Laboratory pipetting

Balances, volumetric flasks, pipets, and ovens are standard pieces of laboratory instrumentation and equipment that are routinely used in almost all analytical work. You should be familiar with the proper use of this equipment. You also should be familiar with how to prepare a stock solution of known concentration, and how to prepare a dilute solution from a stock solution. 

First, let us consider batch mixing processes, as exemplified by ordinaiy laboratory practice in solution kinetics. A portion of one solution (say, of the substrate) is added by pipet to a second solution (containing the reagent) in a flask, the flask is shaken to achieve homogeneity, and then samples are withdrawn at known times for analysis, or the solution is subjected to continuous observation as a function of time, for example, by spectrophotometry. For reactions on a time scale (measured by the half-life) of hours or even several minutes, the time consumed in these operations is a negligible portion of the reaction time, but as the half-life of the reaction decreases, it becomes necessary to consider these preliminary steps. Let us distinguish three stages ... 

Sweden produced a disproportionate number of outstanding chemists in the eighteenth and nineteenth centuries. Jons Jakob Berzelius (1779-1848) determined with amazing accuracy the atomic masses of virtually all the elements known in his time. In his spare time, he invented such modern laboratory tools as the beaker, the flask, the pipet, and the ringstand. 

L.28 Silver nitrate is an expensive laboratory reagent that is often used for quantitative analysis of chloride ion. A student preparing to conduct a particular analysis needs 100.0 ml. of 0.0750 M AgNO,(aq), but finds only about 60 mL of 0.0500 M AgNO,(aq). Instead of making up a fresh solution of the exact concentration desired (0.0750 M), the student decides to pipet... 

A homemade combination scraper-coUector used in my laboratory can be made from a Pasteur pipet (229 mm x 7 mm OD Fisher Scientific Co., Pittsburgh, PA Catalog No. 13-678-6B) [52]. The pipet is cut with a file 60 mm from the top and 65 mm from the tip to produce a pipet that is approximately 100 mm long, which is then plugged with glass wool. The pipet tip is attached to a vacuum pump or... 

Even inside the controlled conditions of a research laboratory, analyzing clean and standardized test samples PCR procedures requires careful quality control, taking into consideration differences in sample preparation, variation in pipetting, differences in reaction tube thickness, poor calibration or instability of the thermal cycler, and reagent quality. 

Because the PCR exponentially copies the target molecule or molecules, amplicon contamination in the laboratory is a serious concern. It is recommended that the mastermix is prepared in an isolated area, such as a PCR station equipped with a UV light. This work area should be exposed to UV radiation after use to destroy any DNA contaminants. The use of dedicated pipets and Altered pipet tips is also recommended. The template DNA should be prepared and added to the reaction in an area that is isolated from the mastermix preparation hood. The thermal cycling and gel electrophoresis should be conducted in a third work area and care should be taken not to introduce amplified PCR products into the mastermix or template preparation work areas. 

Maintaining a moderate, consistent pipetting rhythm is the best way to ensure that all samples and standards are treated equally. This is easy to accomplish with tube assays, because relatively few samples can be analyzed per set. Microtiter plates present more of a challenge, because up to 96 wells may be utilized at the same time. One solution developed in this laboratory involves the use of a microtiter plate not coated with reagent - the reservoir plate." An excess of all samples and standards is loaded into the reservoir plate. If 0.10 mL is needed for the inhibition step, for example, 0.15 or 0.20 mL of each solution is added to a pre-determined position in the reservoir plate the excess amount simplifies the next pipetting step. The location of each sample and standard is identified on a plate layout sheet, a map of the reservoir plate previously completed by the analyst (Figure 3). When the reservoir... 

One alternative method for preparing field fortifications solutions/suspensions is to prepare each fortification sample of each matrix in a separate mini-vial in the analytical laboratory and ship the vials to the field for use. This procedure precludes the use of pipets in the field and may be useful when Field Scientists not experienced in the use of pipets are involved in the field fortification process. One disadvantage of this procedure is that the mini-vials, if not designed correctly, will be hard to handle in the field, and surface tension of the suspension or fortification solution will tend to leave unacceptable amounts of the solution/suspension in the vial or at the lip of the vial and not on the matrix in question. This procedure may lead to cross-contamination of samples as the field fortification liquid is forced from the top... 

I Dispense samples, standards and controls Precision dispensing or pipetting of samples, standards and controls Z510 Master Laboratory Station, or ZI90 Precision Microlitre syringe head... 

In order to determine chemical elements in soil, samples of the soil must undergo a solid-liquid extraction. Sometimes the extracts resulting from this procedure have analyte concentrations that are too high to be measured accurately by the chosen method. Therefore, they must be diluted. At the Natural Resources Conservation Service (NRCS) Soil Survey Laboratory in Lincoln, Nebraska, an automated diluting device is used. Using this device, the analyst accurately transfers aliquots of the extract and a certain volume of extraction solution to the same container. This dilutor may also be used to pipet standards and prepare serial dilutions. 

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. 

Exogenous sources such as a person s hair or skin, doorknobs, laboratory benches, dust, reagents, thermal cyclers, and pipet tips are some of the common sources of DNA contamination. Ideally, a laminar air flow bench with filtered air provides a clean, dust-free environment. Sample preparation should be done in a separate room or area. The addition of sample to the PCR reaction mixture in the... 

Fortunately, protein concentration methods are relatively simple (low-tech) and inexpensive. The simplest assays require only a spectrophotometer calibrated for wavelength and absorbance accuracy, basic laboratory supplies, and good pipetting techniques. Protein concentration assays are quite sensitive, especially given the typical detection limits required for most biopharmaceuticals. 

Time-dependent mass change of low volumes of DMSO under ambient laboratory conditions. Dry DMSO was pipetted (2 or 5 gL) into the wells in alternating rows of a low-volume 384-well microplate, and the plate was incubated on the laboratory bench under ambient conditions (approximately 21°C and 35% relative humidity) and weighed periodically using an analytical balance. Filled triangles are data from wells initiated with 2-gL DMSO open squares are data from wells initiated with 5-gL DMSO. 

Scheduled prevenhve maintenance is performed to prevent breakdowns or mal-fiinchons, to prolong the hfe of an instrument, and to maintain ophmum operating characlerishcs. For automated immunostainers, the performance and documentahon of maintenance/funchon checks should be done as defined by the manufacturer with (at least) the frequency as specified. In general, common laboratory equipment such as pipets, centrifuges, and balances need to be serviced or cahbrated twice yearly. 

Fluid that is flushed from the capillary gap is collected in a waste tray beneath the slide-coverplate assemblies. This tray has a limited capacity and must be drained prior to a staining run. The entire slide-coverplate and reagent carousel area are enclosed within a Plexiglascover during operation, which protects reagents from laboratory conditions (temperature, humidity) and prevents inadvertent contact with the robotic pipet arm during movement. 

The Ventana 320 is designed to be used only with detection reagents, enzymes, chromogens, and counterstains supplied by Ventana, but it allows the use of primary antisera not marketed by the company. To use such antisera, however, the company requires purchase of Ventana pipeters and bar codes for each individual antisera. Although this limits a laboratory s ability to be flexible, it assists in assuring quality control of reagents. 

Indicate which type of measurement scale (nominal, ordinal, interval, or ratio) is usually used for the following characteristics time, mass, library holdings, gender, type of heart attack, cholesterol level as measured by a clinical chemical laboratory, cholesterol level as reported by a doctor to a patient, pipet volume, and leaves on a plant. 

In industrial use, some instances of skin and respiratory tract irritation have been observed but no chronic effects have been reported. A human exposure to 12,000 ppm for 1.5 minutes in a laboratory produced nose irritation and cough mouth pipetting of the liquid caused a severe sore throat and reddened mucous membranes. Workers exposed for several hours to low vapor concentrations complained of foggy vision with rings around lights, the results of corneal edema, which cleared within 3-4 hours after cessation of exposure. ... 

Equipment used in GLP studies must be validated for appropriateness. Each piece of equipment must have SOPs for operation, calibration, and routine maintenance. All routine and nonroutine maintenance must be documented. What is the definition of a piece of equipment Any item that can have an impact on the results of an anal5dical procedure. In the typical non-GLP laboratory, records are kept on analytical equipment such as spectrophotometers or gas chromatography units. Under GLP, however, the definition expands to include items such as pipets, thermometers, incubators, refrigerators, and mixing devices, as long as it is possible that the use of the item can affect the outcome of the test. For the non-GLP lab, implementation of this standard will dramatically increase the number of equipment-related SOPs. 

The use of the Zymate Laboratory Automation System allows the standardization and automation of many routine operations in an analytical chemistry laboratory. It additionally allows for a closing of the analytical automation loop of sample preparation and analysis therefore potentially decreasing the need for personnel with a resultant increase in productivity. These operations include, but are not limited to, weighing, pipetting, diluting, blending, heating, liquid-solid extraction, and filtration. 

Error of Measurement An optimistic experimenter sends two samples of a prepared chemical to the laboratory for analysis, Since the two samples were pipetted from the same flask, he expects the results to be the same. They differ by 0 1% of an important component. 

Standards used for comparators are either well documented materials (U.S.G.S. BCR-1 Basalt, NBS Orchard Leaves, NBS Bovine Liver, etc.) or are prepared in the laboratory by pipetting known quantities of elements onto high purity cellulose material. Standards are weighed into polycarbonate and packaged for irradiation in the same manner as the samples. 

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