Method accuracy

Method (accuracy range, %) Information required Time to develop, weeks... 

Global superposition Local superposition Method accuracy... 

Analytical techniques (including method, accuracy, precision, reproducibility, robustness, limits of detection). 

This factor is most important when results are reported for only a subs the entire collection of calculations. For example, some studies re results only for the atomization energies portion of the set. This subs the calculations does not include some difficult molecules presen other thermochemical properties (e.g. PO, whose geometry car challenging to model accurately), and so results for a subset can be i accurate than they would be for the entire set. This effect becomes r pronounced as overall method accuracy increases. Be cautious v general accuracy and applicability conclusions are drawn from such dal... 

Direct or indirect methods may be used to determine moisture in dehydrated foods. Indirect methods must be calibrated in terms of direct methods—the most common of which are the oven, distillation, and Fischer methods. Accuracy of the direct methods is difficult to evaluate except by comparison with a chosen reference method. Several reference methods are reviewed, but none can be given an unqualified recommendation as most practical and suitable for all foods. An indirect measure of moisture is the equilibrium vapor pressure of water, which can be measured easily and accurately. Arguments are presented to show that vapor pressure may be a better index of the stability of dehydrated foods than the moisture content, which has been frequently used for this purpose. 

The accuracy of a method can only be determined if the true answer is known and, of course, for the majority of analyses it is not. The accuracy of a method is determined during its validation procedure by the analysis of samples containing known amounts of analyte. In order to ensure that the method accuracy is maintained during routine use, samples containing known amounts of analyte are analysed among the unknowns as part of a quality control regime [12, 13]. 

Requirements for standards used In macro- and microspectrofluorometry differ, depending on whether they are used for Instrument calibration, standardization, or assessment of method accuracy. Specific examples are given of standards for quantum yield, number of quanta, and decay time, and for calibration of Instrument parameters. Including wavelength, spectral responslvlty (determining correction factors for luminescence spectra), stability, and linearity. Differences In requirements for macro- and micro-standards are considered, and specific materials used for each are compared. Pure compounds and matrix-matched standards are listed for standardization and assessment of method accuracy, and existing Standard Reference Materials are discussed. 

Accuracy is the term used to describe the degree of deviation (bias) between the (often unknown) true value and what is found by means of a given analytical method. Accuracy cannot be determined by statistical means the test protocol must be devised to include the necessary comparisons (blanks, other methods). 

BINGHAM s (1987) The dietary assessment of individuals methods, accuracy, new techniques and recommendations. NutrnAbsr Rev. 57 705-41. 

The issue of data reproducibility had been the previous focus of the AOAC Official Methods Program. The TDRM will assist AOAC in responding to an expanded scope of it mission to include statements of accuracy with AOAC methods. This extra step requires independent verification of the accuracy of measurements generated by the method. Accuracy of an analytical method must be verified at three separate points ... 

Method accuracy is defined as fhe agreemenf befween fhe measured value and fhe frue value and is usually determined by measuring fhe percenfage recovery of spiked samples. Recovery values of 70-110% are usually desired, allhough fhe EDA and the EU allow for wider ranges for analyses at low concentration levels. 

L and the D/L ratio approaches zero. After the death of the living organism, proteins start to spontaneously break down. An inter-conversion of the amino acids occurs from one chiral form (L) to a mixture of D- and L- forms following protein degradation this process is called amino acid racemisation. The extent of racemisation is measured by the ratio of D/L isomers and increases as a function of time and temperature. The longer the racemisation process continues the closer to 1 the ratio between the D- and L-forms becomes. If the D/L ratio is <1 it may be possible to use it to estimate age. The D/L ratio of aspartic acid and isoleucine are the most widely used for this dating technique [104]. Dates have been obtained as old as 200 000 years. However, it has been used mainly to date samples in the 5000 100 000 year range. Recent studies [ 105] mention an estimation of the method accuracy to be around 20%. 

The accuracy of a method is defined as the closeness of the value obtained to known or accepted values. Accuracy can be determined in a number of ways, depending on the nature of the CZE method and availability of orthogonal techniques to compare results. If practical, spike recovery studies (i.e., testing to determine whether recovery matches the amount of a known analyte or impurity spiked) are good alternatives to orthogonal assay comparisons. ICH guidelines also allow method accuracy to be inferred, once specificity, linearity, and precision are established. 

It is required for quantitative purity assays, and it must be established across the specified range of the analytical procedure. This can be done, by establishing the recovery rate over the range of the method. Alternatively, a method comparison between a validated method and a new method can be performed. Accuracy can be determined by spiking degraded, aggregated, pure or impure material into a known amount of sample. A theoretical recovery would then be calculated and the spike material analyzed using the chosen method. The actual recovery should then be compared to the theoretical recovery to calculate the accuracy of the method. Accuracy in this case would be reported as percent recovery. 

To eliminate problems associated with quantitation in CE—MS and reduce the impact of system variability on method accuracy, it is mandatory to use an IS. The variability obtained in CE—MS, typically around 20%, can be lowered significantly when the IS is taken into account. Using a simple structurally unrelated IS, the precision of a CE—MS method can be improved by a factor of 2 °° and increased up to a factor 4 with a closely migrating... 

What are the analytical requirements of the real-time method (Accuracy and precision, range, speed, sensitivity, etc.)... 

R.L. Green, G. Thurau, N.C. Pixley, A. Mateos, R.A. Reed and J.P. Higgins, In-line monitoring of moisture content in fluid bed dryers using near-IR spectroscopy with consideration of sampling effects on method accuracy. Anal. Chem., 77(40), 4515 522 (2005). 

Step 5 Off-line method or analyzer development and validation This step is simply standard analytical chemistry method development. For an analyzer that is to be used off-line, the method development work is generally done in an R D or analytical lab and then the analyzer is moved to where it will be used (QA/ QC lab, at-line manufacturing lab, etc.). For an analyzer that is to be used on-line, it may be possible to calibrate the analyzer off-line in a lab, or in situ in a lab reactor or a semiworks unit, and then move the analyzer to its on-line process location. Often, however, the on-line analyzer will need to be calibrated (or recalibrated) once it is in place (see Step 7). Off-line method development and validation generally includes method development and optimization, identification of appropriate check samples, method validation, and written documentation. Again, the form of the documentation (often called the method or the procedure ) is company-specific, but it typically includes principles behind the method, equipment needed, safety precautions, procedure steps, and validation results (method accuracy, precision, etc.). It is also useful to document here which approaches did not work, for the benefit of future workers. 

Referee Laboratories and Spike Recovery Testing. Outside laboratories, with demonstrated performance records, can be used to evaluate the suitability of a candidate method when none of the other accuracy testing options is feasible. However, This technique provides a very weak form of accuracy assessment. Indeed, it provides a comparability check, not an accuracy measure. Similarly, spike recovery tests provide only weak evidence of method accuracy. Quantitative spike recovery only indicates that the added form of the analyte was recovered. If the added form responds differently toward sample preparation or detection the utility of spike recovery testing remains doubtful. 

Experimental Requirements. Solutions of known concentrations are used to determine the linearity. A plot of peak area versus concentration (in percent related substance) is used to demonstrate the linearity. Authentic samples of related substances with known purity are used to prepare these solutions. In most cases, for the linearity of a drug product, spiking the related substance authentic sample into excipients is not necessary, as the matrix effect should be investigated in method accuracy. 

Overall Accuracy. In addition to the matrix effect and sample preparation error, method accuracy can also be affected by calculation error for example, difference in relative response, significant -intercept, and nonlinearity. Therefore, a more vigorous approach is to determine the overall accuracy, which incorporates the effect from all aspects of the method ... 

Table 6.2. Method Accuracy (Percent Recovery) for Polysorbate 80...

As another phase of the ongoing quality control program, method accuracy for waste water samples must be assessed and records must be maintained. After the analysis of five spiked waste water samples as in the accuracy check just described, the average (P) and the standard deviation of the percent recovery (sp) are calculated. The accuracy is expressed as a percent interval or range from P — 2sp to P + 2sp. The... 

Accuracy. The results must be sufficiently accurate to interpret the experiments of interest. In a complete quantum-mechanical calculation, this accuracy can be verified by convergence tests within the calculation. In classical, or other approximate methods, accuracy and reliability generally must be judged by experience with test comparisons with complete quantum-mechanical calculations. The numerical stability of the method must also be considered. 

Section 5.1 presents the fundamental method as the heart of the chapter— the statistical thermodynamics approach to hydrate phase equilibria. The basic statistical thermodynamic equations are developed, and relationships to measurable, macroscopic hydrate properties are given. The parameters for the method are determined from both macroscopic (e.g., temperature and pressure) and microscopic (spectroscopic, diffraction) measurements. A Gibbs free energy calculation algorithm is given for multicomponent, multiphase systems for comparison with the methods described in Chapter 4. Finally, Section 5.1 concludes with ab initio modifications to the method, along with an assessment of method accuracy. 

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