Extractables from filter membranes

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... 

NMR analysis, the PHA was extracted from freeze-dried cells. For this purpose, 1.0 g freeze-dried cells were stirred in 200 mL of chloroform for 24 hours at 30°C. The extract was filtered to remove cells debris, and the chloroform was concentrated to a volume of about 15 ruL using rotary evaporator. The concentrated solution was then added drop-wise to 150 luL of rapidly stirred methanol to precipitate the dissolved PHA.The precipitated PHA was then recovered by filtration using a 0.45 pm PTFE membrane and dried overnight at room temperature. The purified PHA was dissolved in deuterated chlorofonn (CDCl ) and subjected to H and NMR analyses. 

Using the optimized filtration conditions, filter a blank sample solution (sample solvent) to determine whether any materials are leached or extracted from the filter s membrane or housing. The response from the filtered sample solvent should not be greater than 1.0% of the average response for the unfiltered standard solution. In addition, for separative finish (e.g., HPLC), no peaks should coelute with the principal peak of the chromatogram. 

Air analysis for some of the individual pesticides of this class has been published by NIOSH. These pesticides include mevinphos, TEPP, ronnel, malathion, parathion, EPN, and demeton (NIOSH Methods 2503, 2504, 1450). In general, pesticides in air may be trapped over various filters, such as Chro-mosorb 102, cellulose ester, XAD-2, PTFE membrane (1 pm), or a glass fiber filter. The analyte(s) are extracted from the filter or the sorbent tube with toluene or any other suitable organic solvent. The extract is analyzed by GC (using a NPD or FPD) or by GC/MS. The column conditions and the characteristic ions for compound identifications are presented in the preceding section. Desorption efficiency of the solvent should be determined before the analysis by spiking a known amount of the analyte into the sorbent tube or filter and then measuring the spike recovery. 

Note The purpose of the in line 1-pm filter is to retain any inorganic particles removed from the swab by the organic extraction. The filter and filter holder are an integral part of a subsequent concentration/cleanup procedure for inorganic FDR as outlined in reference 220. The filter unit consists of a 13-mm-diameter Swinnex disposable filter holder containing a 13-mm-diam-eter, 1-pm pore size, fluoropore membrane filter (Millipore FALP 01300). 

The extract is filtered through a 0.45 ym silver membrane filter and collected in an evaporator tube. The sample is extracted (2 ml solvent) two additional times and these extracts are collected in the evaporator tube. The combined extracts are concentrated to 1.0 ml under a stream of clean, dry nitrogen at 40 C. An appropriate aliquot of the extract is injected for HPLC analysis. Depending on the properties of the sample (e.g., analyte concentration), injection volumes may range from 1-50 yl. In our laboratory, samples are chromatographed utilizing the following conditions and parameters ... 

Improvement of membrane separation technology has resulted in the isolation of MFGM-enriched material from commercially available products. A phospholipid-rich fraction can be extracted from whey (Boyd et al., 1999) and buttermilk (Sachedva and Buchheim, 1997) with a reported yield of 0.25 g of phospholipids/g of protein in buttermilk (Sachdeva and Buchheim, 1997). Microfiltration of whey derived from the Cheddar cheese process, using 0.2 pm ceramic filters results in a fraction containing two major phospholipids, phosphatidylcholine and phosphatidylethanolamine, and lesser amounts of phosphatidylinositol, phosphatidylserine, sphingomyelin and cerebrosides (Boyd et al., 1999). The phospholipid fraction separated from the total lipids contains a larger proportion of mono- and polyunsaturated fatty acids (mainly oleic, Cig i and linoleic, C ) compared to the total lipid and the neutral lipid fraction (Boyd et al., 1999). 

Other potential contaminants are, however, less obvious and these include lubricants (e.g., silicone grease), plasticizers (e.g., phthalates, phenyl phosphates, sebacates, and bisphenol A), slip agents (e.g., oleamide, erucamide, and stearamide), biocides (e.g., quarternary ammonium compounds) and polymers extracted from laboratory consumables (e.g., silicones from laboratory tubing) and membrane filters (e.g., cyclic oligomers and Nylon 66).168 169... 

Membrane-filter immobilized-permeability-botanical The assessment of transport properties of 23 drugs and natural product molecules was made by using the in vitro model based on filter-IAM, assembled from phosphatidylcholine in dodecane, in buffer solutions at pH 7.4. Five of the compounds were lactones extracted from the roots of the kava-kava plant. Experiments were designed to test the effects of stirring (0-600 rpm) during assays and the effects of varying the assay times (2-15 hr). 

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. 

---