Filters, pore sizes

Filter pore size, /Ltm Maximum rigid particle to penetrate, /itm Filter pore size, /Ltm Maximum rigid particle to penetrate, /itm... 

Direct interception refers to a sieve-type mechanism in which contaminants larger than the filter pore size are directly trapped by the filter. This sieve retention mechanism of particle arrest is the mechanism of choice and occurs owing to geometric or spatial restraint. This type of particle arrest is considered to be absolute, that is, it is independent of filtration conditions. 

Membrane filtration is the technique reeommended by most pharmacopoeias and involves filtration of fluids through a sterile membrane filter (pore size = 0.45 im), any microorganism present being retained on the surfaee of the filter. After washing in situ, the filter is divided aseptically and portions transferred to suitable culture media which are then incubated at the appropriate temperature for the required period of time. Water-soluble solids can be dissolved in a suitable diluent and processed in this way. 

SWNTs (HiPco, Carbon Nanotechnologies Incorporated) were shortened by ultrasonication with a probe-type sonicator in mixed acids (H2SO4 and HNO3) under ice-cooling. After diluting the mixture with water (MiliQ), the shortened SWNTs were purified by filtration through a PTFE membrane filter (pore size 1 pm or 0.2 pm) or by chromatography (Sepadex G-50). 

Kennedy VC, Zellweger GW, Jones BF (1974) Filter pore-size effects on the analysis of Al, Fe, Mn, and Ti in water. Water Resource Res 10 785-790... 

In another procedure [522] the sample of seawater (0.5-3 litres) is filtered through a membrane-filter (pore size 0.7 xm) which is then wet-ashed. The nickel is separated from the resulting solution by extraction as the dimethylglyoxime complex and is then determined by its catalysis of the reaction of Tiron and diphenylcarbazone with hydrogen peroxide, with spectrophotometric measurement at 413 nm. Cobalt is first separated as the 2-nitroso-1-naphthol complex, and is determined by its catalysis of the oxidation of alizarin by hydrogen peroxide at pH 12.4. Sensitivities are 0.8 xg/l (nickel) and 0.04 xg/l (cobalt). 

A further method for the determination of caesium isotopes in saline waters [60] is based on the high selectivity of ammonium cobalt ferrocyanide for caesium. The sample (100-500 ml) is made 1 M in hydrochloric acid and 0.5 M in hydrofluoric acid, then stirred for 5-10 min with 100 mg of the ferrocyanide. When the material has settled, it is collected on a filter (pore size 0.45 im), washed with water, drained dried under an infrared lamp, covered with plastic film and / -counted for 137caesium. If 131caesium is also present, the y-spectrometric method of Yamamoto [61] must be used. Caesium can be determined at levels down to 10 pCi/1. 

The dust content of the air in the cowsheds was measured in connection with routine care of the cattle. Measurements were made over a period of 1-3 hours. Dust samples were collected by drawing the air through a filter at the rate of 1.7 1/min. The filter pore size was 0.8 um. 

Fig- 2. Radioelement concentrations in solutions contacted with powdered spent fuel (UO2 bum-up 50 MW d/kg U -y-dose rate 10 Mrad/h solid surface/solution volume ratio 1000/m at 25 °C) after sequential filtration (filter pore size 450 nm - white bars filter pore size 1.8 nm -> grey bars) solutions consist of concentrated brine (5 mol/kg NaCl) and simulated granitic groundwater (I = 2.8 x 10 1 mol/L, pH 8) (Geckeis et at. 1998). 

Fig. 3, Evolution of Am(HI), Eu(III) and U concentrations with time in spent fuel pellet leaching experiments (leachate 5 mol/kg NaCl solution anaerobic conditions) radionuclides found in ultrafiltered samples (uf filter pore size 1.8 nm) arc considered as truly dissolved radionuclide concentrations found in filtered samples (f filter pore size 450 nm) are attributed to truly dissolved + colloidal species the grey shaded area marks the fraction of colloidal radioelement species in solution the black arrow indicates the pH increase in solution during the leaching experiment (Geckeis et al. 1998).

Clean steam is supplied to the sterilizer jacket and the chamber via the clean steam generator. Compressed air is supplied to the chamber through a (provide filter pore size) xm hydrophobic filter by an oil-free (manufacturer name) compressor. 

Filter housings fitted with (provide filter pore size) X filter cartridges (product specific)... 

Figure 5. Concentration-depth profiles of filtered Fe (<0.45 pm filter pore size), particulate Fe, and Fe(H) at the end of stagnation (November 8,1989). (Reproduced with permission from reference 38. Copyright 1991 Elsevier Science Publishers, Amsterdam.)...

Figure 8. Seasonal variations of filtered Zn (<0.45 xm filter pore size) and of dissolved Si in the water column of Lake Greifen mixed lake (January 14, 1989) summer stagnation (July 26 and September 20,1989) end of stagnation (November 14, 1990).

To prepare water and water-ethanol (1 1) extracts of fresh juices, 2g of the sample is added to 10 ml of extragent and stored at room temperature for 18-24 h. The extract is separated from solid material with glassy filter (pore size 100-160 pm) and analyzed as follows ... 

Chemotaxis experiments (see Note 2) Use blind well Boyden chambers, that contain a volume of 100 pL in the lower compartment (Costar, Bodenheim, Germany). As filters use selfpunched (7 pm punch) polyvinylpyrrolidone containing polycarbonate filters (pore size 3 mm, Costar), which prior to use need to be washed with 1 M NaOH in 50 % (v/v) aqueous ethanol for 7 min followed by three washes in water (see Note 3). Use p-nitrophenyl-p-D-glucuronide (Sigma) at 10 mM in 0.1 M aqueous sodium acetate, pH 4.0, for p-glucuronidase detection (see Note 4). 

Fig. 3. TEER values of Calu-3 on Transwell filters (pore size 0.4 pm) are reduced by PEI, EC50 value = 0.0007 pg/niL, n = 6.

Fig. 4. Comparison of the transport rates of FITC-dextrans with and without PEI as delivery enhancer across a Calu-3 monolayer on Transwell filters (pore size 0.4 im). Transport was documented over a period of 250 min.

Chlorophyll concentrations were estimated from 40 ml subsamples following Suzuki and Ishimaru (1990). Samples were filtered on Whatman GF/F glass-fibre filters (pore size 0.45 pm). Chlorophyllous pigments were extracted by direct immersion of the filters in 5 ml of N,N-dimethylformamide, and actual extractions were made in the dark at 20°C. Concentrations of chlorophyll a in the extracts were determined following Strickland and Parsons (1972) using a Turner 450 fluorometer previously calibrated with chlorophyll a extracted from Anacystis nidulans (Sigma Chemicals, St Louis). 

Samples were filtrated by Mi Hipore membrane filter (pore size 0.45 ym). 

Figure 4. Rate constant of oxidation of S(IV) and metallic Ion concentration in rain water Filtrated by Millipore membrane filter (pore size 0.45ym)...

---