The Vx multiphase technology’s in-line H2S measurement allows a continuous monitoring of the H2S content in well effluents without any need for physical sampling. This monitoring feature can be implemented in all existing multiphase flowmeters without adding any hardware or additional sensors, thus can be deployed in the existing pool of over 1,400 surface meters worldwide. The in-line H2S measurement capability continuously monitors the total H2S mass fraction in the flow, in addition to the conventional measurement of oil, gas, and water flow rates without any separation or sampling of fluids.