Method For Determination Of pH Research Articles

A high-throughput spectroscopic method for pH determination in lactic acid bacteria screening

In this study, a colorimetric method was developed to enable the rapid determination of lactic acid bacteria (LAB) acidification ability by assessing the pH drop during juice fermentation. The proposed method used spectrophotometry to track pH variations induced by LAB, utilizing bromophenol blue as a pH indicator. This colorimetric method demonstrated linearity within the pH range of 2.50–5.70. Optimal performance was achieved with 5.0 % bromophenol blue, yielding a linear equation of y = 1.25x-0.78, with an R2 value of 0.99 upon regression analysis. The method's high accuracy, repeatability and reproducibility were validated through comparisons of pH values obtained using different matrices with those measured using glass electrodes/pH meters. Several Lactiplantibacillus plantarum strains with excellent acid-producing properties were identified through this method. Specifically, the growth of L20, L2 and L6 in MRS medium with a glucose concentration of 200 g/L for 24 h led to a pH decrease of 1.00 unit, while the growth of L20 and L21 in MRS with an ethanol concentration of 12 % (v/v) for 24 h resulted in a similar pH decrease. Strains L12, L14, and L18 could lower the pH of banana and lychee juices by more than 0.30 units at both 25 and 36°C. These results highlight the effectiveness of the method for rapidly screening LAB acidifying activity.

Determination of local pH in CO2 electroreduction.

The electrocatalytic conversion of CO2 and H2O into fuels and valuable chemicals has gained significant interest as a prospective method for the storage of renewable energy and the utilization of captured CO2. In the process of electroreduction of CO2, pH near the surface of the electrocatalysts plays an important role in the catalytic selectivity and activity. However, to elucidate the local pH effect on the fundamental reaction mechanism and modify the catalytic CO2 reduction performance, the localized pH determination method is highly desirable. In this minireview, we present the recent advances in the strategies of the local pH probe for CO2 electrolysis in both H-type cell reactors and GDE-type flow electrolyzers, followed with a better understanding of the local reaction environment in CO2 reduction. Additionally, pertinent advantages and drawbacks of the different localized pH probe techniques are discussed, and perspectives on future research efforts are also provided in this minireview.

Development of a non-destructive method for determination of PH of paper artifacts using diffuse reflectance spectroscopy and regression analysis

Development of a non-destructive method for determination of PH of paper artifacts using diffuse reflectance spectroscopy and regression analysis

A DNA-Based FLIM Reporter for Simultaneous Quantification of Lysosomal pH and Ca2+ during Autophagy Regulation.

SummarypH and Ca2+ play important roles in regulating lysosomal activity and lysosome-mediated physiological and pathological processes. However, effective methods for simultaneous determination of pH and Ca2+ is the bottleneck. Herein, a single DNA-based FLIM reporter was developed for real-time imaging and simultaneous quantification of pH and Ca2+ in lysosomes with high affinity, in which a specific probe for recognition of Ca2+ was assembled onto a DNA nanostructure together with pH-responsive and lysosome-targeted molecules. The developed DNA reporter showed excellent biocompatibility and long-term stability up to ∼56 h in lysosomes. Using this powerful tool, it was discovered that pH was closely related to Ca2+ concentration in lysosome, whereas autophagy can be regulated by lysosomal pH and Ca2+. Furthermore, Aβ-induced neuronal death resulted from autophagy abnormal through lysosomal pH and Ca2+ changes. In addition, lysosomal pH and Ca2+ were found to regulate the transformation of NSCs, resulting in Rapamycin-induced antiaging.

Novel Carbon Dioxide-Based Method for Accurate Determination of pH and pCO2 in Mammalian Cell Culture Processes

In mammalian cell culture, especially in pharmaceutical manufacturing, pH is a critical process parameter that has to be controlled as accurately as possible. Not only does pH directly affect cell culture performance, ensuring a comparable pH is also crucial for scaling and transfer of processes. A sample-based offline pH measurement is commonly used to ensure correct bioreactor pH probe signals after sterilization and as a detection measure for drifts of probe signals. However, the sample-based pH offline measurement does not necessarily deliver required accuracy. Offsets between bioreactor pH and sample pH heavily depend on equipment, local procedures and the offline measurement method that is used. This article adequately describes a novel, non-invasive method to determine pH and pCO2 in sterile bioreactors without the need to sample and measure offline. This method utilizes the chemical correlation between carbon dioxide in the gas phase, dissolved carbon dioxide, bicarbonate and dependent proton concentrations that directly affect the pH in carbonate buffered systems. The proposed carbon dioxide-based pH reference method thereby is able to accurately determine the true pH in the bioreactor without the need to sample. The proposed method is independent of scale and bioreactor configuration and does not depend on local procedures that may differ between sites, scales or operators. Applicability of the method for both stainless steel and single use bioreactors is shown. Furthermore, the very same principles are applicable for non-invasive, online pCO2 monitoring.

NUTRITIONAL AND THERAPEUTIC EVALUATION OF SPIRULINA PLATENSIS

Objective: The present investigation was to isolate and produce Spirulina platensis on high scale for food pharmaceutical and aquaculture due to the presence of high protein content.
 Methods: Cultivation of Spirulina preparation of culture medium, inoculums build up, growth monitoring, harvesting, drying, procedure for protein estimation, sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and DNA isolation of Spirulina platensis.
 Results: The study shows that protein content of S. platensis was found to be 62% protein profile was studied through SDS-PAGE, the bands were in the range of 35 kDa–44 kDa. S. platensis contain high molecular weight DNA. The bands was seen and visualize under the transilluminator it reveals that the alga S. platensis contain high molecular weight DNA.
 Conclusion: The production of Spirulina by simple pH determination method suggests economic production of alga by a simple process. The DNA isolation showing that these algae contain high molecular weight DNA. However, utilization of this biomass for varied end uses, such as food, feed, aquaculture, and pharmaceuticals.

A novel strategy for quantitative analysis of soil pH via laser-induced breakdown spectroscopy coupled with random forest

pH is one of the significant properties of soil, and is closely related to the decomposition of soil organic matter, anion-cation balance, growth of plants and many other soil processes. In the present work, laser-induced breakdown spectroscopy (LIBS) technique coupled with random forest (RF) was proposed to quantify the pH of soil. First, LIBS spectra of soil was collected, and some common elements in soil were identified based on the National Institute of Science and Technology database. Then, in order to obtain a better predictive result, the influence of different input variables (full spectrum, different spectral ranges, the intensity of characteristic bands and characteristic lines) on the predictive performance of RF calibration model was explored with the evaluation indicators of root mean square error (RMSE) and coefficient of determination (R2), the characteristic bands of four elements (Al, Ca, Mg and Si) were determined as the optimal input variables. Finally, the predictive performance of RF calibration model was compared with partial least squares calibration model with the optimal input variables and model parameters, and RF calibration model showed a better predictive performance, and the four evaluation indicators of RMSEP, mean absolute error and mean relative error were 0.9687, 0.1285, 0.1114 and 0.0136, respectively. It indicates that LIBS technique coupled with RF algorithm is an effective method for pH determination of soil.

NMR-Based Determination of pH, Free of Electrodes and Reference Compounds.

A novel method was elaborated, and a set of 1H NMR-pH indicator molecules was selected to develop an NMR-based pH determination method, which does not need any glass or other electrodes or any separate reference compound, being thus devoid of the usual acid and base errors of the glass and combined electrodes. The method utilizes organic compounds of accurately known basicity and two or more carbon-bound protons, whose chemical shifts respond differently to pH changes. Accurate determination of protonation constants in pH extrema was achieved by the method of relative basicities using compounds of sequentially incremented protonation constants. The entire pH scale can be covered by six indicator molecules. The method was developed for two ionic strengths, 1.00 and 0.15 M.

Simultaneous SIA analysis of pH and total acidity measurements in milk

The development of a sequential injection analysis method for automatic determination of pH and total acidity in milk is proposed. For this purpose, firstly, three micro-sized composite pH electrodes were prepared and tested. A microliter dead volume flow-cell was designed for composite pH and reference electrodes. Potentiometric performance characteristics of the pH electrodes were examined by a computer-controlled potentiometric system in both stagnant and flowing environments. Three different micro-columns with the best working pH electrode were applied on the flowing stream line in the sequential injection analysis system to fulfill the titration efficiency for total acidity. The sequential injection analysis system was optimized for two parameters (pH and total acidity) by testing all the variables. Mobile phase concentration, volume and flow-rate together with sample concentration, volume and sample flow-rate were fixed for the best stable values by arranging the experimental programming steps. Total acidity of ten different milk samples was analyzed using the sequential injection analysis system developed. The same samples were also titrated in the classical way using phenolphthalein indicator for the comparison. The results of both methods analyzed statistically by SPSS software were found to be compatible with each other. pH analysis of ten different milk samples carried out by using the sequential injection analysis system were also measured with a glass electrode. The results obtained by both methods analyzed by SPSS were also found to be compatible with each other.

A review of sample preparation and its influence on pH determination in concrete samples

If we are to monitor the chemical processes in cementitious materials, then pH assays in the pore solutions of cement pastes, mortars, and concretes are of key importance. However, there is no standard method that regulates the sample-preparation method for pH determination. The state-of-the-art of different methods for pH determination in cementitious materials is presented in this paper and the influence of sample preparation in each case. Moreover, an experimental campaign compares three different techniques for pH determination. Its results contribute to establishing a basic criterion to help researchers select the most suitable method, depending on the purpose of the research. A simple tool is described for selecting the easiest and the most economic pH determination method, depending on the objective; especially for researchers and those with limited experience in this field.

An Optical Dye Method for Continuous Determination of Acidity in Ice Cores.

The pH of polar ice is important for the stability and mobility of impurities in ice cores and can be strongly influenced by volcanic eruptions or anthropogenic emissions. We present a simple optical method for continuous determination of acidity in ice cores based on spectroscopically determined color changes of two common pH-indicator dyes, bromophenol blue, and chlorophenol red. The sealed-system method described here is not equilibrated with CO2, making it simpler than existing methods for pH determination in ice cores and offering a 10-90% peak response time of 45 s and a combined uncertainty of 9%. The method is applied to Holocene ice core sections from Greenland and Antarctica and compared to standard techniques such as electrical conductivity measurement (ECM) conducted on the solid ice, and electrolytic meltwater conductivity, EMWC. Acidity measured in the Greenland NGRIP ice core shows good agreement with acidity calculated from ion chromatography. Conductivity and dye-based acidity Hdye+ are found to be highly correlated in the Greenland NEGIS firn core (75.38° N, 35.56° W), with all signals greater than 3σ variability coinciding with either volcanic eruptions or possible wild fire activity. In contrast, the Antarctic Roosevelt Island ice core (79.36° S, 161.71° W) features an anticorrelation between conductivity and Hdye+, likely due to strong influence of marine salts.

Smartphone-Based Extension of the Curcumin/Cellophane pH Sensing Method

Smartphone-based extension of the previously published (Food Anal Meth doi:10.1007/s12161-015-0102-1 2015a) curcumin-coloured cellophane test strip pH sensing method is reported. Replacement of the ultraviolet-visible (UV–VIS) spectrophotometer with an android-based device can reach a wider audience, in accordance with the ongoing, significant increase in the field of smartphone-based analytical applications. On the basis of the colouring effect of curcumin on biopolymers, a new, qualitative, quick and low-cost method for pH determination is developed, which provides more sensitive detection than the bare eye checking. Next to cellophane substrate, curcumin/gelatine sensor arrays are studied, too. Food-industrial and health-care products are targeted with a modular system based on the curcumin-coloured cellophane/gelatine sensor array, a free android application running on a smartphone, together with a home-written data analyser software. In situ monitoring and local pH mapping in liquid cell, investigation with curcumin dotted cellophane array and long-time stable, dried curcumin-coloured gelatine capsules are discussed.

A high-throughput colourimetric method for the determination of pH in crystallization screens.

The crystallization of proteins is dependent on the careful control of numerous parameters, one of these being pH. The pH of crystallization is generally reported as that of the buffer; however, the true pH has been found to be as many as four pH units away. Measurement of pH with a meter is time-consuming and requires the reformatting of the crystallization solution. To overcome this, a high-throughput method for pH determination of buffered solutions has been developed with results comparable to those of a pH meter.

Quantitative pH assessment of small-volume samples using a universal pH indicator

We developed a hue-based pH determination method to analyze digital images of samples in a 384-well plate after the addition of a universal pH indicator. The standard error of calibration for 69 pH standards was 0.078 pH units, and no sample gave an error greater than 0.23 units. We then used in-solution isoelectric focusing to determine the isoelectric point of Wnt3A protein in conditioned medium and after purification and applied the described method to assess the pH of these small-volume samples. End users may access our standard to assay the pH of their own samples with no additional calibration.

Evaluation of experimentally measured and model-calculated pH for rock–brine–CO2 systems under geologic CO2 sequestration conditions

Reliable pH estimation is essential for understanding the geochemical reactions that occur in rock–brine–CO2 systems when CO2 is injected into deep geologic formations for long-term storage. Due to a lack of reliable experimental methods, most laboratory studies of CO2–rock–brine interactions conducted under geologic CO2 sequestration (GCS) conditions have relied on thermodynamic modeling to estimate pH; however, the accuracy of these model predictions is typically uncertain. In this study, we expanded the measurement range of a spectrophotometric method for pH determination, and we applied the method to measure the pH in batch-reactor experiments at 75°C and 100atm utilizing rock samples from five ongoing GCS demonstration projects. A combination of color-changing pH indicators, bromophenol blue and bromocresol green, was shown to enable measurements over the pH range of 2.5–5.2. In-situ pH measurements were compared with pH values calculated using geochemical models. Calculations with four different thermodynamic databases resulted in a maximum difference of 0.16pH units. Among these databases, the Phrqpitz database generally provided the most accurate pH predictions for rocks comprised of carbonate, siltstone, and sandstone. With Phrqpitz, the differences between measured and calculated pH values were within 0.03pH units for these three rocks. However, for basalt, significant differences (0.10–0.25pH units) were observed even with Phrqpitz. These discrepancies may be due to the models' failure to fully account for certain proton consuming and producing reactions that occur between the basalt minerals and CO2-saturated brine solutions.

Validation of the dye colour chart method for pH determination of rice grains

During storage of rice, acidity is gradually generated in the rice grains. This increase in acidity results from an accumulation of compounds including tricarboxylic acid cycle metabolites, amino acids, and free fatty acids, and is used as an index for the length of storage or the freshness of rice grains. The acidity can be conventionally determined and expressed using a pH meter. A dye colour-chart method has been developed and is currently used to determine the pH of rice grains by using a bromothymol blue-methyl red dye solution and a pH colour chart. The method is low cost and convenient. To validate the repeatability and reproducibility of the dye colour-based method in measuring the pH of rice grains, an international ring test including 14 laboratories was performed. The high consistency and low standard deviation of repeatability and reproducibility showed that this method was acceptable and worthy to promote. The results show that the dye colour chart method is conditionally acceptable and highly comparable to the conventional pH meter method. In addition, training in this method is suggested for reducing variation.

Electrodeless, accurate pH determination in highly basic media using a new set of 1H NMR pH indicators

A set of indicator molecules was selected and applied to elaborate an NMR-based pH determination method, free of glass electrode errors in highly basic media. Accurate measurement of pH values and protonation constants was achieved by a successive build-up of overlapping, increasingly high pH solutions, using a collection of 8 compounds of appropriately incremented basicities. In order to verify the method, acid–base properties were quantified for two compounds with very high basicities in conflicting reports: two pharmaceutically important biguanidine drugs, metformin and phenformin.

Electrochemical microsensors for cutaneous surface analysis: Application to the determination of pH and the antioxidant properties of stratum corneum

Potentiometry and cyclic voltammetry were proposed as simple, reliable and non invasive methods for the simultaneous determination of pH and antioxidant properties of skin. Experiments were performed with microelectrodes just deposited on skin surface without any gel or water added. pH was measured by means of the zero current potential of a tungsten W/WO 3 sensor. A nerstian response was recorded in pH range 4 to 6 corresponding to the normal skin pH values. The global antioxidant capacity was deduced from the anodic charge passed during the plotting of cyclic voltammograms on platinum or gold microelectrodes. Comparing the half wave or peak potentials of these curves with those recorded for experiments performed in aqueous solution, the main hydrophilic antioxidants species were detected, i.e. ascorbic acid, uric acid and glutathione. This relatively easy-to-use analytical method made it possible to follow in real time the efficiency of topic treatment as well as to study the influence of oxidative stress.

Soilless Root Substrate pH Measurement Technique for Titration

Measurement of substrate pH entails procurement of the substrate solution and measurement of the solution pH. Acid-base reactions are completed at the time of testing. Determination of substrate pH during development of a titration curve is more complex because it involves initially the reaction of a base with the substrate. Five factors that can influence the resulting pH values were investigated in this study and include amount of water added to substrate, method to procure substrate solution for pH determination, chemical form of base used, time allowed for acid-base reaction and the addition of CaSO4. Substrate in this study consisted of 3 sphagnum peatmoss: 1 perlite (by volume) amended with wetting agent. Dolomitic limestone (6 g·L-1 substrate) was added to substrate for the water amount and solution procurement method experiments. Except for the water amount experiment, deionized water was added by weight to achieve 95% container capacity. Dishes were incubated at 20 °C for specified times. To identify the minimal level of water necessary to ensure complete contact between base and substrate for neutralization, additions equivalent to 95%, 100%, 120%, and 150% container capacity were tested. The 95% level proved adequate. The saturated media extraction and pour-through bulk solution displacement methods for pH determination resulted in higher pH measurements in the incubated substrate than the squeeze bulk solution displacement method. This indicated that the former two methods diluted the soil solution. The squeeze method was deemed most effective. NaOH resulted in higher pH endpoints than Ca(OH)2. This was apparently due to a higher affinity of Ca2+ for peatmoss exchange sites. Since Ca2+ is the predominant cation associated with liming materials for soilless substrates, Ca(OH)2 is more appropriate for titration. From the tested incubation times of 0, 2, 4, 8, 24, 48, and 96 hours, the duration of 24 hours was found to be adequate to allow complete reaction of base with substrate acidity. The best procedure for determining pH in a substrate titration situation included a water level of 95% container capacity, Ca(OH)2 base, an incubation time of 24 hours and the squeeze solution displacement method. The additional CaSO4 was not necessary. Chemical names used: calcium sulfate (CaSO4), sodium hydroxide (NaOH), calcium hydroxide [Ca(OH)2], calcium ion (Ca2+).

In Situ pH Probing of Hydrothermal Solutions by NMR

An NMR method for pH probing of hydrothermal solutions is described. NMR tubes withstanding autogenous pressures at temperatures up to 200 °C are used in conventional NMR probe heads. After selection, several molecules stable in aqueous solutions up to 200 °C are shown usable as pH probes. Two amines, imidazole and 1,4-diazabicyclo[2.2.2]octane, are complementary pH indicators. Both together permit a range of about 9 pH units to be covered. Calibration of the amine 14N chemical shift (δ) versus pH is established. The dependence on temperature of the amine parameters, Kai (dissociation constants) and δi (chemical shifts of the different protonation states), is investigated. Both amines present high NMR sensitivities to protonation changes, expressed as d[δ(14N)]/d[pH], and have a very small sensitivity to medium effects. This pH determination method is successfully applied to follow the pH evolution during hydrothermal synthesis of aluminum hydroxide, and of AlPO4−CJ2.