Highly selective determination of perchlorate by a novel potentiometric sensor based on a synthesized complex of copper

Plasmonic surface-enhanced Raman scattering nano-substrates for detection of anionic environmental contaminants: Current progress and future perspectives

Surface-enhanced Raman scattering spectroscopy (SERS) is a powerful technique of vibrational spectroscopy based on the inelastic scattering of incident photons by molecular species. It has unique properties such as ultra-sensitivity, selectivity, non-destructivity, speed, and fingerprinting properties for analytical and sensing applications. This enables SERS to be widely used in real-world sample analysis and basic plasmonic mechanistic studies. However, the desirable properties of SERS are compromised by the high cost and low reproducibility of the signals. The development of multifunctional, stable and reusable nano-engineered SERS substrates is a viable solution to circumvent these drawbacks. Recently, plasmonic SERS active nano-substrates with various morphologies have attracted the attention of researchers due to promising properties such as the formation of dense hot spots, additional stability, tunable and controlled morphology, and surface functionalization. This comprehensive review focused on the current advances in the field of SERS active nanosubstrates suitable for the detection and quantification of anionic environmental pollutants. The common fabrication methods, including the techniques for morphological adjustments and surface modification, substrate categories, and the design of nanotechnologically fabricated plasmonic SERS substrates for anion detection are systematically presented. Here, the need for the design, synthesis, and functionalization of SERS nano-substrates for anions of great environmental importance is explained in detail. In addition, the broad categories of SERS nano-substrates, namely colloid-based SERS substrates and solid-support SERS substrates are discussed. Moreover, a brief discussion of SERS detection of certain anionic pollutants in the environment is presented. Finally, the prospects in the fabrication and commercialization of pilot-scale handheld SERS sensors and the construction of smart nanosubstrates integrated with novel amplifying materials for the detection of anions of environmental and health concern are proposed.

Perchlorate-reducing bacteria from Antarctic marine sediments

Perchlorate is a contaminant that can persist in groundwater and soil, and is frequently detected in different ecosystems at concentrations relevant to human health. This study isolated and characterised halotolerant bacteria that can potentially perform perchlorate reduction. Bacterial microorganisms were isolated from marine sediments on Deception, Horseshoe and Half Moon Islands of Antarctica. The results of the 16S ribosomal RNA (rRNA) gene sequence analysis indicated that the isolates were phylogenetically related to Psychrobacter cryohalolentis, Psychrobacter urativorans, Idiomarina loihiensis, Psychrobacter nivimaris, Sporosarcina aquimarina and Pseudomonas lactis. The isolates grew at a sodium chloride concentration of up to 30% and a perchlorate concentration of up to 10,000 mg/L, which showed their ability to survive in saline conditions and high perchlorate concentrations. Between 21.6 and 40% of perchlorate was degraded by the isolated bacteria. P. cryohalolentis and P. urativorans degraded 30.3% and 32.6% of perchlorate, respectively. I. loihiensis degraded 40% of perchlorate, and P. nivimaris, S. aquimarina and P. lactis degraded 22%, 21.8% and 21.6% of perchlorate, respectively. I. loihiensis had the highest reduction in perchlorate, whereas P. lactis had the lowest reduction. This study is significant as it is the first finding of P. cryohalolentis and. P. lactis on the Antarctic continent. In conclusion, these bacteria isolated from marine sediments on Antarctica offer promising resources for the bioremediation of perchlorate contamination due to their ability to degrade perchlorate, showing their potential use as a biological system to reduce perchlorate in high-salinity ecosystems.

Perchlorate Contamination: Sources, Effects, and Technologies for Remediation

Perchlorate is a persistent pollutant, generated via natural and anthropogenic processes, that possesses a high potential for endocrine disruption in humans and biota. It inhibits iodine fixation, a major reason for eliminating this pollutant from ecosystems. Remediation of perchlorate can be achieved with various physicochemical treatments, especially at low concentrations. However, microbiological approaches using microorganisms, such as those from the genera Dechloromonas, Serratia, Propionivibrio, Wolinella, and Azospirillum, are promising when perchlorate pollution is extensive. Perchlorate-reducing bacteria, isolated from harsh environments, for example saline soils, mine sediments, thermal waters, wastewater treatment plants, underground gas storage facilities, and remote areas, including the Antarctica, can provide removal yields from 20 to 100%. Perchlorate reduction, carried out by a series of enzymes, such as perchlorate reductase and superoxide chlorite, depends on pH, temperature, salt concentration, metabolic inhibitors, nutritional conditions, time of contact, and cellular concentration. Microbial degradation is cost-effective, simple to implement, and environmentally friendly, rendering it a viable method for alleviating perchlorate pollution in the environment.

Single-Walled Carbon Nanotubes (SWCNTs) as Solid-Contact in All-Solid-State Perchlorate ISEs: Applications to Fireworks and Propellants Analysis

Herein, we present reliable, robust, stable, and cost-effective solid-contact ion-selective electrodes (ISEs) for perchlorate determination. Single-walled carbon nanotubes (SWCNTs) were used as solid-contact material and indium (III) 5, 10, 15, 20-(tetraphenyl) porphyrin chloride (In^III-porph) as an ion carrier. The sensor exhibited an improved sensitivity towards ClO₄⁻ ions with anionic slope of −56.0 ± 1.1 (R² = 0.9998) mV/decade over a linear range 1.07 × 10⁻⁶ – 1.0 × 10⁻² M and detection limit of 1.8 × 10⁻⁷ M. The short-term potential stability and the double-layer capacitance were measured by chronopotentiometric and electrochemical impedance spectroscopy (EIS) measurements, respectively. The sensor is used for ClO₄⁻ determination in fireworks and propellant powders. The results fairly agree with data obtained by ion chromatography.

Perchlorate-Reducing Bacteria from Hypersaline Soils of the Colombian Caribbean

Perchlorate (ClO₄ ^-) has several industrial applications and is frequently detected in environmental matrices at relevant concentrations to human health. Currently, perchlorate-degrading bacteria are promising strategies for bioremediation in polluted sites. The aim of this study was to isolate and characterize halophilic bacteria with the potential for perchlorate reduction. Ten bacterial strains were isolated from soils of Galerazamba-Bolivar, Manaure-Guajira, and Salamanca Island-Magdalena, Colombia. Isolates grew at concentrations up to 30% sodium chloride. The isolates tolerated pH variations ranging from 6.5 to 12.0 and perchlorate concentrations up to 10000 mg/L. Perchlorate was degraded by these bacteria on percentages between 25 and 10. 16S rRNA gene sequence analysis indicated that the strains were phylogenetically related to Vibrio, Bacillus, Salinovibrio, Staphylococcus, and Nesiotobacter genera. In conclusion, halophilic-isolated bacteria from hypersaline soils of the Colombian Caribbean are promising resources for the bioremediation of perchlorate contamination.

Ecotoxicological assessment of perchlorate using in vitro and in vivo assays

Perchlorate is an inorganic ion widespread in the environment, generated as a natural and anthropogenic pollutant, with known endocrine disruption properties in the thyroid gland. Nonetheless, there are few reports of its ecotoxicological impact on wildlife. The aim of this study was to evaluate the adverse effects of KClO₄ exposure on different cell lines, HEK, N2a, and 3T3, as well as in ecological models such as Vibrio fischeri, Pseudokirchneriella subcapitata, Daphnia magna, and Eisenia fetida. Perchlorate exhibited similar toxicity against tested cell lines, with LC₅₀ values of 19, 15, and 19 mM for HEK, N2a, and 3T3, respectively; whereas in V. fischeri, the toxicity, examined as bioluminescence reduction, was considerably lower (EC₅₀ = 715 mM). The survival of the freshwater algae P. subcapitata was significatively impaired by perchlorate (LC₅₀ = 72 mM), and its effect on the lethality in the crustacean D. magna was prominent (LC₅₀ = 5 mM). For the earthworm E. fetida, the LC₅₀ was 56 mM in soil. In this organism, perchlorate induced avoidance behavior, weight loss, and decreased egg production and hatchling, as well as morphological and histopathological effects, such as malformations, dwarfism, and necrosis. In conclusion, perchlorate toxicity varies according to the species, although E. fetida is a sensitive model to generate information regarding the toxicological impact of KClO₄ on biota.

Novel miniaturized sensors for potentiometric batch and flow-injection analysis (FIA) of perchlorate in fireworks and propellants

Three planar miniaturized perchlorate membrane sensors (3×5 mm(2)) are prepared using a flexible Kaptan substrate coated with nitron-perchlorate (NT-ClO4) [sensor 1], methylene blue-perchlorate (MB-ClO4) [sensor II] and indium-porphyrin (In-Por) [sensor III] as electroactive materials in PVC membranes plasticized with 2-NPPE. Sensors I, II and III display near-Nernstian response for 1.0×10(-5)-1.0×10(-2), 3.1×10(-5)-1.0×10(-2) and 3.1×10(-6)-1.0×10(-2) mol L(-1) ClO4(-) with lower detection limits of 6.1×10(-6), 6.9×10(-6) and 1.2×10(-6) mol L(-1), and anionic calibration slopes of 50.9±0.4, 48.4±0.4 and 57.7±0.3 mV decade(-1), respectively. Methods for determining perchlorate using these sensors offer many attractive advantages including simplicity, flexibility, cost effectiveness, wide linear dynamic response range (0.1-1000 ppm), low detection limit (<1.2×10(-6) mol L(-1)≡0.1 ppm), small sample test volume (100 μL), safety, short response time (<20 s), long life span (~8 weeks), and extended wide working pH range (4.5-8.0). The sensors show high selectivity in the presence of some inorganic ions (e.g., PO4(3-), SO4(2-), S2O3(2-), NO2(-), NO3(-), N3(-), CN(-), Cl(-), Br(-), I(-)) and automation feasibility. Indium-porphyrin based membrane sensor (sensor III) is used as a detector in a wall-jet flow injection set-up to enable accurate flow injection analysis (FIA) of perchlorate in some fireworks without interferences from the associated reducing agents (sulfur and charcoal), binders (dextrin, lactose), coloring agents (calcium, strontium, copper, iron, sodium), color brighten (linseed oil) and regulators (aluminum flakes) which are commonly used in the formulations. The sensor is also used for perchlorate assessment in some propellant powders. The results fairly agree with data obtained by ion-chromatography.