Analytical performance criteria

In evaluation of the performance characteristics of a candidate method, precision, accuracy (trueness), analytical range, detection limit, and analytical specificity are of prime importance. The sections in this chapter on method evaluation and comparison contain a detailed outline of these concepts and their assessment. The estimated performance parameters for a method can then be related to quality goals that ensure acceptable medical use of the test results (see section on Analytical Goals), From a practical point of view, the ruggedness of the method in routine use is of importance. Reliable performance when used by different operators and with different batches of reagents over longer time periods is essential. 

When a new clinical analyzer is included in the overall evaluation process, various instrumental parameters also require evaluation, including pipetting precision, specimen- 

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The use of the sample compaction and secondary cathode sampling methodologies has certain positive attributes based on the initial sample form, analysis time constraints, and analytical performance criteria of a given application. A common shortcoming of both approaches is that a material other than the analytical specimen is subjected to the GD atomization/ionization processes, inflicting additional... 

Pubhshed literatare on measurements of DOC by HTCO has shown that, currently, the most commonly adopted standard material used for analytical accuracy is potassium hydrogen phthalate (KHP). A summary of analytical performance criteria for several HTCO systems using predominantly KHP is provided in Table 1. 

Lenters-Westra E, Slingerland RJ. Three of 7 Hemoglobin ale Point-of-Care Instruments Do not Meet Generally Accepted Analytical Performance Criteria. Clin. Chem. 2014 60 1062-72. 

Analytical techniques generally involve two areas. The first is the direct solution of the system differential equations in the Aime domain, usually by state variables. The second area is optimization of a specific performance criterion. The criteria for optimization by analytical techniques usually involve minimum response time or an integral time-cost function. 

If one or more analytical performance parameters fail to meet criteria the simplest way of estimating the deviation range to be used in daily practice is to construct a response window for the limit values of a criterion in a given variable range, as illustrated in Figure 8. 

Another aspect of cost reduction would be solvent economy. The need to preferentially select inexpensive solvents and employ the minimum amount of solvent per analysis would be the third performance criteria. Finally, to conserve sample and to have the capability of determining trace contaminants, the fourth criterion would be that the combination of column and detector should provide the maximum possible mass sensitivity and, thus, the minimum amount of sample. The performance criteria are summarized in Table 1. Certain operating limits are inherent in any analytical instrument and these limits will vary with the purpose for which the instrument was designed. For example, the preparative chromatograph will have very different operating characteristics from those of the analytical chromatograph. 

As another criterion of purity, the amino acid content of heparins should be determined. This is usually performed by ion-exchange88 or liquid89 chromatographic analysis of hydrolyzates. Reasonably pure heparin preparations contain < 1% of total amino acids, mostly L-serine and glycine. Heparin preparations should also be analyzed for residual solvents, and analytical (as well as biological) data be expressed on a dry basis. (Heparins equilibrated with atmospheric humidity contain up to 15%, or even more, of water.) Unless volatile materials are completely removed or accounted for, elemental analyses of heparin are meaningless. 

For each analyte in a round a criterion for the performance score may be set, against which the score obtained by a laboratory can be judged. A running... 

For each dmg substance, the maximum acceptable levels of the various impurities are described in the drug substance monograph or the specification included in the submissions to the regulatory authorities. In this chapter, the ICH Q6A [4] and Q6B [5] definition of specification is used. A specification consists of three parts the test (e.g. moisture content, impurities), references to the analytical procedure (e.g. high-performance liquid chromatography [HPLC], gas chromatography [GC]), and the acceptance criterion (e.g. not more than 0.50%). 

Analytical Methods and Identification of Asbestos Fibers In a general way, the identification of asbestos fibers can be performed through morphological examination, together with specific analytical methods to obtain the mineral composition and/or structure. Morphological characterization in itself usually does not constitute a reliable identification criterion. Hence, microscopic examination methods and other analytical approaches are usually combined,... 

Speed. For applications where a great number of analyses must be performed on a routine basis, speed is perhaps the most important criterion for a system. Analytical procedures which often take more time than the actual analysis itself include such sample pretreatment procedures as dissolution and digestion. If these pretreatment steps could be kept to a minimum, analysis time would be cut down considerably. Also, mimimum pretreatment reduces the chances of sample contamination by the reagents used, or the loss of volatile elements during pretreatment. Thus the ideal system would require no sample pretreatment at all real systems should strive for minimum sample pretreatment. 

Weyland et al. [560,561] used this method to optimize ternary mobile phase compositions for the separation of sulfonamides by RPLC. They fitted the retention surfaces to a quadratic model similar to eqn.(3.39), and also used a combination of a threshold resolution and minimum analysis time (min tm fl / vmin> 1.25 eqn.4.24) [560]. This criterion may yield a good optimum if the optimization is performed on the final analytical column (see table 4.11). 

First, the role of rubber modification in high rate impact is to suppress spallation by inducing the material to yield in the presence of dynamic tensile stresses arising from impact. Second, this yield-spall transition occurs at different strain rates for different rubber contents and may be predictable using quasistatic, low temperature tests of this type. These tests can also provide information concerning the basic nature of the yield process in these materials through the activation parameters which are obtained. Third, the Bauwens-Crowet equation seems to be a good model for the rate and temperature sensitive behavior of the American Cyanamid materials and is therefore a likely candidate for a yield criterion to use in the analytical code work on these materials which we hope to perform as a continuation of this work. 

Analytes A and B can be considered to be distinguishable on axes whemdy a,B)> 1, that is, the distance between the average ratios exceeds the sum of the standard deviations. For identification of multiple analytes it is not sufficient to consider the distance between each pair of analyte. It is also necessary to take into accoimt the position of the remaining analytes and define selection criteria. Figure 5 displays three criteria we have used to select axes (a) one analyte is best separated from all others, (b) best separation for each pair of analytes, and (c) all analytes are separated. The last criterion, of course, describes the ideal situation where one axis is sufficient to perform class identification on the selected set of analytes. 

The details of the assessment of stability data are under intense discussion within the scientific community. A majority of laboratories evaluate data with acceptance criteria relative to the nominal concentration of the spiked sample. The rationale for this is that it is not feasible to introduce more stringent criteria for stability evaluations than that of the assay acceptance criterion. Another common approach is to compare data against a baseline concentration (or day zero concentration) of a bulk preparation of stability samples established by repeated analysis, either during the accuracy and precision evaluations, or by other means. This evaluation then eliminates any systematic errors that may have occurred in the preparation of the stability samples. A more statistically acceptable method of stability data evaluations would be to use confidence intervals or perform trend analysis on the data [24]. In this case, when the observed concentration or response of the stability sample is beyond the lower confidence interval (as set a priori), the data indicate a lack of analyte stability under the conditions evaluated. 

A major factor affecting the quality of the final result is the suitability of the analytical method applied. Ensuring that the method is fit for purpose can be considered a basic quality control criterion. It is important that laboratories restrict their choice of methods to those that have been characterized as suitable for the matrix and analyte of interest, and at the level of interest. In the EU, and in many other countries and regions, the regulatory limit for authorized veterinary medicinal products is the maximum residue limit (MRL), and for contaminants the maximum permitted limit. Eor prohibited or unauthorized analytes, there is often a threshold or action limit set in Europe, for example, the appropriate regulatory limit is the minimum required performance limit (MRPL) or the reference point for action (RPA), as defined in Article 4 of Commission Decision 2002/657/EC, Article 2 of Commission Decision 2005/34/EC, and Articles 18 and 19 of Council Regulation (EEC) 470/2009.2 ... 

The detection limit indicates the performance of an instrument at low analyte concentrations. This indication may be used as a guide to instrument optimization, as a gauge of the suitability of an instrument for a particular application, or as a criterion for the interpretation of low concentration measurements. This paper concentrates on the latter use of detection limits and expands the discussion to include all aspects of statistical inference on low concentration measurements. In this case, the use of the detection limit is confined to the measurements in question and to the study at hand. The use of detection limits for instrument optimization and for suitability judgments requires a broader perspective that covers the various conditions under which the instrument might be used. 

This paper examines theoretically the continuous flow extraction by emulsion globules in which the transferring solute reacts with an internal reagent. The reversible reaction model is used to predict performance. These results are compared with advancing front calculations which assume an Irreversible reaction. A simple criterion which indicates the Importance of reaction reversibility on performance is described. Calculations show that assuming an irreversible reaction can lead to serious underdesign when low solute concentrations are required. For low solute concentrations an exact analytical solution to the reversible reaction problem is possible. For moderate solute concentrations, we have developed an easy parameter adjustment of the advancing front model which reasonably approximates expected extraction rates. 

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