Method performance terms precision

To improve the method performance, notably precision, in these circumstances. The advances made have been commonly termed automation . 

Repeatability is a measure of the short-term variation in measurement results and is the precision that can be most easily determined. It is often used to establish compliance with method performance criteria. While repeatability is a... 

In order that the soHds robotic system could be vaHdated fully, each separate step or component of the procedure was isolated and the results verified gravimetrically. The vahdated results showed that the TS, TSS, and TDS-ROE robotic methods performed excellently in terms of precision, accuracy, and method detection Hmit (MDL). These results were found to be equivalent to, or better than, results obtained by manual... 

Use of Standardized Methods The first level of AQA is the use of validated or standardized methods. The terms validated and standardized here refer to the fact that the method performance characteristics have been evaluated and have proven to meet certain requirements. At least, precision data are documented, giving an idea of the uncertainty and thus of the error of the analytical result. In both validated and standardized methods, the performance of the method is known. 

Laboratories need to monitor their performance on a regular basis to ensure methods are producing precise and accurate results. Some of the terms to do with this topic are ... 

The combined uncertainty for quinizarin, which is significantly greater than that calculated for the other markers, is dominated by the precision and recovery terms. The results of the precision study indicated variable method performance across different matrices and analyte concentrations. The uncertainty, u(Rs), asso-... 

Another major change in the final rule was the elimination of an earlier provision that would have required the FDA to review a manufacturer s QC instructions. That was a key provision for allowing laboratories to simply follow a manufacturer s directions. However, with elimination of that provision, laboratories now have more responsibility for establishing effective QC systems that will monitor the complete analytical process, take into account the performance specifications of the method, detect immediate errors, and monitor long-term precision and accuracy. 

With the label-free methods in the repertoire of quantitative proteomics practitioners, there is still a need for label-assisted methods to perform quantitation with improved accuracy and precision. Label-assisted methods incorporate stable isotope labels into internal standards (IS) for quantitation this MS-based quantitation method is termed stable isotope dilution. The incorporation of stable isotope labels can be achieved either with or without... 

Performance of a group of laboratories which are well-controlled in terms of the above requirements has been shown to be superior to that of other industry laboratories based on the in-house repeatability and their performance in ASTM interlaboratory crosscheck programs. Their repeatability in the laboratory is even superior to that advocated in the ASTM test methods themselves. Such precise data have implications beyond simple good analysis. A properly calculated product specification is usually set based on both the manufacturing and analytical testing variance. 

During crop gathering, some parts of Solanaceae plants may be occasionally included. A method for the simultaneous determination of tropine, atropine, scopolamine, homatropine, anisodamine, a-solanine, and a-chaconine in grains and seeds (wheat, rye, maize, soybean, linseed) has been reported by Jandric et al. [84]. The analytes were separated by isocratic HPLC on a Chirobiotic V column and detected by ESl-MS/MS detector operating in the MRM mode. The method performances were presented in terms of linearity in the range 5-80 ng g, specificity, selectivity, accuracy (recoveries from 61 % to 111 %), precision (CV <5 %), and ruggedness. The limits of quantitation (LOQ) were in the range 2.2-4.9 ng g . ... 

The performance of measurement systems has been traditionally defined in terms of accuracy and precision. Accuracy can be defined as a measure of how close a result is to the actual value and precision is thought of as the uncertainty of the result, which we could identify with the standard uncertainty. Modem usage in the context of quality of analytical results tends to avoid these terms. This is because there has been a more fundamental appreciation of the actual measurement process. For example, accuracy or, perhaps we should say, inaccuracy, involves bias within a measurement process as well as statistically determined factors that cause the result to be different from the true result What, at one time, we would have blithely termed precision is now discussed as repeatability, the variability of a method when applied to measurements on a single sample within a laboratory, and reproducibility, which applies to measurements of that sample when appUed by different laboratories using different instruments operated by different operators. 

The answer to this question as well as the question of the precise meaning of the term ab initio itself in the context of quantum chemistry seems to differ considerably according to the particular researcher that one might consult.3 Some authors I have questioned claim that the two terms are used interchangeably to mean calculations performed without recourse to any experimental measurement. This would include Hartree-Fock, and many of the DFT functionals, along with quantum Monte Carlo and Cl methods. 

Option (Valid) presents a graph of relative standard deviation (c.o.v.) versus concentration, with the relative residuals superimposed. This gives a clear overview of the performance to be expected from a linear calibration Signal = A + B Concentration, both in terms of (relative) precision and of accuracy, because only a well-behaved analytical method will show most of the residuals to be inside a narrow trumpet -like curve this trumpet is wide at low concentrations and should narrow down to c.o.v. = 5% and rel. CL = 10%, or thereabouts, at medium to high concentrations. Residuals that are not randomly distributed about the horizontal axis point either to the presence of outliers, nonlinearity, or errors in the preparation of standards. 

If analytical methods are validated in inter-laboratory validation studies, documentation should follow the requirements of the harmonized protocol of lUPAC. " However, multi-matrix/multi-residue methods are applicable to hundreds of pesticides in dozens of commodities and have to be validated at several concentration levels. Any complete documentation of validation results is impossible in that case. Some performance characteristics, e.g., the specificity of analyte detection, an appropriate calibration range and sufficient detection sensitivity, are prerequisites for the determination of acceptable trueness and precision and their publication is less important. The LOD and LOQ depend on special instmmentation, analysts involved, time, batches of chemicals, etc., and cannot easily be reproduced. Therefore, these characteristics are less important. A practical, frequently applied alternative is the publication only of trueness (most often in terms of recovery) and precision for each analyte at each level. No consensus seems to exist as to whether these analyte-parameter sets should be documented, e.g., separately for each commodity or accumulated for all experiments done with the same analyte. In the latter case, the applicability of methods with regard to commodities can be documented in separate tables without performance characteristics. 

There is some help in terms of setting some of the performance characteristics. The European Community implementing Council Directive 96/23/EC has considered the level of bias (trueness) and precision appropriate for analytical methods used to monitor the concentrations of certain substances and residues of the substances in animal products for concentrations ranging from 1 ig kg-1 to 1 mg kg l. Their recommendations for the trueness and precision of analytical methods are shown in Tables 4.2 and 4.3, respectively. However,... 

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