontamination of air in mechanical ventilators (glass fibre filters) treatment of exhausted air ftom microbiological safety cabinets (HEPA filters) and the clarification and sterilization of medical gases (glass wool depth filters and hydrophobic membrane filters). 

Pipework systems, valves and vent filters should be properly designed to facilitate cleaning and sterilization. The use of clean in place and sterilize in place systems should be encouraged. Valves on fermentation vessels should be completely steam sterilizable. Air vent filters should be hydrophobic and validated for their scheduled lifespan. 

The inside surface should be 316L electro-polished (Ra < 0.8 p) the tank must be totally drainable. Storage tanks must be equipped with a spray ball on the circulation return line to sanitize all internal parts of the tank and to assure that the tank interior surfaces above the water level are continuously flushed. Tanks must be equipped with a vent hlter (0.2 pm hydrophobic) installed in such a way as to prevent condensate from being trapped. The technical services manager and QA manager must approve the model. 

Water storage tank vent filters must be equipped with a sterilizing air filter in order to prevent the air, which displaces water drawn from the tank, from microbiologically contaminating the water. The filter must be hydrophobic in order to prevent condensation from blinding the filter and preventing air entry or escape from the tank. It also must have a mean porosity of less than 1 pm. 

Figure 2. Radioactivity chromatogram of sulfur compounds derivatized with monobromobimane. The reversed-phase HPLC separation is based on the hydrophobic properties of the bimane-sulfur adducts but peak area is based on "S-radioactivity of the compounds. At time 0 sulfite and thiosulfate impurities are present before addition of the hepatopancrease tissue homogenate. This was a 60 min experiment to determine the sulfide detoxifying functions of the hepatopancrease of the hydrothermal vent crab Bythograea thermydron. During this time the proportion of radioactivity in sulfide rapidly decreases and thiosulfate and sulfate accumulate as end products. Two intermediates, pi and p2 accumulate then decrease during the experiment. The two intermediates are believed to be polysulfides based on similar elution times of polysulfide standards. (Figure is the unpublished chromatograms from the data in Vetter et al. (24)-) continued on next page.

A micromixer in which the fluid can be stirred by periodically pumping through the side channels is shown in Figure 3.45 [481]. The periodic perturbation applied via the side channel allows liquids A and B to be mixed. Other mixers based on oscillating pressure-pumped flow have also been reported [482,483]. Two droplets (600 pL) were merged and mixed by a push-pull (shuttling) method in a PDMS device consisting of a hydrophobic microcapillary vent (HMCV) [364]. 

Hosokawa, K., Fujii, T., Endo, I., Hydrophobic microcapillary vent for pneumatic manipulation of liquid in aTAS. Micro Total Analysis Systems 98, Proceedings pTAS 98 Workshop, Banff, Canada, 13-16 Oct. 1998, 307-310. 

In both reversed-phase and hydrophobic interaction HPLC, the change in free energy, the equilibrium association constant Kassoc, and the retention behavior (expressed as the logarithm of the capacity factor k ) following an increase in concentration [Solvent]m or volume fraction i/fS0 vent of an organic solvent, or a decreasing concentration of a salt species [Salt]m in the mobile phase can be empirically evaluated from the following expressions ... 

PTFE membranes are highly hydrophobic and, therefore, are used as air filters. Air filters have to be highly hydrophobic to avoid water blockage due to moisture or condensate, especially after steam sterilization of these filters. Water blockage could be detrimental, if the filter is, for example, used in a tank venting application to overcome condensation vacuum of a non-vacuum resistant tank. If the filter would not allow a free flow of air into the tank, it may implode. Therefore, vent filters for this application have to be chosen and sized with care. PTFE membranes are also highly mechanical and thermal resistant, which is required, because such filters are used over several... 

In the case of air-vents, even if the filter has been sized adequately to handle the passage of air commensurate with liquid filing and withdrawal rates, the use of hydrophilic filters has caused the implosion or collapse of more than one storage tank. A hydrophobic filter passes air preferentially indeed, a water intrusion pressure is required to force water into the pores. 

WFI storage tanks are equipped with hydrophobic bacterial retentive vent filters. 

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