Poor Calibration of

A poor calibration of is a systematic error and is additive across all H . This means that a 10% error in leads to a 10% error in the amount adsorbed. As errors go, this is not bad. Furthermore, a post calibration can correct all preceding errors directly. A 10% error in would also be unlikely, since even a crude measurement of volume should yield a number within 1%. 

In determining the pore sizes using the modified Kelvin, a poor calibration of Vj is not critical since the primary size determination is with the pressure measurement. It will directly affect the pore volume measurement. 

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One oil was inhomogeneous due to a high water content causing phase Separation. This may lead to erroneous results. The oil producer pointed out some problems during production, which now have been at least partly solved. In general, the accuracy of all physical analyses was good. Some results were systematically on high side, which most probably is due to poor calibration of the equipment. 

Inhomogeneity in the applied rf field means not all nuclei within the sample volume experience the desired pulse flip angle (Fig. 9.1b), notably those at the sample periphery. This is similar in effect to the (localised) poor calibration of pulse widths and references to rf (or Bi) inhomogeneity below could equally read pulse width miscalibration . Modifications that make sequences... 

Systematic deviations are caused by several reasons the most common ones being inadequate stoichiometry, inappropriate kinetic model and poor calibration of die analytical equipment. That the kinetic model is wrong is easily recognized from graphical plots (see Figure 10.18). The further measures are clear an improved kinetic model is tried to the data, and a new comparison is made. The iteration is continued imtil an adequate fit is obtained. 

Inadequate stoichiometry and poor calibration of the analytical device are interconnected problems. The kinetic model itself follows the stoichiometric rules, but an inadequate calibration of the analytical instrument causes systematic deviations. This can be illustrated with a simple example. Assume diat a bimolecular reaction, A + B P, is carried out in a liquid-phase batch reactor. The density of the reaction mixture is assumed to be constant. The reaction is started with A and B, and no P is present in the initial mixture. The concentrations are related by cp=CoA-Cj=Cob -Cb, i e. produced product, P, equals with consumed reactant. If the concentration of the component B has a calibration error, we get instead of the correct concentration cb an erroneous one, c n ncs, which does not fulfil the stoichiometric relation. If the error is large for a single component, it is easy to recognize, but the situation can be much worse calibration errors are present in several components and all of their effects are spread during nonlinear regression, in the estimation of the model parameters. This is reflected by the fact that the total mass balance is not fulfilled by the experimental data. A way to check the analytical data is to use some fonns of total balances, e.g. atom balances or total molar amounts or concentrations. For example, for the model reaction, A + B P, we have the relation ca+cb+cp -c()a+c0 -constant (again c0p=0). 

The device for field applications has been standardized by American Society for Testing and Materials (ASTM D2573). A symposium on vane testing was held by ASTM in 1988 (Richards, 1988). Sources of error in the vane shear test are poor calibration of torque measurement, damaged vanes, or variation in rate of vane rotation. 

You may be perplexed by the fact that the molecular ion from 12 appears to have m/z 161 rather than the expected value of 160.17. This could be the result of poor calibration of the instrument, so that the m/z values are inaccurate proper calibration of the instrument is critical for proper interpretation of GC-MS data. The actual explanation in this case, though, is that diethyl malonate apparently has a projjensity to be protonated under the conditions of the mass spectrometric analysis, so it is this ion rather than the molecular ion that is being detected. This is yet another phenomenon that can make interpretation of GC-MS data difficult for a begirmer. In any event, a single GC-MS analysis of the mixture of 8 and 12 allows... 

Liquid level above seal pan in bottom of column. Poor stripping of bottoms product. High pressure drop across section. Board mounted instrument improperly calibrated. Level gauge in field not properly blown down or even checked. Operation problem. 

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. 

For the extraction of rubber and rubber compounds a wide variety of solvents (ethyl acetate, acetone, toluene, chloroform, carbon tetrachloride, hexane) have been used [149]. Soxtec extraction has also been used for HDPE/(Tinuvin 770, Chimassorb 944) [114] and has been compared to ultrasonic extraction, room temperature diffusion, dissolution/precipitation and reflux extraction. The relatively poor performance of the Soxtec extraction (50% after 4h in DCM) as compared with the reflux extraction (95% after 2-4 h in toluene at 60 °C) was described to the large difference in temperature between the boiling solvents. Soxtec was also used to extract oil finish from synthetic polymer yam (calibration set range of 0.18-0.33 %, standard error 0.015 %) as reference data for NIRS method development [150]. 

The dependence of precision on different parameters has already been discussed. Precision is strongly dependent on the constancy of migration data. Thus, the stability of the EOF is most important. Buffer recipes describe clearly the preparation and avoid errors caused by, e.g., a poorly calibrated pH electrode. 

Errors may be due to the instrumentation itself. Improper calibration of condensation nuclei counters may lead to poor nuclei concen-... 

For insulating materials, on the contrary, the Fermi level lies in the gap, so that it is not detected on the photoelectron spectra. A possible calibration method stems from the gold decoration technique the binding energies can then be referred to the Au 4f doublet. This leads, however, to a poor reproducibility of the calibration Neither is the 1 s line of adventitious carbon a better energy standard. 

To reduce the source of bias, it is important to have an authentic reliable reference standard, a properly maintained and calibrated balance, knowledge of the purity and form of the standard, calibrated glassware, calibrated pipettes, analyte-free matrix, and pooled and individual lots. Poor calibration, incorrectly or poorly prepared standards, interaction between analytes and container, and incomplete reactions will lead to bias. Some further precautions can be taken to minimize the possibility of errors, such as preparing QC samples in bulk (pools) and separately from the calibrators, which are prepared fresh everyday. 

Quantitative evaluation of a force-distance curve in the non-contact range represents a serious experimental problem, since most of the SFM systems give deflection of the cantilever versus the displacement of the sample, while the experimentalists wants to obtain the surface stress (force per unit contact area) versus tip-sample separation. A few prerequisites have to be met in order to convert deflection into stress and displacement into tip-sample separation. First, the point of primary tip-sample contact has to be determined to derive the separation from the measured deflection of the cantilever tip and the displacement of the cantilever base [382]. Second, the deflection can be converted into the force under assumption that the cantilever is a harmonic oscillator with a certain spring constant. Several methods have been developed for calibration of the spring constant [383,384]. Third, the shape of the probe apex as well as its chemical structure has to be characterised. Spherical colloidal particles of known radius (ca. 10 pm) and composition can be used as force probes because they provide more reliable and reproducible data compared to poorly defined SFM tips [385]. 

Systematic error arises from imperfections in an experimental procedure, leading to a bias in the data, i.e., the errors all lie in the same direction for all measurements (the values are all too high or all too low). These errors can arise due to a poorly calibrated instrument or by the incorrect use of volumetric glassware. The errors that are generated in this way can be either constant or proportional. When the data are plotted and viewed, this type of error can usually be discovered, i.e., the intercept on the y-axis for a calibration is much greater than zero. 

Spreadsheets are often used to maintain recipes or analytical methods that directly include calculations. This may be very helpful to overcome the disabilities of LIMS systems or the poor functionality of an ERR Analytical method validation, calculations of cleaning validation, and calibration lists are other areas where spreadsheets may be used within the pharmaceutical industry. This category of spreadsheet typically takes the form of preconfigured templates. Before spreadsheets were so widely used, programmable pocket calculators were used to perform such functions. 

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