Volumetric pipettes

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. 

Note all reusable glassware (except volumetric pipettes) should be baked in a mufAe oven at 450 °C for at least 2 h to remove possible contamination before use. 

When measuring liquids, use a class A volumetric pipette unless otherwise specified. 

Using a 10-ml volumetric pipette, deliver 10 ml of filtered toluene to bulb A of the Ubbelohde viscometer (Fig. 17.1) (see Note 3). 

Using a 5-ml volumetric pipette, add 5 ml of the filtered stock polystyrene) solution to the solvent in bulb A. 

Step 3. Prepare and weigh eight clean, dry planchets as in Step 1. Deliver 1 mL of water with a 1 mL volumetric pipette designated TD to each of 4 planchets and 0.010 mL of water with a 10-X pipette (TD) to each of the other 4 planchets and weigh them again. Record the measurements in Data Table 1.2. 

Do not let the designation Class A mean more than it was meant to. Class A can only mean that it is the best tolerance readily available for that specific type of volumetric ware. Class A volumetric ware is not consistent across volumetric ware type. For example, a Class A volumetric pipette does not have the same degree of tolerance as a Class A measuring pipette. Equally, a Class A graduated cylinder does not have the same degree of tolerance as a Class A volumetric flask. See Table 2.6 for a representative cross comparison of Class A tolerances. 

For example, say you had a 100-mL borosilicate volumetric pipette whose liquid was measured at 24°C. Table 2.10 shows -0.09 for these conditions, which... 

There are three types of volumetric pipettes volumetric transfer, measuring, and serological. The differences are based on whether the volume within the pipette is subdivided and if the volume in the tip is included in the calibration (see Fig. 2.19). 

Volumetric pipettes are used solely to deliver in both drain and blow-out models. They are calibrated in both Class A and Class B tolerances based on guidelines established in the ASTM Designation E 969 - 83. Tolerances are provided in Table 2.16. 

The color-coding band(s) on the end of the volumetric pipette are used for quick identification purposes only. The repetition of the colors is sufficiently separated by the size of the pipette to not confuse (for instance) the 10-mL and 50-mL sizes. 

Fig. 3.2 Glass pipettes (a) graduated pipette, reading from zero to shoulder (b) graduated pipette, reading from maximum to tip, by gravity (c) bulb (volumetric) pipette, showing volume on bulb.

There are various designs, including graduated and bulb (volumetric) pipettes (Fig. 3.2). Take care to look at the volume scale before use some graduated pipettes empty from full volume to zero, others from zero to full volume some scales refer to the shoulder of the tip, others to the tip by gravity. Never blow out volumetric (bulb) pipettes, just touch the tip against the inside wall of the vessel. 

Q8.8 How can you confirm that the volumetric pipettes you will be using are operating correctly ... 

A volumetric transfer pipette (Figure 1-1, A) is calibrated to deliver accurately a fixed volume of a dilute aqueous solution. The reliability of the calibration of the volumetric pipette decreases with a decrease in size, and therefore special micropipettes have been developed. 

Ostwald-Folin pipettes (Figure 1-1, B) are similar to volumetric pipettes but have their bulb closer to the delivery tip and are used for the accurate measurement of viscous fluids, such as blood or serum. In contrast to a volumetric pipette, an Ostwald-Folin pipette has an etched ring near the mouthpiece, indicating that it is a blow-out pipette. With the use of a pipetting bulb, the liquid is blown out of the pipette only after the blood or serum has drained to the last drop in the delivery tip. When filled with opaque fluids, such as blood, the top of the meniscus must he read. Controlled slow... 

Accurately measure sample to be diluted. Deliver aliquot for dilution by a microliter syringe or volumetric pipette. Quickly weigh solid samples. If it is necessary to deliver quantities larger than those a pipette can accommodate, weigh the aliquot and dilute. 

While this technique has mostly been replaced by automated techniques described previously, the principle remains the same wherein a pH electrode and a volumetric pipette are used. The technique may be carried out on compounds with reasonable aqueous solubilities (>0.0025 M), and that are available in amounts greater than 30 mg. This method is rapid, simple, and accurate however, very low pfCgS... 

The sampling step can be a limiting factor in the analysis of liquors, honeys, oils and other viscous samples, because a precise sample aliquot cannot easily be taken with volumetric pipettes. Therefore sampling under warm conditions and/or mass-based evaluation of the sampled amount is often required [43,44],... 

Analytical chemistry began in the late eighteenth century with the work of French chemist Antoine-Laurent Lavoisier and others the discipline was further developed in the nineteenth century by Carl Fresenius and Karl Friedrich Mohr. As a pharmacist s apprentice in Frankfurt, Germany, Fresenius developed an extensive qualitative analysis scheme that, when it was later published, served as the first textbook of analytical chemistry. He built a laboratory at his house that opened in 1848. Here he trained students in gravimetric techniques that he had developed. Mohr developed laboratory devices such as the pinch clamp burette and the volumetric pipette. He also devised a colorimetric endpoint for silver titrations. It was his 1855 book on titrimetry, Lehrhuch der Chemisch-Analytischen Titromethode, that generated widespread interest in the technique. 

You have been asked to dilute a drug solution 10 times, using mobile phase as the solvent. You have a starting volume of 50 mL (solution A). Using a 5 mL volumetric pipette, draw up 5 mL of solution A and dispense this into a 50 mL volumetric... 

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