Minimum detectable mass function

Consideration must be given to the quantity of sample needed for the minimum detection ]imits of the instrumental technique used. A number of techniques have been ranked in order of increasing amounts of material needed as follows mass spectroscopy (1 - 10 yg), chemical spot tests (1 - 100 yg), infrared and ultraviolet spectroscopy (10 - 200 yg), melting point (0.1 -1 mg), elemental analysis (0.5 - 5 mg), boiling point (1 - 10 mg), functional group analysis (1 - 20 mg), and nuclear magnetic resonance spectroscopy (1-25 mg). 

The most important detector specification is probably detector sensitivity as it not only defines the minimum concentration of solute that can be detected but also allows the overall mass sensitivity of the chromatographic system to be calculated. The detector sensitivity also places a limit on the maximum (k ) (capacity factor) at which a solute can be eluted from a chromatographic column. In order to calculate the mass sensitivity or the maximum (k ) value, the detector sensitivity must be available in concentration units, e.g. g/ml. Moreover, if all detector sensitivities were given in units of g/ml, then all detecting devices, functioning on quite different principles, could then be rationally compared. 

Next, determine the mass of sample that is required for detection limits of 0.05 pg/L based on GC/MS analysis of atrazine. Detection limits for a typical GC/MS are calculated as follows. The GC/MS has a detection limit of 100 pg when 2 pL of solvent are injected. The microvials for the GC/MS require 100 pL of solvent in order to function properly on the autosampler of the GC/MS therefore, the minimum mass of analyte required for a detection limit of 0.05 pg/L is given as ... 

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