Detection limit and limit of quantitation
The 3 times signal-to-noise ratio is the detection limit, and the 10 times signal-to-noise ratio is the limit of quantitation. In addition, the detection limit indicates the lowest concentration at which the substance can be detected. The limit of quantitation indicates that the method accurately quantifies the lowest concentration of the substance.
Specifically:
Detection limit: The minimum or minimum amount of the component to be tested can be detected by the analytical method under the specified experimental conditions;
Quantification limit: The analytical method can quantitatively determine the lowest or lowest amount of the component to be tested in the sample.
The difference between the detection limit and the limit of quantitation is:
Detection limit:
The detection limit refers to the lowest concentration or content that the sample can be detected under the determined experimental conditions. It is a limit test performance indicator and does not need to be quantitatively determined, as long as it is indicated above or below the specified concentration.
Non-instrument analysis visual method:
The lowest concentration or amount that can be reliably detected is tested with a known concentration of the analyte.
Signal to noise ratio method:
It is used to analyze the baseline noise (instrument analysis method), compare the signal measured by the known low concentration sample with the signal measured by the blank sample, and calculate the lowest concentration or amount that can be reliably detected. Generally, the detection limit is determined by the corresponding concentration at the signal-to-noise ratio of 3:1 or 2:1 or the amount of the instrument injected. The standard deviation method can also be used: blank value = 0;
1 Set the background 10 times or more to find the standard deviation σ.
2 multiply σ by three times;
3 Find the concentration X corresponding to 3σ on the working curve, which is the detected value of the method; the blank value is not equal to 0;
The limit of quantitation:
1. Refers to the minimum amount of the sample in the sample that can be quantitatively determined. The result should have certain accuracy and precision requirements.
2. The common signal-to-noise ratio method is used to determine the limit of quantification. Generally, the corresponding concentration or the amount of instrument injected is determined by the signal-to-noise ratio (S/N) of 10:1. The standard deviation of the blank background response (SD) can also be measured by the instrument. The 10 times is the estimated value, and the actual lower limit of the method is determined by experiment.
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