Patent ID: 8009293
Filing Date: 2011-08-30
Classification: G01N

Abstract:
1. A method of measuring a concentration of a first and a second compound in a sample composition comprising; a) providing at least first and second modulated light beams having first and second wavelengths, respectively, wherein the modulation of the second modulated light beam is phase shifted from the modulation of the first modulated light beam; b) passing the first and the second modulated light beams through a reference composition, wherein said reference composition comprises a reference concentration of the first and the second compound; c) detecting a reference signal resulting from the absorption of the first and second modulated light beams by the reference composition; d) adjusting the amplitude of the second modulated light beam such that no reference signal is detected; e) passing the first modulated light beam and the second modulated light beam through a sample composition; and f) detecting a sample signal so as to measure the concentration of the first and the second compound in the sample composition.