Development of a portable laser-induced fluorescence system used for in situ measurements of dissolved organic matter

A portable laser-induced fluorescence system (total weight about 1.7 kg) has been developed for detecting the level of dissolved organic matter in water. The portable system consists of a high pulse repetition frequency (10-kHz) microchip laser at 405 nm, a reflective fluorescent probe and a broadband micro spectrometer. The stability and sensitivity of the new instrument were studied. The detection limit of this new instrument was 0.75 ug/L, and its baseline drift was only 0.45% per hour. Field results showed that the portable system can work as well as commercial laboratory spectrophotometers. A significant correlation (R2=0.96) was found between measurements taken by the new instrument and thoses measured by laboratory spectrophotometer. In addtion, influence of temperature variation on measurements by the new instrument was investigated. The portable system is promising for monitoring dissolved organic matter in water, especially in the field.