Filter membranes extractables

The principle of a three-phase membrane extraction is illustrated in Figure 1.28. An organic solvent is immobilized in the pores of a porous polymeric support consisting of a flat filter disc or a hollow fiber-shaped material. This supported liquid membrane (SLM) is formed by treating the support material with an organic solvent that diffuses into its pores. The SLM separates an aqueous... 

The principle behind the test method(s) is that antibodies are made of proteins that recognize and bind with foreign substances (antigens) that invade host animals. Synthetic antibodies have been developed to complex with petroleum constituents. The antibodies are immobilized on the walls of a special ceU or filter membrane. Water samples are added directly to the cell, while soils must be extracted before analysis. A known amount of labeled analyte (typically, an enzyme with an affinity for the antibody) is added after the sample. The sample analytes compete with the enzyme-labeled analytes for sites on the antibodies. After equilibrium is established, the cell is washed to remove any um-eacted sample or labeled enzyme. Color development reagents that react with the labeled enzyme are added. A solution that stops color development is added at a specified time, and the optical density (color intensity) is measured. Because the coloring agent reacts with the labeled enzyme, samples with high optical density contain low concentrations of analytes. Concentration is inversely proportional to optical density. 

Filter the extract while it is still warm, through a 0.45- J,m NYL membrane filter into amber vials. Analyze it immediately by injecting 10 jL of the sample solution into the HPLC. 

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 ... 

Air drawn through 5- xm PVC membrane filter analyte extracted with a mixture of 0.005 M Nap IP()4 in 5% methanol (95% water) at pH 7 in ultrasonic bath for 10 min analyte detected by HPLC using an UV detector (at 225 nm) (NIOSH Method 5030, 1989). 

Extractables from filter membranes can be classified into two groups, inorganic ions and organic molecules. The organic components are residual components from either the polymerization process or a chemical modification step. Filters are deliberately washed to remove these components, and the extent to which they remain in the membranes is... 

Membrane LLE (MLLE) or sorptive membrane extraction (SME) is an alternative to LLE, and is an extension of the LLE principles. A membrane is used as a selective filter of the analytes, limiting diffusion between two solutions or as an active membrane in which its chemical... 

Apparatus end-over-end shaker, centrifuge, 0.45 pm membrane filter, polyethylene extraction bottles (200 mL), polyethylene bottles (50 mL)... 

Extract 20 mL of coffee with 20 mL of chloroform (note 1). Separate and centrifuge the organic layer for 10 min at 8000g. Filter the extract through 0.22 pm teflon membranes. 

Several processes are based on blends of UHMWPE and oil (22) where the oil acts as a diluent rather than a solvent. The UHMWPE particles imbibe the oil, swell and form gels. Unlike UHMWPE alone, the resulting gel can then be extruded on modified plastic screw extruders and fiber lines. Subsequent extraction of the oil from the formed sheets results in a porous material suitable for battery electrode plate separators or filter membranes. The majority of automotive lead acid batteries manu ctured today contain UHMWPE electrode plate separators produced in this manner. 

The exhaust air from a radio-chemical laboratory should be filtered to extract dust. In general, however, no additional exhaust air treatment is necessary in a water laboratory measuring radioactivity in water samples. The exhaust air is monitored for radio-active aerosols by filtration of a specific quantity of air via membrane filters, and by measuring the deposit on the membrane filter. 

Four types of analyses can be performed in metal determinations, dissolved, suspended, total, and acid extractable metals, based on different sample pretreatment steps. The term total metals includes all inorganically and organically bound metals and requires a vigorous digestion step of the unfiltered sample before analysis. Dissolved metals determination requires filtration of unacidified sample that passes through a 0.45 pm membrane filter. Suspended metals refer to the metals that are retained by a 0.45 pm filter. Acid-extractable metals are determined after the unfiltered sample is treated with hot dilute mineral acid before analysis. 

Flow-cell for optosensing detection Incorporating filtering membranes for extraction purposes. (For color version of this figure, the reader is referred to the online version of this book.)... 

Concentration polarization is an another key parameter of polysaccharide filtration. When the MWCO of the membrane is adapted to the composition of the extract, hollow fibers seem to be more efficient than flat sheet membranes. Flat sheet membranes with turbulence promoters in the feed channel are used with low tangential velocity because turbulences are created by the screen. When filtering polysaccharides extracts, the viscosity of the solution is high, particularly in concentration mode, and the efficiency of the turbulence promoters is too low to avoid the creation of a gel layer. Hollow fibre membranes, which are used with high tangential velocity, thus give the higher permeate fluxes. 

---