Filter paper disks

The spacers initially used to separate the electrodes were epoxy resin-gasketed glass cloth about 2 mils thick. The spacers were successively replaced by filter paper disks fitted to polyethylene rings 0.02 inch thick and then by Dacron felt Vie inch thick. With the latter spacers, the gasketing material enclosing the periphery of the l1/4-inch-diameter Dacron separator was polyethylene rings 0.10 inch thick. 

Bone marrow is placed into a balanced salt solution containing preservative-free heparin and a single cell suspension prepared by passing the marrow through a fine wire mesh. Alternatively, a small Potter-Elvehjem tissue homogenizer (Hll) may be used. The nucleated cell count is adjusted to 5-10 X 106 ml of balanced salt solution and deoxyuridine added. Following incubation, 5 p,Ci of tritiated thymidine is added and the mixture incubated for an additional hour. The cells are then washed and the nucleated cell count determined. A 0.1 ml aliquot is then placed on a filter paper disk and dried. The activity of the dried disks is then measured in a scintillation... 

The diffusion method uses an agar layer impregnated with the organism being tested a filter paper disk containing the sample is placed on top. After an appropriate incubation time, the paper disk is removed and the average diameter of each zone of growth inhibition is measured. 

Mercuric bromide papers. Place thin, compact filter paper disks (about 20 mm in diameter) in a freshly prepared 5 % HgBr2 solution in ethanol for 30 min. Lay the papers on a watch-glass to dry in air. The papers may be stored in an amber-glass jar for not longer than a week after preparation. 

To separate bacteria cells, force-meat sample was soaked with saline (5 g in 25 mL) and homogenized in homogenizer (3 min) or incubated in shaker (15 min, 100 min, 37 °C). 5 mL of a force-meat suspension obtained were added to the flask with BCN-reagent and incubated (15 min, 100 min", 37 °C). After incubation 2-3 mL of the suspension were filtered through double filter paper disk ( blue strip grade) placed into Swinnex Disk Filter Holder, 25 mm, from Millipore. 0.1-1 mL of the suspension clarified was filtered through Filtravette . The Filtravette was washed with 0.3 mL of saline followed by addition of 0.02 mL of DMSO or 1.5% Neonol-10... 

Figure 3. Filter paper disks on which honeydew of l. lugens (Biotype 1) females was collected when they fed on susceptible fTNlf plants sprayed with steam distillate extract of resistant fARC6650f, fPtb 33, or susceptible TNI1 rice varieties. Control plants were sprayed with acetone. Dark spots on ninhydrin-treated filter paper disks indicate the amount of honeydew excreted by females on treated rice plants.

Average of 4 replications. In each replication, honeydew of 10 newly-emerged females was collected on a 9-cm-diameter filter paper placed around the base of the seedlings. Red honeydew spots indicated xylem feeding on safranine-dyed seedlings and bluish amino acid spots indicated phloem feeding when filter paper disks were treated with a 0.1% ninhydrin/acetone solution. 

Sampl,ing PCB on Concrete. A template was used to demarcate 10 X 10 cm squares on contaminated concrete surfaces. Isooctane (1.5 mL) was applied and after about 45 seconds the solvent was imbibed on two filter paper disks. The filter paper disks were held in stoppered, prerinsed test tubes for shipment to the laboratory. Filter paper disks were extracted by immersion in 40 mL of petroleum ether for one hr and the extracts dried (NaCl) and diluted with isooctane prior to analysis. 

For antimicrobial assays, there are several common methods employed. Due to its ease of operation, the most common method used is the disk diffusion method, which involves the application of a material onto a filter paper disk, and then the disk is placed onto solid medium previously seeded with the test microorganism of interest. Sometimes, the sample is dissolved in an appropriate solvent before application onto the paper disk. This method is very common in the evaluation of antibiotics and is the method adopted by the National Committee for Clinical Laboratory Standards (NCCLS). The method depends on the aqueous solubility of the antibiotics in order to facilitate diffusion through the solid medium. Essentials oils, however, are generally hydrophobic, do not readily diffuse through an aqueous medium and, therefore, the prevalence of false negatives or reduced activity might then be anticipated. 

A dead-ended laboratory filtration apparatus is relatively simple. It consists of a vacuum rated filter flask, large filter funnel with perforated plate, and a filter paper disk covering the perforations. The filter paper should be wetted and vacuum applied to hold the paper against the funnel while a precoat water slurry of filter aid is applied to the funnel to create a precoat layer of approx 0.5 in. thickness. Additional filter aid should be added to the fermentation broth and well mixed before pouring broth onto the funnel. Amount of filter aid added depends on the broth characteristics, but a typical starting point would be 50 g/L of broth. 

Fig. 38.2. Looking down on a Petri dish containing solidified nutrient agar to which had been added a suspension of a bacterial species. Next, six filter-paper disks containing six different antimicrobials was added followed by overnight incubation. The antimicrobials in disks 1, 4, and 5 were inactive. Of...

The test material is first dissolved in ethanol and lOpl are transferred to a small (5mm diameter) filter paper disk. The disks are dried and sandwiched between the lower part of the internode and the moistened sponge close to the vial. The position of the apical portion of the section is recorded and the vial is placed in a high humidity chamber. Subsequent measurements are taken at hourly intervals, over a period of 4 hours. 

Source description Dried deposit ofbarium chloride on a filter-paper disk sealed between two layers of polyester tape that are supported on an aluonnuna annulus ... 

Mortality after 4 hours of confinement in 5.5 cm Petri dish containing 5 cm filter paper disk treated with 2-tridecanone at the indicated concentration. Values are means of 10 replicates with 50 adults/replicate. Mean separation vertical by LSD at P 0.05. 

In a related study, Kauffman and Kennedy (65) demonstrated that the toxicity of PI 134417 and BC2 foliage to sonorensis larvae during cocoon spinning was eliminated when the glandular trichomes were removed. They further demonstrated the acute toxicity of 2-tridecanone and 2-undecanone to sonorensis larvae on treated filter paper disks (2-tridecanone LC50 = 13.0, 95% fiducial limits =... 

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