Comparison of Some Methods

A compilation of different catalytic systems in the rhodium-catalyzed hydroformylation of 1-octene or 1-hexene was made by Cole-HamUton [125], which gives an illustrative impression about the efficiency of each methodology (Table 7.1). 

System References Ligands P (bar) T CO TOP (h-i) Rate (moldm h ) i/b Linear aldehyde (%) Rh loss (mg (mol product) ) Problem 

(eds) (1998) Aqueous-Phase Organometallic Catalysis, Wiley-VCH Verlag GmbH, Weinheim (b) Wasserscheid, P. and Welton, T. (eds) (2003) Ionic Liquids in Synthesis, Wiley-VCH Verlag GmbH, Weinheim (c) Cornils, B., Herrmann, 

Horvath, I.T., Leitner, W Mecking, S., Olivier-Bourbigou, H., and Vogt, D. (eds) (2005) Multiphase Homogeneous Catalysis, vol. 1 and 2, Wley-VCH Verlag GmbH, Weinheim (d) Cole-Hamilton, D.J. and Tooze, 

(eds) (2006) Catalyst Separation, Recovery and Recycling, Springer, Dordrecht (e) Dixneuf, P, and Cadierno, V (eds) (2013) Metal-Catalyzed Reactions in Water, Wiley-VCH Verlag GmbH, Weinheim (f) Fehrmann, R., Riisager, A., and Haumann, M. (eds) (2014) Supported Ionic Liquids Fundamentals and Applications, Wiley-VCH Verlag GmbH, Weinheim. 

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R. Heikka and P. Minkkinen, Comparison of some methods to estimate the limiting value of the variogram, vfj), for the sampling interval j=0 in sampling error estimation. Anal. Chim. Acta, 346, 277-283 (1997). 

Kujawski, M. and Tuszynski, T. 1987. A comparison of some methods for the determination of methoxyl groups in commercial pectin preparations, Nahrung, 31(3) 233-238. 

Abbt-Braun G., Frimmel F.H., Lipp P. (1991), Isolation of organic substances from aquatic and terrestrial systems-comparison of some methods, Z. Wasser- Abwasser-Forsch., 24, 285-292. 

Duff I.S., Reid J.K. (1976) A Comparison of some Methods for the Solution of Sparse Overdetermined Systems of Linear Equations. J. Inst. Math. Appl. Vol. 17 pp 267-280. 

Soon YK, Kalra YP, and Abboud SA (1996) Comparison of some methods for the determination of total sulfur in plant tissues. Communications in Soil Science and Plant Analysis 27 809-818. 

Such equations have worked well in practice, but published work would suggest that the use of NIRS for predicting intake significantly improves prediction. A comparison of some methods of prediction is given in Table 19.11. 

Fig. 5.7. A comparison of some methods used for aroma compound isolation (according to Jennings and Filsoof, 1977).

Gower JC. A comparison of some methods of cluster analysis. Biometrics 1967 23 623-8. 

Table 3.4 shows a comparison of some of the elements for which the MNDO, MNDO/ d, AMI, PM3, SAMI and SAMld methods have been parameterized. 

The objective indication of color differences in foods has usually been attempted in a simplified, indirect way that involves a comparison of some physical characteristic of the samples or, more often, an extracted fraction that is assumed or has been proved to be largely responsible for the associated color characteristics. Although such a method does not measure the actual visual color of the samples, a measure of relative amounts of color-characteristic pigments or a comparison of physical properties of extracts of color-critical fractions (which may be mixtures of several pigments) may prove to be very sensitive indications of differences that are closely related to color. 

In this method a 2-inch diameter screen is sprayed with w from a nozzle at a definite pressure for a definite time (Ref 45). A comparison of some sieve data by this method for different materials is shown in Table 4... 

The latter three of the above points are dealt with in the following parts (see parts 4.2-4.5). Experimental investigations of the inner structure of the cations can be supplemented by quantum chemical calculations 104 106). For example, the MINDO/3 method allows the heats of formation of carbocations to be calculated 107). A comparison of some calculated and experimental values (Fig. 6) shows that the reproduction quality of MINDO/3 varies. 

We have made some preliminary comparisons of the methods used in this research.7 In general the dialysis experiments give the most reliable results. These experiments can not, however, be run with all compounds. 

Barrett, J. C. and N. A. Webb (1998). A comparison of some approximate methods for solving the aerosol general dynamic equation. Journal of Aerosol Science 29, 31-39. 

A comparison of some of the above-mentioned preliminary prescreening results with those of a regular 4-hour test of acute inhalation toxicity (see Section 5.1.2.1.) demonstrates the reliability of this inexpensive and rapid method for orientation purposes in most cases (Table 18). 

For a compound to contribute to the aroma of a food, the compound must have odor activity and volatilize from the food into the head-space at a concentration above its detection threshold. Since aroma compounds are usually present in a headspace at levels too low to be detected by GC, headspace extraction also requires concentration. SPME headspace extraction lends itself to aroma analysis, since it selectively extracts and concentrates compounds in the headspace. Some other methods used for sample preparation for aroma analysis include purge-and-trap or porous polymer extraction, static headspace extraction, and solvent extraction. A comparison of these methods is summarized in Table Gl.6.2. 

A simple and effective chemical method was developed for quantitatively reducing quinones, based on their reaction with metallic zinc and zinc ions [248]. Comparison of this method with conventional electrochemical reduction [249-252] revealed the chemical method to be considerably superior. A reduction reaction of vitamin Kj and other quinones in the presence of Zn° and Zn2+ eliminates the need to apply large negative potentials and may also be performed in the absence of any applied electrochemical potential. Some quinones used, such as UQ-10, menadione, and vitamin K, of the menaquinone series (MKs 4-10) could all be reduced to their corresponding hydroquinones in these conditions. 

An informative study on excited states of diatomic molecules has been made by Sattelmeyer et al. [69], This study includes a comparison with FCI results as well as a comparison of some extended basis set CC values of re, coe, and Te with experimental data. A total of 7 valence excited states were studied BH (1n) CH+ (1I1) C2 ( u and 1FLU) CO (1I1) N2 Ilg and 1 ). First, for BH and CH+ CCSD, CC3, CCSDT-3, CCSDT, CCSDTQ, and FCI results were obtained with the cc-pVDZ basis set. Next, all molecules were studied with the CCSD, CC3, and CCSDT-3 methods and the cc-pVDZ, cc-pVTZ, cc-pVQZ, and cc-pV5Z basis sets. Diffuse functions were not included since the excited states considered are of valence character. 

Three-membered rings with one selenium or tellurium atom have attracted some theoretical attention since the last review <1996CHEC-II(1)259>. Of particular interest are the comparison of theoretical methods, computations on a reaction course (that of selenirane with silylene), and the valence tautomerization of [3]chalcogena[3]pericyclynes. 

Comparison of incubation methods The inhibitor methods using have advantages in higher sensitivity, smaller sample volume, easier analysis and therefore greater throughput than the tracer approaches. Therefore, in spite of the potential artifacts mentioned above, the inhibitor approach remains attractive to some investigators. Incubations of 24 h up to 12 days were used to compare the inhibitor, NH4+ oxidation and dilution methods to estimate nitrification... 

It would be difficult to find more comprehensive or more detailed studies on the physical chemistry of seawater than those done at the University of Miami (Millero, 2001). Several programs were developed for calculation of activity coefficients and speciation of both major ions and trace elements in seawater. The activity coefficient models have been influenced strongly by the Pitzer method but are best described as hybrid because of the need to use ion-pair formation constants (Millero and Schreiber, 1982). The current model is based on Quick Basic computes activity coefficients for 12 major cations and anions, 7 neutral solutes, and more than 36 minor or trace ions. At 25 °C the ionic strength range is 0-6 m. For major components, the temperature range has been extended to 0-50 °C, and in many cases the temperature dependence is reasonably estimated to 75 °C. Details of the model and the parameters and their sources can be found in Millero and Roy (1997) and Millero and Pierrot (1998). Comparison of some individual-ion activity coefficients and some speciation for seawater computed with the Miami model is shown in Section 5.02.8.6 on model reliability. 

The GC route is particularly attractive for it requires no a priori information on the polymer. With the exception of X-ray measurements, most methods of measurement involve a comparison of some property of the polymer, such as density, with that of the totally amorphous or crystalline material. Furthermore neither the mass of polymer in the column nor the flow rate of carrier gas need to be measured since a ratio of retention volumes is computed in Eq. (21). It should be added, however, ttiat for the successful application of the method it is essential that the measured retention volumes correspond effectively to equilibrium bulk sorption, both above and below. Low molecular weight compounds are known to exhibit apparently similar discontinuities in retention diagrams at their melting points but this is to be ascribed to a change in retention mechanism, from surface adsorption for the solid to bulk sorption for the liquid stationary phase. For a detailed discussion of retention characteristics of low molecular weight substances near their transition temperatures the reader is referred to a recent review by McCrea (8J). 

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