I need to calculate LOD in Hg analysis of fish sample. My method is;
Blank: put 10 mL nitric in microwave vessels and run the program and volume up to 50 mL and read (result received in microgram/L)
Sample: take 1 g sample+10 mL nitric acid in microwave vessels, then run the program,
My equation is for LOD=mean+ 3*standard deviation
But I receive blank reading in microgram/L unit (See attached excel sheet), then how I calculate LOD? Can you give the example or correct my excel sheet
Here are some definitions that may help you out. This link explains LOD, LOQ, and MDL.
https://archive.epa.gov/pesticides/trac/web/pdf/trac3b012.pdf
You would need to assume that you are extracting a certain amount of fish (even though you are not adding). So if you want to express LOD in different units, say ug/g, you would use the amount specified in your method (say 1.0 gram fish).
If your calibration standards are in ug/L you would do this.
ug/L x (final volume L) which would give you ug, then you would divide by 1 gram to give ug/g.
1st line of your spreadsheet assuming 50 mL final volume:
2.24 ug/L x 0.050L = 0.112ug / 1g = 0.112 ug/g
You don't need to convert each measurement. Your machine LOD (µg/L) that you calculated in the spreadsheet can directly be converted to the method LOD (µg/g):
2.46µg/L x 0.050L / 1g = 0.123 ug/g
I have a new AAS instrument, so can you give an idea what I need to do to validate the method using AAS. such as LOD, LOQ, sensitivity etc. ?
@Henrik
You are correct, assuming each sample is exactly 1.00g, and the volume is 50 mL. Your calculation assumes that all 15 weight measurements are exactly 1 gram. The spreadsheet should have separate columns for the weight extracted and volume used of each sample.
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