Hypochlorite Concentration Research Articles

Physicochemical and Morphological Properties of Litchi Seed Starch Oxidized by Different Levels of Sodium Hypochlorite

AbstractNon‐conventional starch sources have emerged as an interest due to their inherent physicochemical properties similar to conventional starches. This study aimed to enhance the value of non‐conventional litchi seed starch by employing anoxidizing process using different concentrations of sodium hypochlorite (NaOCl)(0.5, 1.5, 2.5, 3.5, 4.5%). The carbonyl and carboxyl content of oxidized starch was in the range of (0.019 – 0.323%) and (0.044 – 0.425%) showing an increase with the increasing concentration of NaOCl. The native and oxidized starches were further characterized for their functional and structural properties. The amylose content of native starch was 21.52% which was reduced to (19.34 – 13.43%) upon oxidation. The water and oil absorption capacities increased with theoxidation level. The swelling power(g/g) and solubility (g/100g) for native starch were 16.17 and 16.20 and 9.5 and 31.40 for modified starch. The oxidized starch produced clearer pastes. Scanning electron microscopy revealed surface erosion and cavities in oxidized starch granulesat higher concentrations. The oxidized starch showed higher relative crystallinity. FTIR was further used to assess structural changes in starches. Therefore, it can be concluded that oxidation significantly altered the characteristics of litchi seed starch, expanding its potential applications in various industries.

Interleukin-8 (IL-8) levels in gingival crevicular fluid during root canal treatment of molar teeth with symptomatic irreversible pulpitis: impact of varying sodium hypochlorite concentrations

BackgroundThe aim of this study was to evaluate the effect of the use of different NaOCl concentrations (1%, 2.5%, and 5.25%) during root canal treatment of molar teeth with symptomatic irreversible pulpitis on the change of the IL-8 level in gingival crevicular fluid (GFC).MethodsGCF sampling was performed on experimental tooth with irreversible pulpitis before and after treatment and also contralateral healthy tooth of 54 patients. The patients were divided into three groups according to concentration of NaOCl solution (n = 18); 1%, 2.5%, and 5.25% NaOCl solution. GCF sampling from experimental teeth was repeated one week after root canal treatment. Statistical analysis was performed using Mann-Whitney U, Wilcoxon test, one-way ANOVA and Pearson correlation analysis.ResultsThere was a significant correlation between IL-8 levels in GCF samples taken from teeth with pulpitis before treatment and from healthy contralateral teeth (p = .000). Furthermore, the pretreatment IL-8 level was significantly higher than the posttreatment IL-8 level(p < .05). The effect of the NaOCl concentration on the change in IL-8 level betweeen pre and post treatment was not found statistically significant (p > .05).ConclusionsThe use of NaOCl during root canal treatment can effectively reduce the levels of IL-8 in GCF and improve clinical outcomes.Trial registrationThis study was registred in the Institutional Review Board and the Ethics Committee of the University (No:11) on 15/12/2021.

Cyanine based ratio fluorescent probe and its application in hypochlorite detection

Hypochlorite (ClO−), a weakly acidic reactive oxygen species, plays a crucial role in antibacterial and anti-inflammatory defense mechanisms. However, elevated levels of ClO− or disruptions in endogenous sites can lead to tissue damage and various diseases including cardiovascular disease, neuronal degeneration, and arthritis. To address this, the development of a specific fluorescent probe with a built-in self-calibration ratio mode for the analysis and biological imaging of ClO− is essential. In this study, a cyanine-based fluorescent probe (Cy-H) was designed for ratiometric fluorescent detection of ClO−, utilizing its aggregation behavior as a novel approach in this field. Upon exposure to ClO−, the phenolic hydroxyl group in probe Cy-H was oxidized into benzoquinone, leading to the formation of cyanine products that displayed a strong tendency to aggregate. As a result, the maximum emission peak of the probe shifted from 700 nm to 485 nm. Notably, a linear relationship was observed between the peak intensity ratio (I485/I700) and the concentration of hypochlorite, with a limit of detection (LOD) of 0.49 μM. Furthermore, this probe was successfully employed for imaging analysis of hypochlorite in living cells and zebrafish.

Effects of Sodium Hypochlorite Concentration and Application Time on Bacteria in an Ex Vivo Polymicrobial Biofilm Model

IntroductionIn endodontic treatment, it is important to remove or inactivate biofilms in the root canal system. We investigated the effects of different concentrations and application times of sodium hypochlorite (NaOCl) on the viability of bacteria in ex vivo polymicrobial biofilms of different maturation levels. MethodsPolymicrobial biofilms were prepared from dental plaque samples and grown for 1, 2, and 3 weeks under anaerobic conditions on collagen-coated hydroxyapatite discs as an ex vivo biofilm model. The biofilms were then exposed to NaOCl at concentrations ranging from 0.1% to 2% for 1 or 3 minutes. The control group was exposed to sterile distilled water. Viability staining was performed and examined by confocal laser scanning microscopy to determine the percentage of biofilm bacteria killed by NaOCl. Scanning electron microscopy was also performed to visually examine the biofilms. ResultsApplication of NaOCl at 0.5%–2% for both 1 and 3 min killed significantly more bacteria when compared to the controls (P < .05). Cell viability tended to be lower after the application of NaOCl for 3 minutes than that for 1 minute. ConclusionsOur experiments using an ex vivo model showed that within the range of 0.1%–2% of NaOCl, higher NaOCl concentrations and longer application times were more effective in killing biofilm bacteria, and that mature biofilms were more resistant to NaOCl than younger biofilms.

Influence of the Use of Irrigation Solution Inhibitors in Improving Dentine Adhesion: A Systematic Review and Meta-Analysis.

This systematic review examined the effect of neutralizing agents on bond strength after irrigation with sodium hypochlorite and their existing protocols in literature. This present study adhered to the PRISMA guidelines and was registered at PROSPERO. Five electronic databases were searched (sept-2020/jan-2021) in English, Spanish, and Portuguese, without any restrictions on publication date. Cases reports, editorials and literature reviews were not included. The risk of bias was assessed using the Cochrane Collaboration tool. From the initial 7,147 studies, 2,745 were removed as duplicates and 4,382 were excluded after a title/abstract screen. Seventeen in vitro studies were included. The results showed that the higher the concentration of sodium hypochlorite, the lower the bond strength at dentine/restoration interface (p⟨0.01). Among the studies, sodium ascorbate was the most widely used neutralizer and showed the most significant results in increasing bond strength (p⟨0.01). The bond strength values were found to increase with longer application time of the neutralizing substances (p⟨0.01). The use of sodium ascorbate as a neutralizing agent can reverse the negative effects of the sodium hypochlorite and improve the bond strength between dentine and resin cement, however, it isn't possible to determine the best protocol for use.

Deep learning for predicting the residual concentration of sodium hypochlorite in the cooling water OF nuclear power plants

Sea water is used as cooling water in several operating nuclear power plants, as well as in other industries such as petrochemicals. Biofouling is a common problem in systems that use sea water, causing corrosion in pipes and equipment, blockages, and loss of efficiency in heat exchangers. The use of sodium hypochlorite has proven to be effective in minimizing the damages caused by biofouling, provided that the residual chlorine concentration remains within a specific range, as low dosages will not protect the equipment and high dosages can cause environmental damage. With the aim of reducing maintenance and operation costs of equipment, and particularly ensuring the operability of systems related to the safety of nuclear power plants that use sea water, this study developed deep artificial neural networks (ANN) models capable of predicting the residual chlorine concentration in the main cooling and safety systems of a nuclear power plant. This prediction is based on environmental and process parameters that influence the residual chlorine concentration. Proposed model achieved average mean squared error of 0.002 and correlation coefficient (R2-Score) of 0.934, demonstrating to be a promising tool for predicting residual chlorine concentration.

Effect of sodium hypochlorite temperature and concentration on the fracture resistance of root dentin

BackgroundSodium hypochlorite (NaOCl) is the most efficient root canal irrigant to date. The aim of this study was to compare the effect of NaOCl used at different temperatures and concentrations on the compressive strength of root dentin.Materials and methodsSeventy-two extracted human single-canaled straight roots of comparable size and length were selected and randomly divided into six groups (n = 12): Group (A) served as a control with unprepared canals. The other groups were instrumented with rotary ProTaper Universal files up to size F3. Group (B) was irrigated with 1% NaOCl at room temperature, Group (C) with 1% NaOCl heated to 70 °C, Group (D) with 5.25% NaOCl at room temperature, and Group (E) with 5.25% NaOCl heated to 70 °C. Saline was used in Group (F). The roots were sectioned into 2-mm-thick disks that underwent compression testing using a universal testing machine. Data were analyzed using one-way ANOVA and post hoc Tukey tests. The significance level was set at p ≤ 0.05.ResultsA total of 255 disks were tested. The control group showed the highest compressive strength (p = 0.0112). However, this did not differ significantly from that of heated (p = 0.259) or unheated (p = 0.548) 1% NaOCl. There were no statistically significant differences between the groups of instrumented teeth.ConclusionWithin the conditions of this study, irrigation with NaOCl at different concentrations and temperatures during root canal preparation did not affect the compressive strength of root dentin. Clinical Relevance: This study demonstrates that the use of NaOCl as a root canal irrigant is not associated with a clinically relevant decrease in root compressive strength, especially when compared to saline.

Electrogeneration of Hypochlorite Ions using a Dimensionally Stable Anode-Type (Ti/PtPd(10%)Ox) Electrode

&lt;p&gt;The study examined the electrogeneration of hypochlorite ions (ClO&lt;sup&gt;−&lt;/sup&gt;) via electrolysis of aqueous NaCl solutions using a dimensionally stable anode-type (DSA-type) electrode based on platinum and palladium oxides supported on titanium mesh (Ti/PtPd(10%)O&lt;sub&gt;x&lt;/sub&gt;). The electrogenerated ClO&lt;sup&gt;−&lt;/sup&gt; was quantified on the basis of the absorption band at 292 nm (A&lt;sub&gt;λ&lt;/sub&gt; = 292) of the UV-Vis spectrum. The effect of initial pH, concentration of NaCl, cell potential difference and electrolysis time were investigated in this study. The results showed that the electrolysis of aqueous NaCl solutions increases the solution pH up to high values (≥ 8.0) that favor the formation of ClO&lt;sup&gt;−&lt;/sup&gt; over chlorine or hypochlorous acid. The hypochlorite concentration increases significantly at pH values &gt; 7.0 and shows a linear trend with increasing NaCl concentration and with increasing cell potential difference. When the cell potential and NaCl concentration are held constant, the maximum hypochlorite value during electrolysis depends on both the cell potential and NaCl concentration. The Ti/PtPd(10%)O&lt;sub&gt;x&lt;/sub&gt; anode favors the production of hypochlorite ions, making this anode a promising material for use in electrochemical oxidation of wastewater via an indirect mechanism.&lt;/p&gt;

Optimizing the Antimicrobial Activity of Sodium Hypochlorite (NaClO) over Exposure Time for the Control of Salmonella spp. In Vitro.

Fish is a nutritionally rich product; however, it is easily contaminated by pathogenic microorganisms, such as Salmonella spp. Therefore, this study aimed to identify the best concentration of sodium hypochlorite (NaClO), exposure time, and water temperature that allow the most effective antimicrobial effect on the viable population of Salmonella spp. Thus, Salmonella Enteritidis ATCC 13076 and Salmonella Schwarzengrund were exposed to different time frames, ranging from 5 min to 38.5 min, temperatures between 5 and 38.5 °C, and NaClO concentrations ranging from 0.36 to 6.36 ppm, through a central composite rotational design experiment (CCRD). The results demonstrated that the ATCC strain exhibited a quadratic response to sodium hypochlorite when combined with exposure time, indicating that initial contact would already be sufficient for the compound's action to inhibit the growth of the mentioned bacteria. However, for S. Schwarzengrund (isolated directly from fish cultivated in aquaculture), both NaClO concentration and exposure time significantly influenced inactivation, following a linear pattern. This suggests that increasing the exposure time of NaClO could be an alternative to enhance Salmonella elimination rates in fish slaughterhouses. Thus, the analysis indicates that the Salmonella spp. strains used in in vitro experiments were sensitive to concentrations equal to or greater than the recommended ones, requiring a longer exposure time combined with the recommended NaClO concentration in the case of isolates from aquaculture.

Optimization of extraction conditions for cellulose from jackfruit peel using RSM, its characterization and comparative studies to commercial cellulose

A high level of research effort is now being focused on the use of bio-based materials to address the 21st century's developing problems. Thus, the search for new possible source of cellulose has been explored in this scientific work. In jackfruit, the pulp accounts for 30 % and 70–80 % of jackfruit components are non-edible; about 60 % of them are the outer rind, perianth, and central core, which are usually discarded. So, in order to utilize this underutilized fruit, jackfruit peel has been taken into consideration as a source for cellulose (C6H10O5) n extraction. Cellulose extraction was improved using the response surface methodology (RSM) approach by optimizing the extraction parameters viz. concentration of sodium hydroxide and sodium hypochlorite respectively. The results showed that the best conditions for the highest production of 64–65 % of cellulose were 5 % of sodium hydroxide and 2 % of sodium hypochlorite. The presence of α -cellulose and the absence of hemicellulose and lignin were detected using FTIR frequencies. According to the results of the thermogravimetric investigation, the maximum decomposition occurred between 200 ºC and 300 ºC. Energy dispersive X-ray analysis revealed that jackfruit peel cellulose displayed 44 % carbon as compared to 3 % carbon in commercial cellulose, indicating a higher purity. Compared to commercial cellulose, jackfruit peel cellulose shows better water binding capacity and oil holding capacity. The findings imply that jackfruit peel has a considerable amount of cellulose and has the potential to be used in various industries such as food, paper, paints etc.

Antimicrobial Efficacy of Different Concentrations of Sodium Hypochlorite in the Elimination of Enterococcus Faecalis: An In-vitro Study

Introduction: Primary teeth are equally important as permanent teeth. Endodontic therapy aids in the preservation and maintenance of extremely carious primary teeth. For root canal therapy to be successful, root canals must be properly prepared and effectively irrigated. Sodium Hypochlorite (NaOCl) has been the gold standard for root canal treatment of primary teeth. However, there are a few drawbacks to using higher concentrations of sodium hypochlorite, such as toxic reactions from its apical penetration. In addition, an excess of irrigation fluid via the apical region could harm the permanent tooth underneath. Therefore, it is crucial to select the proper concentration to preserve the delicate balance between effectiveness and safety. Aim: The present in-vitro study was conducted in the city of Chennai, Tamil Nadu, between March and June 2022. The study aimed to evaluate the effectiveness of lower concentrations of sodium hypochlorite, such as 1%, 0.5%, and 0.25%, against Enterococcus faecalis. Materials and Methods: The antibacterial activity of different concentrations of sodium hypochlorite (1%, 0.5%, and 0.25%) against Enterococcus faecalis was performed using Muller Hinton agar. Three Mueller Hinton agar plates were prepared and sterilised for 15 minutes for each concentration. The volumes used were 25 μL, 50 μL, and 100 μL, respectively. E. faecalis was swabbed and poured into the sterilised plates. The plates were incubated for 24 hours at 37°C. After incubation, the plates were examined, and their zone of Inhibition was determined. ANOVA test was applied with Post-hoc Tukey’s analysis. Results: One-way ANOVA test showed that there was a significant difference with a p-value &lt;0.001 in all three groups. Post-hoc Tukey’s analysis was done, and the test showed that the highest zone of inhibition was seen with 1% sodium hypochlorite at 100 μL, with zone diameter of 39 mm, and the least zone of inhibition was seen with 0.25% sodium hypochlorite solution at 25 μL, with zone diamter of 22 mm. Conclusion: The results of the present study show that a 1% sodium hypochlorite solution can be used to successfully disinfect root canals, indicating its potential as an effective antimicrobial agent in endodontic procedures.

Synthesis and characterization silica-MB@GO-NH2 particle as fluorescence-based chlorine sensor

In this research, we developed a fluorescence-based sensor to determine the sodium hypochlorite concentration (NaOCl) in tap water and swimming pool water samples. The detection of NaOCl was conducted by measuring the luminescence response of analyte in the paper-based sensor modified Silica-MB@GO-NH2 material were synthesized using Hummer's and Stober's methods under UV Light irradiation. Additionally, the prepared material exposed a couple peak 2D and 2G at 2938 cm-1 and 3286 cm-1 with ID/IG ratio 0.98 using Raman characterization which appropriate with the presence of GO structure in the mixture. This result was validated by the appearance of several functional groups like Si-O-Si, NH, OH, and C-C at 1079, 1391, 1611, and 3457 cm-1, respectively. Moreover, the existence of Si-O-Si bond indicates that the silica-MB interaction was perfectly formed, which plays the main role to absorb ultraviolet light that is used as sensor probe. The morphology of particles depicted an aggregated formation of spherical structure with 288 nm particle size, indicating the existence of silica-coated methylene blue. In this work, the paper-based sensor modified Silica-MB@GO-NH2 can detect the NaOCl species with concentration range 10-150 µM (R2 = 0.9757), a detection limit at 2.60 µM and quantification limit at 7.88 µM. Furthermore, this developed sensor has stable measurement with recovery performance 3.65%-6.67% for tap water and 0.05%–0.14% for swimming pool water. This result indicates that the prepared sensor can be potentially applied to calculate the hypochlorite species in the aquatic environment.

Effect of sodium hypochlorite concentration on contamination and oxidation of meristems in banana micropropagation

El experimento se realizó en el Laboratorio de Biotecnología de la Facultad de Ciencias Agrarias de la Universidad Nacional de Asunción, con el objetivo de evaluar dos tratamientos de desinfección de explantes para la micropropagación del banano (Musa spp.) variedad Nanicao. Se utilizaron 80 hijuelos de 30 - 40 cm de los cuales se extrajeron los ápices meristemáticos que fueron sembrados en medios MS (Murashige y Skoog 1962) con el agregado de 1 g.l-1 de carbón activado como antioxidante. Los tratamientos consistieron en dos concentraciones de NaClO (5 y 10 %) durante cinco minutos. El diseño experimental utilizado fue completamente al azar. Las variables evaluadas fueron: porcentaje de supervivencia, grado de oxidación y porcentaje de contaminación de plántulas. Los datos obtenidos fueron sometidos al análisis de varianza al 5 % de probabilidad de error. No se registraron diferencias significativas entre los tratamientos de desinfección aplicados relacionados a la sobrevivencia de explantes de banano cultivados in vitro, aunque existieron diferencias significativas con respecto al grado de oxidación y contaminación microbiana. Se logró una regeneración de 12,5% de los segmentos nodales de banano sembrados. En conclusión, al incrementar la concentración de hipoclorito de sodio, el porcentaje de explantes contaminados con hongos y bacterias fue menor, sin embargo, esto se tradujo en un incremento del grado de oxidación de explantes de Musa spp variedad Nanicao.

Assessment of different procedures for in vitro propagation of Salix miyabeana

Despite the large popularity of Salix miyabeana for various environmental applications in different parts of the world, most propagation techniques rely mainly on cuttings. However in vitro propagation seems a more reliable solution when selection of new commercial clones and varieties is the goal of propagating willows. The current study is the first attempt to propagate S. miyabeana via in vitro propagation, focusing on two specific aspects: different surface sterilization procedures (i.e. combinations of different sodium hypochlorite concentrations and soaking times) and different types of explants (apical vs. lateral). Our findings show that 3% sodium hypochlorite for 20 min represents the most effective sterilization procedure to ensure healthy plants. Additionally, the material obtained from apical explants showed higher survival rate, budding ability and lower microbiological contamination compared to lateral explants.

Pulsing Effect of Sucrose and Sodium Hypochlorite on Vase Life of Cut Chrysanthemum cv Arcticqueen Flower

An experiment was executed to investigate the role of different concentrations of sucrose and sodium hypochlorite as pulsing solution on post harvest storage life and other characteristics of cut chrysanthemum cv Arctic queen flower after harvest. The experiment was framed as completely randomized design with factorial concept with three levels of sucrose (5, 10, 20 %) and with 50 ppm NaOCl with 3 replications. The output of the experiment revealed that flower weight (8.26 g), water uptake (13.76 g), fresh weight change (123.76g), and maximum vase life (10.23 days) was achieved in 10% sucrose for 4 hrs pulsing treatment.

Clostridioides difficile spores tolerate disinfection with sodium hypochlorite disinfectant and remain viable within surgical scrubs and gown fabrics.

Clostridioides difficile is the most common cause of antibiotic-associated diarrhoea globally. Its spores have been implicated in the prevalence of C. difficile infection due to their resistance and transmission ability between surfaces. Currently, disinfectants such as chlorine-releasing agents (CRAs) and hydrogen peroxide are used to decontaminate and reduce the incidence of infections in clinical environments. Our previous research demonstrated the ability of C. difficile spores to survive exposure to recommended concentrations of sodium dichloroisocyanurate in liquid form and within personal protective fabrics such as surgical gowns; however, the present study examined the spore response to clinical in-use concentrations of sodium hypochlorite. Spores were exposed to a 10 min contact time of 1000, 5000 and 10 000 p.p.m. sodium hypochlorite, and spore recovery was determined. To understand whether biocide-exposed spores transmitted across clinical surfaces in vitro, biocide-exposed spores were spiked onto surgical scrubs and patient gowns and recovery was determined by a plate transfer assay. Scanning electron microscopy was used to establish if there were any morphological changes to the outer spore coat. The results revealed that viable biocide-exposed C. difficile spores can be recovered from surgical scrubs and patient gowns, with no observable changes to spore morphology, highlighting the potential of these fabrics as vectors of spore transmission. This study demonstrates that alternative strategies should be urgently sought to disinfect C. difficile spores to break the chain of transmission in clinical environments.

Viability of human Mesenchymal stem cells from the periradicular region at different concentrations of sodium hypochlorite – systematic review

Viability of human Mesenchymal stem cells from the periradicular region at different concentrations of sodium hypochlorite – systematic review

Evaluation of anti-biofilm effect of antimicrobial sonodynamic therapy-based periodontal ligament stem cell-derived exosome-loaded kojic acid on Enterococcus faecalis biofilm.

Introduction. Antimicrobial sonodynamic therapy (aSDT) is an approach that uses ultrasound waves (UWs) and a sonosensitizer to generate reactive oxygen species (ROS) to damage microbial cells in biofilms. Using nano-carriers, such as exosomes (Exos), to deliver the sonosensitizer can potentially enhance the effectiveness of aSDT.Hypothesis/Gap Statement. aSDT can downregulate the expression of gelE and sprE genes, increasing the production of endogenous ROS and degradation of pre-formed Enterococcus faecalis biofilms.Aim. This study investigated the anti-biofilm effect of aSDT-based periodontal ligament stem cell-derived exosome-loaded kojic acid (KA@PDL-Exo) on pre-formed E. faecalis biofilms in root canals.Methodology. Following the isolation and characterization of PDL-Exo, KA@PDL-Exo was prepared and confirmed. The minimal biofilm inhibitory concentration (MBIC) of KA, PDL-Exo, KA@PDL-Exo and sodium hypochlorite (NaOCl) was determined, and their anti-biofilm effects were assessed with and without UWs. The binding affinity of KA with GelE and SprE proteins was evaluated using in silico molecular docking. Additionally, the study measured the generation of endogenous ROS and evaluated changes in the gene expression levels of gelE and sprE.Results. The results revealed a dose-dependent decrease in the viability of E. faecalis cells within biofilms. KA@PDL-Exo was the most effective, with an MBIC of 62.5 µg ml-1, while NaOCl, KA and PDL-Exo had MBIC values of 125, 250 and 500 µg ml-1, respectively. The use of KA@PDL-Exo-mediated aSDT resulted in a significant reduction of the E. faecalis biofilm (3.22±0.36 log10 c.f.u. ml-1; P<0.05). The molecular docking analysis revealed docking scores of -5.3 and -5.2 kcal mol-1 for GelE-KA an SprE-KA, respectively. The findings observed the most significant reduction in gene expression of gelE and sprE in the KA@PDL-Exo group, with a decrease of 7.9- and 9.3-fold, respectively, compared to the control group (P<0.05).Conclusion. The KA@PDL-Exo-mediated aSDT was able to significantly reduce the E. faecalis load in pre-formed biofilms, decrease the expression of gelE and srpE mRNA, and increase the generation of endogenous ROS. These findings imply that KA@PDL-Exo-mediated aSDT could be a promising anti-biofilm strategy that requires additional in vitro and in vivo investigations.

Real-time monitoring of chlorination treatment in Microcystis cells by simultaneously measuring the polarized light scattering and fluorescence

Chlorination treatment is widely used in cyanobacterial blooms to reduce harmful impacts on aquatic systems. However, it is hard to timely monitor the effect of treatment and formation of disinfection by-products (DBPs) produced by intracellular organic matter (IOM) may cause second damage to the environment. In this work, we used a conceptual setup to simultaneously measure the polarization and fluorescence parameters (PFPs) from single Microcystis cells for monitoring a continuous process of chlorination. Both the cultured samples and the field-collected samples were firstly treated with different sodium hypochlorite (NaClO) concentrations, and then they were respectively measured by the setup. Results showed that PFPs changed significantly during the chlorination treatment, which had a strong correlation with the concentration of NaClO solution. Based on the machine learning model, the proportions of dead cultured cells in different concentrations (1, 5, and 10 mg/L) grew to 35.59%, 57.10%, and 84.54% respectively after 10 min. Besides, the proportion of dead field-collected cells under chlorination (10 mg/L) for 10 min was 75.11%. Graphs from SEM and TEM revealed that cell membrane damage commonly occurred with a concentration of 10 mg/L NaClO during the same period. The optical density at 680 nm obtained by spectrophotometer decreased as increasing chlorine concentrations, which agreed with changes in fluorescence intensity at low concentrations. This paper demonstrates the feasibility of this setup and PFPs for real-time monitoring of cyanobacterial bloom chlorination treatment in aquatic environments.

A new hydrazone linkage-based covalent organic framework for ratiometric fluorescent probe detection of hypochlorite

A new hydrazone-linked covalent organic framework (TFTH-COF) was synthesized and characterized. TFTH-COF has porous crystalline framework structure with high thermal stability. TFTH-COF exhibited highly selective fluorescence blue-shift response towards hypochlorite (ClO−) in ethanol and accompanied by the obvious color change under both day light and UV light. TFTH-COF has the ratiometric fluorescence sensing ability for hypochlorite with high sensitivity. The ratiometric fluorescence intensity of TFTH-COF presented a linear change against hypochlorite concentration with a low detection limit of 0.417 μM. The results of XPS, FT-IR and fluorescence lifetime indicated the formation of hydrogen bond between the O and N atoms of hydroxyl and amine of TFTH-COF with hypochlorite. The DFT calculation further confirmed the formation of hydrogen bond and resulted in the change of fluorescence spectra. Its practical application ability was confirmed by good recovery rate of TFTH-COF in the quantitative detection of hypochlorite in 84 disinfectants and water samples. Moreover, TFTH-COF can also identify hypochlorite through fluorescent test strips by the naked eye. This work sheds light on the fabrication of COFs as ratiometric fluorescence probes for easily-operable, instantaneous and accurate detection and identification of different analytes.