Precision and reproducibility

The development of precise and reproducible methods of sensory analysis is prerequisite to the determination of what causes flavor, or the study of flavor chemistry. Knowing what chemical compounds are responsible for flavor allows the development of analytical techniques using chemistry rather than human subjects to characterize flavor (38,39). Routine analysis in most food production for the quaUty control of flavor is rare (40). Once standards for each flavor quaUty have been synthesized or isolated, they can also be used to train people to do more rigorous descriptive analyses. 

Estimations based on statistics can be made for total accuracy, precision, and reproducibility of results related to the sampling procedure being applied. Statistical error is expressed in terms of variance. Total samphng error is the sum of error variance from each step of the process. However, discussions herein will take into consideration only step (I)—mechanical extraction of samples. Mechanical-extracdion accuracy is dependent on design reflecding mechanical and statistical factors in carrying out efficient and practical collection of representative samples S from a bulk quantity B,... 

There are numerous early scientific works concerning the presence of shock waves and the influence of explosions, impacts, and shock waves on matter. The earliest work, however, did not lead to a delineation of the phenomenon as a distinct scientific enterprise. This distinction rests with a group of visionary scientists assembled at Los Alamos for the development of the atomic bomb during World War II. Having learned the methods and developed the technology to explosively load samples in a precise and reproducible manner, they realized that they had in their hands, for the first time, the ability to study matter in an entirely new range of pressure. After several precursor publications beginning in 1955, the existence of the new scientific field was reported to the world in the classic work by Melvin Rice, John Walsh, and... 

The Ramsbottom test (ASTM D-524) is also used to measure carbon residue. The test calls for introducing 4 grams of sample into a preweighed glass bulb, then inserting the bulb in a heated bath for 20 minutes. The bath temperature is maintained at 1,027°F (553°C). Af 20 minutes, the sample bulb is cooled and reweighed. Compared with the Conradson test, Ramsbottom is more precise and reproducible. 

Precise and reproducible deposition of thin films is another area of great importance in the chemical processing of materials and devices for the information age. 

The methylxanthines can be determined in foods and biological systems by the chromatographic methods of TLC, GC, HPLC, or CE. Ultraviolet spectroscopy following a separation procedure can also be used. More recently, immunoassay methods have been developed. There is no single best method the analyst must balance the features of each assay with the final requirements for data precision and reproducibility. 

Two features of expression profiling make it the most productive approach to study biological systems for the immediate future. First, the present efficiency with which investigators can obtain global and quantitative information with DNA arrays exceeds that of proteomic techniques. Second, RNA expression profiles provide an extremely precise and reproducible signature of the state of the cell that probably reflects albeit indirectly, the functional state of all proteins (Young, 2000, p. 13)-... 

The determination of precision can divided into three categories, namely repeatability, intermediate precision, and reproducibility. Repeatability, or intraassay within-day precision, is determined when the analysis is performed in one laboratory by one analyst, using one definite piece of equipment, and is performed within one working day. Intermediate precision is obtained when the analysis is performed within a single laboratory by different analysts over a number days or weeks, using different equipment, reagents, and columns. Reproducibility represents the... 

The CL system luminol-hydrogen peroxide was characterized by Hoshino and Hinze in HTAC reversed micelles, formed in a 6 5 (v/v) chloroform-cyclohexane mixture [63], The results indicate that such a CL system can be used from an analytical point of view in a pH interval of 7.8-9.0 without the need to add a catalyst or a co-oxidant. In these conditions an analytical method was established for determination of hydrogen peroxide that, apart from supplying much milder conditions compared to the usual situation in an aqueous medium, is also acceptably precise and reproducible. 

Method reproducibility — Individual incurred samples from four subjects (approximately 5% of all samples) were re-assayed individually to evaluate reproducibility. The four samples set for reanalysis and evenly spaced throughout the study were designated 101, 123, 145, and 166. The values generated from the reassays were used only to assess reproducibility and were not used in pharmacokinetic calculations. Table 2.2 summarizes the method reproducibility results. The analytical method used in study M06-830 was accurate, precise, and reproducible. 

In the new Stratus CS system results are available in less than 15 min after sample draw and the system has the capability to analyze four samples in less than 30 min. Ease of use, analytical sensitivity, accuracy, precision, and reproducibility makes this system suitable for use in chest pain centers, emergency departments, critical care units, observation wards and clinical laboratories. 

Provide dependable, accurate and precise and reproducible results. 

Always use only HPLC-Grade solvents for better precision and reproducibility of results. 

The ELISA is a versatile method that can be used throughout the biopharmaceutical product development process, from small-scale research to cell-line selection, to monitoring fermentation and downstream processing, and to product release testing. The use of the microtiter plates allows for high sample throughput and various degrees of automation. ELISAs satisfy the biopharmaceutical production requirements for specific, accurate, precise, and reproducible assays. 

To maximize analytical precision and reproducibility, Marshall and DePaolo (1982) chose n = 42, and hence report all data in terms of Ca/ Ca ratios normalized to RJa/ Ca = 0.31221. This choice allows one to use an isotope ratio spanning two mass units ( RJa/ Ca) to make a correction (for instrumental mass discrimination) to another isotope ratio spanning two mass units ( Ca/ Ca). The only other likely choice is to use Ca/ Ca (i.e., n = 44), which spans four mass units and hence would have twice as large a correction for instrumental mass discrimination. 

Precision is a measure of the ability of the method to generate reproducible results. The precision of a method is evaluated using three separate determinations for repeatability, intermediate precision, and reproducibility. 

Precision measures how close data points are to each other for a number of measurements under the same experimental conditions. According to the ICH, precision is made up of three components repeatability, intermediate precision, and reproducibility. The term ruggedness, which has been used in the USP, incorporates intermediate precision, reproducibility, and robustness. 

Method precision refers to the variability in measurement of the same sample. There are three main components of method precision repeatability (also known as system or intraassay precision), intermediate precision (also known as inter-assay or intra-laboratory precision), and reproducibility precision (also known as ruggedness, overall or inter-laboratory... 

Source and detector selection are interrelated, where the output of the source is matched to the sensitivity range of the detector. However, the exact nature of the source is also dependent on the type of sample(s) under consideration, the intended optical geometry, the type of measurement technique, and the final desired performance. The bottom line is that adequate source energy must reach the detector to provide a signal-to-noise performance consistent with the required precision and reproducibility of the measurement. This assumes that the detector is well matched, optically and performance-wise, and is also capable of providing the desired performance. 

There is usually no problem of access to basic laboratory instruments and associated glassware, however, the only means of handling large numbers of tests is to apply some form of automation. An added advantage is that it improves the analytical precision and reproducibility. The most suitable technique has been based on the segmented continuous-flow principle invented by Skeggs (1957), and which was first marketed as the Technicon AutoAnalyzer. The system consists of a number of modules powered from a stabilized 110 V supply, and a typical layout is shown in Fig. 1.1. 

The precision of an analytical procedure expresses the closeness of agreement (degree of scatter) between a series of measurements obtained from multiple samples of the same homogeneous sample under prescribed conditions. Precision is usually investigated at three levels repeatability, intermediate precision, and reproducibility. For simple formulation it is important that precision be determined using authentic homogeneous samples. A justification will be required if a homogeneous sample is not possible and artificially prepared samples or sample solutions are used. 

The more traditional distinction of error components is between random errors and systematic errors. In this classical approach, random errors are generally referred to as precision (repeatability, intermediate precision, and reproducibility), while systematic errors are typically attributed to the uncertainty on the bias estimate and... 

Calculated repeatability, intermediate precision, and reproducibility values can be compared with those of existing methods. If there are no methods with which to compare the precision parameters, theoretical relative reproducibility and repeatability standard deviations can be calculated from the Horwitz equation and the Horrat value (Table 5). Horwitz RSD values are reported in Table 6. Higher variability is expected as the analyte levels approach the detection limit (see below). Next to the Horwitz equation, the AOAC s Peer Verified Program proposes its own levels of acceptability of %RSD as a function of analyte concentration level [56,72]. 

Recovery of the analyte need not be 100%, but the extent of recovery of an analyte and of the internal standard should be consistent, precise, and reproducible. Recovery experiments should be performed by comparing the analytical results for extracted samples at three concentrations (low, medium, and high) with unextracted standards that represent 100% recovery. 

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