you can proceed as follows :

1. Take 'n' replicate Y measurements of your blank solution, calculate the mean YBAR and the std deviation s, compute YBAR + 3*(s/sqrt(n)), sqrt stands for square root of the argument.

2. From your regression line Y= m*X+c, calculate the X value corresponding to Y=YBAR + 3*(s/sqrt(n)), the corresponding X value is an estimate of the Limit of detection (LOD).

The response Y is not, in general, a linear function of concentration over the entire range, it is because the sensitivity (dY/dX) is a function of X, however, for a concentration range, small enough, you can approximate the actual response function Y by a low order polynomial, e.g a linear or quadratic functional forms, therefore, over a wide range of concentrations, it is advisable that the interval be subdivided into smaller intervals, and you can attempt to fit linear regression functions to data over the individual sub-intervals, the form of regression problem here can be handled much better, in a single framework, using the concept of " Dummy Regression ", you can look into this concept for more details.

a Standard text that covers this concept well is " Applied Regression Analysis " by Draper and Smith, you can also find details of Dummy regression method in the following online courses portal:

https://nptel.ac.in/courses/111104074/

Dear dr Gosh, can you please provide me with any article that support your comment? So that i can easily follow the exact procesure. Thanks in advance!

Title of book: Measurement, Statistics and Computation, ACOL series, Authors: David McCormick and Alan Roach, pages 508-513.

Thanks@ Debopam Ghosh

https://m.youtube.com/watch?v=L3WIEKDL7cc

LOD (limit of detection ) = 3.3(Standard deviation of intercept/slope)

LOQ (limit of quantification) = 10(Standard deviation of intercept/slope)

Standard deviation of intercept = Standard error of intercept *√n

n= Number of concentrations

Standard error of intercept = Calculate from regression ( Excel -> data analysis -> regression)

https://youtu.be/Ii2Z3hqwRGM

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/

dear Jayan Thermadom Rappai do you have an advice for calculation the LOQ and LOD without the slope? For my bradford assay I am using a x²-function instead of a linear calibration curve, so unfortunately I have no slope. Do you have any suggestion to calibrate those parameter for example with my Blank Value?