Trace analysis of oil-in-water by using visible LED and metal waveguide capillary

Trace analysis of oil-in-water (O/W) has wide applications in life science, industry and environmental monitoring (such as oil spilling). In this paper, with the aid of surfactant, diesel was dispersed in water as O/W emulsion, which can be detected by using visible LED and metal-waveguide-capillary (MWC). Due to the enhancement of optical-path and related light-droplet interaction in MWC, detecting diesel of a concentration as low as 2.14 ng/ml was realized with a 7cm long MWC. The detection limit was improved 125 fold compared with that of commercial spectrophotometer with 1 cm-cuvette. The detecting system features compact, low cost and high sensitivity.