Range of an analytical

The range of an analytical procedure is the interval between the upper and lower concentration (amounts) of analyte in the sample (including these concentrations) for which it has been demonstrated that the analytical procedure has a suitable level of precision, accuracy and linearity. 

According to USP 28 [1], the range of an analytical method can be defined as the interval between upper and lower levels (in the Pharmaceutical Industry usually a range from 80 to 120% of the target concentrations tested) of the analyte that have been demonstrated to be determined with a acceptable level of precision, accuracy, and linearity. Routine analyses should be conducted in this permitted range. For pharmacokinetic measurements, a wide range should be tested, where the maximum value exceeds the highest expected body fluid concentration, and the minimum value is the QL. 

Before a calibration is started, the lowest and highest concentration, i.e., the concentration range of interest, must be defined. Then the method must be validated over the entire range. The range of an analytical method is the interval between the upper and... 

The working range of an analytical method is the interval between the upper and lower concentrations of the analyte in the sample for which it has been demonstrated that the method has acceptable precision, accuracy and linearity. This interval is normally derived from linearity studies and depends on the intended application of the method. However, validating over a range wider than actually needed provides confidence that the routine standard levels are well removed from nonlinear response concentrations, and allows quantitation of crude samples in support of process development. The range is normally expressed in the same units as the test results obtained by the analytical method. 

The linear range of an analytical method is the analyte concentration range over which response is proportional to concentration. A related quantity defined in Figure 4-12 is dynamic range—the concentration range over which there is a measurable response to analyte, even if the response is not linear. 

The range of an analytical method is the interval between the upper... 

In geochemical analysis the concentration range of an analyte often spans several orders of magnitude, and dilutions are frequently required to bring the sample solution within the calibration range. An automatic variable-ratio diluter is essential for this purpose. Many manufacturers produce suitable models, but corrosion problems are almost inevitable with the acidic solutions which are regularly used. Small amounts of acid can escape between the piston and the barrel, and cause corrosion, especially where metal parts are enclosed. 

The situation is equally ambiguous when discussing the concentration ranges measured. Four terms are commonly used to describe the concentration range of an analyte measured in a sample ... 

The limits of quantification of an analytical procedure are the lowest and largest amounts of the targeted substance in the sample that can be quantitatively determined under the prescribed experimental conditions with well-established measurement error (analytical bias and precision). Consequently, the dynamic range of an analytical procedure is the range between the lower and the upper limits of quantification within which a measured result is expected to have acceptable levels of bias and precision. 

The working range of an analytical method denotes the range between the lower and upper concentration, for which accurate determinations are feasible. 

A linear relationship must be demmistrated across the range of an analytical procedure. Where a 10 % deviation from linearity occurs will be the upper limit of the calibrated range of the technique. In general, five cmicentratiiHis over a relevant range are required. Mathematical transformation of data may be useful. Ideally the range of the method should cover 70-130 % of label claim, to allow for variation within the product to still be measured accurately. 

Figure 1-13 illustrates the definition of the dynamic range of an analytical method, which extends from the lowest concentration at which quantitative measurements can be made (limit of quantitation, or LOO) to the concentration at which the calibration curve departs from linearity by a specified amount (limit of linearity, or LOL). Usually, a deviation of SSI. from linearity is considered the upper limit. Deviations from linearity are common at high concentrations because of nonideal detector responses or chemical effects. The lower limit of quantitative measurements is generally taken to be equal to ton times the standard deviation of repetitive measurements on a blank, or 10j . At this point, the relative standard deviation is about 3(1% and decreases rapidly as concentrations become larger. 

FIGURE 1-13 Useful range of an analytical method. LOQ = limit of quantitative measurement LOL = limit of linear... 

The range of an analytical method is the (inclusive) interval between the upper and lower levels of analyte that have been demonstrated to be determined with precision, accuracy, and linearity using the method. 

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