Monitoring nano-flow rate of water by atomic emission detection using helium radio-frequency plasma

Abstract

Recently, high-performance nano-scale flow pumping systems have been developed for micro and miniaturized analysis systems. A novel device capable of measuring and monitoring nanoliter scale flow rates has been required for the further development of the pumping system. In this study, an atomic emission detector using helium radio-frequency plasma (RFP-AED) was used for the measurement of the nanoliter scale flow rate of water by quantitatively detecting the emission from hydrogen in the water molecules. Monitoring nano-flow rates of water in the range up to 1.0 µl min⁻¹, and the change in the flow rate by the indication of the ratio of the emissions of H (656.3 nm) and He (667.8 nm) were successful. At present, the lowest flow rate that could be determined reproducibly was 4 nl min⁻¹ calculated as five times the standard deviation of the background noise. Additionally, similar evaluations for the deviation of each flow rate by using the RFP-AED and a flow-injection system were produced.