for a given analytical method, we have to find out the minimum detectable limit /Limit of Detection). below that value, we can say" not detected). i want to know, how to find a detection level (lower detection level)
(1)for example argentometric titration in determination of chloride
(2) total hardness determination (EDTA titration)
The approach based on Signal-to-Noise can only be applied to analytical procedures which exhibit baseline noise. In case of titration, you can approach based on the Standard Deviation of the response and the slope.
6.3 Based on the Standard Deviation of the Response and the Slope
The detection limit (DL) may be expressed as: DL = 3.3 σ /S
where σ = the standard deviation of the response
S = the slope of the calibration curve
The slope S may be estimated from the calibration curve of the analyte. The estimate of s may be carried out in a variety of ways, for example:
6.3.1 Based on the Standard Deviation of the Blank
Measurement of the magnitude of analytical background response is performed by analyzing an appropriate number of blank samples and calculating the standard deviation of these responses.
6.3.2 Based on the Calibration Curve
A specific calibration curve should be studied using samples containing an analyte in the range of DL. The residual standard deviation of a regression line or the standard deviation of y-intercepts of regression lines may be used as the standard deviation.
You can find out the above information in the ICH Guidelines Q2(R1).
Hi, in addition of the answer above I recommend you to check the newest regulation of USP 41: general information Validation of Compendial Procedures, and , Statistical tools for Procedure Validationm and Eurachem 2014, kind regards
https://www.eurachem.org/images/stories/Guides/pdf/MV_guide_2nd_ed_EN.pdf
Some papers will help you. they are atteched below, Have a nice day....
Perhaps I may also refer to “Quantifying Uncertainty in Analytical Measurement” 2nd Edition (2000), which can be downloaded free of charge from www.eurachem.org. Examples A2 and A3 describe in detail how to create an uncertainty budget for titrations. From the uncertainty budget it is easy to estimate the LOD if needed.
I hope this can help. This is an extract from the sources, pdf doc. given above. Methods for the determination of detection of limit. pp. 19. 'The detection limit for titrimetric procedures can be defined by the smallest amount of reagent that can be added during a titration to cause a chemical change. This is typically determined by the smallest size of the drop that can be produced on a particular buret or other titrating device. Drop size can be estimated by averaging the size of several (5 to 10 is a good number) repeated drops. The detection limit can then be calculated based on the titrant concentration, the sample size, and the minimum drop size. For example, laboratories using the titration method for ammonia determination are expected to achieve a detection limit of 1.0 mg/L.'
Limit of quantitation (LOQ) is defined as the minimum concentration of the analyte in the sample that produces quantitative measurements with acceptable precision and accuracy. LOQ is determined by titrating several sample series. Each series is titrated with a continuously reduced amount of sample. The relative standard deviation (RSD) of the precision of six repetitive injections is plotted against the analyte amount. The amount that corresponds to the below defined required precision is equal to the limit of quantitation. Recommendation The Limit of Quantitation is the smallest amount of substance in mmol, which can be titrated with a good precision, expressed as RSD ≤ 0.3%
The Limit of Detection (LOD) for a titrimetric method is a measure of the lowest concentration or amount of an analyte (substance being analyzed) that can be reliably detected but not necessarily quantified. Determining the LOD involves statistical analysis and is based on the standard deviation of blank measurements. Here's how you can calculate or find out the LOD for a titrimetric method:
Keep in mind that the LOD is the lowest concentration at which the analyte can be reliably detected but not necessarily quantified. If you want to determine the Limit of Quantification (LOQ), which is the lowest concentration that can be accurately quantified, it is typically set at a higher level, such as 10 times the standard deviation of the blanks (LOQ = 10 x SD).
The LOD is an important parameter in analytical chemistry and helps researchers and analysts understand the sensitivity and reliability of their analytical methods.
l This protocol list might provide further insights to address this issue.
Be careful with the term "analyte", which has several meanings!
Accred. Qual. Assur. 2 (1997) 204-205
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