Single-point determination

Chee K.K. A critical evaluation of the single-point determination of intrinsic viscosity. Journal of Applied Polymer Science 34, 3 (1987) 891-899. 

The expression given above for R indicates that the exchange process is first order, and it will remain so provided tracer quantities are employed. It is also possible to roughly measure R by single-point determinations, but it is preferable to use several sampling times and to confirm the first-order nature of the measured exchange... 

It is clear then, that the measurement of non-Newtonian materials presents special challenges for a viscometer. Many industrial viscometers designed to give a single point determination have a deceptively simple operating principle. Examples include the speed at which a liquid flows out of a container through a known orifice, a bubble rises in a column of fluid, or a ball falls in a column of fluid. These simple devices are actually very complex in terms of the shear field that is generated. The shear field is the variation of shear stress or shear rate as a function of position within the... 

The linear ramps (continuous or stepped) have the advantage of speed and work best for simple shear-thinning or shear-thickening materials. They should compare with single-point determinations from other equipment if the sample is Newtonian. If the sample is non-Newtonian then there may be discrepancies. This will occur if the single-point device uses a complex shear field (e.g., Zahn or Ford cup). 

Lin YS, Lockwood GF, Graham MA et al. (2001) In-vivo phenotyping for CYP3A by single-point determination of midazolam plasma concentration. Pharmacogenetics, 11 781-791... 

D-4567 Single-point Determination of the Specific Surface Area of Catalysts Using Nitrogen Adsorption by the Continuous Flow Method Single-point surface area using continuous flowing nitrogen-helium gas mixture ... 

Molecular Weight. The viscosity average molecular wei t of the homopolymer and copolymers was determined from single point determinations of viscosity of a 0.25% solution in Fisher purified cyclohexane at 30.0 + 0.01° C. The molecular wei t is calculated from the intrinsic viscosity, [q], using the relationship ( ... 

As the surface area exposed to the site of administration determines the speed with which a particle dissolves in accordance with the Noyes-Whitney equation, these determinations are important. In addition, in those instances where the particle size is difficult to measure, a gross estimation of the surface area is the second best parameter to characterize the drug. The most common methods of surface area measurement, including gas adsorption (nitrogen or krypton), based on what is most commonly described as the Braunauer, Emmet, and Teller (BET) method, is applied either as a multipoint or single-point determination. 

Many laboratory tests to find the emulsification behavior of inks have been proposed during the past several decades, an early one being Bowles and Reich (3),but only one, Surland (15, 16) suggested that measurement of the rate was more important than the amount emulsified. Since the ink/water interaction on the press is a dynamic one, this approach seems more rational than single point determinations of the percent emulsified, which are widely used in industry. 

Single Point Determinations Incorporating Blank Determinations... 

A comparison of the relative efficiency of different carbons should be based on the amount of each that is required to provide filtrates of equal purity. As normally conducted, this can necessitate several dosages of each carbon and the total task can be formidable when several carbons are to be compared. For some purposes, the procedure can be shortened by making single point determinations conjoined with a relative efficiency chart. 

Every substituent which only once occurs in the data set, leads to a single-point determination the corresponding group contribution contains the whole experimental error of this one biological activity value. 

Effects data applicable for QSAR analyses are reported in terms of a constant equivalent response - that is, isoeffective concentrations that correspond to the number of moles of the compounds evoking the same effect. Activity measures such as toxicity parameters should be based on a dose-response curve, not only on a single point determination. Various factors act as determinants in dose-response relationships, such as route of exposure, duration of exposure and species sensitivity (Figure 2.8). 

Test Method for Single-Point Determination of the Specific Surface... 

Shroff RN (1965) Single-point determination of intrinsic viscosity. J Appl Polym Sci 9 1547-1551... 

ASTM D4567. Standard Test Method for Single-Point Determination of Specific Surface Area of Catalysts and Catalyst Carriers Using Nitrogen Adsorption by Continuous Flow Method. ASTM Book of Standards Volume 05.05. Pennsylvania ASTM International ASTM D5604. Standard Test Methods for Precipitated Silica-Surface Area by Single Point B.E.T. 

Only limited practical information is available on the onset and magnitude of shear thickening In reservoir rock. In publications dealing with practical aspects of shear thlckening the viscoelasticity was mostly appraised by the screen factor. This empiric parameter Is obtained from a single point determination and can be applied meaningfully in the quality control of the solution properties. However, it is not a basic rheological parameter, because it still combines viscous and elastic effects and it can not directly be used in pressure calculations. 

Atkins [163], using this apparatus, obtained a relative standard deviation varying from 1.76% to 2.99% according to sample material, with ten single point determinations, each with a new sample. With his own equipment the standard deviation varied between 0.25% and 1.35%. 

A schematic of the apparatus is shown in Figure 2.12. A nitrogen/helium mixture is used for a single point determination and multiple points can be obtained using several such mixtures or premixing two streams of gas. Calculation is essentially the same as for the static method but no dead space correction is required. 

The stability constant of [ -lH C 2] (Kee) was obtained in different solvents at 298 K by single-point determination from NMR speetra. In acetonitrile, which is the solvent of choice for all the sueeessive experiments, Kee — 820 M . The equilibrium between the complex and its free components was established... 

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