Broadband cavity-enhanced absorption spectroscopy for real time, in situ spectral analysis of microfluidic droplets

Abstract

Broadband cavity-enhanced absorption spectroscopy has been used to record, in real time, the absorption spectrum of microlitre volume aqueous phase droplets within a microfluidic chip assembly. Using supercontinuum radiation and broadband coated external mirrors, the full visible spectrum (430 nm < λ < 700 nm) of each passing droplet is acquired in situ at high repetition rates (273 Hz/3.66 ms acquisition time) and high sensitivity (α_min < 10⁻² cm⁻¹). The possibilities for further improvements in sensitivity and acquisition rate using custom designed chips are discussed.