According to ICH:

DETECTION LIMIT: " LOD"

1)Based on Visual Evaluation:

2)Based on Signal-to-Noise

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

(A)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.

(B)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

Same thing is applicable for the LOQ but change in point 3)

Based on the Standard Deviation of the Response and the Slope

The quantitation limit (QL) may be expressed as:

QL =10* 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

same examples and for both

Recommended Data

The quantitation limit and the method used for determining the quantitation limit should be presented.

The limit should be subsequently validated by the analysis of a suitable number of samples known to be near or prepared at the quantitation limit.

and this is othentic document proceder as Per ICH-Q2(R1)

dear Harshad,

it is very difficult to find from signal to noise ratio, just prepare LOQ and LOD standerd which you want find, and inject in your system.

regards,

AmilA.

Dear Mr Paithankar:

You should prepare a standard with a concentration of 5 times your estimated LOD

Analyse it 10 times, and calculate the standard deviation on these reults : s

so you have: LOD = 3 * s and LOQ = 10* s

this is not so simple. There are three different ways of calculation of LODs and LOQs , depending on the blank result, and S/N ratio. further you can see:

Sanagi MM, Ling SL, Nasir Z, Hermawan D, Ibrahim WA, Abu Naim A. Comparison of signal-to-noise, blank determination, and linear regression methods for the estimation of detection and quantification limits for volatile organic compounds by gas chromatography. J AOAC Int. Nov-Dec;92(6):1833-8. 2009.

or other papers

As per ICH guideline if your developing an assay method; there is no need of practically find out the LOD and LOQ level. It can be directly calculated from calibration curve. If you are developing method for impurity profiling you have to prepare serial dilution of your standard solution and inject in decreasing order. after that calculate the s/n ration. For LOD it should be 3:1 and for LOQ it should be 10:1.

I forgot to tell you that confirm you true LOQ and LOD value with the help of ffive replicates and find out the %RSD which should more thane 2%.

According to ICH:

DETECTION LIMIT: " LOD"

1)Based on Visual Evaluation:

2)Based on Signal-to-Noise

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

(A)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.

(B)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

Same thing is applicable for the LOQ but change in point 3)

Based on the Standard Deviation of the Response and the Slope

The quantitation limit (QL) may be expressed as:

QL =10* 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

same examples and for both

Recommended Data

The quantitation limit and the method used for determining the quantitation limit should be presented.

The limit should be subsequently validated by the analysis of a suitable number of samples known to be near or prepared at the quantitation limit.

and this is othentic document proceder as Per ICH-Q2(R1)

Thank for the information above.

Hello everyone! I don't really understand.. If S/N(signal to noise)=2H/h (from Ph.Eur.) and LOD(e.g.) is S/N=3, then result that LOD is 2H/h=3 and therefore, LOD is 3/2, and is not 3 or 2, but LOD=1.5H/h and LOQ is 5(not 10)H/h. Am I right? or I misunderstood something.

"Most workers calculate S/N just as the ratio of the signal to the noise, so S/N = 367/66 = 5.56 in this example. However, The United States Pharmacopoeia (USP) and European Pharmacopoeia (EP) use a different calculation where only half of the noise band is considered. In their documentation, they call the signal H and the noise h, defining S/N = 2H/h. You can see that this reported value would give S/N = (2 x 367) / 66 = 11.1 in the present case, which is twice the intuitively defined ratio."

Look at this website:

http://www.sepscience.com/Information/Archive/HPLC-Solutions/3229-/HPLC-Solutions-124-How-to-Determine-Signal-to-Noise-Ratio-Part-3

The matrix may influence the LOD / LOQ ?. I do not know to use. Standard curve matrix of Negative samples or Standard curve without sample´s matrix?

The analyte in the standard curve is well exposed (plasmid), however the analyte in the sample (genome) is not.

We have developed a new approach to use metrology: it is a software platform able to organize the metrology in different application field, such as an analytical laboratory, etc. Specifically, it permits to organize the calibration of all laboratory instrumentations (e.g. scales, pipettes, thermometers, etc.) and the intermediate checks by the use of control charts, to elaborate data and estimate the uncertainty of measurement with the use of different approaches, to verify during the time the metrological characteristics of the test methods by means different tools that assure the quality. Moreover, the validation protocols of the methods for the measurements can be organized by the use of statistic tests to realize the same protocol, in accordance with the technical sectorial standard.

If you are interested in this software platform, please, contact me.

Here you can also find good information:

http://www.chem.utoronto.ca/coursenotes/analsci/stats/LimDetect.html

Follow all the above

i calculte the LOD and LOQ using standard deviation of response

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

Article Limit of detection and limit of quantification development p...

Just follow the ICH guidelines.

https://www.ich.org/fileadmin/Public_Web_Site/ICH_Products/Guidelines/Quality/Q2_R1/Step4/Q2_R1__Guideline.pdf

You can use it for validation of any analytical method :)