Raman Spectroscopy for Monitoring of Microcystins in Water

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Virginia Tech


Cyanobacterial blooms are of great concern to the drinking water treatment industry due to their capacity to produce microcystins and other cyanotoxins that are deadly to humans, livestock, pets, and aquatic life at low doses. Unfortunately, the strategies currently employed for cyanotoxin detection involve laborious analyses requiring significant expertise or bioassay kits that are subject to numerous false positives and negatives. These methods are incapable of providing rapid, inexpensive, and robust information to differentiate between the >80 cyanotoxin variants potentially present in an aqueous sample.

The use of Raman spectroscopy for identification and quantification of the ubiquitous cyanotoxin microcystin-LR (MC-LR) was examined. Raman spectra readily reflect minute changes in molecular structure, spectra can be collected through water or glass, portable Raman spectrometers are increasingly available, and through surface enhanced Raman spectroscopy (SERS) it is possible to achieve femto or picomolar detection limits for a variety of target species. Drop coating deposition Raman (DCDR) was successfully implemented for quantitation of 2-100 ng of MC-LR deposited in 2 ?L of aqueous sample, even without the use of a specifically designed DCDR substrate or Raman signal enhancements. Reproducible MC-LR Raman spectra were observed for both fresh and aged DCDR samples, and the MC-LR Raman spectrum remained identifiable through a matrix of >80% DOM by mass. DCDR methods show tremendous potential for the rapid, simple, and economical detection of cyanotoxins in environmental matricies at environmentally relevant concentrations.



Raman Spectroscopy, microcystin-LR, detection, cyanotoxin, Water, SERS, DCDR