Smallest detectable partial pressure ratio concentration

5 Smallest detectable partial pressure ratio (concentration) 

This definition, which is somewhat clumsy for practical use, is to be explained using the detection of argon36 in the air as the example Air contains 0.93 % argon by volume the relative isotope frequency of At q to ATjg is 99.6 % to 0.337 %. Thus the share of Argg in the air can be calculated as follows  

5 10 2 A/2.4 10 A = 1.875. The smallest detectable concentration is then derived from this by calculation to arrive at  

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