Cyanobacterial blooms pose a dire threat to the drinking water treatment industry and their ability to produce microcystins and other cyanotoxins may cause fatal results to humans, livestock, pets, and aquatic living beings even at trace concentrations. Among those cyanotoxins Microcystin-LR(MC-LR) is one of the most toxic cyanotoxin. Surface Enhanced Raman spectroscopy (SERS) is considered as one of the most reliable, ultra-sensitive and cost-effective analytical tool. It has become a selective and label free technique for non-destructive molecular analysis through the amplification of electromagnetic fields and/or creation of charge transfer states between the chemisorbed species and SERS active platform. Metal nanoparticles (eg: -Au, Ag and Cu) have been commonly exploited as SERS active platforms. In this study the obtained Raman peaks for silver nanoparticles bounded MC-LR samples were boosted using MgSO₄as an enhancement reagent. In this study qualitative and semi quantitative determination of cyanotoxin microcystin-LR was carried out under various optimizations and the method was optimized by changing the matrix parameters. The best enhancement along with the MgSO₄ was given by the 1:4 Ag nanocolloid to MC-LR ratio. To perform a relatively better qualitative and semi quantitative experiment a calibration plot is expected to be developed under different aggregating agents. Concentrations of 0.001ppm (1ppb) level were sensed with this optimized technique. According to the results of UV analysis the obtained λ_max for synthesized stable Ag nanocolloid was 408nm. However, with further optimizations we believe that this method could serve as a useful technique in the ultra-low detection of MC-LR in various aquatic resources.

Figure 1: Raman spectra of 1ppb MC-LR (a) surface modified Ag nanocolloid by MC-LR, (b) surface modified Ag nanocolloid by MC-LR with MgSO<sub>4</sub>

Figure 1: Raman spectra of 1ppb MC-LR (a) surface modified Ag nanocolloid by MC-LR, (b) surface modified Ag nanocolloid by MC-LR with MgSO₄

Lakshan Silva

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