Measurement reproducibility

Streaming potentials, like other electrokinetic effects, are difficult to measure reproducibly. One means involves forcing a liquid under pressure through a porous plug or capillary and measuring E by means of electrodes in the solution on either side [6, 23, 71-73]. 

Dissociation of the second proton is insignificant. The pH of its aqueous solutions can be measured reproducibly with a glass electrode, but a correction dependent on the concentration must be added to obtain the tme pH value. Correction values for the most common commercial solutions are Hsted in Table 3. The apparent pH of commercial product solutions can be affected by the type and amount of stabilizers added, and many times the pH is purposely adjusted to a grade specification range. 

Hot tack strength is the abiUty of a heat-seal layer to hold together while molten, before the seal cools and sets up. This is a technically important property which is difficult to measure reproducibly in the laboratory. Owing to the reinforcing effect of ionic bonding on melt strength, ionomer sealing layers provide superior performance in a wide spectmm of appHcations. 

The photographs of cyclopentane have the general appearance indicated by the calculated curve of Fig. 4. The shelf on the third ring, which can barely be seen on the photographs, seems to be displaced outward, however, the fourth minimum appearing flat rather than sharp neither of the two corresponding s0 values could be measured reproducibly. The estimated relative intensities... 

ID-ICP-MS [425,426], Certified values for the 4 PE/Cd materials (VDA-001 to -004) with nominal Cd concentrations of 0.35 to 3.6mmolkg 1 were established by IDMS, using an enriched mCd spike [427]. The results did not show significant differences between bottles at the 300-mg level. For the sample with the highest Cd content (VDA-004 407 ppm) the measurement reproducibility was worse, which stands in relation to heterogeneity problems, as confirmed by GF-ZAAS results. 

Fig. 6 The relative intensity of the 6.78 A line of anhydrous carbamazepine (/3-form) as a function of its weight fraction in binary mixtures of anhydrous carbamazepine (/3-form) and carbamazepine dihydrate. The line is based on theoretical values (Table 5), while the data points are experimental measurements. (Reproduced with permission of the copyright owner, Plenum Press, from Ref. 47.)...

Fig. 3. Electrochemical cell for In situ Hossbauer spectroscopy measurements. (Reproduced with permission from ref. 3. Copyright 1985 Elsevier.)...

In the system which uses crystalline alexandrite as the sensor material/381 a measurement reproducibility of 1 °C is achieved over a wide temperature region from 20 to 700°C. The same technique is applied to another fiber optic thermometer system which is designed for biomedical sensing applications and uses LiSrAlF6 Cr3+ as sensor material/391 The standard deviation of the measurement recorded by this system is better than 0.01°C within the 20 Cand 50°C region. 

Elliott et al. (2003). The data set for unmetasomatized peridotite xenoliths is too sparse to aid much in this controversy at present. As measurement reproducibility betters the 0.5%o barrier, it is just a matter of analyzing the most appropriate samples before such questions can be answered and an accurate estimate can be made of the Li isotopic composition of the mantle, and hence of the bulk Earth. 

Figure 1. Technique for electrochemical measurements. Reproduced with permission from Reference 12. Copyright 1985, National Association of Corrosion Engineers.

Up to today it has been impossible to measure reproducible microhardness data of non-metallic crystals. This was due to the too high indentation forces of commercial available hardness testing devices. Today with the new ultra-microhardness devices, which allow to reduce the indentation force down to 5 - 10 N, it is no longer the limiting problem to measure the Vickers hardness of such brittle crystals. 

Fig. 18 a Schematic of probe tack measurements of a thin adhesive film along a temperature gradient, b Compilation of probe tack data during loading and unloading cycles for different temperatures. c Total adhesion energy, calculated from the area under the load-displacement curve shown in b divided by maximum contact area, as a function of temperature. The error bars represent one standard deviation of the data, which is taken as the experimental uncertainty of the measurement. (Reproduced with permission from [86])... 

CD spectra in the near-UV region are of much lower intensity than those in the far-UV, in part as a result of the much lower concentration of the chromophore, but can be measured reproducibly with due care. They are very important in characterizing the degree and correctness of folding of recombinant proteins and their mutants. 

Figure 6. CFT feedback circuit and instrumentation for AC measurements. Reproduced with permission from reference 17. Copyright 1982 Institute of Electrical and Electronics Engineers.

The electron-diffraction measurements reproduce the twist angle to 42° with an error estimate of about 5 °. This value corresponds to the angle of maximum probability. An exact location of the minimum of the potential function is not easy to derive with present knowledge, but the discrepancy between the electron-diffraction value and the one obtained by ab initio calculation is too large to be accepted. 

Figure 1.4. Reproducibility as a function of concentration during analytical measurements. (Reproduced from Ref. 3 with permission from LC-GC North America.)...

Fig. 12.1. Equilibration of tritiated thymidine with the acid-soluble pool and incorporation into DNA. Mouse L929 cells, growing in 5 cm dishes, were incubated with [3H]thymidine (0.7/iCi/ml 5/tM) for the indicated times after which the cells were quickly washed three times with ice-cold BSS. The acid-soluble material (AS) was extracted into cold i% TCA and after further acid and ethanol washes the cells were solubilised in 0.3 N NaOH and incorporation into DNA measured. (Reproduced from Adams, 1969a, with kind permission of the publisher.)...

FIGURE 10.13 Char strength measurement. (Reproduced from Jimenez, M. et al., Ind. Eng. Chem. Res., 45, 4500, 2006. With permission.)... 

If the abundances of the entire ethanol contracted spectrum are lowered — keeping their relative heights the same as in the reference spectrum — a point is reached where none of the unknown ions is of lower abundance than the corresponding ethanol peaks. In the example shown in Figure 7, this occurs when the mass 46 ions become the same height. If a measurement reproducibility of 20% is assumed, two other ions (m/e 43 and 45) are found to agree with the abundances required by the ethanol reference spectrum because they fall within the prescribed tolerance window. In this example, the mixture was about 50% ethanol the excess intensities at m/e 31 and 32 were due to methanol and the excess intensity at m/e 44 was due to the additional presence of CO2. 

FIGURE 29. Correlation of -log-on vs is, v for 161 organic compounds in the gas phase at 300 K. Ref 257-259 should be consulted for further elaboration. Open circles refer to aromatics and closed circles to aliphatics. The lettered data points, a-t, indicate reference chemicals260 measured. Reproduced by permission of IUPAC from Reference 259... 

FIGURE 16 Raman spectra recorded during propane ammoxidation on alumina-supported nanocrystalline V-Sb-O system and simultaneous activity data determined by online gas chromatography (Guerrero-Perez M.O., and Banares, M.A. Chem. Commun. 1292 (2002), Operando Raman study of alumina-supported Sb-V-O catalyst during propane ammoxidation to acrylonitrile with on line activity measurement, reproduced with permission of the Royal Society of Chemistry) (Guerrero and Banares, 2002). 

Bubble electrodes — Figure 1. Bubble electrode for analytical measurements (reproduced from [vii])... 

Fig. 8.32. Spectra of divalent rare-earth ions in CaF2 host crystal showing the f" - f" 1 d absorption bands. The arrows show the position of 4f internal transitions as found in the fluorescence measurements. (Reproduced from J. Chem. Phys. [182] with the kind permission of the American Institute of Physics.)...

Figure 6. Demonstration of reproducibility in current versus time measurement. (Reproduced with permission from Ref. 13. Copyright 1987 The Metallurgical Society.)...

Figure. 10.8. Dependence of ultrasonic velocity on temperature In (A) Aipechfn under various experimental vacuum conditions and agitation. (B) Water, oil and aipechfn. (C) Aipechfn with variable oil contents as determined from In-line measurements. (Reproduced with permission of Elsevier, Ref. [80]).

With regard to our turbidimeter, the Variable MSA determined that the device exhibits a tolerable amount of variation (only 0.25 NTUs above the reference value of 10 NTUs). However, the study did not measure reproducibility (variation that may result when the device is used by different fishermen). For this, we would need to run an MSA study that measures both the repeatability and reproducibility of the device by testing 10 samples, three times each, with three appraisers. 

Fig. 9-3. The observed magnetic field dependence of the a value for the photodecomposition of DBK in a HDTCL micellar solution at room temperature. It is possible to measure the a value by two different methods (o) mass spectral analysis and (x) quantum yield measurements. (Reproduced from Ref. [2] by permission from The...

Figure 1 Frequency spectrum of dielectric measurements (Reproduced by permission from Pure Appl. Chem., 1962, 5, 723)...

Fig. 13. In situ absorption spectra of ITO/Nf/Ru-red dipped in water (pH 7.4 phosphate buifer) at 0.5 mVs" scan rate. The directions of the absorption and the potential range are indicated in the figure. Inset Cyclic voltammogram recorded during the in situ absorption spectral measurements. (Reproduced with permission from The Royal Society of Chemistry)...

A number of environmental regulations governing allowable toxin concentrations in materials such as soils are based on the total concentration of the toxin in the material, a parameter that is generally easiest to measure reproducibly. However, the above relationship shows that equating the total concentration of a toxin in an administered substance to its bioavailability is the worst-case scenario. This is truly valid only in the rare circumstances when the toxin is completely released from the administered substance and is in the appropriate chemical form to permit complete absorption. 

Film thickness measurement reproducibility (for SiO, single layer films at 3E) < 4 nm... 

Figure 22. Conductivity probe for local solids concentration measurement (Reproduced with permission from reference 24. Copyright 1987.)...

Fig. 7.17. High-pressure flow-cells. (A) Cell for voltammetric measurements in water-in-CO, microemulsions a working electrode, b reference electrode, c supercritical fluid inlet, d supercritical fluid outlet, e sample port, f Teflon O-ring. (B) Fibre optic-assisted cell for fluorimetric measurements. (Reproduced with permission of the American Chemical Society.)...

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