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It is the lowest concentration of analyte in a sample that can be detected but not necessarily quantified.The limit of quantitation is the minimum injected amount that gives precise measurements, in chromatography typically requiring peak heights to times higher than baseline noise.Several approaches for determining detection and quantitation limit are possible, depending on whether the procedure is a noninstrumental or instrumental.In chromatography the LOD is the injected amount that results in a peak with a height at least twice or three times as high as the baseline noise level.This approach can only be applied to analytical procedures that exhibit baseline noise.Determination of the signaltonoise ratio is performed by comparing measured signals from samples with known low concentrations of analyte with those of blank samples and by establishing the minimum concentration at which the analyte can be reliably quantified.The range is normally expressed in the same units as the test results obtained by the analytical method.For the determination of a methods robustness a number of chromatographic parameters, for example, flow rate, column temperature, injection volume, detection wavelength or mobile phase composition are varied within a realistic range and the quantitative influence of the variables is determined.If the influence of the parameter is within a previously specified tolerance, the parameter is said to be within the methods robustness range.Obtaining data on these effects will allow to judge whether a method needs to be revalidated when one or more of parameters are changed, for example to compensate for column performance over time.In the ICH document it is recommended   to consider the evaluation a methods robustness during the development phase, but it is not required to be included as part of a registration application.More steps in analysis introduce errors to some degree.Simple methods are needed for the adoption by small laboratories of limited.The term specific generally refers to a method that produces a <a href="http://www.targetmol.com/compound/Sotalol-hydrochloride">sell Sotalol hydrochloride</a> response for a single analyte only while the term selective refers to a method which provides responses for a number of chemical entities that may or may not be distinguished from each other.If the response is distinguished from all other responses, the method is said to be selective.Since there are very few methods that respond to only one analyte, the term selectivity is usually more appropriate.The USP monograph defines selectivity of an analytical method as its ability to measure accurately an analyte in the presence of interference, such as synthetic precursors, excipients, enantiomers and known degradation products that may be expected to be present in the sample matrix.Selectivity in liquid chromatography is obtained by choosing optimal columns and setting chromatographic conditions, such as mobile phase composition, pH, column temperature and detector wavelength.It is a difficult task in chromatography to ascertain whether the peaks within a sample chromatogram are pure or consist of more than one compound.The true value for accuracy assessment can be obtained in several ways.One alternative is to compare results of the method with results from an established reference method.This approach assumes that the uncertainty of the reference method is known.

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