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In analytical chemistry, the detection limit, lower limit of detection, also termed LOD for limit of detection or analytical sensitivity (not to be confused with statistical sensitivity), is the lowest quantity of a substance that can be distinguished from the absence of that substance (a blank value) with a stated confidence level (generally 99%).
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]
Validation of analytical procedures is imperative in demonstrating that a drug substance is suitable for a particular purpose. [5] Common validation characteristics include: accuracy, precision (repeatability and intermediate precision), specificity, detection limit, quantitation limit, linearity, range, and robustness.
Typical amplitudes of these pulses range between 10 and 50 mV, whereas pulse duration is 20 to 50 ms. The difference between both current values is the analytical signal. This technique results in a 100 to 1000-fold improvement of the detection limit, because the capacitive component is effectively subtracted.
In selective ion monitoring (SIM) certain ion fragments are entered into the instrument method and only those mass fragments are detected by the mass spectrometer. The advantages of SIM are that the detection limit is lower since the instrument is only looking at a small number of fragments (e.g. three fragments) during each scan.
An example of a Levey–Jennings chart with upper and lower limits of one and two times the standard deviation. A Levey–Jennings chart is a graph that quality control data is plotted on to give a visual indication whether a laboratory test is working well. The distance from the mean is measured in standard deviations.
Detection limits for most trace elements are between 10 12 and 10 16 atoms per cubic centimetre, [12] depending on the type of instrumentation used, the primary ion beam used and the analytical area, and other factors. Samples as small as individual pollen grains and microfossils can yield results by this technique.
[28] [29] An example of this technique has been employed for sensitive detection of environmental contaminants in near real-time. [ 30 ] Standard equilibrium affinity analysis