Precision analytical method

As probabilistic exposure and risk assessment methods are developed and become more frequently used for environmental fate and effects assessment, OPP increasingly needs distributions of environmental fate values rather than single point estimates, and quantitation of error and uncertainty in measurements. Probabilistic models currently being developed by the OPP require distributions of environmental fate and effects parameters either by measurement, extrapolation or a combination of the two. The models predictions will allow regulators to base decisions on the likelihood and magnitude of exposure and effects for a range of conditions which vary both spatially and temporally, rather than in a specific environment under static conditions. This increased need for basic data on environmental fate may increase data collection and drive development of less costly and more precise analytical methods. 

Schaefer, M. Froemmel, C., A precise analytical method for calculating the electrostatic energy of macromolecules in aqueous solution, J. Mol. Biol. 1990, 216, 1045-1066... 

The relatively small mass differences for most of the elements discussed in this volume requires very high-precision analytical methods, and these are reviewed in Chapter 4 by Albarede and Beard (2004), where it is shown that precisions of 0.05 to 0.2 per mil (%o) are attainable for many isotopic systems. Isotopic analysis may be done using a variety of mass spectrometers, including so-called gas source and solid source mass spectrometers (also referred to as isotope ratio and thermal ionization mass spectrometers, respectively), and, importantly, MC-ICP-MS. Future advancements in instrumentation will include improvement in in situ isotopic analyses using ion microprobes (secondary ion mass spectrometry). Even a small increase in precision is likely to be critical for isotopic analysis of the intermediate- to high-mass elements where, for example, an increase in precision from 0.2 to 0.05%o could result in an increase in signal to noise ratio from 10 to 40. 

The difficulty in detecting surface hydride formation is that hydrogen is nearly always contained in the bulk structure of the carbons. Hydrogen is not easily determined with sufficient accuracy if only small concentrations are present. Precise analytic methods should be used in the measurement of the hydrogen uptake of carbons that were prepared with rigorous exclusion of hydrogen-containing contaminants. Carbon formed by the disproportionation of carbon monoxide... 

In the modem world, trace analysis plays an important role in such areas as ecology, chemical engineering, food processing, biomedical analysis, and dmg chemistry. Advanced, sensitive, and precise analytical methods allow identification and quantification of different compounds, both organic and inorganic, including macro-molecular complexes. All these methods present very good detection and quantification levels, up to parts per trillion (ppt) or parts per quadrillion (ppq). 

It is often claimed that the analytical quality should be better when determining reference values than when producing routine values. This may be true for accuracy aU measures should be taken to eliminate bias. The question of imprecision is more difficult because it depends partly on the intended use of the reference values. Increases in analytical random variation result in widening of the reference intervals For some special uses of reference values, the narrower reference interval obtained by a more precise analytical method may be appropriate. However, this is usually not true... 

During the course of setting up a rapid and precise analytical method, we examined several approaches to this problem with the objective of selecting one that would give the most reliable results in the shortest possible time. 

Note that the change in composition between the inlet and exit streams must be large enough for precise measurement otherwise the rate of conversion in the reactor cannot be accurately established. This restriction imposes a limitation on the applicability of the method. If precise analytical methods of determining small composition changes are not available for the particular reaction, a close approach to a point value of the rate cannot be ascertained. 

Ingamell s equations show how the size of the sample needed to minimise sampling error is dependent on the maximum particle size of the sample, using a sampling constant Ks, the amount of sample required to ensure that the sampling uncertainty will not exceed a desired level assuming a precise analytical method (Vander Voet Riddle 1993). 

Precise, analytical methods and computer analysis, should be limited to critical and hazardous lines. The term critical applies to lines with high or... 

The present authors have recently described (I, 2) the development of an accurate and precise analytical method using ion-exchange concentration and flame photometry to measure the strontium and barium concentration of sea water from the same sample. Initial analyses indicated that there is possibly a small, but significant, variation in the strontium/ chlorinity ratio with respect to depth (2, 3). The results of the analyses for barium indicated that, as expected, the variation in the barium/ chlorinity ratio is much larger. This communication reports the results of the analyses of samples from several ocean stations for strontium and barium. 

The first discussion of different substances which contmn the same atoms bonded in various manners was presented in 1811 by Gay-Lussac [24]. Experimental evidence presented by Liebig after he introduced his precise analytical methods [25] having discovered silver fulminate in 1823, Liebig showed that it had the same formula as silver cyanate which had been characterized earlier as a different... 

Following the development of more precise analytical methods for the lanthanides about 20 years ago, a quantitative approach to modelling trace element distribution during crystal-liquid equilibria was developed (see Haskin 1984 and DePaolo 1981b for relevant equations). The distribution coefficient, K, is a measure of the partitioning behaviour of an element between a crystal and a co-existing melt ... 

The square root of the Rs is numerically equal to the relative standard deviation of a set of results obtained from 1 g samples by a precise analytical method with negligible This is one of the experimental approaches for determining Rj. Actually, one can estimate R for given w by repeated precise analysis using expression [25]. Once is evaluated for the sample population, the minimum weight, w, needed for a maximum acceptable relative standard... 

If precise analytical methods are available for determining both the total fraction of diene in the copolymer and the fraction of either cyclic units or pendant vinyl groups, then by making a series of such measurements for different initial monomer feed compositions, values for r, r, and a could be obtained from Equation (11). Then the remaining two parameters, r2 and could be obtained from Equation (10). 

The key to the success in aluminum monitoring lies in the availability of accurate and precise analytical methods together with guidelines for contamination-free specimen collection and the performance of quality assurance. Savory and Wills [19,20], Oster and Prellwitz [21], and Taylor and Walker [22] reviewed the analytical methods for the determination of aluminum in biological materials and the problems associated with aluminum measurements, and provided reconunenda-tions for the preanalytical phase and control of contamination. 

The routine measurement of a characteristic or quantity in a dosage form by an accurate and highly precise analytical method will reduce the risk of rejecting batches when these truly comply or alternatively reduce the risk of falsely accepting batches, when batches do not comply. 

While the term electronic materials commonly refers to the silicon-based materials from which computer chips and integrated circuits are constructed, it technically includes any and all materials upon which the function of electronic devices depends. This includes the plain glass and plastics used to house the devices to the exotic alloys and compounds that make it possible for the devices to function. Production of many of these materials requires not only rigorous methods and specific techniques but also requires the use of high-precision analytical methods to ensure the structure and quality of the devices. 

Precision (analytical method only) The pooled coefficient of variation obtained from replicate determinations of analytical standards over the range of 0.4 to 2 times the target concentration was 0.0052 for formaldehyde (Section 4.3). 

Mass spectrometry (MS). MS is an analytical technique used to separate and detect an ionized molecule by its mass-to-charge ratio. LC-MS is an analytical system used to separate and detect an ionized molecule after separation by HPLC. When MS is combined with gas chromatography (GQ, the system is called GC-MS. The advantages of LC-MS and GC-MS are very high selectivity and sensitivity, and thus these procedures are considered to offer the most precise analytical methods. 

A more precise analytical method permits measurement of the specific polysaccharides other than starch (section 4.2.1.6) that are the main constituents of dietary fibre the results of such analysis are quoted as non-starch polysaccharides (nsp). 

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