Determination heavy metal using ICP-OES

When you say the linearity "didn't meet" can you give an example? Because the concentration levels of these heavy metals are low, you don't need to calibrate very high in concentration. Are you using the most sensitive wavelengths? Using adequate read time of at least 30 seconds? Tell us more about your method please.

I mean the graphic didn't linear, i used the 1st wavelength which recommend by software, and for read time i read the sample at 10 seconds, can you give me more advices about how to develop method for determination of heavy metals (esp. Pb, Cd, As, Hg, Sn) by using ICP-OES? thank you 

What are the concentrations of your calibration standards?

it's consist of 5,10,15,and 20 ppb for each element, but i didn't mix them, i read them separately 

OK, first you need to increase your read time to at least 30 seconds, preferably 60 seconds. At 10 seconds, you are probably not seeing a peak for the 5ppb standard, which is why your calibration is failing (not linear). How low are you trying measure? Turn on the Polyboost and read in the axial view only. For Pb, try using the Pb 182nm wavelength and 220nm. For As use 188 and 193nm.  For Hg use 184 and 194nm. For Sn, use 189 and 283nm. Cd is very sensitive at 214 and 226nm.   I

OK, first you need to increase your read time to at least 30 seconds, preferably 60 seconds. At 10 seconds, you are probably not seeing a peak for the 5ppb standard, which is why your calibration is failing (not linear). How low are you trying measure? Turn on the Polyboost and read in the axial view only. For Pb, try using the Pb 182nm wavelength and 220nm. For As use 188 and 193nm.  For Hg use 184 and 194nm. For Sn, use 189 and 283nm. Cd is very sensitive at 214 and 226nm.   I