Devsharan Verma

How to calculate Limit of Detection (LOD)

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For LOD

According to ICH guidelines, several approaches for determining LOD are possible, depending on whether the procedure is non-instrumental or instrumental. These approaches include:

1. Based on Visual Evaluation

The visual evaluation may be used for non-instrumental methods but may also be used with instrumental methods. The detection limit is determined by the analysis of samples with known concentrations of analyte and by establishing the minimum level at which the analyte can be reliably detected.

2. Based on Signal-to-Noise

This approach can only be applied to analytical procedures which exhibit baseline noise. Determination of the signal-to-noise ratio is performed by comparing measured signals from samples with known low concentrations of analyte with those of blank samples and establishing the minimum concentration at which the analyte can be reliably detected. A signal-to-noise ratio between 3 or 2:1 is generally considered acceptable for estimating the detection limit.

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 σ may be carried out in a variety of ways, for example:

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.

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.

4. Recommended Data

The detection limit and the method used for determining the detection limit should be presented. If DL is determined based on visual evaluation or based on signal to noise ratio, the presentation of the relevant chromatograms is considered acceptable for justification.

Popular Answers (1)

CSIR - Institute of Himalayan Bioresource Technology

LOD=3.3 x standard deviation of the regression line () /Slope(S)

All Answers (37)

Hankuk University of Foreign Studies

CSIR - Institute of Himalayan Bioresource Technology

LOD=3.3 x standard deviation of the regression line () /Slope(S)

CSIR - Institute of Himalayan Bioresource Technology

LOD=3.33 x standard deviation of the regression line () /Slope(S)

South China Agricultural University

maybe is ok, 3 times of singal to noise in chromatography

University of Al-Qadisiyah

By running the instrument with lowest conc. and highest conc. of standared that will give you the minimum of conc. can be detecting and maximum of conc. can be detecting

Indian Institute of Integrative Medicine

LOD is one of the parameter of validation of any analytical method. Its mean you can detect but can not calculate exact value. LOD is 3 times of noise of the detector, when only mobile phase is running.

Aurigene Discovery Technologies

LOD and LOQ are the parameters in analytical method validation . LOD is three times lesser than LOQ(LIMIT OF QUANTITATION).Signal to noise ratio should be greater than 3 and less than 10.

iThemba Labs - Laboratory for Accelerator Based Science

the blank signal (yB) plus three standard deviations of the blank (sB), LOD = yB + 3sB

Savitribai Phule Pune University

Dear Verma,

see the ICH guidelines for this .....detailed explanation is given their.....if you can't get......let me know

Sidi Mohamed Ben Abdellah University

Beijing University of Chemical Technology

Dear all, I did a calorimetric sensing study in which calibriation is ploted between abs and concentration of some mercury metal ion(uM). I need to find LOD of my method. Now in this case i can get the formula LOD=3.3 x standard deviation of the regression line /Slope(S) from regression line. However i dont understand for the 2 nd formula of LOD= (3(STd of blank/slope) . In calorimetric sensing what would be the blank (uv spectroscopy), the inital abs of sensor ?? or some thing else? please comment.

University of Saskatchewan

While there are standard formula's for LOD in my opinion it depends very much on the method of analysis and how the investigator wished to express his confidence in the result. I use a range of approaches depending on the instrument and analysis used - but always the LOD has to ultimately reflect my level of confidence in the result.

According to IUPAC defination, in atomic spectrometry LOD is 3 times the standard deviation of blank absorbance signal divided by slope of the regression equation, where we get the LOD with unit.

GITAM University,hyderabad

Please see this vedio to caliculate LOD and LOQ

Indian Pharmacopoeia Commission Ministry of Health and Family Welfare Government of India Raj Nagar Ghaziabad

Vietnam National University, Hanoi

How to explain the meaning of the coefficient 3.3 in equation LOQ = LOD*3.33? thanks!

University of California, San Diego

Dear Valerie please go through this link, Theodorsson very well explained about 3.3 and 1.65 numerical value which is commonly used for LOD calculation.

I recommend this article:

MRM College of Pharmacy, Hyderabad

Narayana Dental College and Hospital

For chromatography a test sample with the analyte at the level at which detection is required or determined is chromatographed over a period of time equivalent to 20 times the peak width at half-height. The signal-to-noise ratio is calculated from Equation

Methods for the determination of limit of detection and limit of ...

Narayana Dental College and Hospital

Al-Qasim Green University

Université Kasdi Merbah Ouargla

to prepare known dilute concentration and go through the detector

The University of Edinburgh

Yes, the above mentioned methods are widely used in LOD etc calculation. I have but one doubt. Since slope is in denominator, its understandable that less slope means less sensitivity because of low resolution (High LOD). But I don't understand why the absolute value of blank should affect the LOD. I mean Sb or standard deviation of blank is a function of blank response. If response for blank is, say, 30 mAmps for one method and 100 mAmps for another method then why should second method be less sensitive? (Say deviation is same in both cases, like, 5% of the values 30 and 100 respectively)

CE.RI.COL Colorobbia Research Centre

Please consider the fact that a high blank signal generally results in less slope of your calibration curve, thus generating less sensitivity and a higher LOD.

Institute of Engineering & Management

Important discussions for good question.

The LOD was calculated as𝐿𝑂𝐷=10(𝑌+3𝑆𝐷)―𝐴/𝐵

Y= Y blank + 3SD

what are the basis for this equation to calculate the LOD.@richa sharama@ Robin Joshi @ Riccardo Rapini @all

Detection limits LOD, LOQ can be calculated using following equation (as per ICH Q2 guide lines) DL = 3.3 * Sigma/ Slope. , and LOQ = 10* Sigma/ slope, Where Sigma is Residual of standard deviation of regression or STD deviation of y intercept. Sigma can be calculated by following Microsoft office Excel functions 1.Regression 2.Formula ""STYEX"" - 3.Array Function "" LINEST"" - For tutorial of the use of above functions are watch the youtube video.. https://youtu.be/Ii2Z3hqwRGM/

LOD's may be calculated based on the standard deviation of the response (Sy) of the curve and the slope of the calibration curve (S) at levels approximating the LOD according to the formula: LOD = 3.3(Sy/S). The standard deviation of the response can be determined based on the standard deviation of y-intercepts of regression lines. Note: the slope and S can be obtained with one order of magnitude of calibration curve.

I often use Kalman method and CLS method with full spectra for simultaneous determination substances in mixtures. So I can not use calibration curve to find LOD, LOQ. In this case, how can I find the way to know LOD, LOQ value?

SRM Institute of Science and Technology

wat is the difference between LOD and resolution. both formula is similar

The following formula for the calculation of LOD might be helpful,

LOD = t (n-1,1-∝= 0.99)(S)

where: t (n-1, ∝-1= 0.99)= the students' t value appropriate for a 99% confidence level (one tail) and a standard deviation estimate with n-1 degrees of freedom (n= number of replicates). T-distribution table may help to find the degree of freedom value at different confidence levels.

S = standard deviation of the replicate analyses.

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