Editing Analytical chemistry (section)

== Standards ==
{{see also|Analytical quality control}}

=== Standard curve ===
[[File:Calibration curve.png|thumb|upright=1.2|A calibration curve plot showing [[Detection limit|limit of detection]] (LOD), [[Detection limit|limit of quantification]] (LOQ), dynamic range, and limit of [[linearity]] (LOL)]]
A general method for analysis of concentration involves the creation of a [[calibration curve]]. This allows for the determination of the amount of a chemical in a material by comparing the results of an unknown sample to those of a series of known standards. If the concentration of element or compound in a sample is too high for the detection range of the technique, it can simply be diluted in a pure solvent. If the amount in the sample is below an instrument's range of measurement, the method of addition can be used. In this method, a known quantity of the element or compound under study is added, and the difference between the concentration added and the concentration observed is the amount actually in the sample.

=== Internal standards ===
Sometimes an [[internal standard]] is added at a known concentration directly to an analytical sample to aid in quantitation. The amount of analyte present is then determined relative to the internal standard as a calibrant. An ideal internal standard is an isotopically enriched analyte which gives rise to the method of [[isotope dilution]].

=== Standard addition ===
The method of [[standard addition]] is used in instrumental analysis to determine the concentration of a substance ([[analyte]]) in an unknown sample by comparison to a set of samples of known concentration, similar to using a [[calibration curve]]. Standard addition can be applied to most analytical techniques and is used instead of a [[calibration curve]] to solve the [[matrix effect]] problem.