pH Indicator Research Articles

Quality assessment of various Xiushui Ninghong tea types.

Xiushui Ninghong tea (XSNH) has a long history and is renowned both in China and internationally. Based on different processing techniques, XSNH can be classified into Ninghong Congou, Ninghong Tea Jinhao, Ninghong Tea Longxucha and other types. To investigate the differences in nutrient compounds and mineral element contents among various types of XSNH, 34 samples from seven types were collected, primarily from tea-producing areas. Statistical analysis indicated no significant differences in the contents of crude polysaccharides, K, Mg and Fe, whereas significant differences were observed in the levels of moisture, free amino acids, caffeine, tea polyphenols, thearubigin, theaflavins, Zn, P, Mn, Cu and Se. The data were analyzed using various statistical methods such as hierarchical cluster analysis, principal component analysis and partial least squares discriminant analysis. Characteristic compounds and elements such as theaflavin, Se, free amino acids, P and tea polyphenols were identified as key differential components for distinguishing different sample types. Our research has highlighted the differences in chemical indicators among various types of XSNH, providing a crucial theoretical basis for the future classification and grading of XSNH quality. © 2024 Society of Chemical Industry.

Evaluating water quality of rock glacier outflows in the Western Alps, Italy: a regional perspective.

Intact rock glaciers (RG) are considered valuable water storage because containing permafrost ice volumes. The hydrological relevance of RG is forecasted to increase with respect to glaciers under climate change scenarios, as well as RG's role as water resources in alpine basins for multiple uses. Besides the assessment of water amount stored in intact rock glaciers, the evaluation of water quality is of primary importance. Here, we present the results of a chemical survey performed on five outflows from intact RG in 2020-2023 in the Piedmont region, Western Alps, Italy, along a latitudinal gradient and in different geological settings. The survey aimed to assess the water quality of RG outflows based on chemical indicators (major ions, nutrients, trace metals). Sampling and analyses were performed according to standard methods for freshwater samples, paying specific attention to the analytical quality and consistency of the data. We considered seasonal and interannual variability of the main chemical variables and the possible effects of RG outflows on the chemistry of lakes and ponds located in proximity to the RG. All the investigated sites were characterized by low to moderate ion content, low nutrients, and trace metals close to or below the detection limit, indicating a good water quality status. Results suggested lithology as the main factor affecting the chemical composition of RG outflows. The results of this study indicate it is advisable to develop shared protocols and joint monitoring programs for data collecting at RG outflow sites all over the Alps, possibly integrating chemical and biological indicators, with the final aim of monitoring the water quality of these valuable resources and its temporal evolution under climate change.

Organic Fertilization Improves Soil Multifunctionality in Sugarcane Agroecosystems

Soil multifunctionality is closely tied to soil health, yet a comprehensive understanding of this link in agricultural soils is lacking. The aim of this study was to understand how long-term fertilization practices affect the provision of multiple services by comparing the multifunctionality of soils. The three objectives were to (i) determine whether the effect of fertilization is consistent across soil types, (ii) describe the effect of the different fertilizers on soil multifunctionality, and (iii) identify soil chemical properties that can be easily used proxies of soil multifunctionality. The descriptors belong to three functioning indexes associated with nutrient availability, carbon transformation, and soil structure maintenance. This study is the first to investigate the effect of a variety of organic fertilizers on the health of three soil types by combining physical, chemical, and biological indicators in sugarcane agroecosystems. An increase in soil multifunctionality was obtained, with no effect on yield. The effect of fertilizers was consistent across soil types. Filter mud and green waste compost significantly increased the multifunctionality and functioning indexes compared to mineral fertilizer. Modifications in soil properties did not fully explain the observed variations. Our results confirm the high potential of organic fertilization to improve multifunctionality and provide ecosystem services.

Sucralose and caffeine as chemical indicators of domestic wastewater contamination in the Laurentian Great Lakes Basin.

Surface waters within the basin of the Laurentian Great Lakes are impacted by microbial contamination from municipal wastewater and agricultural runoff, as well as from other sources. In particular, microbial contamination of drinking water is an ongoing problem within many Indigenous communities located in the basin. However, it is difficult to identify the sources of microbial contamination using the traditional monitoring approaches with fecal indicator bacteria, such as total coliforms and Escherichia coli (E. coli). In this study, we evaluated whether surface waters in the basin are contaminated with fecal bacteria of human origin using chemical indicators of domestic wastewater (i.e., caffeine and sucralose) and with Bacteroidales 16S rRNA markers. Study areas included the Grand River watershed within the Lake Erie basin and three nearshore locations within the Great Lakes basin. Two of these sites are sources of drinking water for Indigenous communities. We assessed whether there were relationships between the concentrations of fecal indicator microorganisms and chemical indicators of domestic wastewater at selected study locations. Analysis of genetic markers indicated that about 30% of the Bacteroidales bacteria present at a site in the Grand River were of human fecal origin and the balance were of bovine or general animal origin. The presence of caffeine and sucralose in surface waters indicated that there was upstream contamination by domestic wastewater. However, in the drinking water treatment plant operated by Six Nations of the Grand River, the levels of these chemical indicators and fecal bacteria were reduced by the advanced water treatment technologies. The concentrations of sucralose and caffeine collectively were strongly correlated with the levels of total coliforms in samples from the Grand River (R2 = 0.75) and with levels of E. coli in samples from the Great Lakes basin (R2 = 0.97), but there appeared to be an upper threshold for this relationship. These data indicate that analysis of caffeine and sucralose and genetic markers for strains of Bacteroidales fecal bacteria may be useful tools for identifying the sources of microbiological contamination of surface waters and drinking water.

საქართველოსა და უცხოეთის ქვეყნების ზოგიერთი საბადოს ბენტონიტების შედარებითი ტექნოლოგიური შეფასება

An assessment of the technological characteristics of bentonites from some deposits in Georgia and foreign countries was carried out. The superiority of Georgian bentonite clays in terms of basic physical and chemical indicators is shown; of the bentonites from foreign countries, the sample from Hungary turned out to be the best. The adsorption capacity of bentonites in relation to methylene blue (MB) has been studied. It has been established that heat treatment at a temperature of 500 0C leads to a decrease in the adsorption activity of bentonites towards MB.

Main spatial-temporal regularities of the state of the chemical composition of groundwater of the oligocene aquifer in the Shaim oil and gas bearing area

The constantly growing need for fresh water in the Shaim oil and gas region necessitates the exploration of new areas and the development of measures to improve the operation of water intakes. To predict the quality of groundwater, which is an operational parameter of the aquifer aquifer, it is needed up-to-date information on the chemical composition of ground-water. The aim of this study to identify main spatial-temporal regularities of the state of the chemical composition of groundwater of the oligocene aquifer in the Shaim oil and gas bearing area, compared to average values from adjacent areas. Research methods include the systematization of laboratory data on water samples, analysis of groundwater chemistry, and mapping of the main spatial-temporal patterns in component concentration changes. The average values of chemical composition indicators in the studied area are similar to those of neighbouring areas, with some indicators exceeding drinking water standards. Similarities are observed in the variability of the chemical composition, spatial patterns of changes in most chemical indicators, and the presence of areas with extreme values. Current data on the chemical composition of the oligocene aquifer ground-water, including key characteristics and spatial-temporal trends presented in distribution maps, can be used in designing groundwater intakes and forecasting long-term groundwater quality.

Spatial Distribution of Physical and Chemical Properties of Deep Sea Water in Xisha, South China Sea

Deep sea water (DSW) is a globally utilized source of renewable energy and other resources. To understand the characteristics of DSW resources in the South China Sea, in July 2022, the Guangzhou Marine Geological Survey (GMGS) investigated temperature, salinity, pH, dissolved oxygen (DO), inorganic salts (DIN, PO43−-P, and SiO3-Si), heavy metals (Hg, Pb, As, and Cd), trace elements (Cu, Zn, Fe, Mn, Ni, Se, and Mo), and other related indicators. The results of this investigation elucidate the horizontal and vertical changes in the physical and chemical properties of deep sea water in the Xisha Sea. The surface seawater quality in Xisha was found to be excellent and to meet first-class seawater survey standards. However, the concentrations of various nutrient salts in the surface layer were relatively low. As the seawater depth increased, different trace elements and heavy metals exhibited variations, and the concentrations of various nutrients also gradually increased.

ОЦЕНКА АНТРОПОГЕННОЙ НАГРУЗКИ НА ВОДОСБОР БАССЕЙНА РЕКИ ТОБЫЛ ОТ ИСТОЧНИКОВ ЗАГРЯЗНЕНИЯ С МАТЕМАТИЧЕСКИМ МОДЕЛИРОВАНИЕМ КАЧЕСТВА ПОВЕРХНОСТНЫХ ВОД

Based on a systematic analysis of the structure and dynamics of water resource usage in the catchment area of the Tobyl River basin, the dynamics of the formation of geoecological conditions of water use in the economic sectors within the Kostanay region of the Republic of Kazakhstan were studied. The analysis revealed a significant load from return waters and pollutants, indicating a high and potentially catastrophic pressure that requires regulation of both natural and anthropogenic activities to ensure the region’s sustainable development in the future. A generalized water use scheme for the Kazakh part of the Tobyl River basin was developed, which facilitates the formation of mathematical, physical, and chemical indicators for water management and hydrochemical balance equations. This, in turn, allowed for the creation of a mathematical model of water quality and the determination of the maximum permissible discharge volume of return waters in the river basins. The model ensures compliance with sanitary-epidemiological standards and helps preserve the ecological state of water bodies while supporting the planning of water protection measures to achieve the desired level of water quality in the river.

Evaluation of Water Quality and Eutrophication of Typical Lakes in Southeast Hubei, China

Field surveys and sample analyses were conducted from January 2018 to December 2019 on Daye Lake, Cihu Lake, Baoan Lake, and Xiandao Lake to understand the water quality characteristics of typical lakes in southeast Hubei. A fuzzy comprehensive evaluation was conducted and the comprehensive trophic level index was applied to evaluate the lakes’ water quality. The results showed differences in the regional, spatial, and temporal distributions of physical and chemical indicators in typical lakes in southeast Hubei. The fuzzy comprehensive evaluation showed that the water quality levels in Daye, Cihu, Baoan, and Xiandao Lakes for 2018 and 2019 were IV, IV, III, and II and V, IV, III, and II, respectively, with seasonal variations in water quality occurring during the year. The trophic level index results showed that Cihu Lake was mildly eutrophic in 2018 and moderately eutrophic in 2019, and Daye, Baoan, and Xiandao Lakes were mildly eutrophic, mildly eutrophic, and mesotrophic, respectively. Lake water quality was influenced by land use types, landscape configuration, inflowing rivers, precipitation, and interactions between land use and seasons. This study helps us to understand the trend and causes of lake pollution in Southeast Hubei, which is conducive to watershed management and the control of water quality deterioration, and also has an important role in regulating the sustainable development of industry and agriculture in the watershed.

Fermented buttermilk drinks fortified by plant raw materials

The research featured fortified fermented drinks from pasteurized buttermilk with such natural additives as Jerusalem artichoke syrup and beetroot dietary fiber. The optimal symbiotic culture included Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus: it provided rapid fermentation and a creamy, homogeneous structure with delta pH time = 3.5 h. Jerusalem artichoke syrup was added in amounts of 3, 6, and 9%. Its optimal share proved to be 6% by the weight of the finished product. Beet dietary fiber was added in amounts of 2, 4, and 6%, where the optimal amount was 4%. A higher percentage affected the consistency of the finished product but not its clotting or taste. The experimental drinks were produced by the tank method and fermented at 42 ± 2°C until dense clotting and titratable acidity = 72 ± 2°T. The finished product was stored at 4 ± 2°C. The shelf-life was 12 days for the sample with Jerusalem artichoke syrup and 14 days for the drink fortified with beetroot fiber. The physical and chemical indicators showed that the energy value of the fortified fermented buttermilk drinks was on average 45.3% lower compared to conventional fermented dairy drinks. As a result of research, it has been established that the use of plant components, namely Jerusalem artichoke syrup and beet dietary fiber in the production technology of fermented milk drink from buttermilk makes it possible to obtain a finished product with improved consumer properties.

Intelligent Packaging Systems with Anthocyanin: Influence of Different Polymers and Storage Conditions

With the aim of meeting the growing demand for safe food, intelligent packaging has emerged, which monitors the conditions of the food and informs the consumer about its quality directly at the time of purchase. Among intelligent packaging options, colorimetric indicator films, which change color in response to changes in the food, such as the release of volatile compounds, have been widely studied. Among them, pH indicator films composed of dyes sensitive to small variations in the pH value of the food surface have received greater attention in recent years. Anthocyanins, which are natural pigments, have stood out as one of the most commonly used sources of dyes in the production of these indicator films. In this context, the present review aims to present an updated overview of research employing anthocyanins in indicator films, including their stability under different storage conditions, the influence of different polymers used in their production, and alternative techniques for maintaining stability.

Smart photonic crystal hydrogels for visual glucose monitoring in diabetic wound healing

Diabetes is a global chronic disease that seriously endangers human health and characterized by abnormally high blood glucose levels in the body. Diabetic wounds are common complications which associate with impaired healing process. Biomarkers monitoring of diabetic wounds is of great importance in the diabetes management. However, actual monitoring of biomarkers still largely relies on the complex process and additional sophisticated analytical instruments. In this work, we prepared hydrogels composed of different modules, which were designed to monitor different physiological indicators in diabetic wounds, including glucose levels, pH, and temperature. Glucose monitoring was achieved based on the combination of photonic crystal (PC) structure and glucose-responsive hydrogels. The obtained photonic crystal hydrogels (PCHs) allowed visual monitoring of glucose levels in physiological ranges by readout of intuitive structural color changes of PCHs during glucose-induced swelling and shrinkage. Interestingly, the glucose response of double network PCHs was completed in 15 min, which was twice as fast as single network PCHs, due to the higher volume fraction of glucose-responsive motifs. Moreover, pH sensing was achieved by incorporation of acid-base indicator dyes into hydrogels; and temperature monitoring was obtained by integration of thermochromic powders in hydrogels. These hydrogel modules effectively monitored the physiological levels and dynamic changes of three physiological biomarkers, both in vitro and in vivo during diabetic wound healing process. The multifunctional hydrogels with visual monitoring of biomarkers have great potential in wound-related monitoring and treatment.Graphical abstract

Dynamics of digestive vacuole differentiation clarified by the observation of living Paramecium bursaria.

Paramecium bursaria is a ciliate species that has a symbiotic relationship with Chlorella spp. This study aimed to elucidate the dynamics of digestive vacuole (DV) differentiation in P. bursaria, using yeast stained with a pH indicator. Previously, DV differentiation in P. bursaria has been classified into eight periods based on fixed-cell observations. However, to understand the behavior and physiology of P. bursaria in its natural state, it is essential to observe living cells. This study presented a novel method using Cornig® Cell-Tak™ to immobilize living P. bursaria cells, which enabled long-term observation of the same cell from the same direction. This technique allowed for real-time observation of DV differentiation, including the relationship between changes in the internal pH of DV and the diameter of DV, yeast budding from the DV membrane by a single cell into the cytoplasm, and separation of a DV containing multiple yeasts into two DVs. This study provides new insights into the dynamic process of DV differentiation in P. bursaria. These findings contribute to a better understanding of the cellular mechanisms underlying the symbiotic relationship between the two organisms and shed light on the complex process of intracellular digestion in ciliates.

Environmentally Friendly Chemical–Magnetorheological Finishing Method for Ti–6Al–4V Biological Material Based on Fe3O4@SiO2, Oxaloacetate Acid and H2O2

Titanium alloy is extensively utilised in various advanced equipment across multiple industries, especially in biological implantable devices. The surface machining of such devices is required to provide a finished surface with high precision and gloss. This study presents an established ecofriendly slurry for a hybrid polishing process utilising a highly efficient chemical and magnetorheological fluid (C-MRF) to obtain ultraprecise surface quality. This slurry incorporated Fe3O4@SiO2 abrasive particles, oxaloacetate acid (C4H6O5), deionised water and hydrogen peroxide (H2O2) as an oxidiser. Ti–6Al–4V workpieces polished with C-MRF based on Fe3O4@SiO2 abrasives and polishing performance were used to investigate the influence of the oxidising agent H2O2 and oxaloacetate acid (monitored with a pH indicator) on the surface finish of Ti–6Al–4V biomaterial. In contrast to the traditional mechanical and chemical polishing methods for titanium alloys that often include strong bases and acids along with chemicals that endanger the environment and humans, the proposed polishing process based on the newly developed ecofriendly magnetic composite leveraged the advantages of magnetorheological fluid with chemical reactions to create an ultra smooth surface. Experiments were performed to investigate the influence of different polishing durations and factors on the quality of polished surfaces, thereby optimising technological parameters, reducing time and improving surface quality. Various technological parameters were evaluated through single-factor and orthogonal experiments to assess their distinct effects on surface quality and material removal capability. This work proposed an environmentally friendly C-MRF method for finishing Ti–6Al–4V biomaterial with high efficiency and industrial applicability.

Computationally Optimized Graphene-Based Electrochemical Sensor with Enhanced Signal Stability for the Determination of the Antimicrobial Agent 9-aminoacridine

A hydrophobic aryl diazonium salt has been synthesized from 3,5-bis(trifluoromethyl)aniline and utilized to covalently modify graphene nanoplatelets and carbon nanotubes. The modified nanomaterials were applied on a screen-printed electrode/ion sensing membrane interface resulting in reduced potential drift to 100 μV h−1 compared to control sensors. Characterization was achieved through X-ray photoelectron spectroscopy. The electrode’s response was optimized using response surface methodology and then utilized for determination of 9-Aminoacridine (9-AA) in pharmaceutical gel dosage form and spiked human plasma without prior extraction steps. 9-AA is a fluorescent dye with antimicrobial activity that eradicates a range of microorganisms that can cause oral sores or broken skin and it has been recently used as anticancer among other uses as fluorescent dye and pH indicator. Accurate determination of 9-AA could help in adjusting dosages for each application. The optimized sensor was validated per IUPAC guidelines and obtained a wide linearity range from 1.0 × 10–7 M to 1.0 × 10–2 M, correlation coefficient of 0.9997, improved Nernstian slope 59.72, long term stability, and lower limit of detection (9.0 × 10–8 M). Furthermore, Analytical Eco-scale and AGREE methods were utilized to evaluate the presented method’s greenness.

Economic optimization of sustainable soil management: a Dutch case study

Soil quality is pivotal for crop productivity and the environmental quality of agricultural ecosystems. Achieving sufficient yearly income and long-term farm continuity are key goals for farmers, making sustainable soil management an economic challenge. Existing bio-economic models often inadequately address soil quality. In this study, we apply the novel FARManalytics model, which integrates chemical, physical, and biological indicators of soil quality indicator, quantitative rules on how these indicators respond to farmers’ production management over time, and an economic calculation framework that accurately calculates the contribution of production management decisions towards farm income. This is the first study applying this model on existing arable farms. FARManalytics optimizes crop rotation design, cover crops, manure and fertilizer application and crop residue management. Nine Dutch arable farms were analyzed with a high variation in farm size, soil type, and cultivated crops. First, we assessed farm differences in soil quality and farm economics. Second, we optimized production management to maximize farm income while meeting soil quality targets using farm-specific scenarios. Third, we explored the impact of recent policy measures to preserve water quality and to increase the contribution of local protein production. The results show that the case farms already perform well regarding soil quality, with 75% of the soil quality indicators above critical levels. The main soil quality bottlenecks are subsoil compaction and soil organic matter input. We show that even in front-runner farms, bio-economic modeling with FARManalytics substantially improves economic performance while increasing soil quality. We found that farm income could be increased by up to €704 ha−1 year−1 while meeting soil quality targets. Additionally, we show that to anticipate on stricter water quality regulation and market shift for protein crops, FARManalytics is able to provide alternative production management strategies that ensure the highest farm income while preserving soil quality for a set of heterogenous farms.

A commercially available dye as a highly versatile colorimetric fluoride sensor

Reported herein is the successful use of the commercially available organic dye bromocresol green (compound 1) for high-performing and practical fluoride detection. This dye responds to fluoride anion with high selectivity (virtually no response to other halide anions), excellent sensitivity (limits of detection as low as 0.22 ppm) and rapid response times, and maintains functionality when it is adsorbed on filter paper. Mechanistic studies determined that the fluoride-induced colorimetric changes were due to intermolecular hydrogen bonding between compound 1 and fluoride. Finally, the broad applicability of this sensor was demonstrated through the colorimetric response of compound 1 – functionalized paper to fluoride in commercial mouthwash. These findings underscore compound 1’s potential as a practical and commercially viable fluoride sensor, in addition to compound 1’s better-known role as a colorimetric pH indicator.

A novel ZIF-8 mediated nanocomposite colorimetric sensor array for rapid identification of matcha grades, validated by density functional theory

The rapid and intelligent assessment of matcha grades remains crucial in quality control. This study proposed a colorimetric sensor array (CSA) mediated with zeolitic imidazolate framework-8 (ZIF-8) to identify matcha grades. The ZIF-8 mediated CSA was innovatively developed by encapsulating the pH indicator and metal porphyrin within the ZIF-8 structure, improving their stability and functionality. ZIF-8 mediated CSA exhibited significantly increased sensitivity towards matcha samples driven by the preconcentration of volatile organic compounds (VOCs) facilitated by ZIF-8. As a result, the response signal values of the CSA increased by 1.13–4.75 times after ZIF-8 mediation. Subsequently, qualitative models for identifying matcha grades were established using K-Nearest Neighbor and Artificial Neural Network (ANN). The ANN model showed the higher discrimination accuracy. Compared with common CSA, the ANN model based on ZIF-8 mediated CSA achieved a better identification rate of 95 %, and recognition accuracy was improved by 7.5 % in the model. These results indicated that the ZIF-8 mediated CSA with a porous structure demonstrated enhanced specificity in capturing VOCs. Ultimately, the density functional theory has confirmed that the ZIF-8-mediated CSA exhibits high selectivity towards matcha's characteristic VOCs. These results highlight the potential of this novel CSA for the rapid identification and grading of matcha.

Antioxidant activity evaluation of the combination of oregano (Origanum vulgare) and laurel (Laurus nobilis) essential oil as two natural “chain-breaking” antioxidants by direct measurement of sunflower oil oxidation

Antioxidants are commonly used to reduce oxidative damage in lipids, and essential oils offer natural alternatives with antioxidant properties. This research seeks to determine the antioxidant efficiency of the combination of laurel (laurus nobilis) and oregano (origanum vulgare) essential oils exhibiting a chain-breaking mechanism. To this end, an accelerated oxidation of sunflower vegetable oil was carried out at 60 °C for 28 days, in combination with concentrations of 0.05% w/w (1) and 0.02% w/w (2) of the essential oils. BHT at 0.02% w/w was used as a reference antioxidant. The chemical indicators of oxidation (dienes conjugated, peroxides, anisidine and TOTOX values) and volatiles (2-heptenal Z, 2,4-Decadienal EZ and EE) were determined. While no substantial differences were found between the studied concentrations of the essential oils, a decrease in the protective effect was observed when the concentration of laurel was increased. Interestingly, the antioxidant effect of both oregano and laurel essential oils was observed to be similar to that of BHT. The results suggest that the combination of these essential oils with chain-breaking antioxidant mechanisms might be used as an antioxidant in food.

Synthesis, Characterization and Analytical Study of New Azo Compounds for using as acid-base indictors

A diazotization method was used to synthesize new azo compounds, to which phenol was subsequently added to diazonium salt solution in basic medium at temperatures ranging from 0 to 5 °C and compounds were characterized by FT-IR, 1H-NMR, and 13C-NMR spectroscopy. The potential of the compounds as acid-base indicators was tested by determining their ionization and protonation constants at different pH levels (1 to 14) using a DMSO solution of the synthesized compounds. UV-Vis spectra shown as maximum wavelength (380-390 nm) observed at pH 1-7 occurs, indicating the cationic formula (protonated form of compound H2 and H4), another peak (470-530 nm) appears at pH 8-13, indicating the ionic formula (deprotonated form of compound H2 and H4), where for compound H5 observed at 560 nm at pH 1-7. Another peak appears 505 nm at pH 8-13 attributable to absorption the ionic formula (deprotonated form of compounds H5). Molecules H2, H4, and H5 showed distinct color changes when shifted to acidic and basic conditions. Furthermore, these compounds showed exceptional accuracy in drawing conclusions about the phenomenon.