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Using fluorescence to measure water quality parameters is an established approach; dissolved organic matter (DOM), chlorophyll and algal biomass can all be detected in this way (Envirotech Online, 2017<ref name="Envirotech Online 2017">Envirotech Online (2017). The Use of Tryptophan-like Fluorescence as an Indicator of Organic Pollution — Dec 03 2013 — Keiran Khamis and Rob Stevens — Environmental Science News Articles — Envirotech Online. Retrieved July 19, 2017, from https://www.envirotech-online.com/article/water-wastewater/9/rs-hydro/the-use-of-tryptophan-like-fluorescence-as-an-indicator-of-organic-pollution/1530</ref>). A fluorimeter works by emitting light at a specified wavelength and detecting light emitted at a different wavelength from a target molecule or groups of molecules of similar chemical composition.

Tryptophan is an amino acid associated with cellular activity but is also associated with extracellular material and fluoresces at low excitation and emission wavelengths. TLF sensors target the approximate excitation-emission wavelength pair Ex280 nm/Em350 nm, where the TLF signal is greatest. A range of TLF probes/sensors are available on the market, but all aim to quantify the presence and intensity of fluorescence in the TLF region.

Recently, this technology has been applied to groundwater and early studies show that TLF has the potential to become a rapid screening tool for assessing levels of faecal contamination (Sorensen et al., 2015<ref name="Sorensen 2015">Sorensen, J P R, Lapworth, D J, Marchant, B P, Nkhuwa, D C W, Pedley, S, Stuart, M E, and Chibesa, M. 2015. In-situ tryptophan-like fluorescence: A real-time indicator of faecal contamination in drinking water supplies. ''Water Research'', 81, 38–46. http://doi.org/10.1016/j.watres.2015.05.035 </ref>, 2018a<ref name="Sorensen 2018a">Sorensen, J P R, Baker, A, Cumberland, S A, Lapworth, D J, MacDonald, A M, Pedley, S, Taylor, R G, and Ward, J S T. 2018a. Real-time detection of faecally contaminated drinking water with tryptophan-like fluorescence: defining threshold values. ''Science of the Total Environment'', 622, 1250–1257. https://doi.org/10.1016/j.scitotenv.2017.11.162 </ref>). TLF data has been found to correlate with thermotolerant coliform (TTC) counts, which are used as an indicator of pathogens (Sorensen et al., 2018b<ref name="Sorensen 2018b">Sorensen, J P R, Vivanco, A, Ascott, M J, Gooddy, D C, Lapworth, D J, Read, D S, Rushworth, C M, Bucknall, J, Herbert, K, Karapanos, I, Gumm, L P, and Taylor, R G. 2018b. Online fluorescence spectroscopy for the real-time evaluation of the microbial quality of drinking water. ''Water Research'', 137, 301–309. https://doi.org/10.1016/j.watres.2018.03.001 </ref>, Nowicki et al., 2018<ref name="Nowicki 2018">Nowicki, S, Lapworth, D J, Ward, J S T, Thompson, P, and Charles, K. 2018. Tryptophan-like fluorescence as a measure of microbial contamination risk in groundwater. ''Science of the Total Environment'', 646, 782–791. https://doi.org/10.1016/j.scitotenv.2018.07.274 </ref>., Sorensen et al., 2016<ref name="Sorensen 2016">Sorensen, J P R, Sadhu, A, Sampath, G, Sugden, S, Gupta, S D, Lapworth, D J, Marchant, B P, and Pedley, S. 2016. Are sanitation interventions a threat to drinking water supplies in rural India? An application of tryptophan-like fluorescence. ''Water Research'', 88, pp.923–932. </ref>, Baker et al., 2015<ref name="Baker 2015">Baker, A, Cumberland, S A, Bradley, C, Buckley, C, and Bridgeman, J. 2015. To what extent can portable fluorescence spectroscopy be used in the real-time assessment of microbial water quality?. ''Science of the Total Environment'', 532, pp.14–19.</ref>).

[[Image:OR18042fig2.1.jpg|thumb|center|400px| '''Figure 2.1'''    Excitation-emission matrix (EEM) highlighting peaks and wavelength pairs used quantifying TLF and humic-like substances. ]]

==References==

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[[Category:OR/18/042 Assessing microbiological contamination in groundwater sources: Field note on using Tryptophan-like Fluorescence (TLF) probes | 03]]

OR/18/042 Tryptophan-Like Fluorescence - Revision history

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Ajhil at 16:00, 13 February 2019