Syringe pipettes

When checking the volume of water delivered by weighing. Table 3.2 will enable a graph to be plotted and the volume at the exact temperature of measurement determined. 

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For dealing with smaller volumes of solution, micropipettes, often referred to as syringe pipettes, are employed. These can be of a push-button type, in which the syringe is operated by pressing a button on the top of the pipette the plunger travels between two fixed stops and so a remarkably constant volume of liquid is delivered. Such pipettes are fitted with disposable plastic tips (usually of polythene or polypropylene) which are not wetted by aqueous solutions, thus helping to ensure constancy of the volume of liquid delivered. The liquid is contained entirely within the plastic tip and so, by replacing the tip, the same pipette can be employed for different solutions. Such pipettes are available to deliver volumes of 1 to 1000 pL, and the delivery is reproducible to within about 1 per cent. 

Microlitre syringe pipettes are available with capacities ranging from 10 to 250 ph and with the body of the pipette calibrated. When fitted with a needle tip they are particularly useful for introducing liquids into gas chromatographs (Chapter 9). 

Micrometer syringe pipettes are fitted with a micrometer head which operates the plunger of the syringe, and when fitted with a stainless steel needle tip can be used for the dropwise addition of liquid the volume added is recorded by the micrometer. 

Volumetric flasks (5 mL) Syringes/pipettes for accurate dilution NMR tubes... 

With almost all adsorption materials, the column chromatography is superior to the batch method. Commercial columns (Pharmacia, Bio-Rad) are preferable to makeshift contraptions made from syringes, pipettes, and rubber plugs. The required time and the chance of misfortune increases with homemade devices. And in the end, it is not the doctoral candidate s money that is spent on proper columns but her own time that is saved. 

Various syringe pipettes with standardised stroke, operated by pressing a knob, have become commercially available in connection with quantitative clinical chemical analysis in the pi domain (Firm 53). Contmuous infusion apparatus with small syringe pipettes (Firm 27) can be used to apply aqueous solutions in the form of very small start points to several chromatograms simultaneously [441]. Morgan [456] has described an easily constructable device (Firm 136) for simultaneous spot application of 19 different solutions or for band application of a single sample. 

Forceful ejection of the contents of pipettes or syringe, especially if already containing gas bubbles... 

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. 

Moreover, such solutions can also canse the sample to crystallize out in the syringe. In this case it is recommended to dilnte the sample and apply larger volumes. Of course, a further possibility is the application of highly concentrated solutions manually with a pipette or, if the sample does not crystallize out in the syringe, semiautomated by the Alltech TLC sample streaker. 

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. 

The amount of water with which to dilute the test materials is measured into a plastic bucket. Amounts of test materials are measured with a pipette, syringe or graduated cylinder and poured into the plastic bucket. After thorough agitation, the diluted test solution in the bucket is poured into the application equipment. 

Use the syringe of each assembly to fill the pipette tubing and about 1 mL of the syringe with the indicator solution. Make sure there are no air bubbles in either assembly. 

Saliva Collect 3 mL aliquot with sterile pipette introduce into 2-ounce glass container and cap incubate 24 hours at 37°C withdraw through cap with gas-tight syringe. GC/FID, microcoul-ometric tritration NR NR Solis and Volpe 1973... 

Phase separation of the saturated solution from the excess solid solute is a critical process. If a filter is employed, it must be inert to the solvent, it must not release plasticizers, and its pore size must be small enough to retain the smallest particles of the solid solute. Furthermore, steps must be taken to monitor, minimize, and preferably avoid losses of the dissolved solute by adsorption onto the filter material [27-30] and/or onto the vessels, pipettes, and syringes. Typically, the first small volume of filtrate is discarded until the surfaces of the filter and/or vessels are saturated with the adsorbed solute, to ensure that the filtrate analyzed has not suffered significant adsorption losses. Adsorption can be a serious problem for hydrophobic solutes, for which filtration would not be recommended. 

Syringe-barrel cartridges, disk-holders, plastic pipette-tips, well plates vacuum manifolds for semiautomatic batch processing fully automated autosamplers, xyz liquid handlers and robot-controlled work stations. 

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). 

Transfer samples if required Transfer sample aliquots to an syringe head with pipette appropriate tube or container tips Z9I0 Precision Microlitre... 

Suspensions can be introduced in a variety of ways. Some examples are to manually use syringes or pipettes, pour from a fared beaker, or automate delivery using calibrated pipettes. Each method has its own set of limitations, although automated methods may show less variability. Mixing of the suspension sample will generate air bubbles therefore, the mixing time of suspension samples must be strictly uniform to reduce erroneous or biased results. 

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