Accurate determination of formaldehyde amount fraction in cylinders using mixtures of primary standards of formaldehyde in nitrogen prepared by a gravimetric permeation method

Abstract

A reliable method for the quantification of formaldehyde (HCHO) amount fractions is required, because the results of comparisons between individual techniques used for the quantification of HCHO amount fractions often disagree owing to unknown causes. One reliable method comprises the quantification of HCHO using working gas standards in which the HCHO amount fraction is linked to the International System of Units (SI). In this work, the SI traceability of HCHO amount fractions in mixtures of commercial HCHO in nitrogen in cylinders used as working gas standards was established by calibrating them against primary gas standard mixtures (mixtures of HCHO in N2), which were prepared by a permeation method and were traceable to SI. The expanded relative uncertainties (k = 2) of the amount fractions in the primary gas standard mixtures were less than 0.6 %. The quantitative values of the amount fractions in the working gas standards had relative expanded uncertainties (k = 2) of 0.7 %–0.9 %.