Microstructured coiled flow inverter (MCFI) as a helically coiled tubular device with 90 alternating bends provides enhanced radial mixing due to secondary flow (Dean vortices) in different planes. Liquid-liquid mass transfer characterization in MCFI revealed higher mass transfer rates compared to other capillary setups. However, the influence of Dean vortices and 90 bends on gas-liquid mass transfer has not been investigated and described yet. Different reactor setups, i.e. MCFI, straight capillary, helical coil, and bend reactor were fabricated from FEP tubes (ID = 1 mm). Gas-liquid mass transfer performance was investigated for a gas-liquid reaction system, i.e. cobalt (II) catalyzed air oxidation of sodium sulfite. Two-phase slug flow hydrodynamics and pressure drop were experimentally characterized, while the influence of operating and geometrical reactor parameters on conversion was investigated for reactor setups. MCFI offers up to 14% higher conversion in comparison to other capillary setups. Mixing within the liquid phase is enhanced by the formation of Dean vortices and additional direction change via 90 bends, which contribute to the internal diffusion in the liquid phase. (C) 2017 Elsevier Ltd. All rights reserved.