Cellulose filter membranes

Apart from not requiring filtering aids, such as a-cellulose, membrane filters are very simple to automate, since they can be immediately brought on-line after back-pulsing. Registers that are suitable for retrofitting have been developed by Permas-cand and Akzo Nobel and are employed by many other plants, such as those at Bayer Uerdingen. Their operation at these plants has been successful. 

An Intercomparison study of trace element determinations In simulated and real air particulate samples has been published by Camp, Van Lehn, Rhodes, and Pradzynskl ( ). This Involved twenty-two different laboratories reporting up to thirteen elements per sample. The simulated samples consisted of dried solution deposits of ten elements on Mllllpore cellulose membrane filters. In our data analysis a set of energy dispersive X-ray emission results restricted to eight laboratories reporting six elements (V, Cr, Mn, Fe, Zn, Cd) was... 

Bovine serum albumin (BSA), fraction V, B-lactoglobulin, gum arabic, and alginic acid, low viscosity, were purchased from Sigma Chemical Co. (St. Louis, MO). The proteins were used without further purification. Aqueous solutions of gum arabic and alginic acid were filtered successively through cellulosic membrane filters of 5.0 fan and 0.45 fan pore size to remove insoluble particulate matter. The filtrate was frozen and lyophilized prior to use. 

Molybdenum. Molybdenum can be analyzed by P CAM 173 for total Mo, by S-193 (12) for soluble Mo, or by S-376 for insoluble Mo. The standard nitric wet ashing used in P CAM 173 does not distinghish between soluble and insoluble Mo which have OSHA standards of 5 mg/cu m and 15 mg/cu m. Nitric acid digestion may not dissolve some insoluble Mo that require nitric/perchloric acid or base/nitric acid depending on the solubility properties. Soluble Mo compounds are hot water leached from the cellulose membrane filter used in all three methods. A fuel-rich air/acetylene flame used in P CAM 173 is replaced by an oxidizing nitrous oxide/acetylene flame to achieve total atomization of Mo as detected at 313.3 nm. Aluminum and traces of acid enhance the Mo flame response therefore, 400 ppm A1 is added to the final solution of both S-193 and S-376 and 0.1 N nitric acid is added to the water leach-soluble Mo final solution, S-193. 

A single method of analyzing tetryl in air was located (NIOSH 1977). The method utilized spectrophotometric analysis. Air samples were collected on a cellulose membrane filter and then extracted with N,N-diethylethanolamine. 

Ai r Collect sample on a cellulose membrane filter extract with N, Nidi ethyl ethanol ami ne Spectrophotometry 0.15 mg/nr NR NIOSH 1977 (Method S225)... 

Mobile phases containing Brij 35 (ionic strength 0.10 M) were filtered through a 0.45 ym cellulose membrane filter (Millipore). Each solute was dissolved in Brij 35 solutions before the runs 5-10 yl of the sample solution at a concentration in the range 0.001-0.003 M were injected and the elution was performed at constant flow rate (1-2 ml/min), at a fixed pH (2 or 6), at room temperature (25+ 1°C). The absorbances were monitored at 280 nm. 

We will perform the Leaf disk test, also known as leaf disk assay or leaf disk choice test, the second of two bioassays of tannins in the diet of insects in this book. In this often used bioassay, leaf sections of a standard size are treated with the compound(s) in question. Several circular leaf sections ( leaf disks ) (Ali et al. 1999, Filho and Mazzafera 2000, Shields et al. 2008, Wheeler and Isman 2000) or cellulose membrane filters (Hollister and Mullin 1999, Larocque et al. 1999) are presented to a caterpillar in a choice experiment. We measure how much chow the caterpillar has consumed and whether any feeding inhibition is concentration dependent. Regardless of what compounds are being tested, leaf disk tests serve as an important tool in bioassaying feeding inhibitors and stimulants in insects. The cited references are examples of such studies. (In the first tannic acid experiment - Chap. 18 - the tannic acid was mixed into diet in varying concentrations.)... 

Cellulose membrane filter disks have been used in the following studies... 

For the determination of dissolved metals the sample needs to be filtered through a 0.45 p cellulose membrane filter as soon after collection as possible. An initial portion of the sample is used to rinse the filter apparatus and then discarded. After the sample has been filtered the filtrate must be acidified with high quality nitric acid to a pH of <2. Normally 3 mL/liter is sufficient to preserve the integrity of the sample. The metals of interest can be determined using the appropriate and/or available instrumentation. 

For the determination of suspended metals a representative volume of unpreserved sample must be filtered through a 0.45 p cellulose membrane filter. The filter containing the insoluble material is transferred to a beaker and cautiously digested with concentrated nitric acid until complete. The solution is evaporated to near dryness and either dilute hydrochloric acid or nitric acid is added depending on the instrumental technique used and/or the metal determined. The solution should be filtered and diluted to a specified volume. 

DEP, DIBP, DBP, BBP, DEHP, DINP. Cellulose membrane filters in holders of styrene-acrylonitrile polymer mounted on a sampler of polypropylene connected to a vacuum cleaner (>25 mg dust) Solvent extraction with 2 mT dichl(H ometliane (agitadon 30 min) (x2) NR GC/MS, GC/HD NR Bomdiag et al. (2005)... 

Sampie assembly (The assembly is shown in Figure 3). Conductive filter holder consisting of a 25-mm diameter, 3-piece cassette having a 50-mm long electrically conductive extension cowl. Backup pad, 25-mm, cellulose. Membrane filter, mixed-cellulose ester (MCE), 25-mm, plain, white, 0.4-to 1.2- j,m pore size. 

Track-etched polycarbonate filters and hydrophilic cellulose membrane filters (both 0.2 micron pore diameter, Whatman Filter Co.) were used to recover supernatant solutions. Total chelating agent and metal ion-chelating agent complex concentrations were determined using a Quanta 4000E capillary electrophoresis instrument (Waters Corp.) and bare fused-silica capillaries (75 microns wide, 60 cm long. Polymicro Technol.). The capillary electrolyte consisted of 25 mM phosphate buffer (pH 7.0) and 0.5 mM tetradecyl trimethylammonium bromide (TTAB) electroosmotic flow modifier (see (29)). 

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