Pipets mechanical

Measuring pipet A pipet calibrated to deliver any desired volume up to its maximum capacity compare with volumetric pipet. Mechanical entrapment The incorporation of impurities... 

Never use mouth pipetting mechanical pipetting devices should be used for the manipulation of all liquids. 

Sensor layers are mostly attached to a solid support since their mechanical stability is generally quite low. In most cases, all components (polymer, plasticiser, additives and indicator dyes) are dissolved in a common solvent and spin-coated, spray-coated, dip-coated or simply pipetted onto the support material (Figure 10). The solid support can be a glass plate which is mounted in a photometer and exposed to the analyte in a... 

B. l,3-Bis(methylthio)-2-methoxypropane. In a dry, 1-1., threenecked flask equipped with a mechanical stirrer, a 60-ml. pressureequalizing dropping funnel, and a thermometer is placed 13.8 g. (0.34 mole) of sodium hydride dispersed in mineral oil (Note 8). The mineral oil is removed by washing the dispersion with five 100-ml. portions of hexane (Note 9). The hexane is removed with a pipet after the sodium hydride has been allowed to settle (Note 10). 

The increased demand for analyses has led to the introduction of machines that will perform all or part of an analytical procedure. Many of the manipulations in laboratory methods are common to a variety of different tests (e.g. pipetting) and lend themselves readily to mechanization. 

The first so-called automated analysers were developed to carry out analyses by replacing manual pipetting by the mechanical transfer of fixed volumes of sample and reagents. They were designed to mimic the manipulations of a convential manual procedure and sometimes had the capacity to measure the amount of reaction product, usually spectrophotometrically. The... 

Idle mechanical functions of a robot can be hkened to those of the human body. The basic element is the trunk, to which is attached one or two arms which in some instruments have elbow joints. A variety of accessories can be attached to the end of the arm, such as a hand, fingers or special devices for pipetting etc. TTie range of these accessories varies between manufacturers, but they are not necessarily interchangeable between different robots. The accessories available should therefore be taken into account before choosing a robot. 

Micropipets (Figure 2-12) deliver volumes of 1 to l 000 jxL (1 jjlL = 10-6 L). Liquid is contained in the disposable polypropylene tip, which is stable to most aqueous solutions and many organic solvents except chloroform (CHC13). The tip is not resistant to concentrated nitric or sulfuric acids. To prevent aerosols from entering the pipet shaft, tips are available with polyethylene filters. Aerosols can corrode mechanical parts of the pipet or crosscontaminate biological experiments. 

Mechanical pipet fillers (sometimes called safety pipet fillers, propipets, or pi-fillers) are more convenient than latex bulbs (Figure 1.4C,D). Equipped with a system of hand-operated valves, these fillers can be used for the complete transfer of a liquid. The use of a safety pipet filler is oudined in Figure 1.5. Never allow any solvent or solution to enter the pipet bulb. To avoid this, two things must be kept in mind (1) always maintain careful control while using valve S to fill the pipet, and (2) never use valve S unless the pipet tip is... 

C Mechanical pipet filler courtesy of VWR Scientific, Division of Univar. 

Never pipet any solutions by mouth always use a dedicated mechanical pipet filler. Wear gloves, lab coat, and goggles. 

A Latex bulb courtesy of VWR Scientific Division of Umvar B Pipet filler courtesy of Curtin Matheson Scientific, Inc C Mechanical pipet filler courtesy of VWR Scientific, Division of Univar... 

Weigh and finely powder twenty tablets. Weigh accurately a portion of the powder, equivalent to about 100 mg of cimetidine and transfer to a 200 ml volumetric flask. Add 75 ml of 0.1N sulfuric acid, and shake mechanically for thirty minutes. Dilute to volume with the same solvent, mix, and filter through Whatman 1 filter paper, discarding the first 15 ml of filtrate. Pipet 5.0 ml of filtrate into a 200 volumetric flask, add 0.1N sulfuric acid to volume, and mix. Record the ultraviolet absorption spectrum of this solution frcm 300 to 215 nm in a 1 cm cell... 

Fig. 13. Automatic pipet. This automatic pipet (Analmatic Baird and Tatlock) is another application of the syringe pipet. This pipet acts by means of electrical controls as compared to the mechanical or motor-driven ones. The filling is accomplished by hydrostatic pressure and the discharge by means of the weighted pipet piston. The inlet and outlet valves are electromagnetically activated. The pipet has been employed in the dispensing unit shown in Fig. 14.

DNA is extremely sensitive to mechanical shearing forces because of its huge length. Routine laboratory manipulations such as pipetting can break DNA into shorter fragments. However, once isolated, DNA is a relatively stable macromolecule and can remain so when stored dry or under ethanol... 

In a 500-mL, three-necked Morton flask fitted with a condenser, mechanical stirrer, and gas inlet tube is placed 8.6 g (0.375 g atom) of sodium and 75 mL of dry xylene (Note 6) the unstirred mixture is heated at reflux under a nitrogen atmosphere. After the xylene has reached its boiling point and the sodium has melted, the solution is rapidly stirred to produce a very fine-grained sodium sand. Quickly the heating mantle is removed and stirring stopped (Note 7), After cooling, the xylene is pipetted or siphoned away from the sodium sand and stored for future use. 

Sample Preparation Accurately weigh 1.5 g of a solid-mbber sample, transfer it into a 4-oz bottle, and pipet 25.0 mL of the Dilute Internal Standard Solution into the bottle. Stopper the bottle, and shake mechanically overnight to dissolve the mbber. Add 50 mL of methanol to precipitate the polymer, and shake vigorously for 15 min. Allow the mixture to settle, and decant the liquid phase into a 250-mL separator. Wash the polymer with 25 mL of methanol, and add the wash to the separator. Add 50 to 75 mL of cold water to the separator, and shake vigorously for 1 min, venting periodically to release any pressure. Allow the phases to separate, drain off the bottom (aqueous) phase, and rewash the isooctane phase with a second 50-mL portion of cold water. Shake again, allow to separate, and drain off the bottom layer. Transfer 10 mL of the isooctane phase to a 20-mL vial for the analysis. 

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