Pipette pump

Pipettes of this type possess only one graduation mark and are used for delivery of that single volume of solution. Common sizes are 10, 20 and 50 mL. These pipettes are filled to a little above the mark by use of a pipette pump or a bulb. The pump is removed and the solution is allowed to run out until the mark is reached, the flow of solution being controlled all the way by use of the index finger over the end of the pipette. Most transfer pipettes are calibrated to allow a small volume of solution to remain in the tip of the pipette once it has been drained and no attempt should be made to blow this drop out of the bottom of the pipette. 

Dissolve approximately 0.01 g of sodium lauryl sulfate in between 50 and 10 mL of MeOH in a 50-mL beaker. Transfer the contents of the beaker to a 10-mL volumetric flask and adjust to the mark with MeOH. This yields a stock solution whose concentration is 1000 ppm. Transfer 1 mL using a glass pipette and pipette pump to a 10-mL volumetric flask. Adjust to the mark with DDL This yields a primary dilution reference standard whose concentration is 100 ppm. 

Never draw liquids into the pipettes using mouth suction. A pipette bulb or a pipette piunp, not a rubber dropper bulb, must be used to fill pipettes. We recommend the use of a pipette pump. A pipette fits snugly into the pipette pump, and the pump can be controlled to deliver precise volumes of liquids. Control of the pipette pump is accomplished by rotating a knob on the pump. Suction created when the knob is turned draws the liquid into the pipette. Liquid is expelled from the pipette by turning the knob in the opposite direction. The pump works satisfactorily with organic, as well as aqueous, solutions. 

If a calibrated pipette fitted with a pipette pump is provided, you may adjust the pipette to 10 mL and deliver the solvent-nucleophile medium directly into your 20-mL round-bottom flask (temporarily placed in a beaker for stability). Alternatively, you may use a warm 10-mL graduated cylinder to obtain 10.0 mL of the solvent-nucleophile medium. The graduated cylinder must be warm in order to prevent precipitation of the salts. Heat it by running hot water over the outside of the cylinder or by putting it in the oven for a few minutes. Immediately pour the mixture into the roimd-bottom flask. With either method, a small portion of the salts in the flask may precipitate as the solution cools. Do not worry about this the salts will redissolve during the reaction. 

Liquids may be measured and transferred using a graduated pipette and a pipette pump. The style of pipette pump shown in Figure 5.3A is available in four sizes. The 2-mL size (blue) works well wifh the range of pipettes previously indicated. To fill the pipette, one simply rotates the knurled wheel forward so that the piston moves upward. The liquid is discharged by slowly turning the wheel backward until the proper amount of liquid has been expelled. The top of the pipette must be inserted securely into the pump and held there with one hand to obtain an adequate seal. The other hand is used to load and release the liquid. 

Excellent results may be obtained with graduated pipettes if you fransfer by difference between marked calibrations and avoid transferring the entire contents of fhe pipette. When expelling the liquid, be sure to touch the tip of fhe pipette to the inside of fhe container before withdrawing the pipette. Graduated pipettes are commonly used when dispensing corrosive liquids, such as sulfuric acid or hydrochloric acid. The pipette will be supplied with a bulb or pipette pump. 

Saug-luft, /. vacuum, suction inlet air. -luft-anlage, /. vacuum equipment or plant, -liifter, m. exhauster, -luftkessel, m. vacuum vessel, -maschine, /. exhauster aspirator, -messer, m. vacuometer. -nkpfchen, n. suction cup. -papier, n. absorbent paper, -pipette, /. suction pipet(te). -pumpe, /. suction pump, -raum, m. suction chamber, -rohr, n., -rohre,/. suction tube or pipe, sucking pip siphon Venturi tube, -rdhrehen,... 

Using a burette or a pipette with a safety pump (this is necessary owing to the poisonous properties of the solution) measure out 25.0 mL of the arsenite solution into a 250 mL conical flask, add 25-50 mL of water, 5g of sodium hydrogencarbonate, and 2 mL of starch solution. Swirl the solution carefully until the hydrogencarbonate has dissolved. Then titrate slowly with the iodine solution, contained in a burette, to the first blue colour. 

Figure 12.6 illustrates the outline of such an analysis. An automatic pipette extracts a preset volume of the liquid sample (or solution) from a cup presented to it on a turntable. The measured sample is mixed with the reagents in the appropriate proportions, and propelled through the instrument by the peristaltic proportioning pump. This pump operates by means of moving bars, attached to a chain drive, which sequentially compress the plastic sample and reagent tubes to drive the liquids forward through the instrument. The incorporation of a succession of air bubbles at... 

Laboratory results may be reported on an as received by volume basis or dry matter by mass basis, depending on whether the sample is considered to be a solid or a liquid. Samples >10% DM are generally treated as solids, and <10% DM as liquids. However, there are frequently exceptions to this rule, e.g. some fibrous samples <10% DM are difficult to pipette, so are analysed on a weight basis, but reported on a volume basis. Some customers can pump thick samples with >10% DM, so need the fertilizer values reported as liquids on a volume basis. Routine determination of density values facilitates calculation and reporting of fertilizer values in either mass or volume units. 

Avoidance or ban of unsafe techniques in the laboratory, e.g., oral suction of chemicals in pipettes, sucking of halogenated compounds with a water-jet pump because of effluent contamination. 

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. 

Remove the upper hexane phase with the aid of a glass pipette attached to a water pump. 

If excessive tailing of the pyridine peak in the chromatographic trace causes difficulty in interpretation (e.g. with pentoses) proceed as follows. Transfer the supernatant liquid of the centrifuged solution by means of a dry dropper pipette to a small test tube and attach a suitable adapter which is fitted to a cooled vacuum trap and pump. Remove the pyridine under reduced pressure continuous agitation of the tube in a water bath held at about 50 °C is advisable. Dilute the viscous residue with 0.5 ml of dichloromethane and re-chromatograph. 

Sample loading pipette 40 pL of Interleukin IB sample solution in each of the eight reservoirs. In order to establish a calibration curve, interleukin concentrations ranging from 0.2 to 17.5 pM are used in the present example (IL-1B1,1 standards 1-8). The various solutions are then pumped through the micro-channels using 60... 

Fig. 3.1. C02 delivery systems. On the left is a simple arrangement where air (from an air pump) may be mixed with C02 to produce 5% C02 in air for gassing bottles or feeding to an incubator. On the right is an arrangement for measuring out fixed volumes of C02 and delivering them through a three-way tap (at the bottom of the syringe) and a sterile Pasteur pipette to a bottle of cells.

Remove the supernatant fluid using a sterile Pasteur pipette attached through an aspirator bottle to a water pump. 

Fig. 9.1. Pipette aids. The figure illustrates three types of pipette aid which can reduce the chance of contamination. In the centre is a manual model which requires pumping. Although cheap, this model can be tiring to use. The mains operated model at the bottom has the problem of a wire which can interfere with manipulations. The rechargeable battery operated model at the top is preferable and it works for 5-20 h on a single charging. (Courtesy of Flow Laboratories.)...

Remove the [3H]thymidine containing medium using an unplugged Pasteur pipette connected to a vacuum pump through a trap. Quickly replace with prewarmed medium containing 2 X 10"6 M thymidine. 

This is a less accurate but much quicker way to estimate generation time than measuring the amount of outflow over a few hours (Models 1 and 3). Model 2 has incorporated a pipette in the tubing between the bottle of medium and the pump to measure the flow rate. The pipette is filled by gravity when the stopcock leading to the pipette is opened. When the pipette is full, the stopcock to the medium bottle is closed. The rate of removal of medium from the pipette is measured to obtain the flow rate. 

---