Chromatography Forum

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.....

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

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

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