The invention provides a system and a method of eliminating interference for impurities measurement in noble gases based on emission spectroscopy which provide very stable, sensitive and interference free results. The method mainly relies on the use of a combination of particularly designed means serially connected for cancelling interferences and proper means for correcting linearity issues. The proposed method is particularly advantageous since it offers long- term stability while providing very accurate and reliable results, even at sub-ppb and up to 10,000 ppm levels, whatever the surrounding conditions and the additional impurities that could be present in the gas under analysis.