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In Situ Detection of Tryptophan Using Turner Designs' Submersible Fluorometers

Tryptophan is an amino acid dissolved in water that has a specific excitation and emission.  It is classified as protein-like organic matter and sources may include water systems with high biological activity and wastewater or industrial discharge.  Tryptophan is yet another parameter researchers can measure to track wastewater effluent, which may greatly impact habitats and wildlife. 

Many of the instruments available for measuring fluorescence of Tryptophan are cumbersome, complex, expensive, and require a high degree of training and expertise to operate.  These instruments may also provide too much information to end users who are looking for a simple measure of fluorescence response from, and relative changes of, Tryptophan in water.       

Turner Designs’ Cyclops Fluorometers are simple, low-cost, analog output fluorometers that provide a 0-5 volt signal proportional to the fluorescence response of a certain fluorophore in water.  These fluorometers are designed to be integrated with almost any data logger currently on the market.  They are small, lightweight instruments that can be handcarried to multiple locations or moored in a fixed location to be used for in situ fluorescence measurements.  Turner Designs now has optics for Cyclops-7 as well as C3 Submersible Fluorometers capable of detecting Tryptophan concentrations as low as 3 ppb.  The figure below shows a typical response curve for varying Tryptophan concentrations in water.  

Tryptophan-Curve

The calculated maximum for this detection range is 1300 ppb.  However, the fluorometers have the capability to detect beyond this calculated maximum by two orders of magnitude because they utilize three gains to provide users with a broad range of detection.  Because Tryptophan has a saturation point, the overall maximum detection limit is ~20,000 ppb.   

In a recent study, Synchronous Fluorescence Spectroscopy (SFS) was used to detect low levels of Tryptophan in water (Reynolds 2003). Concentrations ranged from  1.7 – 7.0 ppb with 1.7 ppb being the lowest concentration detected in drinking water.  With a limit of detection of 3 ppb Turner Designs' Tryptophan Fluorometers enable users to detect Tryptophan within the stated low level range of Tryptophan in water for the purpose of identifying the presence/absence of protein-like organic matter that may indicate wastewater discharge in the water system under study.