Disposable Membrane Filters

An even jarger cellulose acetate disposable filter of 30 mm diameter was used for the preconcentration of cbppeffiy precipitation of the hydroxide [20]. The large dead volume of the filter seems to have a stronj ihfluence on the perfoimanceTsince CE was estimated to be about 0.7 min (12-fold enrichment in about 3.5 min), with a consumptive index of about 1 ml. Precision data on the method was not available. 

The Author s own experience of using a 25 mm membrane filter for on-line coprecipitation was discouraging, the sensitivity in the determination of lead being only about 20% of that obtained using a knotted reactor (cf. Sec. 7.2.5). 

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Army. 1987c. Losses of explosives residues on disposable membrane filters. Aberdeen Proving Ground, MD U.S. Army Toxic and Hazardous Materials Agency. Document no. AD A180889. 

The sample solutions injected into an ion chromatographic system must be free of particulate matter to avoid plugging of the capillary connecting tubing and the frits at the head of the analytical column. Even samples that appear to be clear may contain unsuspected fine particles. It is more or less standard procedure to filter sample solutions prior to their injection. Disposable membrane filters with a pore diameter of... 

Decant the supernatant liquid and filter through a disposable membrane filter (0.45 pm, nylon 66) attached to a syringe. Collect each in a 100 mL volumetric flask and dilute to volume with 20 mM H2SO4. 

When Bayer started the planning phase for its new membrane cell chlorine plant the company also evaluated new filtration technologies to eliminate costs for the use and disposal of filter aid and to reduce the cost of filter operation significantly. 

Materials. Gelman 37 mm, type A/E glass fiber, GN-4 0.8 metricel, and DM-800 0.8 membrane filters were used in this study. Spectral quality, pyrolytic coated, graphite furnaces and rods were used in the study. The furnace capacity was 5 yL of solution. Manual sample injections were made with a 5 yL Eppen-dorf pipet 4700 using disposable tips. 

SPE disc technology through rigid disc and membrane disc formats provides a way around the above-listed limitations of packed-bed SPE columns. SPE discs closely resemble membrane filters they are flat, usually 1 mm or less in thickness, with diameters varying in size. Some disks are sold loose, and users must install them in a filter holder. Others are sold preloaded in disposable holders with Luer fittings (82). 

Amounts of consumables (resins, membranes, filters, disposable bags, and tubings/connectors) that end up as solid wastes could be large. 

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). 

Cell harvesters were developed to capture multiple samples of cells on membrane filters, wash away unincorporated isotopes, and prepare samples for liquid scintillation counting on special equipment developed to process and count multiple samples. Despite miniaturization and improvements in efficiency of this technique, the disadvantages of multiple liquid handling steps and increasing costs for disposal of radioactive waste materials severely limit its usefulness. Although specific applications require measuring DNA synthesis as a marker for cell proliferation, much better choices are available for detecting viable cell number for HTS. 

Microfilters use membranes with pores in the 0.1-1 pm range. They can filter out particles of dust, activated carbon, and ion exchange resin fines, and most microorganisms. Microfilters require low differential pressures (5-20 psi) and are available both as normal flow ( dead end ) and crossflow configurations. In pharmaceutical water purification systems, they are often used as disposable cartridge filters after activated carbon filters, softeners, and ion exchange beds. 

Membranes are available in sheet, roll, disk, capsule, cartridge, and hollow-fiber formats. For sample filtration, disk-format membranes are the most popular devices. Disks are sold in loose form or packed in disposable syringe filters or cartridges common diameters commercially available are 3, 7, 13, 25, 47, and 96 mm, or even larger. Samples are filtered by manually applying a positive pressure or in a vacuum manifold. 

Membrane filters are used under vacuum, with positive pressure, or with gravity. Filters have been incorporated into certain disposable tips for use with semiautomatic pipettes. These filters minimize the exchange of aerosol droplets between the tips and the pipette. This is of particular importance for DNA amplification and microbiological procedures. Other membrane filters are designed for ultrafiltration and are available with a variety of pore sizes for selective filtration. Ultrafiltration is a technique for removing dissolved particles using an extremely fine filter. It is used to concentrate macromolecules, such as proteins, because smaller dissolved molecules pass through the filter. 

A preliminary economic analysis of the cell separation step indicates that membranes are two-fold more cost effective than centrifuges, and equivalent in cost to using a precoat vacuum filter for this application. Use of a precoat vacuum filter requires disposal of filter aid. This was not considered in the economic comparison, but could represent a significant incremental cost for preooat systems. 

If the side-chain liquid crystalline cyclic siloxane tetramer is pure and free of starting monomer, redissolve the tetramer in the minimum amount of dry dichloromethane and filter using a disposable syringe filter (PTFE membrane 0.45 (Jim) to remove any small particulates. The solvent can then be carefully removed by distillation under reduced pressure (rotary film evaporator) and dried in vacuo overnight. 

NEN 7341 is the test method to check the maximum dissolvable quantity of wastes. It is supposed that waste dumped in a final disposal place releases pollutants to the environment by elution. In this test, a sample of 8 g is added to distilled water of 400 ml. The pH of the solution will be kept 7 for 3 h by adding a nitric acid of 1 N (mol/1) with a pH monitoring automatic titration device. The solution is filtered by a membrane filter of which the pore size is 0.45 pm. The residue is added to distilled water of 400 ml. Subsequently, the pH of the solution will be kept 4 for 3 h by adding a nitric acid of 1 N (molA) with an automatic titration device. 

Measurement of dissolved mercury compounds requires removal of particulate materials from the sample by either filtration or centrifugation. Various types of filters can be employed 0.45 pm membrane filters (precipitation, seawater), disposable polystyrene units (Nalgene) with nitrocellulose membrane filters, and pretreated glass fiber filters. 

Fig. 30.11 A disposable ready-to-use membrane filter unit (Picture Pall). Source Recepteerkunde 2009, KNMP...

For the filtration of small volumes (up to 100 mL), generally a small disposable ready-to-use sterile membrane filter unit is used. The diameter of these filters is usually 25 mm or more. They are sterile and free of endotoxins, packed individually, have a low dead volume, and are dedicated for single-use (see Fig. 30.11). 

Table 30.4 Properties of often used disposable ready-to-use membrane filters ...

Biodegradable bags for trash disposal Membranes for soil Filtering Ultrafiltration... 

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