[Thoraxx]

I need help in determing my detection limit.  Here is what I have done.  I am using a Ion Chromatograph instrument to look for chloride and fluoride.  I am looking for them on contact material.  I have to report the results in ug/dm2.  SO what I ahve done is used a dm2 amount of material and contaminated it with my test subject.  Then I extracted the material in 300 mls of water and concentrated it down to 20 mls.  So my final amount of sample was 20 mls.

My calibration range was 1 ppm to 25 ppm for both chloride and fluoride.  So is my detection limit 20 ug/dm2 since I have 20 mls of sample?

[Demotivator]

In analytical spectroscopy, the instrument is calibrated with a high concentration standard and a blank. The blank is measured as a test solution 3 times. The detection limit is:
DL = 3*sqroot((s1^2 + s2^2 + s3^2)/3)
where s are the stabdard deviations of the three blank replicates.

Probably, ion chromatography is something similar.