Pipets and Syringes

Transfer the pipet to a receiving vessel and drain it by gravity while holding the tip against the wall of the vessel. After the liquid stops, hold the pipet to the wall for a few more seconds to complete draining. Do not blow out the last drop. The pipet should be nearly vertical at the end of delivery. When you finish with a pipet, you should rinse it with distilled water or soak it until you are ready to clean it. Solutions should never be allowed to dry inside a pipet because removing internal deposits is very difficult. 

To use a micropipet, place a fresh tip tightly on the barrel. Keep tips in their package or dispenser so you do not contaminate the tips with your fingers. Set the desired volume with the knob at the top of the pipet. Depress the plunger to the first stop, which corresponds to the selected volume. Hold the pipet vertically, dip it 3-5 mm into the reagent solution, and 

Pipet volume (pL) At 10% of pipet volume At 100% of pipet volume  

Pipets deliver known volumes of liquid. The tranter pipet in Hgure 2-9 is calibrated to deliver one fixed volume. The last drop of liquid does not drain out of the pipet it should not be blown out The measuring pipet is calibrated to deliv a variable volume, which is the difierraice between the initial and final volumes. A measuring pipet could be used to deliver 5.6 mL by starting delivery at the 1-mL mark and taminating at the 6.6-mL mark. 

A transfer pipet is more accurate than a measuring pipet. Tolerances for Class A (the most accurate grade) transfer pipets in Table 2-3 are the allowed error in the volume that is actually delivered. 

Accuracy difference between delivered volume and desired volume 

Pipet volume (liiL) Accuracy (%) at 10% of pipet volume Accuracy (%) at 1(X)% of pipet volume 

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Common types of pipets and syringes (a) transfer pipet (b) measuring pipet (c) digital pipet (d) syringe. 

Figure 22-10, p. 260, shows a microliter pipet and syringe. Use a volatile solvent in which the compound of interest is readily soluble. This allows the solvent to be evaporated rapidly when the sample solution is applied to the plate. The resultant spot will have a smaller diameter. Thoroughly dry each drop of sample before another drop is placed on top of it. This keeps the original spot small while increasing the concentration, and much better separations can be obtained. A hair dryer is preferred for the drying step. Laying the plate on a warm hotplate is not recommended, because plastic plates tend to warp and some samples decompose. 

Pt disks 2 in. diameter Pt wire stirring rods Transfer pipets and syringes... 

The most common instruments or equipment for measuring liquids are the graduated cylinder, volumetric flask, buret, pipet, and syringe, which are illustrated in Figure 2.4. These pieces are usually made of glass and are available in various sizes. 

Volumetric flasks, pipets, and syringes for preparing standards, making dilutions, and performing injections. 

Although improper use of centrifuges and associated equipment leads to fewer accidents than improper use of pipets and syringes and needles, when such accidents do occur they usually result in the formation of aerosols. Because of the size of the equipment, an aerosol produced by a centrifuge accident can potentially affect more people than pipet- or syringe-produced aerosols (502). 

The sample dissolved in a weak (nonpolar for siliea gel), volatile solvent is applied as a narrow band across the plate. Manual applieation can be aehieved with a pipet or syringe gnided by a ruler, or roimd spots ean be placed close together, side by side, in a line. Sample applieation instruments are available commercially, e.g., a meehan-ical streaker from Analtech and an antomated spray-on apparatus from CAMAG. 

Use a sheet of polyethyleneimine cellulose (PEI Cellulose), 50 x 200 mm, for chromatography. Mark the start about 15 mm away of the shorter side with a pencil. Apply the sample with a pipet or syringe. If larger volumes have to be used, apply them in several portions and/or a short line. 

Take 10 mL of 5% adipoyl chloride solution in cyclohexane with a pipet or syringe. Layer the cyclohexane solution slowly on top of the aqueous solution in the beaker. Two layers will form and nylon will be produced at the interface (Fig. 34.1). 

Master laboratory station (MLS) for pipetting and dilution with 3 (A, B, C) 10 ml syringes... 

The quality of apparatus is crucial. The quality of the pipets directly affects the reliability of the analytical information. It is necessary to use measuring pipets of high quality for reliable measures of volume, e.g., clinical, serological pipets, micropipets, syringe pipets. Syringe pipets must be used for measurement of microliter volumes. In volumetric analysis more reliable burets are necessary. For small quantities of sample, micro- and ultramicro-micrometer burets are recommended. Only well-calibrated pipets and burets will assure the accuracy of volume determination. 

Release the embryo from the holding pipet by applying a positive pressure via the micrometer syringe. Pick up the embryo using a Pasteur pipet and place it in the drop of PB1 (Note 21). 

Apply a positive pressure to the de Fonbrune syringe to expel the graft from the pipet as the pipet is slowly withdrawn from the anbryo (Notes 25-27). A coordinated movement of the pipet and the expulsion of the graft is critical to the precise positioning of the graft in the epiblast. 

Figure 1.13 Glassware for measuring volumes of liquids. Clockwise from top center buret, graduated cylinder, syringe, pipet, and volumetric flask.

Mark the center of a clean white filter paper. HU the syringe or pipet and direct 1.5 mL of the solvent-residue mixture at a rate such that the wetted circle is maintained at about 30 to 35 mm in diameter. 

Electronic analytical balance Volumetric flasks 100- to 1000-mL Volumetric glass pipets, various sizes Pasteur pipets, 5.75- and 9-in lengths Refrigerated centrifuge Nalgene centrifuge bottle, 250-mL Disposable syringes, 5-cm ... 

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