Membrane cellulose ester

MCEF Mixed cellulose ester membranes filter... 

Urine Extraction of sample with polydithio-carbamate resin and NaOH filtration on cellulose ester membrane neutralization with NaOH ashing dissolution and heating dilution with distilled water ICP/AES (Method P CAM 8310) 0.005 pg/mL 100 NIOSH 1984... 

The method developed for sodium fluoroacetate is based on collection of the sample with cellulose ester filters especially low in extractables (Toyo-cel cellulosic ester membrane filters from Nuclepore were used). The samples were extracted with water and analyzed by ion chromatography. Other MCE filters contained high levels of extractables Cfrom wetting agents, surfactants) that... 

Three filtering media commercially available from Millipore Corporation were evaluated for the collection of airborne particulates of the organoarsenical compounds. These were (l) cellulose ester membranes (2) Fluoropore and (3) Mitex. The cellulose ester membrane filters (0.8 ym pore size) are the standard Millipore filters used for aerosol sampling and consist of a mixture of cellulose nitrate and cellulose acetate. The Fluoropore filters are made of Teflon (PTFE) and are bonded to a polyethylene net. Fluoropore filters with a pore size of 1.0 ym were selected for this study. 

Between 10 and 180 L of air at a flow rate of 0.5 to 1 L/min is passed through a filter-bubbler assembly of a 0.8-pm cellulose ester membrane and 10 mL of 0.1 N KOH solution. While cyanide particulates retain over the filter membrane, HCN is trapped over the KOH solution in the bubbler. The membrane filter is then placed in 25 mL of 0.1 A KOH solution for 30 min to extract the cyanide particulates deposited on it. The KOH extract and the bubbler KOH solution are analyzed for cyanide by selective-ion electrode technique (see Chapter 1.9 for a detailed analytical procedure) using KCN standards. Calculate the concentration of particulate CN- in the air sampled as follows ... 

Analysis of phthalates in air may be performed by sampling 1 to 200 L air and collecting the esters over a 0.8 pm cellulose ester membrane. The phthalates are desorbed with carbon disulfide and the eluant is injected into a GC equipped with an FID. A stainless steel column 2 m x 3 mm OD, containing 5% OV-101 on 100/120 Chromosorb W-HP was originally used in the development of this method (NIOSH Method 5020) for dibutyl phthalate and bz,v(2-cthylhexyl)phtha-late. Any other equivalent GC column listed above may also be used. 

Air NIOSH Method 5020a Collected over cellulose ester membrane and desorped into CS2 GC-FID... 

Air drawn through a cellulose ester membrane (to remove any arsenic particulate) in front of a charcoal tube (100 mg/50 mg) arsine desorbed into 1 mL 0.01 M HN03 (in an ultrasonic bath for more than 30 min contact time) arsenic analyzed by graphite furnace-atomic absorption spectrophotometer at the wavelength 193.7 nm (NIOSH Method 6001, 1985) recommended air flow rate 0.1 L/min sample volume 5 L. 

Air drawn through a 0.8 to 1.2 mm cellulose ester membrane filter, asbestos fibers counted by positive phase contrast microscopy technique sample prepared by acetone/triacetin method (NIOSH Method 7400, 1985). 

Air drawn through a 0.8-mm cellulose ester membrane (to separate cyanogen from particulate cyanide) followed by 0.1 N KOI I bubbler soln. cyanide ion analyzed by cyanide ion-selective electrode recommended flow rate 200 mL/min sample volume 10 L. 

PTFE filter is used to remove boron-containing particulates. Use of mixed cellulose ester membrane prefilters is not recommended. 

Use a cellulose ester membrane if particulate antimony compounds are suspected to be present in the air. 

In developing a method that requires filtration, adsorption of the analyte onto the filter must be taken into account. For dilute solutions of adriamycin, >95% is adsorbed to cellulose ester membranes and about 40% to polytetrafluoroethylene membranes [19]. For more concentrated solutions, as would be encountered in bulk formulation testing, filter ad-... 

Digitoxin potentially adsorbs onto glass, plastic, and inline intravenous filters containing cellulose ester membranes, some aqueous solutions such as 5% glucose, or 0.9% sodium chloride. The loss in potency may be minimized by pretreatment of the filter with a polymer coating. Such losses in potency were not found with 30% alcohol solutions.103104... 

Air (total chromium) Sample collected on cellulose ester membrane filter dissolved in acid mixtures ICP-AES 1 pg/sample 98% at 2.5 pg/filter NIOSH 1994d (Method 7300)... 

An employee s exposure to asbestos is evaluated by collection of asbestos fibers on a cellulose ester membrane filter. A Gel-lman G N-4 ( J, millipore AA (7J or other cellulose ester membrane which clarifies well in the mounting medium is commonly used. 

Ashing a cellulose ester membrane in a muffle furnace is difficult due to the tendency of the membrane to flash when it is heated. Low temperature ashing is a solution to this problem, expecially if operated at a slow rate, but low temperature ashing equipment will not be available in every laboratory. A cellulose ester membrane can be ashed by folding the membrane, sample side in, moistening with alcohol, then igniting the alcohol with a small flame. 

Mulder MHV, Kruitz F, and Smolders CA. Separation of isomeric xylenes by pervaporation through cellulose ester membranes. J Membr Sci 1982 11 349-360. 

Physical effects caused by polyethylene glycol bases include softening and liquefaction in mixtures with phenol, tannic acid, and salicylic acid. Discoloration of sulfonamides and dithranol can also occur and sorbitol may be precipitated from mixtures. Plastics, such as polyethylene, phenolformaldehyde, polyvinyl chloride, and cellulose-ester membranes (in filters) may be softened or dissolved by polyethylene glycols. Migration of polyethylene glycol can occur from tablet film coatings, leading to interaction with core components. 

Cellulose ester membranes (e.g., cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose cyanoethal-ate, cellulose methacrylate, and mixtures of these) can be employed for the acid components of a natural gas stream. The membranes can be either flat films or hollow fibers. 

Figure 37-8 shows a Fiberglas sheet (2600x). Notice the irregular pore size. Figure 37-9 is a mixed cellulose ester membrane (lOOOx) with 0.45 pm pore size showing bacteria trapped on the surface. This is a popular size for filtering HPLC solutions. 

Phase-Inversion Process. Most tortuous-pore membranes are made by a casting process known as "phase inversion." Figure 2.2 is a simplified schematic of a casting machine which makes cellulose ester membranes. Typically, a casting solution made up of the polymer and a multicomponent solvent system is metered onto a stainless steel belt or web. The belt passes through a series of environmental chambers usually containing water vapor at elevated temperatures. The more volatile solvents evaporate and the water vapor precipitates the polymer around the less volatile solvent which becomes the "pore-former." Subsequently, (not shown in Figure 2.2), after the membrane is formed, the residual solvents are washed out of the pores, surfactants are added, and the membrane is dried. 

To monitorize the exposure of workers OSHA and NIOSH have developed some analytical procedures for the determination of phthalate esters in workers environment. In NIOSH method 5020.2, DBP and DEHP are sampled from air with a 0.8-/rm cellulose ester membrane and... 

Islet isolation methods that yield islets free of contaminating fibroblasts now have been developed. Successful prevention of the growth of dense fibrous tissue on extravascular chambers containing these purified islets would raise new possibilities in the design of islet-transplantation chambers. This chapter contains the initial results of binding enzymes to Millipore AA cellulose ester membranes for application in such chambers. The enzyme chosen for study was collagenase from Clostridium histolyticum (Worthington Biochemicals, Inc.). 

To provide a test of the effect of spacer length on enzyme activity, a third membrane-enzyme system was formed by reacting the product of the reaction between ethylenediamine and the cellulose ester membrane with suc-cinyl anhydride, then coupling this product to an amine on the enzyme using the carbodiimide route. The product may be represented as ... 

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