Analysis accuracy

Accuracy The accuracy of a gas chromatographic method varies substantially from sample to sample. For routine samples, accuracies of 1-5% are common. For analytes present at very low concentration levels, for samples with complex matrices, or for samples requiring significant processing before analysis, accuracy may be substantially poorer. In the analysis for trihalomethanes described in Method 12.1, for example, determinate errors as large as +25% are possible. ... 

The criteria for selection of laboratory reactors include equipment cost, ease of operation, ease of data analysis, accuracy, versatility, temperature uniformity, and controllabihty, suitability for mixed phases, and scale-up feasibility. 

Table 34-6 Individual sample analysis accuracy using Spiked Recovery study...

Blashfield, R. K. (1976). Mixture model tests of cluster analysis Accuracy of four agglomerative hierarchical methods. Psychological Bulletin, 83, 377-388. 

The accuracy of multiple dilutions fades as more and more dilutions are made because of the added errors of additional flow measurements. In the double dilution above, four flow measurements are needed, two for each dilution. Fortunately, however, multiple dilutions are used to produce low concentrations where perhaps analysis accuracy of 10% would be acceptable. 

In any form of analysis, accuracy and precision are required otherwise, the analytical data are suspect and cannot be used with any degree of certainly. This is especially true of analytical data used for commercial operations where the material is sold on the basis of purity. Being a complex material, one may wonder about the purity of coal, but in this sense the term purity refers to the occurrence (or lack thereof) of foreign constituents within the organic coal matrix. Such foreign constituents (impurities) are water, pyrite, and mineral matter. Therefore, at this point, it is advisable to note the differences inherent in the terms accuracy and precision. 

Figure 3.2 The effect of prolonged subcutaneous implantation on biosensor function. Blood glucose values shown in solid circles and glucose sensor values in the continuous lines. The early study (top panel), but not the late study (bottom), shows excellent sensor accuracy and minimal lag between blood glucose and sensed glucose values. MARD (mean absolute relative difference) refers to a sensor accuracy metric. EGA refers to the Clarke error grid analysis accuracy metric.

The XRF analysis accuracy depends on physical properties of the soil, such as particle size, moisture content, homogeneity, and surface conditions. Drying, grinding, and sieving soil prior to analysis reduce the effects of these physical interferences. 

For rapid analysis during the production process atomic absorption is mainly of indirect value because, due to the sequential character of the technique, it cannot be used for complete steel or slag analysis in a two to three minute period. The analytical requirements for the testing of rapid continuous production processes are fulfilled by the techniques of emission and X-ray spectrometry. These techniques are characterised by great speed, high precision and simultaneous multi-element analysis. Accuracy must, however, be constantly checked with a variety of special calibration samples. This requires the determination of the true concentrations of the calibration samples with chemical methods of solution analysis, whose precision is often only equal to or, when compared with X-ray spectrometry, frequently poorer. Chemical analysis is, however, the basis of all comparisons, and must be repeated frequently for the determination of the true concentrations. Atomic absorption, with its relatively good precision, has greatly simplified the analytical control of numerous elements. 

Developing an HPLC method requires a clear specification of the goals of the separation. The primary objective could be (1) resolution, detection and characterisation or quantitation of one or a few substances in a product, so that it is important to separate only a few sample components and complete separation of the sample is not necessary (2) complete resolution, characterisation and quantitation of all sample components (3) isolation of purified sample components for spectral identification or for other assays. Further points that should be considered include the required sensitivity (especially for trace analysis), accuracy, precision, character of sample matrices (which determines sample dissolution, extraction or pretreatment necessary for possible concentration of sample analytes or for removing interference), expected frequency of analyses and the HPLC equipment available. 

To further extend the analysis, accuracies were measured in terms of correlation coefficients and information independently based on protein structural classes in order to check if there are biases particuiar to specific chain folds. The results are shown in figures 1 and 2. 

Selection of the laboratory reactor type and size, and associated feed and product handling, control, and analytical schemes depends on the type of reaction, reaction time scales, and type of analytical methods required. The criteria for selection include equipment cost, ease of operation, ease of data analysis, accuracy, versatility, temperature uniformity, and controllability, suitability for mixed phases, and scale-up... 

An important part of a quality assurance plan includes the external validation of sweat analysis accuracy through participation in proficiency testing. The CAP offers a proficiency testing program consisting of six specimens per year. Participants receive feedback concerning their performance on these specimens relative to others in their peer group. 

These rapid and simple techniques (short column, centrifiigation, batch separation), with reusable supplies and equipment, are cost-effective and provide reasonable accuracy, provided that sources of variation are rigidly controlled. In final analysis, accuracy is to be preferred over rapidity and low cost. Glycosylated hemoglobin assays, in contrast to frequent or daily blood glucose determinations, are only required once every 4-12 weeks for diabetic control surveillance. 

Accuracy, measures the difference between the true value and the mean value obtained from repeated analysis. Accuracy is often calculated as percent recovery by the assay of known, added amounts of analyte to the sample. The ICH documents recommend that accuracy should be assessed using a minimum of nine determinations over a minimum of three concentration levels, covering a specific range. 

Lee Jones, A.O., Jacobs, R.M., Ranney, N.B. and Summers, E.L (1988). Commercial diagnostic hair analysis Accuracy or fantasy-a case study, Trace Element Anal. Chem. Med. Biol. Proc. Int. Workshop, 5th, 251-260. Ed. by Braetter, P. and Schramel, P.de Gruyter Berlin, FRG... 

Particle-induced XRF (PIXE) has many advantages over conventional XRF. Irradiations are performed in ion accelarators (Muminov and Haidarov, 1980). It ensures up to 100 times better detection limits and values of 0.1-1 mg/kg can be obtained even in routine analysis. Accuracy and precision normally lie in the 1-5% range. The proton beam can be focused to a extremely small spot (d I p.m) which permits microdistribution analysis of elements with Z = 25 80. In this interval lies the best sensitivity... 

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