Frequently, natural gas is used as primary feedstock for chemical processes. After purification and fractionation, syngas (a mixture of mainly H2 and CO) is produced from methane in a steam reformer. The syngas can then be used as the feedstock for subsequent processes to produce various commercially viable products such as methanol, ammonia, LPG, and other petrochemicals. Process gas analyzers are used to monitor the efficiency of the methane conversion by measuring the residual CH4. Further downstream low levels of impurities which remain after the syngas shift and purification processes must be monitored.