Investigation of the molecular extraction process in single subpicoliter droplets using a near-infrared laser Raman trapping system

The near-infrared (NIR) laser Raman trapping system was applied to study li quid-liquid extraction in a single droplet in a subpicoliter range. The sys tem trapped a single subpicoliter toluene droplet in water using the NIR la ser beam and provided time-dependent optical images of the droplet during l iquid-liquid extraction. The size of the trapped droplet gradually increase d after p-nonylphenol solution was added in water. The Raman spectra of the droplet prove that the increase of the droplet size was caused by the abso rption of p-nonylphenol from the water. The distribution coefficient of p-n onylphenol in the subpicoliter droplet was much higher than that in bulk so lution.