Accuracy budget of amount-of-substance gaseous standards based on absorption spectroscopy

Spectroscopy has been proposed as a primary method for amount of gaseous substance. That implies the need to declare an accuracy budget where the bias effects are evaluated on the base of suitable a chemical-physical model and of the experimental conditions of the realized standard. In order to be competitive with the gravimetric standards the effects to be considered in defining the accuracy must be at the level of %. This paper describes a realistic model for amount of substances gaseous primary standards based on spectroscopy. On the basis of the results obtained measuring mole fraction of gas SF6 in nitrogen in the range 10-4mol/mol using frequency referred laser spectroscopy, an evaluation of the main systematic effects at the level of 10-4is presented and discussed.