Materials in Colorimetric Detection of Water Pollutants

Estuaries are coastal wetlands that deserve special attention because they are vulnerable, biodiversity- and service-rich environments. However, estuaries of tropical areas have been scarcely studied regarding water quality and biodiversity in spite of strong developments of their agricultural and livestock sectors. Two estuaries on the Pacific Nicaragua in which snapper cages had been set up were studied regarding water physicochemical properties, microalgae and cyanobacteria along with their dynamics over a hydrological year. Both environments showed excellent water quality (oligotrophy and absence of harmful organisms) arising from their fluvial features. During the rainy season, there was a decline in chemical compounds and microorganisms. In the dry period nutrients and salinity promoted different assemblages of microscopic primary producers that were never too dense. Nutrient inputs from shrimp farms, agricultural crops and snapper cages did not appear to increase eutrophication and cyanobacterial blooms did not occur. Furthermore, the strong fluvial character of these estuaries seems to prevent the entry of harmful dinoflagellates from marine areas.

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“…To obtain the nitrate, ammonium and orthophosphate concentration, the reagents from the MQuantTM test strips kit (Merck [35,36]) were used.…”

Section: Obtaining Variables In Situ Sampling and Analysismentioning

confidence: 99%

The River Influence Controls Water Quality and Spatio-Temporal Microalgal Distribution in Pacific Estuaries (Padre Ramos and Salinas Grandes) of Nicaragua

Rojo

Lumbi

Aguilar

et al. 2021

Water

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“…Conversely, these “instrument-free” colorimetric sensors cannot fully meet the criteria of adequate accuracy and sensitivity, which is different from spectroscopic and chromatographic techniques (because the high background noise and the subjectivity of color perception from naked-eye observation). To address these issues, colorimetric sensors are generally coupled with digital imaging techniques [ 8 , 9 ].…”

Section: Introductionmentioning

confidence: 99%

Silver Nanoparticle-Based Sensor for the Selective Detection of Nickel Ions

et al. 2021

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Silver nanoparticles (AgNPs) can be used as a surface plasmon resonance (SPR) colorimetric sensor; the correlation between the SPR phenomenon and the aggregation state of nanoparticle allows the real-time detection of a target molecule. Surface functionalization of NPs with proper molecular baits is often performed to establish the selectivity of the sensor. This work reports on the synthesis of AgNPs under reducing conditions and on the functionalization thereof with mercaptoundecanoic acid (11-MUA). UV-VIS Spectroscopy confirmed the formation of AgNPs, eliciting a surface plasmon absorption band (SPAB) at 393 nm that shifted to 417 nm upon surface coating. Dynamic light scattering was used to investigate the surface coatings; moreover, pelleted AgNPs@11MUA nanoparticles were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analyzers (EDX), and infrared spectroscopy to corroborate the presence of 11MUA on the surface. Most interestingly, the resulting AgNPs@11MUA selectively detected micromolar levels of Ni2+, also in the presence of other cations such as Mn2+, Co2+, Cd2+, Cu2+, Zn2+, Fe2+, Hg2+, Pb2+, and Cr3+.

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