Effect of Experimental Variables

By proper design of experiments, guided by a statistical approach, the effects of experimental variables may be found more efficiently than by the traditional approach of holding all variables constant but one and systematically investigating each variable in turn. Trends in data may be sought to track down nonrandom sources of error. 

Experimental design A number of formal procedures whereby the effect of experimental variables on the outcome of an experiment may be assessed. These may be used to assess the optimum conditions for an experiment and to maximize the accuracy and precision obtained. 

Also, a chromatographic profile or fingerprint of trace unknowns can be established and monitored, so that if product performance unexpectedly changes, there will be a starting point for troubleshooting. The effects of experimental variables on sample recoveries should be measured directly by controlled variation of an experimental factor, using the reference standard, or suitable external standards, or spiked addition of an external standard to the reference standard. A detailed example of the use of internal and external standards is presented in Chapter 4. 

The target for optimization in FTA with CL detection is to adjust all experimental factors in such a way so that the detector views as much radiation as possible while the chemiluminescent solution flows through the cell. Hence the kinetics of the flow and detector system should be monitored to match the kinetics of the reaction and generate maximum intensity inside the cell. The effect of experimental variables on the CL signal cannot be exactly predicted in advance and there is not enough theoretical background to support any suggestion. 

This paper describes a new reaction which may yield useful amounts of the product isotope following neutron capture by lanthanide or actinide elements. The trivalent target ion is exchanged into Linde X or Y zeolite, fixed in the structure by appropriate heat treatment, and irradiated in a nuclear realtor. The (n, y) product isotope, one mass unit heavier than the target, is ejected from its exchange site location by y recoil. It may then be selectively eluted from the zeolite. The reaction has been demonstrated with several rare earths, and with americium and curium. Products typically contain about 50% of the neutron capture isotope, accompanied by about 1% of the target isotope. The effect of experimental variables on enrichment is discussed. 

FURTON REIN Relative Effect of Experimental Variables... 

The Relative Effects of Experimental Variables on Achievable Recoveries... 

Equation 16 tends to underestimate the number of particles except during the earliest few seconds of reaction, but serves as an extremely useful predictor for assessing the effect of experimental variables on the number of primary particles formed as a function of time. In Figure 3 are shown some calculations for styrene polymerization in which results from this approximative equation (curves A) are compared to those for the full numerical solution (curves C) at two values for jcr (30). It can be seen that when the oligoradical solubility is reduced (jcr = 10- 5), the rate of nucleation and final number of particles are greatly increased. This is, of course, in the absence of change in any other variable. 

Khan, M. R., Thermoplastic Properties of Coal Pyrolysis at Elevated Pressures Effects of Experimental Variables, Inorganic Additives, and Preoxidation, Ph D. thesis, The Pennsylvania State University, pp. 333... 

In an extensive study of the effect of experimental variables on the rate and selectivity of this reaction, Denmark et al. found the independent formation of ethylzinc alkoxide and bis(iodo-methyl)zinc to be crucial for effective cyclopropanation [34]. They also detected an autocataly-tic behavior of the reaction due to the generation of zinc iodide. 

Table 4-2 shows, as an example, a summary of the effects of experimental variables on the ion-exchange rate controlled by intraparticle diffusion, and by liquid-phase mass transfer. Further details and special situations will become apparent in the discussion of rate laws to follow. 

The author discusses application of ELM, SLM, and polymer inclusion membrane techniques in separation of metal ions (precious metals, Cu, Ni, Zn, Pb, Cd, Cr(VI), Pu, Am, etc.) and organic pollutants (phenols and its derivatives, carboxylic acids, antibiotics, etc.) from wastewaters using laboratory, pilot, and industrial scale modules. Effects of experimental variables upon the solute flux for the various types of liquid membranes are analyzed. The author discusses potential and commercial aspects of hquid membrane technology in wastewater treatment. 

Table 11.7. Effect of Experimental Variables on the Quadruple Point of CuS04 SH20... 

This paper addresses the general subject of substrate transport in polymer-immobilized catalyst systems. The equations needed to interpret reaction rate data for polymer systems are developed and their applicability is discussed. The effects of experimental variables on observed reaction rates in the presence of substrate transport limitations are discussed. A simple method for estimating substrate diffusion coefficients is presented. Methods for testing reaction rate data to determine if substrate transport is affecting the observed reaction rates are developed and the limitations of these methods are discussed. Finally, examples of recent studies are reviewed and discussed within the framework of the mathematical formalism to demonstrate application of the formalism and to show that carefully designed experiments are required to establish the presence of substrate limitations. 

Table 4.1 The effect of experimental variables on the elution volume (cm )...

The search for suitable animal models for the study of osteoporosis receives its impetus from the protracted periods of time required to monitor the effect of experimental variables on the progress of the disease in humans and the invasive techniques required. Research on animal models also has been fueled by the increasing proportion of aged persons in the population. 

Gonzalez-Pradas, E. Villafranca-Sanchez, M., and Gallego, A.C., Effects of experimental variables on phosphate adsorption on bentonite, J. Chem. Technol. Biotechnol., 54(3), 291-296 (1992). 

An understanding of the normal variability between replicate samples forms a vital background against which the effect of experimental variables should be assessed. One multiple data set submitted to the COTEST survey is shown in Fig. 17.4. This indicates a relatively small variation in the oxidation rate, as seen at 850°C. However, the time to spallation, seen in the data at 950°C, shows much larger specimen-to specimen variability. 

In the field, parameters used in the bioavailability number may be difficult to quantify due to mixed populations of microorganisms, heterogeneous soil samples, and variable moisture conditions and exposure times. However, under controlled experimental conditions, this simplified analysis allows quantification and a relative measure of the effects of experimental variables, e.g. soil type and aging conditions. 

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