pH Values Research Articles

Plant-derived bioactive compounds for the inhibition of biofilm formation: a comprehensive review.

Biofilm formation is a widespread phenomenon that impacts different fields, including the food industry, agriculture, health care and the environment. Accordingly, there is a serious need for new methods of managing the problem of biofilm formation. Natural products have historically been a rich source of varied compounds with a wide variety of biological functions, including antibiofilm agents. In this review, we critically highlight and discuss the recent progress in understanding the antibiofilm effects of several bioactive compounds isolated from different plants, and in elucidating the underlying mechanisms of action and the factors influencing their adhesion. The literature shows that bioactive compounds have promising antibiofilm potential against both Gram-negative and Gram-positive bacterial and fungal strains, via several mechanisms of action, such as suppressing the formation of the polymer matrix, limiting O2 consumption, inhibiting microbial DNA replication, decreasing hydrophobicity of cell surfaces and blocking the quorum sensing network. This antibiofilm activity is influenced by several environmental factors, such as nutritional cues, pH values, O2 availability and temperature. This review demonstrates that several bioactive compounds could mitigate the problem of biofilm production. However, toxicological assessment and pharmacokinetic investigations of these molecules are strongly required to validate their safety.

GAM-7: an organic-inorganic hybrid layered aluminophosphate crystal formed by zeolite transformation.

The interzeolite conversion (IZC) of metallo- and aluminophosphate zeolites was demonstrated using a non-cyclic secondary amine, diisopropylamine, as the organic structure-directing agent (OSDA). The IZC of AlPO4-5 with AFI topology could successfully produce an unknown highly crystalline phase, named GAM-7. In metallo-aluminophosphates (metal-AlPOs), SAPO-5 with a small amount of SiO2 was also interconverted to a single crystal GAM-7, designated as [Si]GAM-7. However, in other metal-AlPOs, the corresponding GAM-7 crystals were formed as either an intermediate or a mixture of plural crystals. Additionally, it was found that GAM-7 could also be obtained by hydrothermal synthesis (HTS), but not synthesized from a silico-aluminophosphate hydrogel, indicating that [Si]GAM-7 can be prepared by only the IZC technique. The obtained GAM-7 crystal was well-characterized to elucidate the framework structure, and this revealed that GAM-7 was a new organic-inorganic hybrid layered aluminophosphate having a terminal POH group in the corrugated layered sheets, and the OSDA molecule between the layers was robustly interacting with an acidic POH site by a hydrogen bond. Furthermore, we have performed the tracking of pH values during the transformation from AlPO4-5 into GAM-7 and have argued a reasonable consideration for the IZC process.

Ecofriendly Controlled-Release Insecticide Carrier: pH-/Temperature-Responsive Rosin-Derived Hydrogels for Avermectin Delivery against Mythimna separata (Walker).

The exploration of environmentally friendly, less toxic, sustained-release insecticide is increasing with the growing demand for food to meet the requirements of the expanding population. As a sustained-release carrier, the unique, environmentally friendly intelligent responsive hydrogel system is an important factor in improving the efficiency of insecticide utilization and accurate release. In this study, we developed a facile approach for incorporating the natural compound rosin (dehydroabietic acid, DA) and zinc ions (Zn2+) into a poly(N-isopropylacrylamide) (PNIPAM) hydrogel network to construct a controlled-release hydrogel carrier (DA-PNIPAM-Zn2+). Then, the model insecticide avermectin (AVM) was encapsulated in the carrier at a drug loading rate of 36.32% to form AVM@DA-PNIPAM-Zn2+. Surprisingly, the smart controlled carrier exhibited environmental responsiveness, strongly enhanced mechanical properties, self-healing ability, hydrophobicity, and photostability to ensure a balance between environmental friendliness and the precision of the drug release. The release experiments showed that the carboxyl and amide groups in the polymer chains alter the intermolecular forces within the hydrogel meshes and ingredient diffusion by changing temperatures (25 and 40 °C) and pH values (5.8, 7.4, and 8.5), leading to different release behaviors. The insecticidal activity of the AVM@DA-PNIPAM-Zn2+ against oriental armyworms was good, with an effective minimum toxicity toward aquatic animals. Therefore, AVM@DA-PNIPAM-Zn2+ is an effective drug delivery system against oriental armyworms. We anticipate that this ecofriendly, sustainable, smart-response carrier may broaden the utilization rosin and its possible applications in the agricultural sector.

Speciation of toxic metals in metal finishing filter cake by X-ray absorption spectroscopy

The speciation of Cr, Zn, Cu and Pb in two metal finishing filter cakes (TX and ST) was investigated by X-ray absorption spectroscopy (XAS) complemented by X-ray fluorescence (XRF) and X-ray diffraction (XRD). XRF showed that concentrations of Cr, Zn, Cu and Pb were 1.4%, 0.19%, 0.20% and 0.01%, respectively, in TX, and 12.6%, 3.3%, 1.3% and 0.21% in ST. No crystalline phases were detected in TX by XRD whereas ST was dominated by calcite. Cr and Fe K edge XAS showed Cr to be trivalent and octahedrally coordinated, co-precipitated with Fe as CrxFe1-x-(oxy)hydroxides in both filter cakes. Zn, P and Ca K edge XAS showed that 2ZnCO3∙3Zn(OH)2 and Zn3(PO4)2 were the dominant zinc-containing phases, with combined tetrahedral and octahedral coordination; Zn phases were slightly more crystalline in TX than ST. Pb L3 edge X-ray absorption near edge spectroscopy (XANES) found that Pb was likely adsorbed on amorphous SiO2. Cu, Si and S K edge XAS showed that all Cu was divalent, and the dominant copper phases were found to be Cu2Cl(OH)3, Cu(OH)2 and CuSO4·5H2O for ST, whereas Cu appeared to adsorb to amorphous SiO2 for TX, which contained much less Pb. Cr is thus immobilized in the filter cakes in a phase with low solubility at environmentally feasible pH values, whereas Zn, Cu and Pb could be released when the pH decreases below 8 or above 11. These findings are significant for the development of waste management regulations and/or metal recovery methods (e.g., hydro/pyrometallurgy).

Use of UV-C radiation and packaging to maintain the quality of minimally processed kale

Kale, a imortant crop for family farms, gains added value through minimal processing, enhancing freshness and convenience. UV-C irradiation emerges as a promising method for extending kale's shelf life without chemicals, although standardization is complex due to varying food resistances to light penetration.The study in question analyzed the effects of two different irradiation times on minimally processed cabbage, packaged in bowls and Styrofoam with plastic film, observing changes in physical-chemical and sensory parameters, such as loss of mass, color, pH, and visual and olfactory signs of deterioration. Six treatments were tested, varying the exposure time and the type of packaging, as well as a treatment with chlorinated sanitizer, using the Tukey test at 5% significance to determine the most effective in preserving the product. It was found that the packaging in the cumbuca resulted in less mass loss compared to the tray, and the lowest pH values were recorded in the treatment with UV-C light in the cumbuca, which may indicate that they are an option for reducing the stress of the product after processing. None of the color parameters a* and b* or the luminosity index differed from each other, so it is valid to say that the UV-C radiation and chlorine sanitization treatments applied in the experiment were able to preserve the color of the cabbage samples for a period of 8 days. Therefore, the application of UV-C light did not negatively affect the color, pH or loss of mass of the minimally processed cabbage and combined with the correct packaging can be an alternative to conventional sanitization, in addition to maintaining the original aroma of the product.

Emulsions Stabilized with an Electrostatic Complex of Quaternized Cellulose Nanofiber and Octanoyl Gelatin and the Effect of pH Value on Their Stability

Emulsions Stabilized with an Electrostatic Complex of Quaternized Cellulose Nanofiber and Octanoyl Gelatin and the Effect of pH Value on Their Stability

Bioreactor Expansion Affects Microbial Succession of Mixotrophic Acidophiles and Bioremediation of Cadmium-Contaminated Soils

Microbial scale-up cultivation is the first step to bioremediating cadmium (Cd)-contaminated soils at the industrial scale. However, the changes in the microbial community as the bioreactor volume expands and their associations with soil Cd removal remain unclear. Herein, a six-stage scale-up cultivation process of mixotrophic acidophiles was conducted, scaling from 0.1 L to 10 m3, to remediate Cd-contaminated soils. The findings showed that bioreactor expansion led to a delay in sulfur and glucose oxidations, resulting in a reduced decline in solution pH and cell density. There were minimal differences observed in bacterial alpha-diversity and community structure as the bioreactor volume increased, except for the 10 m3 scale. However, bioreactor expansion decreased fungal alpha-diversity, changed the community structure, and simplified fungal community compositions. At the family level, Acidithiobacillaceae and Debaryomycetaceae dominated the bacterial and fungal communities throughout the scale-up process, respectively. Correlation analysis indicated that the indirect effect of mixotrophic acidophiles played a significant role in soil Cd removal. Bacterial community shifts, driven by changes in bioreactor volume, decreased the pH value through sulfur oxidation, thereby indirectly enhancing Cd removal efficiency. This study will contribute to the potential industrial application of mixotrophic acidophiles in bioremediating Cd-contaminated soils.

One-pot synthesis of NiCo-phyllosilicate supported on zeolite for enhanced degradation of antibiotic contaminants

The overuse of antibiotics currently results in the presence of various antibiotics being detected in water bodies, which poses potential risks to human health and the environment. Therefore, it is highly significant to remove antibiotics from water. In this study, we developed novel rod-like NiCo-phyllosilicate hybrid catalysts on calcined natural zeolite (NiCo@C-zeolite) via a facile one-pot process. The presence of the zeolite served as both a silicon source and a support, maintaining a high specific surface area of the NiCo@C-zeolite. Remarkably, NiCo@C-zeolite exhibited outstanding catalytic performance in antibiotic degradation under PMS activation. Within just 5 min, the degradation rate of metronidazole (MNZ) reached 96.14%, ultimately achieving a final degradation rate of 99.28%. Furthermore, we investigated the influence of catalyst dosage, PMS dosage, MNZ concentration, initial pH value, and various inorganic anions on the degradation efficiency of MNZ. The results demonstrated that NiCo@C-zeolite displayed outstanding efficacy in degrading MNZ under diverse conditions and maintained a degradation rate of 94.86% at 60 min after three consecutive cycles of degradation. Free radical quenching experiments revealed that SO•− 4 played a significant role in the presence of NiCo@C-zeolite-PMS system. These findings indicate that the novel rod-like NiCo-phyllosilicate hybrid catalysts had excellent performance in antibiotic degradation.

Aluminum Removal from Rare Earth Chloride Solution through Regulated Hydrolysis via Electrochemical Method

Due to the coexistence of Al3+ and RE3+ and their similar properties, the separation of aluminum from rare earths is difficult. In this study, selective precipitation was used to separate aluminum from rare earth chloride solution via electrochemical regulated hydrolysis. By controlling the current density and electrolytic time, the rate of hydroxyl ion production was regulated, and the selective separation of rare earth and aluminum was realized according to the different precipitation sequences. By altering the temperature, current density, pH value, and other parameters, the separation performance of aluminum from rare earth in mixed rare earth chloride systems was systematically investigated. The removal rate of aluminum reached 88.35%, and the loss rate of rare earth was only 5.99% under optimized conditions. Compared with traditional neutralization hydrolysis, the new process showed higher efficiency and lower rare earth loss rate. Furthermore, a kinetic analysis of aluminum precipitation revealed that the reaction adhered to pseudo-first order kinetics. Additionally, the precipitate obtained via separation and filtration was amorphous alumina hydroxide with a small amount of rare earth attached. No reagent was consumed for the new process, which was more efficient and cleaner, providing a new idea for removing aluminum impurities from rare earth solutions.

Characteristics of Secang Jelly Drink as Functional Drink with the Addition of Red Ginger Extract for Antioxidant Source

Secang wood (Caesalpinia sappan L.) and red ginger can be used as alternative functional drinks in form of jelly drinks, due to the antioxidant properties contained in these two ingredients. In this study, we wanted to know the characteristics of secang jelly drinks with addition of red ginger extract at various concentrations. The research was conducted with ginger extract concentrations of 20% (J1), 25% (J2), 30% (J3), 35% (J4), and 40% (J5) executed completely random. The results of the research regarding the characteristics of secang jelly drink with the addition of red ginger extract have significant differences (p<0.05) for viscosity, pH value, antioxidant activity, and sensory as well as hedonic quality. The best treatment is obtained from red ginger extract concentration of 35% with an average viscosity of 986.7 cP, pH of 4.47, antioxidant activity with an IC50 value of 72.97 (strong), sensory score for aroma, texture, and taste is 5, hedonic quality score for aroma, texture, and taste is 4. This treatment also results in average total flavonoid content of 24.29 mg/100 g. No heavy metal contamination was found and total plate number was <102 colonies/mL. Keywords: Antioxidant, Functional drink, Jelly drink, red ginger, Secang woods.

Thermally induced crystal phase transitions in Zn–Al layered double hydroxides: zinc and aluminium pathways at various pH values

Thermally induced crystal phase transitions in Zn–Al layered double hydroxides: zinc and aluminium pathways at various pH values

Assessment of Physicochemical Properties of Orange Juice Concentrate Formulated with Pectin, Xanthan, and CMC Hydrocolloids

Orange concentrate (OC) is one of the main raw materials in the nonalcoholic beverage industry. Considering the difference in orange varieties, preserving its natural quality is essential to yield a product with favorable attributes and physical stability. Thus, the present study is aimed at assessing the effect of pectin, xanthan, and carboxymethyl cellulose (CMC) in a concentration range of 0–0.2% (w/v) along with mixing temperature on Brix, pH, acidity, density, turbidity, and viscosity of OC and at calculating the model equation for each attribute. The results showed that, except for CMC, the influence of concentration, type, and amount of hydrocolloid on pH changes was insignificant. Adding each hydrocolloid individually, in pairs, or threes reduced the density, and the measured density was lower at a mixing temperature of 4°C. Also, it was observed that mixing temperature was the only factor influencing turbidity, and the values were significantly lower at 80°C compared to 4°C. A significant interaction effect of xanthan concentration and mixing temperature on the Brix was observed. Adding hydrocolloids, except pectin, resulted in a significant (p<0.05) increase in viscosity, and xanthan had the greatest effect on the viscosity. A suitable model was designed using pectin and xanthan, pectin and CMC, and all three gums, resulting in a final OC product with high stability and improved physical and chemical attributes. The optimized values for Brix, pH, acidity, density, turbidity, and OC viscosity were achieved using 0.08% pectin, 0.19% xanthan, and 0.08% CMC at 80°C mixing temperature.

The Chemical Profiles and Antioxidant Properties of Live Fruit or Vegetable Vinegars Available on the Polish Food Market

Live vinegar is a product formed through a two-step fermentation process of a sugar substrate that has not been subjected to filtration or pasteurization. This is considered to preserve all nutrients and biologically active microorganisms, making it a product with a valuable composition and beneficial properties. Therefore, the purpose of this study was to analyze the chemical composition and antioxidant properties of the selected vinegars available on the Polish food market. The material in the study consisted of four live (naturally turbid, unfiltered, unpasteurized) fruit or vegetable vinegars: apple, pear, rhubarb, and lemon. Spectrophotometric, HPLC, and GC methods were used. Among the vinegars tested, lemon vinegar had the highest vitamin C content—15.95 mg/100 mL. Apple vinegar proved to be the best source of polyphenols and flavonoids (TPC—191.97 mg GAE/L, TFC—70.22 mg RE/L). All of the vinegars contained dihydroxybenzoic acid, 4-hydroxybenzoic acid, caffeic acid, 2-hydroxycinnamic acid, and myricetin. The acetic acid content of the tested vinegars ranged from 29.180 to 38.125 mM/L. The pH values ranged from 3.14 to 3.41. In conclusion, the most promising nutraceutical with potentially beneficial health-promoting properties seems to be apple vinegar.

Green synthesis and photocatalytic proficiency of tunable SnO2 nanostructures: unveiling environmental-friendly strategies for sustainable water remediation

Abstract This study demonstrates a proficient and eco-friendly synthesis of SnO2 nanostructures using a hydrothermal method, without the requirement of extra surfactants. The synthesis was systematically performed by adjusting the molar ratio of stannic chloride to sodium hydroxide and varying the pH settings. It was noted that the pH value rises according to the concentration of sodium hydroxide. A comprehensive analysis was performed to characterize the resulting nanostructures, which involved studying their structural features, chemical composition, morphology, and optical properties. An X-ray diffraction (XRD) analysis showed that increasing the pH values resulted in a noticeable improvement in the crystalline structure and a decrease in the density of surface defects. The SnO2 nanostructures, synthesized using different pH settings, were subsequently assessed for their photocatalytic performance in the degradation of methylene blue (MB) dye under simulated solar irradiation. Surprisingly, the nanostructure produced at higher pH levels showed outstanding results, as 97% of the dye was broken down in just 70 minutes when exposed to simulated solar radiation. The analysis uncovered a maximum rate constant (k) value of 0.04 min−1, determined using pseudo first-order rate kinetics. In order to better understand the photodegradation process, scavenger experiments were performed to identify the active species involved. These investigations provided valuable insights into the complex mechanisms that drive the observed photocatalytic activity. This study not only enhances the progress of SnO2 nanostructures but also highlights their potential as strong and environmentally friendly materials for effective photocatalytic applications.

The adsorption of U(VI) on chlorite: batch, modeling and XPS study

Abstract A mechanistic modelling of the adsorption processes onto individual minerals presenting in the near- and far-fields can greatly enhance the credibility of long-term safety assessments of granite-based geological repositories. In this study, the titration and U(VI) adsorption characteristics of chlorite, one of the major minerals of rock fractures, have been studied. Potentiometric titration curves at two ionic strengths (0.1 and 0.4 mol/L NaCl) are successfully interpreted by considering protonation/deprotonation reactions on generic edge sites (≡SOH) in the framework of a non-electrostatic surface complexation model (SCM). The adsorption of U(VI) on chlorite was reached after 24 h, the adsorption kinetics can be described by a pseudo-second-order model. A non-electrostatic SCM with three surface complexes (≡SOUO2 +, ≡SO(UO2)3(OH)5 and ≡SO(UO2)3(OH)7 2−) was set up based on pH edges of U(VI) at adsorption equilibrium in the absence of CO2. Additional, experimental data measured as a function of U(VI) concentration, solid-to-liquid ratio and carbonate concentration were well reproduced by the proposed model. Finally, parallel experiments were conducted using X-ray photoelectron spectroscopy (XPS) to analyze the variation of U(VI) surface species speciation at different pH values. The good agreement between SCM prediction and XPS analysis demonstrates the reliability of the model in predicting and quantifying the radionuclides retention by chlorite.

Resources recovery-rubidium recovery from desalination brine through hydrometallurgy techniques

Because of the water scarcity in many regions, different methods have been implemented to address this problem. The desalination technique is known as a practical solution among them. However, brine from the desalination process, which contains high concentrations of salts, minerals, and chemicals, will cause environmental harm to the sea, soil, and groundwater if it is not properly treated. Therefore, recovering critical resources from brine is essential for reducing brine disposal. This study aims to apply two hydrometallurgy systems, namely ion exchange and ionic liquid extraction, to circulate rubidium resources from brine. Dowex G26 resin was employed in the ion exchange system, and the adsorption isotherm model and saturated adsorption capacity were explored initially. The optimal parameters such as pH value, L/S ratio (liquid/solid), adsorption period, and adsorption temperature will then be investigated. In the ionic liquid extraction process, the t-BAMBP/C2mimNTf2 system (4-tert-Butyl-2-(α-methylbenzyl) phenol/1-ethyl-3-methylimidazolium bis(trifluoromethyls​ulfonyl)​imide) was used, and the parameters including pH value, concentrations of t-BAMBP, (O + I)/A ratio (organic + ionic liquid/aqueous), extraction time, and extraction temperature will be optimized as well. The results reveal that adsorption capacity and extraction efficiencies were 14.3 mg g− 1 and 86%, respectively. Furthermore, suitable reagents, including HCl and HNO3, were applied to desorb and strip rubidium from the Dowex G26 and t-BAMBP/C2mimNTf2 systems. To sum up, environmental hazards of desalination brine and rubidium resources can be reduced and recovered through the two different extraction systems.

A hybrid deep learning approach to predict hourly riverine nitrate concentrations using routine monitored data

With high-frequency data of nitrate (NO3–N) concentrations in waters becoming increasingly important for understanding of watershed system behaviors and ecosystem managements, the accurate and economic acquisition of high-frequency NO3–N concentration data has become a key point. This study attempted to use coupled deep learning neural networks and routine monitored data to predict hourly NO3–N concentrations in a river. The hourly NO3–N concentration at the outlet of the Oyster River watershed in New Hampshire, USA, was predicted through neural networks with a hybrid model architecture coupling the Convolutional Neural Networks and the Long Short-Term Memory model (CNN-LSTM). The routine monitored data (the river depth, water temperature, air temperature, precipitation, specific conductivity, pH and dissolved oxygen concentrations) for model training were collected from a nested high-frequency monitoring network, while the high-frequency NO3–N concentration data obtained at the outlet were not included as inputs. The whole dataset was separated into training, validation, and testing processes according to the ratio of 5:3:2, respectively. The hybrid CNN-LSTM model with different input lengths (1d, 3d, 7d, 15d, 30d) displayed comparable even better performance than other studies with lower frequencies, showing mean values of the Nash-Sutcliffe Efficiency 0.60–0.83. Models with shorter input lengths demonstrated both the higher modeling accuracy and stability. The water level, water temperature and pH values at monitoring sites were main controlling factors for forecasting performances. This study provided a new insight of using deep learning networks with a coupled architecture and routine monitored data for high-frequency riverine NO3–N concentration forecasting and suggestions about strategies about variable and input length selection during preprocessing of input data.

Investigation of ionic liquid adsorption and interfacial tension reduction using different crude oils; effects of salts, ionic liquid, and pH

The results revealed the significant effect of NaCl, KCl, CaCl2, MgCl2, CaSO4, MgSO4, and Na2SO4 and pH values of 3.5–11 on the interfacial tension (IFT) reduction using three types of neutral, acidic, and basic crude oils, especially for acidic crude oil (crude oil II) as the pH was changed from 3.5 to 11 (due to saponification process). The findings showed the highest impact of pH on the IFT of crude oil II with a reducing trend, especially for the pH 11 when no salts exist. The results revealed that the salts except MgCl2 and CaCl2 led to a similar IFT variation trend for the case of distilled water/crude oil II. For the MgCl2 and CaCl2 solutions, a shifting point for IFT values was inevitable. Besides, the dissolution of 1-dodecyl-3-methyl imidazolium chloride ([C12mim][Cl]) with a concentration of 100–1000 ppm eliminates the effect of pH on IFT which leads to a reducing trend for all the examined crude oils with minimum IFT of 0.08 mN/m. Finally, the [C12mim][Cl] adsorption (under pH values) for crude oils using only Na2SO4 was measured and the minimum adsorption of 0.41 mg surfactant/g Rock under the light of saponification process was obtained.

Stability-Indicating HPLC Method for Determination of Ibuprofen and Famotidine Degradation Products.

A new stability-indicating high-performance liquid chromatographic method for the quantitative determination of ibuprofen and famotidine degradation products in combined pharmaceutical products was developed and validated. The current aim of this study is to develop a rapid, accurate and robust analytical stability indicating impurity method that can separate ibuprofen, famotidine and their related impurities by using a reversed-phase high-performance liquid chromatography. A Zorbax SB-Phenyl column (4.6 × 150mm2, 5-μm particle size) with mobile phase containing phosphate buffer solution with a pH value of 3.0 and acetonitrile was used. The flow rate was 0.8mL/min and the analytes were detected by UV detector at 265nm. The retention times of ibuprofen and famotidine were 18.43 and 5.14min, respectively. This method was validated to confirm specificity, linearity, sensitivity (limit of detection and limit of quantitation), precision, accuracy, robustness and sample stability according to the International Conference on Harmonization guidelines. Studies have been completed and reported with two active substances in the combined dosage form and seven impurities in total. There is no method in the literature that simultaneously distinguishes and quantitatively analyzes both active substances and degradation products.

Osmolality and Tonicity of Isotonic Beverages

This study aimed to measure and compare the osmolality and tonicity of isotonic beverages that can be bought on the Slovenian market. The main goal was to examine how good is the agreement between the measured osmolalities of the beverages and the requirements for isotonic beverages set up by EFSA. Osmolalities were measured with an osmometer using the freezing point depression method. Afterwards, two complementary methods for the observation of tonicity were developed. Erythrocytes were exposed to standard NaCl solutions of different osmolalities to observe their influence on the volume and shape of cells following the turbidity of the solution and the morphology of erythrocytes. These two methods enabled us to determine whether standard solutions were hypo-, iso-, or hypertonic. In this way, we found that the osmolality of 12 out of the 18 investigated isotonic beverages was in the range of 270–330 mOsm/kg, as required by EFSA. However, six samples did not meet this criterion and should therefore not have the label “isotonic” or be described as such. The measurements of turbidity of solutions indicated that most isotonic beverages exhibit a lower tonicity than standard NaCl solutions of identical osmolality. However, examination of the erythrocytes in isotonic beverages showed that the measurements were additionally complicated by the low pH values of these beverages. Finally, by demonstrating how different components of isotonic beverages pass through the erythrocyte membranes, we found that even isoosmolal beverages are often not isotonic, as the concentration of actively transported sugars in these beverages is relatively high.