Pasteur pipettes

Note 1, A small sample was taken by means of a Pasteur pipette and the liquid was placed on the prism. Care should be taken that no evaporation of THF takes place this will give too high a n. ... 

The construction of two typical infrared cells is shown in Fig. 19.6. Such cells have to be carefully filled by using a syringe or Pasteur pipette to ensure that no air is trapped inside. To prevent evaporation the ports should be plugged with small plastic stoppers once the cell has been filled with the solution. 

FIGURE 5.7 Eiquipment for manual application, e.g., 500-pl Hamilton syringe (lower), Pasteur pipette (middle), and 2-ml measuring pipette (upper). 

Some equipment for manual applieation is shown in Figure 5.7. A Hamilton syringe of 500 pi, or a measuring or volumetric pipette of, say, 1 or 2 ml, with Peleus ball, or a Pasteur pipette with an aspirating bulb can be employed. 

FIGURE 5.8 Manual application by carefully moving the Pasteur pipette over an imaginary line without touching the layer. 

After the identification of the suitable compound bands, silica gel is scraped off the plates, placed in short glass columns, Pasteur pipettes, or sintered filter funnels, and fractions are recovered with such volatile solvents as ethyl acetate or dichloromethane. 

Use a long Pasteur pipette to layer 2.2 ml of the 10% sucrose solution in a Beckman polyallomer tube (14 x 89 mm, 331372). Then, underlay 2.2 ml of the 20% sucrose solution by inserting the tip of the pipette to the bottom of the tube and slowly pipetting the 20% sucrose solution under the 10% solution. Underlay the 30, 40, and 50% sucrose solutions in the same manner. Cover the tube with aluminum foil and store overnight at 4° to establish a linear gradient. 

Two methods of capsule formation were employed static beaker tests and atomizer screenings. In the beaker tests, which comprised the first phase of the screening (Step 2 of Fig. 1), a small volume of inner polymer solution was extruded from a Pasteur pipette as a droplet (nominally 2-3 mm) into a receiv-... 

A cleanup column from a commercial source can be used or can be constructed easily from a Pasteur pipette (see Figure 12.12). A small piece of cotton is placed in the bottom of the pipette. A suitable absorbant, such as a solid coated with or bonded to a high-molecular-weight hydrocarbon such as octadecanol (this is often simply called a C-18 extraction column), can be loaded into the pipette and covered with another small amount of a cotton ball. A list of common extract cleanup absorbants and their characteristics is given in Table 12.3. 

Figure 13.3. Sample application tools from top to bottom, glass capillary, Pasteur pipette with tip drawn out, syringe for HPLC, and syringe for GC. 

In TLC, a 10- iL or larger syringe is often used to place sample spots on the thin layer before development. Alternately, a glass capillary tube or Pasteur pipette may be heated in a burner and pulled to obtain a fine capillary suitable for spotting (see Figure 13.3). 

A steady stream of HBr was introduced via a Pasteur pipette with the tip extending into the solution. 

Transfer the cells to a 25 ml sterile universal vial using a sterile plastic Pasteur pipette. 

Pasteur pipette with rubber squeezer Protein solution Precipitating agents... 

Grease the rim of the plate with oil using a Pasteur pipette and cover the reservoirs with cover slips. 

After diluting the Kjeldahl digest to give a 50% aqueous solution, one observes a residue of silica and a fine white mineral deposit at the bottom of the digestion tube. There may also be some cloudiness in the solution, which should be left to settle for 48-72 hours. Using a disposable pasteur pipette, transfer sufficient of the upper clear solution to almost fill the autoanalyser sample cup. 

Sodium bicarbonate reagent - dissolve 420 g sodium bicarbonate (sodium hydrogen carbonate) in water, add 50 ml of the polyacrylamide solution and dilute to 10 I. Add approximately 50% m/m sodium hydroxide solution, stirring with a glass rod, until the pH meter reading is steady at 8.50 at 20°C (a plastic Pasteur pipette is useful for dropwise addition approaching the required pH). 

Procedure. Weigh 2 g of the oven dried sample ground to 1 mm into a porcelain or glass crucible and place in a cool muffle furnace. Increase the temperature to 550°C and ash for 2 h. Cool and dissolve in nitric acid solution, make up to 20 ml and store in a polythene capped tube. Allow to settle before transferring to another clean sample tube by decanting or using a polythene Pasteur pipette. Analyse the solution by AAS or ICP according to the manufacturer s recommendations. 

Pipet 4 ml of the hot molten Soln. A onto the covered slides laying on a horizontally leveled table. After gelation, punch wells using a stamp as shown in Fig. 4.1. Suck out carefully residual material from the wells using a Pasteur pipette connected to a pump. 

Dilute the shrimp with fresh water at a ratio of 1 volume shrimp to 3 volumes water and feed one Pasteur pipette of diluted shrimp per eight adult fish. 

Follow the procedure described above using 1 g portions in 10 , 10 , 10 , 10 " and 10 M CTAB solutions. Addition of CTAB may cause extensive frothing. Since the powder will be retained in this foam it must be broken up either mechanically using a Pasteur pipette or by the addition of a small amount of ethanol. The powder may also stick to the walls of the apparatus above the collection tube. This powder should be dislodged by gentle tapping on the walls of the apparatus. Calculate the mean flotation efficiency at each concentration and graph the results. 

To a solution of 0.25 mmol (58 mg) of f-)-(S )-l-amino-2-(/e/- -butyIdimelhylsilyloxymcthyi)pyrrolidinc (SASP) and 0.2 g of MgS04 in 2.5 mL of cyclohexane, 0.20 mmol of the aldehyde is added and stirred at r.t. for 20 min. The solution is filtered from the MgS04, the solvent is evaporated under reduced pressure, and the crude product is filtered through a Pasteur pipette filled with silica gel using petroleum ether/elhyl acetate (98 2). The diastereomeric excess (de, which is the ee of the aldehyde) is then determined by analytical HPLC using hexane/elhyl acetate/ isopropyl alcohol (99 1 0.2). 

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