Reproducibility limit

The dynamic behavior of nonisothermal CSTRs is extremely complex and has received considerable academic study. Systems exist that have only a metastable state and no stable steady states. Included in this class are some chemical oscillators that operate in a reproducible limit cycle about their metastable... 

Reproducibility limit The value less than or equal to which the absolute difference between two test results obtained under reproducibility conditions may be expected to be with a probability of 95%. 

The ability to provide accurate and reliable data is central to the role of analytical chemists, not only in areas like the development and manufacture of drugs, food control or drinking water analysis, but also in the field of environmental chemistry, where there is an increasing need for certified laboratories (ISO 9000 standards). The quality of analytical data is a key factor in successfully identifying and monitoring contamination of environmental compartments. In this context, a large collection of methods applied to the routine analysis of prime environmental pollutants has been developed and validated, and adapted in nationally or internationally harmonised protocols (DIN, EPA). Information on method performance generally provides data on specificity, accuracy, precision (repeatability and reproducibility), limit of detection, sensitivity, applicability and practicability, as appropriate. 

Repeatability Intermediate precision Reproducibility Limit of detection + ... 

The PCR results for CaO, Fe203, Si02 and AI2O3 are quite good, as anticipated. The SEPs for CaO and Fe203 of 1.7-1.8 wt % are higher than the ASTM reproducibility limits, but the results for... 

Reproducibility Standard Deviation Reproducibility Limit R Ruggedness Test Selectivity... 

The repeatability and reproducibility limits express the maximum acceptable difference between two consecutive measurements, which are done under repeatability or reproducibility conditions respectively. The factor 2 results from the error propagation of a difference. Each of the two values has a standard deviation of a, so we get r =t - +cr = V2(t = V2 a... 

Average Cetane Number Level Reproducibility Limits, Cetane Number Repeatability Limits, Cetane Number... 

Relative humidity and temperature are two variables which have influence on the chromatographic behavior of the solutes [2] but which can not always be set at desired levels. The relative humidity is expected to have a large influence, while temperature has a small influence. In reference [2] it is stated that a temperature change of 5 degrees seldom exceeds reproducibility limits of the standard working techniques. It is most feasible to discuss the effect of variation in relative humidity and temperature in terms of activity. Therefore in the following paragraphs first the concept of activity will be introduced. Then the concept will be applied in a short examination of the effect of relative humidity and temperature on the retention. 

The average reproducibility of these values is 12%. This uncertainty is high because it includes results accumulated by a number of different analysts and results where rigid procedural control was not yet established. With dedicated control of all variables discussed in the text the reproducibility limit may be decreased to -5%. 

Any analytical method should be validated. The U.S. Food and Drug Administration has proposed guidelines on submitting samples and analytical data for validation (78). In LC one should check at least specificity, selectivity, accuracy, precision, linearity, reproducibility, limit of detection, limit of quantitation, and robustness. 

ISO uses two terms, trueness and precision , to describe the accuracy of a measured value. Trueness refers to the closeness of agreement between the average value of a large number of test results and the true or accepted reference value. Precision refers to the closeness of agreement of test results, or in other words the variability between repeated tests. The standard deviation of the measured value obtained by repeated determinations under the same conditions is used as a measure of the precision of the measurement procedure. The repeatability limit r (an intra-laboratory parameter) and the reproducibility limit R (an inter-laboratory parameter) are calculated as measures of precision. Again, precision and trueness together describe the accuracy of an analytical method. 

The difference between two individual measurement results, reported by two laboratories for identical sample material, will on average not exceed the reproducibility limit R more than one time in 20 cases provided the measurement procedure has been correctly carried out. 

A key step in the application of rapid analysis methods is the collection of high quality NIR spectra. To minimize the effect of water in the biomass spectra, each sample was air-dried to less than 10 percent moisture prior to NIR spectroscopic analysis. Spectroscopic techniques were used that enable a high quality, reproducible, and representative NIR reflectance spectrum to be obtained. For each sample, a total of 35 spectra were collected and averaged to compensate for sample heterogeneity. Each calibration sample was subsampled three times. Sample cells were emptied and repacked between subsamples. Instrument reproducibility tests demonstrated that the reproducibility limits of the NIR spectrometer contributed less than 0.1 percent to the absolute prediction errors in the rapid analysis method. 

Statistical data on the analysis of oxide products should be based on the same criteria as for iron and steel analysis. Reproducibility limits of about 1—2rel.% are valid in the case of direct analysis with A AS. The use of the injection technique leads to reproducibilities of 2—5rel.% for high salt content and 10—20rel.% for the graphite tube technique (low salt content) used as a trace method. 

It is often necessary to estimate the spread of results obtained in different laboratories. A laboratory needs to show that the results from an analytical method are reproducible. Reproducibility is similar to repeatability except that the analyses are carried out on identical samples under reproducibility conditions e.g. different operator, different apparatus, different laboratory, long interval of time). Reproducibility limit is similar to repeatability limit except that the results are obtained under reproducibility conditions. 

To obtain reproducible limiting currents rapidly, either (1) the solution or the electrode must be in continuous and reproducible motion or (2) a dropping mercury electrode must be used. Linear-sweep voltammetry in which the solution is stirred or the electrode is rotated is called hydrodynamic voltammetry. Voltammetry with the dropping mercury electrode is called polarography. 

Figures 2-4 represent results of ESR signal vs. concentration of Mn(II) for solutions of different pH values which have been saturated with N2, C02, or 02, respectively. The slopes of all the curves are, as noted, essentially the same within the 5% reproducibility limit. The ordinate intercept values are very similar for all curves. This suggests that the manganese species giving rise to the ESR signals in the three sets of experiments are very similar in nature.

Therefore if the difference between duplicated results measured under repeatability conditions is greater than 2.8crr there should be concern that there is something wrong with the analysis. This can be used as part of a quality control procedure to ensure consistency of results. An equivalent difference can be defined for a reproducibility standard deviation (checking results found between laboratories. The maximum permissible difference 2.8 x oy is known as the repeatability limit (r) and 2.8 x [Pg.65]

Autoignition Temperatures. The autoignition data (AIT) shown in Table II were determined by ASTM D 2155 (17). The Shale-11 JP-8 and DEM AIT values (238°C) were identical and similar to that of their petroleum derived counterparts. The Shale-II JP-5 AIT (232°C), however, was slightly lower than that of the other two fuels as well as that of a representative petroleum JP-5 (241°C), but was well within the 11°C reproducibility limit set by the method (17). There are no AIT requirements in the military specifications for JP-5, JP-8 and DEM P, 4, 5). 

The most critical criterion for assessing biopharmaceutical comparability is to show that the biophar-maceutical samples that are being compared are identical or more realistically identical within the analytical reproducibility limits of the analytical measurements, for example, limits of quantitation (LOQ). However, this rigorous level of comparability is unrealistic for biopharmaceuticals. This is due to the previously mentioned inherited complexity and heterogeneous nature of these biopharmaceuticals. Attempts to simplify this situation via some purification process are impractical in terms of product yields, associated cost, and the difficulty of trying to purify one uniquely defined structure of a biopharmaceutical from a mixture of very closely related variant forms that show highly similar physical and chemical properties. 

In Tables 4-7, the within-laboratory reproducibility standard deviation (sw), the reproducibility limit (Rw), and the relative standard deviation (RSDw), as well as CV derived from Horwitz equation are given for the contamination levels of 0.1 mg/kg, 0.3 mg/kg, 0.5 mg/kg, and 1.0 mg/kg. The results for sw, Rw and RSDw for each individual trichothecene were calculated from six experiments done in duplicates at the contamination level of 0.1 mg/kg and from ten experiments done in duplicates at the other three contamination levels except those for DON and nivalenol at the concentration levels of 0.3 mg/kg and 1.0 mg/kg which were calculated from nine experiments done in duplicates since one result at each of the two contamination levels was eliminated by the Cochran test. The experimental RSDw values were compared to the CV values derived from Horwitz equation. Majority of experimental RSDw values were lower than reference values, only a few exceeded it. However, they were much lower than upper limits for RSDr given in Regulation (EC) No 401/2006 (European Commission, 2006a) which were 40% for DON and 60% for T-2 and HT-2, thus the determined RSDw are considered acceptable. 

Table 4. Within-laboratory reproducibility of measurements at the contamination level of 0.1 mg/kg, expressed with the standard deviation (sw), reproducibility limit (Rw) and relative standard deviation (RSDw).

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