Patent ID: 8368896

Claim:
A method comprising: receiving a gas sample, the gas sample including sulfur dioxide, water, and sulfur trioxide; utilizing an optical source to generate an optical signal, the optical signal generated at a peak sulfur trioxide absorption frequency in which there is substantially no absorption of the optical signal by the sulfur dioxide present in the gas sample, the peak sulfur trioxide absorption frequency being a frequency in a range of frequencies from 1396.889 cm −1 to 1397.052 cm −1 inclusive; initiating transmission of the optical signal through the gas sample; measuring an amount of the optical signal absorbed by the sulfur trioxide in the gas sample at the peak sulfur trioxide absorption frequency; and based at least in part on the measured amount of the optical signal absorbed by the sulfur trioxide in the gas sample at the peak sulfur trioxide absorption frequency, generating a concentration value indicative of an amount of sulfur trioxide in the gas sample.