US EPA

7415763 

Journal Article 

Drop coating deposition Raman (DCDR) for microcystin-LR identification and quantitation 

Halvorson, RA; Vikesland, PJ; , 

2011 

1 

Environmental Science & Technology
ISSN: 0013-936X
EISSN: 1520-5851 

AMER CHEMICAL SOC 

WASHINGTON 

45 

13 

5644-5651 

English 

21630655 

10.1021/es200255y 

WOS:000292075100028 

https://pubs.acs.org/doi/10.1021/es200255y
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A drop coating deposition Raman (DCDR) method was developed for the analysis of 2-200 ng samples of microcystin-LR (MC-LR), a ubiquitous and deadly hepatotoxin secreted by cyanobacteria. Solid phase extraction (SPE) of the toxin from a water sample enabled identification of MC-LR at 5 μg/L to 100 mg/L concentrations, and the collected results suggest lower detection limits can be readily attained following DCDR substrate modification. The DCDR process was applied to aqueous sample volumes of 0.5-20 μL that generated sample deposits from which MC-LR Raman spectra could be obtained within seconds. Larger volume samples were not required to improve spectral resolution. Volumes of 2 μL were ideal, producing "coffee-ring" MC-LR deposits that displayed distinct MC-LR Raman signals with high signal-to-noise within 1 s for a 200 ng sample and 300 s for a 2 ng sample. A linear correlation between Raman signal intensity and concentration was observed for 2-100 ng MC-LR samples after signal normalization. Reproducible MC-LR Raman spectra were collected from both fresh and aged samples. The presence of dissolved organic matter (DOM) did not preclude MC-LR identification in DCDR deposits of 3 μg of DOM mixed with 0.7 μg of MC-LR. Application of DCDR to environmental samples will require sample purification such as SPE before analysis, including critical cartridge wash and toxin rinsing steps. Raman based methods may one day facilitate simpler and faster sample throughput than traditional MC-LR detection methods. 

Aqueous samples; Detection methods; Dissolved organic matters; Drop coatings; Environmental sample; Hepatotoxins; Linear correlation; Lower detection limit; Microcystin-LR; Raman signal; Raman signal intensity; Signal normalization; Signal to noise; Solid-phase extraction; Substrate modifications; Water samples; Coatings; Deposits; Drops; Raman scattering; Raman spectroscopy; Signal detection; Tissue; Toxic materials; Extraction; microcystin LR; coating; concentration (composition); cyanobacterium; detection method; dissolved organic matter; identification method; linearity; peptide; Raman spectroscopy; signal-to-noise ratio; spectral resolution; toxin; volume; article; drop coating deposition Raman spectrometry; quantitative analysis; Raman spectrometry; signal noise ratio; solid phase extraction; Cyanobacteria; Microcystins; Molecular Structure; Rivers; Spectrum Analysis, Raman; Virginia; Water Pollutants; Cyanobacteria