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A calibration curve plot showing limit of detection (LOD), limit of quantification (LOQ), dynamic range, and limit of linearity (LOL).. In analytical chemistry, a calibration curve, also known as a standard curve, is a general method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration. [1]
A calibration curve is obtained by measuring a series of standard solutions with known concentrations, which can be used to determine the concentration of an unknown sample using linear regression analysis. [10] For example, by comparing the absorbance values of a solution with an unknown concentration to a series of standard solutions with ...
The calibration curve that does not use the internal standard method ignores the uncertainty between measurements. The coefficient of determination (R 2 ) for this plot is 0.9985. In the calibration curve that uses the internal standard, the y-axis is the ratio of the nickel signal to the yttrium signal.
In comparison to the calibration curve method, the standard addition method has the advantage of the matrices of the unknown and standards being nearly identical. [1] This minimizes the potential bias arising from the matrix effect when determining the concentration.
Calibration curves are obtained by plotting measured isotope ratios in the prepared blends against the known ratio of the sample mass to the mass of the spike solution in each blend. Isotope dilution calibration plots sometimes show nonlinear relationships and in practice polynomial fitting is often performed to empirically describe such curves.
[3] [4] The most common approach for accounting for matrix effects is to build a calibration curve using standard samples with known analyte concentration and which try to approximate the matrix of the sample as much as possible. [2] This is especially important for solid samples where there is a strong matrix influence. [5]
A speciation calculation is one in which concentrations of all the species in an equilibrium system are calculated, knowing the analytical concentrations, T A, T B etc. of the reactants A, B etc. This means solving a set of nonlinear equations of mass-balance
The response factor can be expressed on a molar, volume or mass [1] basis. Where the true amount of sample and standard are equal: = where A is the signal (e.g. peak area) and the subscript i indicates the sample and the subscript st indicates the standard. [2]