A flexible device to produce a gas stream with precisely controlled water vapour mixing ratio and isotope composition based on microdrop dispensing technology

Abstract. Here we describe a versatile device to produce a flow of air-vapour mixture with controlled humidity and water isotope composition based on microdrop dispensing technology. By precisely controlling the contribution of water from two dispenser heads into a carrier gas stream, the device allows to set the air-vapour stream to any isotope ratio between two end member waters. In addition to presenting the design and several performance characteristics of the new system, we describe two application examples. First, we utilize the device to determine a common artifact of vapour isotope analyzers, known as the mixing ratio – isotope ratio dependency. Second, we utilize the device to provide a constant background stream of humid air for fluid inclusion water isotope analysis in stalagmites. The observed flexibility and precision of the device underpints its usefulness and potential for a wide range of applications in atmospheric water vapour isotope measurement applications. Future improvements could focus on reducing the number of manual interventions and improved control at high flow rates.