Phase measurement experimental protocols

The above experimental protocol could not be used to measure the IFT of most citrus oil/complex coacervate interfaces. When the Wilhelmy plate was placed in a complex coacervate phase before an oil phase was layered on the coacervate phase, a thick coating of coacervate phase was carried into the oil phase as the plate was drawn into the oil phase and subsequently placed at the... 

Abiotic soil desorption measurements are probably the most important tests to precede measurement of microbial degradation. Desorption tests measure the site-specific soil/water partition coefficients for the contaminants of interest. Several experimental protocols are available for measuring partition coefficients (Wu Gschwend, 1986 Rogers, Tedaldi Kavanaugh, 1993). At the two extremes of bioavailability and biodegradability, contaminants can either be detected near their solubility limit or can be undetectable in the aqueous phase. Measurements of aqueous phase and soil phase concentrations in equilibrium may... 

For TRXRD measurements to be meaningful, special attention must be devoted to the questions posed, to the manner in which the experiments designed to answer these questions are performed, and to the proper choice of materials and complete documentation of experimental protocols and results. As an example, in the case of a T-jump experiment, documentation should include direction, rate and magnitude of the jump, initial and final temperatures, and the thermal history of the sample. Ideally, in-sample temperature should be recorded at or close to the interrogating X-ray beam throughout the course of the transition. The manner in which the characteristic transition time is determined must be adequately described and, where possible, an estimate made of the number of molecules transforming per unit of time and volume. A measure of the sensitivity of the detection system to the presence of intermediates or minor and disordered phases would enormously benefit data evaluation. 

The Tg determination, while not a thermodynamic criteria for misdbility, is an easy and effective method for determination of the phase behavior. The author, having conducted literally thousands of these measurements (primarily by dynamical mechanical methods), has found this to be a viable screening method that is highly reliable. In the borderline cases (xu 0), the experimental protocol is critical and with proper consideration of the experimental details, exceptions to these observations are rare. In the cases of specific interactions xn < 0), the literature is even clearer as glass transition measurements agree well with the results of other characterization methods, including those which meet the criteria of thermodynamic misdbility. 

For electrode (conductor/semiconductor) surfaces, mass transport can be controlled with a variety of experimental protocols and the interfacial flux is measured directly via the current response (measured as a function of potential, time, etc.) [1], This is not true of other interfaces, such as minerals and many biomimetic surfaces in contact with the solution. In these instances, fluxes have often been deduced in a convoluted time- and space-averaged manner by determining the accumulation/loss of material in a bulk phase as a function of time. This leads to a considerable loss of dynamic resolution. Furthermore, in some systems, mass transport between the bulk and the interface is difficult to estimate, leading to incorrect mechanistic interpretation, with major implications for practical applications, whether this concerns drug transport across cell membranes or the growth of crystals. 

We have applied this protocol to the evaluation of the measurement uncertainty for a method for the determination of three markers (Cl solvent red 24, Cl solvent yellow 124 and quinizarin (1,4-dihydroxyanthra-quinone)) in road fuel. The method requires the extraction of the markers from the sample matrix by solid phase extraction, followed by quantification by HPLC with diode array detection. The uncertainty evaluation involved four experimental studies which were also required as part of the method validation. The studies were precision, trueness (evaluated via the analysis of spiked samples) and ruggedness tests of the extraction and HPLC stages. The experiments and uncertainty calculations are described in detail in Part 2. A summary of the uncertainty budget for the method is presented in Fig. 3. 

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