Calculating LOD/LOQ (regression line)

[jdlh199]

I'm banging my head against a wall here trying to figure this out. I'm trying to calculate LOD/LOQ for an HPLC method using the "The residual standard deviation of the regression line" method. I have the following data:

Nominal Area Conc.
0.50 0.01285 0.515
1.00 0.02065 0.969
2.00 0.03845 2.005
5.00 0.09020 5.019
10.00 0.17560 9.992

Slope: 0.017173139
Intercept: 0.004009386
RSQ: 0.999973532

Whichever way I try and calculate LOD/LOQ, I end up with a number mid-curve. With this method the LOD/LOQ should be WAY below 0.5.

Can anybody do a step by step Excel formula on how to calculate LOD/LOQ with this data using the "residual standard deviation of the regression line" method.

Thanks in advance.....

[jdlh199]

OK, I resolved this myself...

If anybody else is interested in this, there are a couple of useful old articles in LCGC:

http://www.lcgceurope.com/lcgceurope/We ... tail/75778

http://www.lcgceurope.com/lcgceurope/da ... rticle.pdf

Now my LOD is 0.08

[yangz00g]

I am very interested in your calculation. Can you show me how to do it step by step? Thanks

[jdlh199]

If you follow the instructions in that first link you can create your own excel spreadsheet which does all the calculations for you. It's not really that difficult but there's a few typos in the article that require correcting.

Here's my version of the spreadsheet. I uploaded it to a file sharing site. Obviously I take no responsibility for the content or accuracy but I believe it is right. Download and use at your own risk!

http://www.savefile.com/files/1512089