OR/18/042 Tryptophan-Like Fluorescence

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Ward, J, Lapworth, D, Sorensen, J, and Nowicki, S. 2018. Assessing microbiological contamination in groundwater sources: Field note on using Tryptophan-like Fluorescence (TLF) probes. Nottingham, UK, British geological Survey. (OR/18/042).

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[1]). 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[2], 2018a[3]). TLF data has been found to correlate with thermotolerant coliform (TTC) counts, which are used as an indicator of pathogens (Sorensen et al., 2018b[4], Nowicki et al., 2018[5]., Sorensen et al., 2016[6], Baker et al., 2015[7]).

Figure 2.1    Excitation-emission matrix (EEM) highlighting peaks and wavelength pairs used quantifying TLF and humic-like substances.


  1. 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
  2. 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
  3. 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
  4. 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
  5. 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
  6. 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.
  7. 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.