Pipetting techniques

Poor well to Poor pipetting technique Check instrument, practice... 

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. 

It has already been stated that a suitable quantitative assay technique must be available to measure the reaction of interest and it is assumed that the experimenter has determined optimal reaction conditions for the enzyme of interest. All kinetic assay techniques assume that v is a variable and that [S] is known as such, preparation of substrate must be meticulous in terms of ensuring that concentrations are correct, and this in turn will rely upon factors such as good weighing and pipetting techniques with calibrated instruments capable of precise, accurate, and sufficiently sensitive measurement. 

Student 3 has obtained a set of results which are widely scattered and hence imprecise, and which give a mean which is less than the correct answer. Thus the analysis contains random errors or possibly, looking at the spread of the results, three defined errors which have been produced randomly. The analysis was thus poorly controlled and it would require more work than that required in the case of student 2 to eliminate the errors. In such a simple analysis the random results might simply be produced by, for instance, a poor pipetting technique where volumes both higher and lower than that required were measured. 

There are, however, a number of stumbling blocks with the PCR assay. Very close attention must be paid to pipetting technique so that stocks (of nucleotide, primers, buffers) do not become contaminated with target DNA. Controls are de rtgueur, and must be run at every amplification. Important, too, is the nature of the template. Because environmental samples usually contain soil, sediment, aquifer material, and/or plant parts, and because these materials also contain substances that interfere with and inactivate the PCR assay, such as humic acids, the bacterial DNA must be extracted free of these contaminating substances. Other compounds, such as metals, also inhibit the reaction, necessitating purification of the DNA prior to amplification. 

For accurate quantification, it is essential that the glucose standard be equilibrated to room temperature before an aliquot is taken for measurement (step 16), and that aliquots be taken using the most accurate pipetting techniques. For further details, see Critical Parameters and Troubleshooting for discussions on glucose standards and pipetting technique. 

Several factors are critical for the accuracy and reproducibility of (3-glucan determination. As with any other analysis, some of these factors relate to the skills of the analyst. Parameters critical for (3-glucan analysis include the following discussed below sample homogeneity, particle size, enzyme purity, glucose standard, pipetting technique, and absorbance measurement. 

Pineapple oil, peel-oil content and aldehyde composition, see also Citrus oils Pin milling, starch isolation, 673, 677 Pipetting technique, 754-755 PL. see Pectic lyase... 

Inoculation Inoculation is the seeding of a culture vessel with the microbial material (inoculum). The inoculum is introduced with a metal wire or loop which is rapidly sterilized just before its use by heating it in a flame. Transfers of liquid culture are often made by using a sterilized pipette. The inoculation is usually done in a laminar flow hood to minimize the risk of contamination. It is important to know proper pipetting techniques for inoculating or sampling during cultivation. 

The practical exercise with the pipette shows how the uncertainty due to one component of a test method could be measured. In this case we expect measurements made with both the balance and the thermometer to be both accurate and precise. Most of the uncertainty in the measurement of the volume of repeated pipettings of water would arise from the pipetting technique. 

Colour transitions of indicators Acid-alkali and iodometric/iodimetric titration Pipetting technique... 

The row that assesses the interaction gives important information. It was quite obvious from the data that the significant difference between the means for the different pipetting techniques was independent of the analyst. However, if the data were as in spreadsheet 4.9, then you would suspect that a significant difference in means between the two pipetting methods would be dependent on whether Quinn was the analyst. The output of the Two Factor with Replicates ANOVA for this data is shown in spreadsheet 4.10. 

Poor pipetting technique Increase volume of sample and detection solution. Use electronic pipettors whenever possible. Compare precision across analysts... 

Liquid handling is a complicated subject due to the sheer number of options available. Most dilutors have extensive sets of settings organized into liquid classes (see Fig. 11.7.) Liquid classes allow the definition of specific pipetting techniques for different types of liquids. 

Pipet 200 /whole blood into a 4 mL acid-washed polystyrene tube. To make a chemical blank 200 fiL of water are pipetted instead of blood. If the calibration is performed by the internal standard addition technique, it is important to pipet exactly 200 juL of blood. This may achieved by the "reverse pipetting technique". 

An accmate and consistent pipetting technique is a prerequisite for limiting pipetting error. Major problems are caused by the following factors ... 

The ELISA data obtained for field samples and spiked samples compared favorably to data obtained by GC. The correlation coefficient (r) exceeded 0.90 In each of two separate comparisons. Other Issues addressed In this study were development of quality assurance criteria, analysis of four parameter standard curves and Interpretation of resulting data, pipetting techniques, and study... 

Hemmings I (2004), Ten Tips to Improve Your Pipetting Technique [available at the website of PipetteDoctor Inc. www.pipettedoctor.com/downloads.asp]. 

Putting a liquid-filled capillary in contact with a surface produces a liquid meniscus, which then spreads onto the substrate, provided the latter is not too hydrophobic. Pipettes have therefore been used for the local deposition of liquids by direct contact on substrates. The downscaling of pipetting techniques by profiling capillaries with micron-scale apertures benefitted from the association with electrochemistry in the conhned droplet volume. Scanning ionic conductance microscopy which has recently become... 

A list of safe pipetting techniques is shown in Table 1.1. Figures 1.2, 1.3, and 1.4 illustrate various pipetting aids. Many more varieties of... 

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