Trace Level Detection Research Articles

Simultaneous Quantitative Determination of Five Process Relevant Impurities in Menatetrenone

ABSTRACTMenatetrenone, a form of vitamin K (MK‐4) is used for various pharmaceutical and agrochemical applications. Monitoring and control of process impurities is crucial in the manufacturing of pharmaceutical‐grade Menatetranone. In this article, we report a gas chromatography (GC)‐based analytical method for the detection and quantification of trace levels of five process‐related impurities in MK‐4 originating from the starting materials and reagents. A GC‐flame ionization detector (GC‐FID)‐based method is presented for simultaneous quantitative estimation of five structurally diverse compounds, some of which are conventionally analyzed by liquid chromatography. After a series of method development trials, an optimized method with a mid‐polar column dura bond‐624 (6% cyanopropyl/phenyl and 94% polydimethylsiloxane) with initial column oven temperature 150°C, detector temperature 280°C was finalized for the separation of these impurities. The developed GC‐FID‐based method was validated for specificity, the limit of detection (LOD), the limit of quantification (LOQ), linearity, range, precision, accuracy, and robustness as relevant to the International Council for Harmonization guidelines. The method was found to be highly sensitive for all the constituents with an LOD ranging from 0.05 to 0.43 pg and a limit of quantification of 0.17–1.41 pg, as estimated by the signal‐to‐noise ratios. This is the first report of an analytical method for the simultaneous quantitative determination of five process impurities of MK‐4.

Carbon Dots Anchored Bacterial Cellulose Hybrid Platform as Fluorescent Sensor and Photocatalytic Remover of Pharmaceutics

In the present work, one arrow two hawk approach was implemented to enable fluorometric trace level detection as well as photocatalytic remediation of antibiotic drugs tetracycline (TET) and doxycycline (DOX)...

Trace level detection of Pb2+ ion using organic ligand as fluorescent-on probes in aqueous media.

In this study, an optical sensor, JA/(2,6-di((E)-benzylidene)cyclohexan-1-one), was synthesized and characterized using 1H NMR and FT-IR spectroscopy. The sensor exhibited high efficiency and selectivity in detecting Pb2+ ions, even in the presence of potential interfering ions such as Mn2+, Cu2+, Co2+, Cr3+, Ni2+, Ce3+, Hg2+, and Cd2+ in aqueous solutions. The interaction of JA with Pb2+ resulted in a significant enhancement of fluorescence intensity, suggesting the formation of a stable complex. A 2:1 binding ratio between JA and Pb2+ was confirmed through fluorometric analysis, absorption spectra, and theoretical calculations (DFT). The association constant for the complex was calculated to be 3×106M-2. The sensor demonstrated high sensitivity towards Pb2+ with a detection limit of 5×10-7M. Additionally, JA was successfully reused by applying EDTA to release Pb2+ from the sensor. Real sample analysis under optimized conditions of pH, time, and concentration of JA and Pb2+ further validated the practical applicability of the sensor.

New room temperature ionic liquids, 1-butyl-3-methylimidazolium o-anisate and 1-butyl-3-methylimidazolium m-anisate as novel sensitizers for Eu3+ fluorescence

Fluorescence enhancement of Eu3+ was achieved using new room temperature ionic liquids, 1-butyl-3-methylimidazolium o-anisate ([Bumim][oA]) and 1-butyl-3-methylimidazium m-anisate ([Bumim][mA]) which was tailored for the purpose. Analytical methodology was developed for the trace level detection of Eu3+ in ionic liquid systems and the best detection limit of Eu3+ was in the order of 10-10 M. In addition, the fluorescence lifetime of Eu3+ in ionic liquid system has increased to about 1000 μs, which is due to the non quenching environment of Eu3+ in ionic liquid relative to aqueous. This is the first study to use new task-specific ionic liquids (TSILs) with anisate as anions for the trace level detection of Eu3+.This paper has also discussed the detailed synthesis and characterization methods adopted for new room temperature ionic liquids.

Nanoporous and Morphology-transforming g-CNNPs for Trace-level detection of Mefenamic Acid in Urine samples and in vitro Protein denaturation inhibition

Water-soluble graphitic carbon nitride nanoparticles (g-CNNPs) were synthesized via a solid-state method, resulting in quasi-spherical particles with an average size of approximately 3.1 nm. Comprehensive characterization was conducted using standard...

Cell-Based Assays to Detect Innate Immune Response Modulating Impurities: Application to Biosimilar Insulin

Characterizing and mitigating factors that impact product immunogenicity can aid in risk assessment and/or managing risk following manufacturing changes. For follow-on products that have the same indication, patient population, and active product ingredient, the residual immunogenicity risk resides predominantly on differences in product and process related impurities. Characterizing differences in innate immune modulating impurities (IIRMI), which could act as adjuvants by activating local antigen presenting cells (APCs), can inform the immunogenicity risk assessment potentially reducing the need for clinical trials. To date, assays to detect trace levels of IIRMI are being used to support regulatory decisions by FDA for selected synthetic peptide drug products that refer to reference listed drugs of rDNA origin but not recombinant protein or peptide products where more complex mixtures of trace impurities including host cell proteins are expected. Here we describe an exercise to explore whether or not there are differences in the innate immune response elicited by an insulin glargine (produced in E. coli) and its interchangeable biosimilar insulin (produced in P. pastoris) that could indicate differences in IIRMI. Our results suggest the two products elicit comparable innate immune responses as determined by the expression of 90 immune-related genes, including IL-1α, IL-1β, IL-6, CCL3, CCL2, and CXCL8. The data suggest that these assays can provide useful information when assessing recombinant proteins for the presence of IIRMI.Graphical

Label-Free Surface-Enhanced Raman Spectroscopy Detection of Amyloid Beta on Silver Nanostructured Substrates for Alzheimer's Diagnosis.

Alzheimer's disease (AD) is a public health concern, for which an early diagnosis is essential. Biomass-derived carbon fibres with surface-decorated silver nanoparticles (Ag@CFs) have been utilized as surface enhanced raman spectroscopy (SERS) sensor platformfor the detection of the amyloid beta Aβ (25-35) for the pre-diagnosis of Alzheimer's disease. Structural and morphological characterizations confirmed the distribution of plasmonic silver nanoparticles over the surface of carbon fibres. The SERS sensor performance of Ag@CFs was evaluated using rhodamine 6G, which showed an enhancement of the order of 106 which proved the effectiveness of the developed SERS sensor towards trace level detection of analyte. A range of amyloid beta concentrations, from 100uM to 10pM, have been analyzed as a proof-of concept for this study, showcasing the efficacy of the Ag@CFs based SERS sensor to detect trace level concentrations of amyloid beta, even as low as 10 pM. This investigation is a promising development in the field of AD diagnostics since it may turn out to be a non-invasive, economical and early diagnostic tool.

Synthesis of a bimetal-organic framework-cobalt oxide nanoflowers (Ni/Co-MOF@Co3O4 NFs) for sensitive tebuconazole extraction from fruit juice and water samples using micro-solid phase extraction-HPLC-DAD

Tebuconazole (TBZ) is a widely used triazole fungicide that poses potential risks to human health and the environment due to its persistence in food and water. Effective monitoring of TBZ residues is crucial for ensuring food safety and environmental protection. This study presents a novel method for synthesizing Ni/Co-MOF@Co3O4 nanoflowers (NFs) and their application in extracting TBZ from water and fruit juice samples via micro-solid phase extraction (µ-SPE). Ni/Co-MOF@Co3O4 NFs was synthesized using the hydrothermal technique followed by calcination. The synthesized nanoflowers were characterized through SEM, XRD, and FT-IR analyses. Optimal extraction conditions were established at pH 8, using 10 mg of adsorbent, with adsorption and desorption times of 3 and 2 min, respectively. TBZ analysis was conducted using HPLC with a Poroshell 120 EC-C18 column and a diode array detector (DAD). The method demonstrates excellent recovery rates (90–102 %) and RSD% of 3.7 % in spiked fruit juice and natural water samples. The analytical performance showed a wide linear range (1–2000 µg L−1) with a high correlation coefficient (R2 = 0.9998), a detection limit of 4.0 ng L−1, and a quantification limit of 13.0 ng L−1. This approach is fast, simple, and highly sensitive, offering a reliable technique for detecting trace levels of TBZ in food and water environments.

High fluorescence quantum yield of methionine-doped carbon quantum dots for achieving rapid assay of tetracyclines in foodstuffs

The trace-level detection of tetracyclines (TCs) in food products is essential to ensure food safety and public health. Herein, we prepared the methionine-doped carbon quantum dots (Met-CQDs) using citric acid as the precursor. Met-CQDs exhibited a Gaussian unimodal peak centered at 440 nm in the fluorescent excitation spectrum, along with a remarkable greenish-blue emission and a fluorescent quantum yield of 33.5 %. Furthermore, the presence of TC (the quencher) caused a rapid quenching of the fluorescence of Met-CQDs, accompanying with a color transition from light blue to dark bule as TC concentrations increased. The coloring variation was also detected by the images captured by smartphones and RGB analysis software, facilitating portable detection of TC utilizing Met-CQDs as a fluoroprobe. The findings indicate that the Met-CQDs based fluoroprobe exhibits high selectivity, rapid response (only ∼1 min) according to an “ON-OFF” sensing model. This fluorescence sensing method gave a low detection limit (LOD) of 0.032 μM and excellent linearity for TC in the concentration range of 0.1–500 μM. Also, the smartphone-based fluorescence-visualizing approach displayed good linearity with a LOD of 0.33 μM. The interactions between this fluoroprobe and TC occurred by virtue of both inner filter effect (IFE) and static-quenching principle. The average recovery for TC in the milk, honey, and tap water samples was determined to be 98.46 ± 1.71 % by a fluorometric method. Overall, both fluorometric and RGB approaches demonstrate strong correlation with conventional LC-MS/MS, and thus the as-fabricated Met-CQDs are promising for the preliminary screening of TCs’ residues in food products.

Drug molecules beyond chemical biology: fluorescence- and DFT-based investigations for fluoride ion sensing and the trace detection of chloroform.

Excessive unmonitored use of fluoride has remained a threatening issue for a long time now as its long-term use is linked to several health issues. Similarly, chloroform is a highly carcinogenic solvent that requires proper monitoring. The increasing demand for a convenient, selective and sensitive fluoride and chloroform sensor intrigued us to utilize etoricoxib (ECX) as a sensor as it is highly safe and easily available. The photophysical properties of ECX, which were previously unexplored, were now studied with increasing water fractions and a significant aggregation-induced emission enhancement (AIEE) was seen through fluorescence spectroscopy. ECX was also successfully used for the trace level detection of chloroform through a significant emission enhancement. Similarly, the ECX-based sensor successfully detected fluoride ions by showing enhancement in emission intensity with maximum emission wavelength at 373 nm. Through fluorescence titration experiments, the effects of different conditions and interfering species on the sensing efficiency of ECX were studied, and the results showed that the sensor was highly selective and sensitive towards fluoride, with a limit of detection of 20 nM. Other than fluorescence spectroscopy, the type of interaction between the sensor and analyte was also studied through UV-Vis spectroscopy, revealing a non-covalent type of interaction, which was further validated through DFT studies. Frontier molecular orbital (FMO) analysis was performed along with density of state (DOS) studies to investigate the energy levels of the orbitals. Non-covalent interaction (NCI) and natural bond orbital (NBO) analysis provided information about the types of interaction and charge transfer. ECX has the potential to be used for real-time sensing applications and could be used for sensing moisture and fluoride in real samples.

Enhancing NPK Detection in Agriculture through Electrochemical Sensors Utilizing 2D Nanomaterials

NPK electrochemical soil sensors are essential tools for sustainable agriculture, enabling farmers to optimize nutrient management practices, improve crop productivity, and protect the environment for future generations. Those sensors are designed to primarily measure the levels of nitrogen (N), phosphorus (P), and potassium (K) in the soil. These are essential nutrients for plant growth and health, and monitoring their levels can help optimize fertilizer application and improve crop yield, while minimizing environmental impact, effectively supporting precision agriculture practices.Novel 2D nanomaterials can enhance the electrochemical properties of the sensors, enabling them to detect trace levels of nutrients with high precision. The operation principle of the sensors is based on the electrochemical reactions occurring at the surface of 2D nanomaterials when they come into contact with target ions in the soil solution through an ion-selective membrane. The presence and concentration of these ions cause changes in the electrical properties of the nanomaterial, which are then measured and correlated with the nutrient levels. By applying specially designed composite nanomaterials made of transition metal dichalcogenides, Mxenes, Graphene-based materials, conjugated conducting polymers, and ion-selective membranes, it is possible to precisely and stably measure soil ion content as batch, or continuous readout. These materials offer high surface area-to-volume ratios, excellent electrical conductivity, and sensitivity to changes in the chemical environment, making them ideal candidates for sensing applications. The laboratory experiments show that various combinations of nanomaterials in composites at the sensor working electrode have a high impact in increasing the selectivity of the ISM towards omitting ions in soil, repeatability of measurements, and durability of the sensor, compared to the electrodes with only ISM on top. Several nitrate ionophores and ISM cocktails are tested and compared toward ionic selectivity.The electrochemical sensors are controlled by the electronic circuitry, designed to give input and readout of the data from the sensing elements, as well as for sensor conditioning and calibration, data storage, and wireless communication. Various electrochemical methods through controlling electronics, like Open circuit potentiometry, Chronopotentiometry, and Chronoamperometry are employed for sensor control and data collection. Those methods were tested and compared in terms of the response time and durability of the sensor.Overall, the integration of electrochemical sensors with 2D nanomaterials represents a significant advancement in precision agriculture, offering farmers the tools they need to efficiently manage nutrient levels in soil and improve crop productivity, contributing to traceability and quality assurance in food production.*This work is supported through the ANTARES project that has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement SGA-CSA. No. 739570 under FPA No. 664387. https://doi.org/10.3030/739570 Figure 1

Nanoengineered disposable sensor fabricated with dysprosium stannate/functionalized halloysite nanotube composite for detecting mutagenic pollutant: 4-(Methylamino)phenol

The environmental contaminant 4-(Methylamino)phenol sulfate (4-MAP), commonly used in industrial processes, poses serious ecological and health risks due to its toxicity and persistence in water systems. This study reports a high-performance electrochemical sensor based on a Dysprosium stannate (Dy2Sn2O7) /functionalized halloysite nanotube (F-HNT)-modified screen-printed carbon electrode (SPCE) for the sensitive and selective detection of 4-MAP. The Dy2Sn2O7/F-HNT nanocomposite, synthesized via a hydrothermal approach, was thoroughly characterized using spectroscopic and microscopic techniques to confirm its structural integrity and enhanced surface properties. Electrochemical analyses with cyclic voltammetry and differential pulse voltammetry revealed excellent sensitivity, with a wide linear range from 0.005 μM to 689 μM and a low detection limit of 0.72 nM, enabling trace-level detection of 4-MAP. The sensor demonstrated high selectivity with minimal interference from common co-existing species, along with strong reproducibility and stability, evidenced by a relative standard deviation of less than ±5% across electrode batches. Practical application was confirmed by successfully detecting 4-MAP in spiked environmental samples, including pond, river water, and sediment samples. The superior sensing performance of the Dy2Sn2O7/F-HNT/SPCE is attributed to the nanocomposite’s redox activity, high surface area, and effective electron transfer capabilities, emphasizing its potential as a reliable tool for environmental monitoring and protection.

DFT supported studies of multi-responsive AIE active fluorophores for the sensitive fluorescence recognition of p-nitrophenol and pH: Vapor phase and solution mode sensing

Designing of an aggregation-induced emission (AIE) active multi-responsive fluorophores for the sensitive recognition of targeted analytes has been a hot spot in recent time. In pursuit of this endeavor, two chromene core sensors KG01 and KG02, installed with phenyl rotors, were efficiently designed, synthesized, and characterized through NMR spectroscopy. Proposed fluorophores demonstrated striking features of structure–property relationships, including solvatochromism and J-aggregates-based aggregation induced emission (AIE). Subsequently, well-thought-out developed sensors KG01 and KG02 were subjected to photoinduced electron transfer (PET) operated fluorescence quenching driven optical tracing of p-nitrophenol (p-NP) in the co-existence of competing analytes, with LOD down to 4.7 and 6.6 nM, respectively. Further, diversified theoretical calculations were executed to validate J-aggregates, supreme selectivity of sensors towards p-NP and PET as its primary sensing mechanism. Additionally, Jobs plot experiment, dynamic light scattering (DLS) size distribution, and 1H NMR titration assay also endorsed the selective p-NP sensing. Further, reported sensors were exploited for the fluorescence along with visual recognition of trifluoroacetic acid (TFA) and sodium hydroxide (NaOH). Interestingly, devised sensor KG01 disclosed naked-eye detection of TFA vapors. Furthermore, real water sample analysis, engineering of hand-held thin layer chromatography (TLC) plates-based fluorescent kits, and fabrication of logic devices were carried out to signify the convenient point-of-need applications of the proposed sensors. To the best of our knowledge, sensors KG01 and KG02 are first-ever solvatochromic and AIEgen chromenes with good quantum yield (Φ) and absorption coefficient as potential candidates to establish a range of easy-to-apply platforms for the selective and sensitive distinguishing of different aforementioned analytes. Given the role of p-NP as a priority pollutant from industrial sources with severe ecological and health impacts, these fluorescence sensors offer promising potential for developing cost-effective tools for rapid and precise trace-level detection. Additionally, industrial seepage of TFA and NaOH into water reserves poses serious health risks. These fluorescence sensors could be adapted to create devices capable of detecting these contaminants at nanomolar concentrations.

Trace level detection of putrescine and cadaverine in food samples using a novel rhodanine-imidazole dyad and evaluation of its biological properties

Biogenic amines are important indicators of food spoilage and quality. Food safety is significantly influenced by biogenic amines such as Putrescine and Cadaverine, produced by microbes during food spoilage. Herein, a colorimetric probe for detecting Putrescine and Cadaverine based on a chemo-dosimeter strategy has been proposed. The probe L1 irreversibly binds with Putrescine and Cadaverine through an aza-Michael addition reaction in which the dicyanomethyl group of the probe is substituted by the primary amine group from the biogenic amines. This chemical reaction rapidly changes color from colorless to pale green. The probe could detect Putrescine and Cadaverine in trace levels of 52 nM and 18 nM, without much interference from other common biogenic amines. The binding mechanism of probe L1 with biogenic amines was confirmed using 1H NMR, IR, and DFT studies. The detection procedure is made portable and affordable by using a smartphone camera to capture colorimetric changes and convert them into RGB coordinates. Test paper strips coated with the probe were developed to illustrate its real-world analytical application. The potential application of probe L1 in real samples was demonstrated using in-vivo models of Prawn and Beef using test paper strips. Probe L1 showed satisfactory performance for detecting Putrescine and Cadaverine in the vapor phase.

Streamlined Flow Synthesis of Plasmonic Nanoparticles and SERS Detection of Uremic Toxins with Trace-Level Liquid Volumes in a Microchamber.

Rapid detection of uremic toxins is crucial due to their severe health risks, including oxidative stress, inflammation, neurotoxicity, cardiovascular complications, and progression of chronic kidney disease. Surface-enhanced Raman spectroscopy (SERS) may provide sensitive, fast, and clinical-grade real-time monitoring of these toxins, enabling effective management with timely dialysis treatments. This study introduces a 3D-printed microchamber that integrates the fabrication of plasmonic metal nanoparticles for the in-flow detection of biological toxins and pharmaceutical drugs using SERS, making it ideal for on-site diagnostics in clinical settings. The microchamber supports quantitative and highly reproducible detection with liquid volumes under 100 μL, which is crucial for trace-level biomarker detection and minimizing cross-contamination. It employs a tunable solvent exchange method for the in situ synthesis of silver nanoparticles (AgNPs) on flexible PDMS or rigid Si wafer substrates, avoiding costly nanofabrication techniques. Ultralow detection limits were achieved for two model compounds and three pharmaceutical drugs: 10-11 M for rhodamine 6G, 10-7 M for adenine, and 10-6 M for the pharmaceutical drugs. A total of 13 biological toxins, including three neurotransmitters, one neuromodulator, five amino acids, two polyamines, and two urea cycle metabolites, were detected with quantitative limits ranging from 10-3 to 10-6 M, all below permissible levels and aligning with physiological conditions. SERS detection within microchambers facilitates rapid on-site analysis, proving ideal for personalized health monitoring, point-of-care diagnostics, and environmental pollution assessment.

Post-Functionalization of Fluorinated Dibenzosulfone-Based Conjugated Polymer for Smart 'Turn-off' Sensing of Cu2+ Ions.

Post-functionalization of conjugated polymeric backbone with various N-containing heterocycles through nucleophilic aromatic substitution reaction (SNAr) demonstrates crucial tailoring of their photophysical properties. This study explores an approach of post-polymerization modification of a fluorinated dibenzosulfone-based conjugated polymer aiming to incorporate functional groups having coordinating sites to bind metal ions. The resulting polymers, namely BDT-DBTS-IM, BDT-DBTS-TR, and BDT-DBTS-PY revealed successful substitution reactions with imidazole, triazole, and pyridine respectively, and showed significant changes in their absorption and emission properties. Notably, BDT-DBTS-IM demonstrated exceptional performance as a chemosensor, exhibiting a dramatic fluorescence turn-off response specifically to copper ions (Cu2+) with the limit of detection of 26 nM and Stern-Volmer quenching constant (KSV) of 8.2×105 Lmol-1. This high selectivity and sensitivity are attributed to the ability of the imidazole group to form a stable complex with Cu2+, resulting in both static and dynamic quenching efficiently. Our findings underscore the potential of post-polymerization modifications to significantly enhance the functionality of conjugated polymers. The ability of BDT-DBTS-IM to detect trace levels of copper ions with high precision highlights its practical utility in environmental and biological monitoring. This research not only demonstrates an approach for post-polymeric modification through SNAr reaction but also opens new avenues for developing sensors.

Trace-level quantification of NDMA in levosulpuride active pharmaceutical ingredient and tablet formulation Using UFLC-MS/MS

Nitrosamine impurities identified in several pharmaceuticals during recent times has raised concerns leading to product recalls worldwide and necessitating sensitive liquid and gas chromatographic methods for trace level detection of nitrosamine impurities. This study developed and validated a ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) method for the quantification of NDMA in Levosulpuride drug substance and tablet formulation. Current method utilizes a triple quadrupole analyzer, atmospheric pressure chemical ionization (APCI) ionization source and multiple reaction monitoring (MRM) scan mode for the analysis. Chromatographic separation was achieved on a Gemini NX-C18 column (150 × 4.6 mm, 3 µm) maintained at 40 °C. The mobile phase consisted of a binary gradient of solvent A (0.1 % formic acid in water) and solvent B (methanol), with a total run time of 18 minutes. Current method achieved excellent linearity, recovery, precision, and sensitivity. Greenness of the developed method was evaluated using the GAPI, AGREE, and AES metrics. Current method is sensitive and selective for NDMA in levosulpuride drug substance and tablet formulations and can be employed for routine quality control analysis in pharmaceutical industry.

Enhanced SERS signal in the hybrid substrate through electronic modulation of CVD grown single-layer graphene

The ever-growing demand for sensitive and reliable detection of hazardous material in the food chain and trace detection of chemical entities in a variety of field attracted advanced Surface Enhanced Raman Spectroscopy (SERS) active materials such as graphene-based hybrid SERS. The graphene silver nanostructures (AgNS) based hybrid SERS substrates are explored to understand the critical role of pristine graphene grown by chemical vapor deposition (CVD) on SERS signal and its possible mechanism. A lithography-free fabrication process has been developed for growth of uniform array of AgNS with varying both particle sizes and inter-particle gaps. The optimal AgNS with average feature size ∼40 nm and average inter-particle spacing of ∼13 nm demonstrated the maximum SERS enhancement with rhodamine 6G (R6G). The single-layer graphene (SLG) grown by CVD with the aid of controlling the reaction geometry with growth under a free molecular regime leads to the highest quality graphene with I2D/IG ratio of ∼3.58 and ID/IG ratio of ∼0.154. The flow regime-controlled CVD-grown SLG integrated with AgNS and its SERS enhancement mechanism is explored for trace detection of R6G. The graphene with its ability to modulate the electronic structure and tune it relative to the highest occupied molecular orbital-lowest occupied molecular orbital (HOMO-LUMO) levels of R6G molecules resulted in improved SERS signal by about an order for graphene-AgNS hybrid structure as compared to bare AgNS. The obtained findings paved the way for the futuristic and reliable hybrid SERS substrate for trace-level detection of a wide range of chemical entities.

An Efficient Fluorescent Chemosensing Probe for Total Determination and Speciation of Ultra-Trace Levels of Mercury (II) Species in Water.

The current study reports a novel fluorescent chemosensor based on the tagging agent 4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein (Rose Bengal, RB) for detection of trace levels of Hg2+in environmental water. The established probe has been based upon liquid-liquid extraction (LLE) of the developed ternary complex ion associate {[Hg (bpy)2]2+.[RB]2-} of Hg2+ -2,2- bipyridyl complex [Hg (bpy)2]2+ and RB at pH 9.0 onto chloroform and measuring the resulting fluorescence enhancement signal intensity at λex/em = 570/ (580-600) nm. The limits of detection (LOD) and quantification (LOQ) of for Hg2+ was calculated to be 6.06 and 20 nM with a linear dynamic range (LDR) of 0.02-20µM, respectively. The stability constant, stoichiometry, chemical equilibria, and the thermodynamic parameters (ΔH, ΔS, and ΔG) of the developed ion associate were evaluated and assigned. Student's t and F tests at 95% confidence were fruitfully used for validation of the proposed methodology for Hg2+ detection in water samples with the aid of inductively coupled plasma-optical emission spectrometry (ICP-OES). The established strategy was successfully applied for detection of trace levels of Hg2+ in water samples with acceptable results. The proposed probe was satisfactorily applied for total determination and speciation of Hg in various water samples. Integrating the functional chelating agent onto associate formation to improve the selectivity and sensing properties of the LLE combining sensing probe towards target analyte in water represent the main interest.

Trace level detection of the azo base of organic dye by surface-enhanced Raman spectroscopy

Water pollution with synthetic pigments is becoming an emerging problem due to the potential damage to aquatic sources and its consequences for flora, fauna, and human health. Currently, techniques to detect the presence of these pollutant pigments in water reach concentrations of µg/L and require pretreatment to detect them. In this work, we present a quick and easy methodology to determine the presence of the basic unit used in textile pigments, 4-(pyridin-4-yldiazenyl)phenyl-amine (4-PDPA), in a synthetic seawater matrix and a real one from the coast of the city of Valparaíso, Chile, using Surface Enhanced Raman Spectroscopy (SERS). Colloidal gold was used as the active surface, spectra corresponding to the pigment profile were recorded without pretreatment of the matrix used, and the pigment was detected at concentrations 0.00198 µg/L up to two orders of magnitude lower than current methods (0.0198 µg/L).