A Compact Fluorescence Lifetime Instrument for In Situ Chemistry Measurements

Schuyler Senft-Grupp, Massachusetts Institute of Technology, Cambridge, MA, United States; California Institute of Technology, NASA Jet Propulsion Laboratory, Pasadena, CA, United States, Harry Hemond, Mass. Institute of Technology, Cambridge, MA, United States and Kelvin Chee-Loon Ng, Singapore-MIT Alliance for Research and Technology (SMART) Centre, CENSAM, Singapore, Singapore
Abstract:
A fluorescence lifetime instrument for in situ investigation of natural waters is developed. The instrument utilizes a pulsed laser at 266 nm to excite water samples, a monochromator and photomultiplier tube (PMT) for wavelength tunable photon detection, and a custom high speed (1 GHz) data acquisition board for signal storage and data reduction. Water samples are pumped through a custom flow cell that has been previously tested on board autonomous underwater vehicles (AUVs). The raw fluorescence data is processed with a nonnegative least-squares method to extract wavelength specific fluorescence lifetime estimates. Instrument performance is quantified with aqueous solutions of pyrene at environmentally relevant concentrations and determined to have a pyrene detection limit of 3 ng / l. The overall instrument size and power requirements meet the constraints of typical AUVs allowing for future integration and field deployment.
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