Photocatalytic CO2 reduction can produce CO, CH4, methanol, formate and higher hydrocarbons, often simultaneously and each in small quantity. When one run reports 12 micromoles of CO and the next reports 18, the difference is more often analytical than catalytic. Making the analysis trustworthy is the foundation of any meaningful catalyst comparison.
Calibrate with certified gas mixtures spanning the expected concentration range, not a single point. For each target product, build a multi-point curve under the same carrier flow and pressure as the experiment. Recalibrate after any change of column, detector or flow setting, and verify with an independent standard after calibration.
The reactor headspace is saturated with water vapor and rich in CO2. Both can bias detectors and columns. Use a moisture trap or heated lines as appropriate, and validate calibration in a matrix that mimics the real sample, for example CO2 saturated with water vapor, rather than dry calibration gas.
Carrier flow drift directly scales every calculated amount; regulate it or measure it. Dead volume between reactor and detector delays and dilutes peaks; keep lines short and swept. Sensor drift over long runs; bracket experiments with standard checks. Product cross-sensitivity, CO sensors responding to H2 and vice versa; confirm selectivity in mixed-gas tests.
Report products with units, detection limits, calibration dates and flow conditions. Distinguish clearly between detected products and products below detection limit, over-claiming product scope is a common review finding.
Perfectlight's online gas analysis systems are designed for multi-product CO2 reduction monitoring, and the photocatalysis solutions page describes complete evaluation setups.
