Colorimetric Sensors: Methods and Applications.

Colorimetric sensors have attracted considerable attention in many sensing applications because of their specificity, high sensitivity, cost-effectiveness, ease of use, rapid analysis, simplicity of operation, and clear visibility to the naked eye [...].

Impacts of pyrolysis temperatures on physicochemical and structural properties of green waste derived biochars for adsorption of potentially toxic elements.

This study comparatively investigated the influence of changes in pyrolysis temperature on the physicochemical, structural, and adsorptive properties of biochars derived from a green waste (Cynodon dactylon L.). For this purpose, the biophysically dried green wastes were pyrolyzed at 400 °C, 600 °C, and 800 °C under the same pyrolysis conditions. The results revealed that the physicochemical and structural properties were varied, depending upon the pyrolysis temperatures. With the increase of pyrolysis temperature, the surface functional groups were escaped, the structure became more porous (pore volume of 0.089 ± 0.001), the metal oxides were remained consistent, and the biochars turned into more alkaline nature (pH of 11.9 ± 0.2). Furthermore, as referring to the adsorptive performance for potentially toxic elements, with experimental adsorption capacity of up to 33.7 mg g-1 and removal rate up to 96% for a multi-metals containing solution, the biochars pyrolyzed at high temperature (800 °C) was significantly (p < 0.05) higher than those pyrolyzed at low temperature (400 °C). According to the physicochemical and structural properties, and the adsorptive performances of the biochars, the optimal pyrolysis temperature was herein recommended to be 800 °C.

Two-stage microbial conversion of crude glycerol to 1,3-propanediol and polyhydroxyalkanoates after pretreatment.

With increasing demand for biodiesel, crude glycerol as a by-product in biodiesel production has been generated and oversupplied. This study, therefore, explored the pretreatment and a subsequent two-stage microbial system to convert crude glycerol into high value-added products: 1,3-propanediol (1,3-PDO) and polyhydroxyalkanoates (PHAs). After pretreatment, long chain fatty acids (LCFAs) could be effectively removed from crude glycerol to eliminate the inhibition effects on subsequent microbial process. In the anaerobic fermentation, when fed treated crude glycerol increased from 20 g/L to 100 g/L, 1,3-PDO yield decreased from 0.438 g/g to 0.345 g/g and accompanied carboxylic acids shifted from acetate and lactate dominant to lactate overwhelmingly dominant. Meanwhile, the relative abundance of Clostridiales sustained around 50% but Enterobacteriales increased from 19% to 53%. Further fed glycerol increase to 140 g/L resulted in severe substrate inhibition, which could be relieved by intermittent feeding. In aerobic process, glycerol anaerobic digestion effluent (ADE) was fed to the consortium of Bacillus megaterium and Corynebacterium hydrocarbooxydans for selectively consumption of carboxylic acids and residual glycerol from 1,3-PDO to produce PHAs as a secondary high value-added product. The consortium accumulated maximum 8.0 g/L poly (3-hydroxybutyrate) (PHB), and 1,3-PDO purity increased from initial 27.7% to almost 100% when fed with 100 g/L glycerol ADE. Overall, this study provided comprehensive and insightful information on microbial conversion of crude glycerol to high value-added products after pretreatment.

A systematic review and meta-analysis of genotypic methods for detecting antibiotic resistance in Helicobacter pylori.

BACKGROUND: Antibiotic susceptibility testing is essential for tailored treatments to cure Helicobacter pylori (H. pylori) infection. However, phenotypic methods have some limitations. OBJECTIVES: To evaluate the feasibility of genotypic detection methods compared with phenotypic detection methods using samples taken from H. pylori-infected patients. METHODS: Literature searches were conducted in the following databases (from January 2000 to November 2016): PubMed, Embase, the Cochrane Library, and Web of Science. A meta-analysis and systematic review was performed for studies that compared genotypic methods with phenotypic methods for the detection of H. pylori antibiotic susceptibility. RESULTS: This meta-analysis showed that the pooled sensitivity, specificity, and diagnostic odds ratio (DOR) for the A2142G/C and/or A2143G combination for the detection of clarithromycin resistance in the strain samples were 0.97 (95% CI: 0.94-0.99), 1.00 (95% CI: 0.99-1.00), and 13 742 (95% CI: 1708-110 554), respectively. The pooled sensitivity, specificity, and DOR for the A2142G/C and/or A2143G combination for the detection of clarithromycin resistance in biopsy samples were 0.96 (95% CI: 0.90-0.99), 0.96 (95% CI: 0.91-0.99), and 722 (95% CI: 117-4443), respectively. The summarized sensitivity, specificity, and DOR value for the ability of the genotypic methods to detect quinolone resistance in biopsy specimens were 0.97 (95% CI: 0.87-0.99), 0.99 (95% CI: 0.92-1.00), and 6042 (95% CI: 486-75 143), respectively. CONCLUSION: The genotypic detection methods were reliable for the diagnosis of clarithromycin and quinolone resistance in the strain and biopsy specimens. The A2142G/C and/or A2143G combination had the best sensitivity and specificity for the detection of clarithromycin resistance.

Sequential versus concomitant therapy for treatment of Helicobacter pylori infection: an updated systematic review and meta-analysis.

BACKGROUND: Sequential and concomitant therapies are two innovative therapies for Helicobacter pylori (H. pylori) eradication. However, the comparative efficacy and safety of these treatments are controversial. Therefore, we aimed to conduct an updated systematic review and meta-analysis of studies that compared these two treatments. METHODS: A search of PubMed, Embase, the Cochrane Library, and Web of Science was carried out. Randomized controlled trials (RCTs) that compared sequential with concomitant therapies were selected for meta-analysis. RESULTS: Twenty RCTs were included in the analysis. The eradication rate of 10-day sequential therapy was superior to that of 5-day concomitant therapy (82.09 versus 77.79%, relative risk (RR) 1.052 (95% confidence interval (CI) 1.004-1.103), P = 0.035)), similar to that of 7-day concomitant therapy (82.40 versus 86.99%, RR 0.959 (95% CI 0.874-1.053), P = 0.382), and inferior to that of 10-day concomitant therapy (78.39 versus 83.32%, RR 0.945 (95% CI 0.907-0.984, P = 0.006); the occurrence of diarrhea was higher in 10-day concomitant therapy than that in 10-day sequential therapy. Compared with the eradication rate of sequential therapy, that of concomitant therapy was higher in metronidazole-resistant strains (RR 0.912 (95% CI 0.844-0.986, P = 0.020)) and strains resistant to metronidazole and clarithromycin (RR 0.542 (95% CI 0.308-0.956, P = 0.035)). CONCLUSION: The efficacy of concomitant therapy was duration dependent, and 10-day concomitant therapy was superior to 10-day sequential therapy. Compared to sequential therapy, concomitant therapy was more efficacious for metronidazole-resistant strains and metronidazole plus clarithromycin-resistant strains. However, diarrhea was more frequent with concomitant therapy than with sequential therapy.

Axonopus compressus (Sw.) Beauv.: A potential biomonitor for molybdenum in soil pollution.

Phytoremediation is an emerging technology that utilizes plants to remediate contaminated environments. In this study, Axonopus compressus (Sw.) Beauv, a fast-growing and hardy groundcover with wide geographical distribution, was exposed to soil Mo treatments ranging from 100 to 1000 mg/kg under tropical greenhouse conditions for five weeks. Generally, Mo accumulation increased as the concentration of Mo in the soil increased. The species was found to accumulate about 4000 mg/kg of Mo without exhibiting severe physiological stress at 600 mg/kg of soil Mo. Maximum accumulation of 6000 mg/kg Mo was observed at the 1000 mg/kg soil Mo treatment, though with severe necrosis and eventual plant mortality. The physiological observations, Mo accumulation behavior, and a bioconcentration factor of about 1 indicated that A. compressus could be a potential biomonitor of Mo.

Progress and development of analytical methods for gibberellins.

Gibberellins, as a group of phytohormones, exhibit a wide variety of bio-functions within plant growth and development, which have been used to increase crop yields. Many analytical procedures, therefore, have been developed for the determination of the types and levels of endogenous and exogenous gibberellins. As plant tissues contain gibberellins in trace amounts (usually at the level of nanogram per gram fresh weight or even lower), the sample pre-treatment steps (extraction, pre-concentration, and purification) for gibberellins are reviewed in details. The primary focus of this comprehensive review is on the various analytical methods designed to meet the requirements for gibberellins analyses in complex matrices with particular emphasis on high-throughput analytical methods, such as gas chromatography, liquid chromatography, and capillary electrophoresis, mostly combined with mass spectrometry. The advantages and drawbacks of the each described analytical method are discussed. The overall aim of this review is to provide a comprehensive and critical view on the different analytical methods nowadays employed to analyze gibberellins in complex sample matrices and their foreseeable trends.

Recent applications of hydrophilic interaction liquid chromatography in pharmaceutical analysis.

Hydrophilic interaction liquid chromatography, an alternative liquid chromatography mode, is of particular interest in separating hydrophilic and polar ionic compounds. Compared with traditional liquid chromatography techniques, hydrophilic interaction liquid chromatography offers specific advantages mainly including: (1) relatively green and water-soluble mobile phase composition, which enhances the solubility of hydrophilic and polar ionic compounds; (2) no need for ion-pairing reagents and high content of organic solvent, which benefits mass spectrometry detection; (3) high orthogonality to reverse-phase liquid chromatography, well adapted to two-dimensional liquid chromatography for complicated samples. Therefore, hydrophilic interaction liquid chromatography has been rapidly developed in many areas over the past decades. This review summarizes the recent progress (from 2012 to July 2016) of hydrophilic interaction liquid chromatography in pharmaceutical analysis, with the focus on detecting chemical drugs in various matrices, charactering active compounds of natural products and assessing biotherapeutics through typical structure unit. Moreover, the retention mechanism and behavior of analytes in hydrophilic interaction liquid chromatography as well as some novel hydrophilic interaction liquid chromatography columns used for pharmaceutical analysis are also described.

[Determination of indigo and brilliant blue in different types of food products by high performance liquid chromatography with solid phase extraction].

OBJECTIVE: To develop and validate a solid phase extraction-high performance liquid chromatographic( SPE-HPLC) method for the simultaneous determination of indigo and brilliant blue in different types of food products. METHODS: The artificial colors in food products were extracted by acetonitrile / water and purified by WAX SPE cartridges, The separation was achieved using a Waters Symmetry C_(18)( 5 µm, 4. 6 mm × 250 mm) column and a binary gradient mobile phase of methanol and 0. 02 mol/L ammonium acetate solution, detected by HPLC-PDA. RESULTS: The validated analytical method showed that there was a good linearity in the range of 0. 05- 20. 00 µg/mL for both indigo and brilliant blue( r > 0. 999). The lowest detection limits of indigo and brilliant blue were 0. 04 and 0. 02 mg/kg, respectively. The average recoveries were among 81. 8%- 101. 1%, with relative standard deviation( RSD) of 2. 1%- 4. 9%( n =6) for both artificial colors. CONCLUSION: The method has high selectivity, high sensitivity, good recovery and reproducibility. It is suitable to simultaneously monitor indigo and brilliant blue in several types of food products based on the food classification system of GB 2760-2014.

Development of an accelerated leaching method for incineration bottom ash correlated to toxicity characteristic leaching protocol.

Heavy metals and some metalloids are the most significant inorganic contaminants specified in toxicity characteristic leaching procedure (TCLP) in determining the safety of landfills or further utilization. As a consequence, a great deal of efforts had been made on the development of miniaturized analytical devices, such as Microchip Electrophoresis (ME) and µTAS for on-site testing of heavy metals and metalloids to prevent spreading of those pollutants or decrease the reutilization period of waste materials such as incineration bottom ash. However, the bottleneck lied in the long and tedious conventional TCLP that requires 18 h of leaching. Without accelerating the TCLP process, the on-site testing of the waste material leachates was impossible. In this study, therefore, a new accelerated leaching method (ALM) combining ultrasonic assisted leaching with tumbling was developed to reduce the total leaching time from 18 h to 30 min. After leaching, the concentrations of heavy metals and metalloids were determined with ICP-MS or ICP-optical emission spectroscopy. No statistical significance between ALM and TCLP was observed for most heavy metals (i.e., cobalt, manganese, mercury, molybdenum, nickel, silver, strontium, and tin) and metalloids (i.e., arsenic and selenium). For the heavy metals with statistical significance, correlation factors derived between ALM and TCLP were 0.56, 0.20, 0.037, and 0.019 for barium, cadmium, chromium, and lead, respectively. Combined with appropriate analytical techniques (e.g., ME), the ALM can be applied to rapidly prepare the incineration bottom ash samples as well as other environmental samples for on-site determination of heavy metals and metalloids.

Comparative analysis of quantitative phosphoproteomics between two tilapias (Oreochromis niloticus and Oreochromis aureus) under low-temperature stress.

As an important farmed fish, tilapia has poor tolerance to low-temperatures. At the same time, different tilapia strains have apparent differences in low-temperature tolerance. In this study, using the iTRAQ method, the phosphorylated proteomics of two tilapia strains (Oreochromis niloticus and Oreochromis aureus) with different tolerances to low-temperature stress were quantitatively and comparatively analyzed, to clarify the physiological mechanism of tilapia's response to low-temperature stress. Through the GO and IPR analyses of differentially phosphorylated proteins, a number of similarities in physiological activities and regulatory effects were found between the two tilapias in response to low-temperature stress. Many differentially phosphorylated proteins are mainly involved in lipid metabolism, cell proliferation and apoptosis. However, the difference in endurance of low temperature of these two tilapias might be related to the differences in categories, expression and modification level of genetic products which were involved in the aforementioned physiological processes. And meanwhile, the enrichment results of KEGG showed the changes of multiple immune-related and growth-related phosphorylated proteins in the cytokine-cytokine receptor interaction pathway in O. aureus are more prominent. Furthermore, the significantly enriched pathway of carbohydrate digestion and absorption in O. niloticus may indicate that low-temperature stress exerts a more severe impact on energy metabolism. The relative results would help elucidating the molecular mechanism by which tilapia responds to low-temperature stress, and developing culture of tilapia species.

Amphiphilic ligand in situ assembly of uranyl active sites and selective interactions of molybdenum disulfide.

Removal of radioactive uranyl ions (UO22+) from water by effective adsorbents is highly desired but remains a challenge. UO22+ are easily combined with H2O, and the polarization of H2O affects the complexation between UO22+ and the adsorbent. Thus, it is necessary to reconstruct the UO22+ active site to improve the adsorption capacity. Herein ，an amphiphilic ligand, namely N, N-dimethyl-9-decenamide (NND), is successfully prepared. NND replace H2O in [UO2(H2O)5]2+ by hydrogen bonding, thereby enhancing the adsorption capacity of MoS2 particles in the reconstituted UO22+ active sites. The predicted maximum adsorption capacity increased from 50.7 to 500.7 mg g- 1 (by a factor of 9.87) with the presence of NND, which is higher than other functional group-modified MoS2 adsorbents. Furthermore, NND and MoS2 can retain UO22+ uptake under extreme conditions including high acid-base and gamma irradiation. Theoretical Calculations of NND through H bonding produces an increased amount of charge transfer and a reduced adsorption energy between UO22+ and MoS2, which weakens the polarization effect of H2O. The findings showed that NND appeared to be a promising amphiphilic to improve the adsorption efficiency of UO22+ from water.

Waste-derived nanobiochar: A new avenue towards sustainable agriculture, environment, and circular bioeconomy.

The greatest challenge for the agriculture sector in the twenty-first century is to increase agricultural production to feed the burgeoning global population while maintaining soil health and the integrity of the agroecosystem. Currently, the application of biochar is widely implemented as an effective means for boosting sustainable agriculture while having a negligible influence on ecosystems and the environment. In comparison to traditional biochar, nano-biochar (nano-BC) boasts enhanced specific surface area, adsorption capacity, and mobility properties within soil, allowing it to promote soil properties, crop growth, and environmental remediation. Additionally, carbon sequestration and reduction of methane and nitrous oxide emissions from agriculture can be achieved with nano-BC applications, contributing to climate change mitigation. Nonetheless, due to cost-effectiveness, sustainability, and environmental friendliness, waste-derived nano-BC may emerge as the most viable alternative to conventional waste management strategies, contributing to the circular bioeconomy and the broader goal of achieving the Sustainable Development Goals (SDGs). However, it's important to note that research on nano-BC is still in its nascent stages. Potential risks, including toxicity in aquatic and terrestrial environments, necessitate extensive field investigations. This review delineates the potential of waste-derived nano-BC for sustainable agriculture and environmental applications, outlining current advancements, challenges, and possibilities in the realms from a sustainability and circular bioeconomy standpoint.

Paper-based enzyme immobilization for flow injection electrochemical biosensor integrated with reagent-loaded cartridge toward portable modular device.

Paper-based enzyme immobilization for a flow injection electrochemical biosensor integrated with a reagent-loaded cartridge toward a portable device was developed. A paper disk was immobilized with enzyme, then it was integrated in a flow cell as an electrochemical biosensor. A silicon tube reagent-loaded cartridge was integrated into the system, a complicated procedure was simplified as a one-click operation toward development for point-of-care applications. In this research, glucose oxidase (GOx) was employed as a model enzyme, silver ion as an inhibition reagent for GOx, and EDTA as a regeneration reagent. When GOx was inhibited by silver ions, glucose was introduced for electrochemical measurements before and after inhibited enzyme regeneration and the difference was caused by silver inhibition. The modular device has great potential for other applications, e.g., detection of enzyme activity and substrate. The platform based on double-test mode provided accurate results due to elimination of an average or control value in comparison with classical routine approaches.

Detection of the cell viability and proliferation using two-signal electrochemical method.

Two electrochemical signals of the MCF-7 cell were simultaneously detected by using multiwall carbon nanotubes and room temperature ionic liquid composite film modified electrode. The signal at +0.726 V due to the oxidation of xanthine and guanine, was obviously improved. And the signal at +1.053 V due to the oxidation of hypoxanthine and adenine was found for the first time. This two-signal electrochemical method is credible to detect cell viability and proliferation.

Facile synthesis of electrocatalytically active bismuth oxide nanosheets for detection of palladium traces in pharmaceutical wastewater.

Current synthesis routes of bismuth oxide nanosheets (BiONS) are relatively complicated, requiring the use of halogens or metalloids. Herein, a facile method to synthesize BiONS without the addition of halogens or other metalloids was developed. The synthesized BiONS were identified to have flake-shaped structures (300-1000 nm in width) with the thickness of 6-10 nm, which were predominantly made of ß-Bi2O3. Such BiONS were applied to modify the surface of screen-printed carbon electrodes (BiONS-SPCEs) for the development of a robust palladium (Pd2+) sensor. After optimizing the electrochemical parameters of the sensor, it was found that the linear sensor response range and limit of detection for Pd2+ were 40-400 and 1.4 ppb, respectively. The electrocatalytic activity of the Pd2+-sensor was validated in the competing environment of other metal and metalloid ions. Real samples collected during a Pd recovery process from pharmaceutical wastewater were used to verify the application of BiONS-SPCEs in control of palladium recovery process. The quantitative results of post recovery palladium concentrations obtained using BiONS-SPCEs in treated pharmaceutical wastewater samples were in good agreement with those obtained by inductively coupled plasma-optical emission spectrometry (ICP-OES). Thus, such Pd2+-sensor provided the possibility of on-site process control of complex industrial samples for obtaining near-instant information that would lead to better management of resources used in the process, and same time assure environmental standards for both recovered products and processed discharge.

Surfactant-assisted pressurized liquid extraction for determination of flavonoids from Costus speciosus by micellar electrokinetic chromatography.

Micellar electrokinetic chromatography (MEKC), a mode of capillary electrophoresis (CE), is considered an efficient analytical technique allowing for the reduction of organic solvent consumption during the experimental procedure. However, during sample preparation of natural products, the usage of large amount of organic solvent is generally unavoidable. In this article, therefore, a fast, simple, efficient, highly automatic and organic solvent-free sample preparation method, namely surfactant-assisted pressurized liquid extraction (PLE), was developed for the extraction of flavonoids in Costus speciosus flowers before MEKC analysis. The various experimental parameters such as the type and concentration of surfactant, and extraction time were evaluated systematically. Under the optimized conditions, the extraction efficiencies of surfactant-assisted PLE methods were comparable with Soxhlet extraction using organic solvent. The combination of surfactant-assisted PLE and MEKC was shown to be a green, rapid and effective approach for extraction and analysis of flavonoids in C. speciosus flowers.

Highly reproducible solid contact ion selective electrodes: Emerging opportunities for potentiometry - A review.

The solid contact ion-selective electrodes (SC-ISEs) have been extensively studied in the field of ion sensing as they offer the possibility of miniaturization, are relatively inexpensive in comparison to other analytical techniques and allow straightforward and routine analyses of ions in a number of clinical, environmental and industrial process samples. In recent years, significant interest has grown in the development of SC-ISEs with well-defined interfacialpotentials at the membrane, solid contact, and substrate electrode interfaces. This has resulted in interesting SC-ISEs exhibiting high electrode-to-electrode potential reproducibility, for those made in a single batch of electrodes, some approaching or exceeding those observed in liquid-contact ISEs. The advancement in the potential reproducibility of SC-ISEs has been partially achieved by scrutinizing insufficiently reproducible fabrication methods of SC-ISEs, or by introducing novel control measures or modifiers to components of the ISEs. This paper provides an overview of the methods as well as the challenges in establishing and maintaining reproducible potentials during the fabrication and use of novel SC-ISEs. The rules outlined in the works reviewed may form the basis of further development of cost-effective, user-friendly, limited calibration or calibration-free potentiometric SC-ISEs to achieve reliable ion analyses here and now.

Near real-time analysis of para-cresol in wastewater with a laccase-carbon nanotube-based biosensor.

Para-Cresol is a water-soluble organic pollutant, which is harmful to organisms even at low concentrations. Therefore, it is important to rapidly detect the p-cresol in wastewater as well as natural water. In this work, a new, simple and stable biosensor was developed for on-site quantitatively determination and near real-time monitoring p-cresol in wastewater. The new biosensor was designed and fabricated using a screen-printed carbon electrode (SPCE) modified by waste-derived carbon nanotubes (CNTs) immobilized with laccase (LAC). The fabrication processes and performance of the biosensors were systematically characterized and optimized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and electrochemical methods. With improved conductivity, the proposed biosensor could provide the direct quantitation of p-cresol. The linear range of the biosensor is 0.2-25 ppm of p-cresol with a detection limit of 0.05 ppm. Additionally, the biosensor exhibited high reproducibility, stability and reusability during the validation. More importantly, the biosensor was successfully applied for the rapid detection of p-cresol in environmental lab wastewater under the interference of metal ions and other organics, and the results were consistent with high-performance liquid chromatography (HPLC). Finally, the biosensor with a portable potentiostat was approved as an easy-to-use, sensitive and inexpensive platform that could provide near real-time monitoring of p-cresol concentration in wastewater during Fenton oxidation treatment process.

Gold-silver nanoparticles modified electrochemical sensor array for simultaneous determination of chromium(III) and chromium(VI) in wastewater samples.

The oxidation state of ions is a crucial aspect that often has been overlooked when determining the toxicity of chromium (Cr) species in environmental samples. In this study, a novel electrochemical sensor array based on gold-silver nanoparticles modified electrodes was developed for simultaneous determination of the two main chromium species (Cr(III) and (VI)). Specifically, the working electrodes of screen-printed carbon electrodes (SPCEs) were modified with silver-gold bimetallic nanoparticles through electrochemical deposition for detection of Cr(VI). The silver-gold bimetallic nanoparticles were further oxidized to form stable silver-gold bimetallic oxide nanoparticles for the detection of Cr(III). The results showed that the addition of silver with a theoretical value of 1% of gold could contribute to the formation and stabilization of oxides on the surface of gold nanoparticles. After characterization, the two kinds of electrodes were integrated as an electrochemical sensor array for selective and sensitive detection of Cr(VI) and Cr(III). The linear range and limit of detection (LOD, identified by three times of signal-to-noise ratio) were found to be 0.05-5 ppm and 0.1 ppb for Cr(VI), and 0.05-1 ppm and 0.1 ppb for Cr(III), respectively. Finally, the electrochemical sensor array was proven for successful detection of Cr(VI) and Cr(III) in tap water, artificial saliva and artificial sweat samples, and monitoring of Cr(VI) and Cr(III) in chromium-containing wastewater treatment process. Combined with a handheld dual-channel electrochemical device, the simultaneous determination of Cr(VI), Cr(III) and total chromium contents can be easily achieved for various samples.