Search

Measurement of pCO2 in highly dynamic coastal zones such as the southern Baltic Sea presents many challenges. In this study, we designed a system to measure pCO2 and then validated it in a series of laboratory and seagoing tests. The fast response time of the system was shown to provide a better resolution of CO2 system gradients. In the open waters of the Baltic Sea, the accuracy of the pCO2 measurements (±1.3 µatm) met the requirements of the ICOS (±2.0 µatm). In the coastal zone, there was less consistency between pCO2, DIC and pH measurements, suggesting the need to redefine the quality assurance and control requirements for the measurement of pCO2 in dynamic regions.

Animal mummies from ancient Egypt are not extensively studied in comparison with human mummies. Dogs mummies were very rare in ancient Egypt, and at the same time were not adequately studied by researchers from conservation point of view. Dog mummy in the present study is dated back to late period (664−333 BC.) and is preserved in the agriculture museum (Egypt). It suffers from different aspects of deterioration such as dirt, holes, wrinkles, missing tissue, accumulated dust, etc. This study aims to evaluate the preservation state of the mummy and explain the deterioration mechanisms to help the conservators later to choose the appropriate materials and methods for the conservation treatment. The analytical techniques used were Auto-Cad, scanning electron microscope (SEM), determination of moisture content, pH measurement, amino acid analysis (AAA), fourier transform infrared (FTIR), portable X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS) and X-ray diffracion analysis. The results obtained showed different forms of deterioration. Moisture content measurement proved that the mummy was dehydrated. The pH measurement of the mummy components is in acid level. FTIR and amino acid analysis proved that the mummy have been exposed to oxidation process. The analysis by XRF, ICP-MS and XRD proved that bone of the mummy suffered from deterioration.

It is known that there are many ways to manage food waste, however, no specific work has ever been reported on the easiness and economics of treatment mainly at the source. This study hopes to fulfill the gap by constructing a novel waste bin layered with plastic that can continuously accommodate and decompose food waste produced at the source. After several months of use, the bin has been found to be effective and no foul odor has been detected at least 1 ft away. In addition, produced leachate has been found to be nontoxic and can be used to water plants as evidenced by the pH measurements. Furthermore, introduction of additional features such as covering the bin with a painted cloth and putting a chimney on its top has been observed to enhance the performance.

This investigation addresses the impact of the carbonate medium in the sol-gel processes of stone consolidants and the possible detrimental effects in practical applications. The results demonstrate that the carbonate medium influences the sol-gel paths and that silicate materials developed in the carbonate stone pores can be structurally different from those formed within “inert” conditions, as a consequence of the combined effect of pH and ionic interactions between Si-O− and Ca2+. The trend is that the formation of the silica films around stone grains (silica growth mechanism through typical condensation) evolves into less advantageous growth processes (Oswald ripening and/or coagulation), resulting in a material that is unlikely to consolidate carbonate stone. Furthermore, pH measurements and different ratios between NMR Q3:Q4 species along stone depth showed that this effect seems more important at greater depths. The results underline the importance of the carbonate medium in the failure of alkoxysilane-based treatments and, accordingly, that an efficient design and development of new alkoxysilane-based consolidants must consider this effect.

Three experiments were conducted to determine the effects of increased CO2 concentration during the first 3 d of incubation on albumen height and pH, embryonic mortality, and hatchability of broiler hatching eggs. Hatching eggs were obtained from commercial broiler breeder flocks of Ross 308 at 39 and 37 wk of age in Experiments 1 and 2, respectively. In Experiment 3, eggs were collected at 28 and 35 wk of age. Eggs were incubated under either standard conditions (Control-CO2) for the entire incubation or increased CO2 concentrations during the first 3 d of incubation (High-CO2) in 3 experiments. In Experiments 1 and 2, the CO2 concentration was gradually increased from the beginning of incubation onwards to reach 0.80% at 72 h by manual injection of CO2 into airtight laboratory incubators. In the control incubators, the CO2 concentration remained below 0.10% during the same period. Prior to setting, and at 3 d of incubation, the eggs were opened for albumen height and pH measurements in Experiments 1 and 2. In Experiment 3, the eggs were set in commercial incubators. During the first 3 d of incubation, the CO2 concentration was gradually increased to reach 0.70% at 72 h naturally (High-CO2). In the Control-CO2 incubator, the CO2 concentration remained below 0.10%. After 3 d, incubation was continued with the control incubator conditions for all eggs from both groups in the 3 experiments. The albumen height was not affected by CO2 treatment, but the treatment significantly decreased albumen pH at 3 d in Experiments 1 and 2 (P < 0.05). A greater CO2 concentration during early incubation reduced fertile hatchability due to increased early embryonic mortality by 2% in the 3 experiments (P ≤ 0.05). The differences in pH might provide one explanation why increased CO2 concentration during early incubation resulted in increased early embryonic mortality. These data indicated that at the beginning of the incubation, ventilation was necessary to prevent increases in CO2 concentration for optimum hatchability results.

To endow fluorescent functions to the inverse electron demand Diels–Alder (IEDDA) reaction products, introduction of extraneous fluorophores is usually inevitable. However, this strategy is blamed for complex construction and background fluorescence. It is desirable to construct IEDDA fluorescent products in a more convenient manner. In this work, we reported the in-situ generated green fluorescence in IEDDA reaction. The fluorescence intensity of IEDDA products RA-TZ-1 and RA-TZ-2 decreased in reduced pH values (from pH 7.0–3.0). Based on this novel property, we developed a ratiometric fluorescent probe RB–RA-TZ-2 by conjugation with another probe RB-NH2 (Em = 584 nm) with inverse response toward pH values. By single excitation, the fluorescence intensity ratio (I584/I488) showed a linear response (R = 0.9797) to H+ in pH range of 3.5–5.0. Colocalization imaging with LysoTracker Green indicated the capacity of RB–RA-TZ-2 to detect lysosomal pH (Pearson’s coefficient 0.81). Confocal microscopy was applied to measure and image intracellular pH in living cells.

Currently, there are diversified presentation styles and processes on creative artwork. Although we are appreciated its value through various media, we do not concern deeply on its process that some harmful results might have affected to an environment and the artists themselves. Hence, art creation through printmaking is one of risking activities. The research studied the uncomplicated printmaking process that utilized acid from nature including lime, tamarind, and kaffir lime that are inexpensive and could be found locally. Additionally, there is no dangerous effect on our physical body. The objective of this research was to find the replacing of artificial acid with natural substance. The three acid samples were experimented by separating water from fiber residue and pH measurement. The extracted natural acid was tested on wax pencil drawing on aluminum foil. The results showed that all three samples had slightly differences on pH value. The artworks were same as their original works. Moreover, it could be reproduced many times with similar quality. Consequently, the finding of these replaced natural acid substances could be an intelligent method in art creation.

In paper conservation practice, adhesives are used for several purposes, such as mending tears and gaps, or paper consolidation. The criteria to choose one or another adhesive should be based on the knowledge of the properties and stability of those adhesives. However, the several different adhesives available on the market still lack enough information to help the process of a rational decision-making. In the present work, five adhesives currently used in the paper conservation field (starch paste, unsupported ArchibondTM, carboxymethylcellulose, hydroxypropylcellulose and methylcellulose) were analyzed for their chemical stability and fungal bioreceptivity (the ability of a material to be colonized by fungi). Bioreceptivity of products used in conservation and restoration is a still poorly explored subject, despite its great relevance for the preservation of objects. The chemical and physical properties of the adhesives, before and after moist heat artificial ageing, were analyzed by thermogravimetry, capillary viscometry, measurement of water absorption capacity, colourimetry, and pH measurement. Fungal bioreceptivity of the adhesives was tested on two different substrates (paper and glass) against three fungal species: Aspergillus niger, Aureobasidium pullulans and Penicillium pinophilum. Along 56 days of incubation, the colonization area on the adhesives was measured through digital photo analysis. Starch paste was the most bioreceptive adhesive, but on other hand was also the most stable adhesive to artificial ageing, regarding colour alteration, degree of polymerization and pH. Carboxymethylcellulose and ArchibondTM showed chemical deterioration with ageing. Nevertheless, these two adhesives presented only scarce bioreceptivity to the tested fungi. Methylcellulose and hydroxypropylcellulose showed the best relationship between higher chemical stability with artificial ageing and lower fungal bioreceptivity.

Liesegang patterns of silver dichromate (Ag2Cr2O7) are studied in two different gel media: agar and gelatin, based on the work of Lagzi and Ueyama (2009). Whereas in gelatin, standard Liesegang bands are obtained as a result of the interdiffusion of Ag+ and Cr 2 O 7 2 - , random crystallites with dendritic ramifications are observed in agar. We revisit this phenomenon and demonstrate the proposed mechanism, wherein dense heterogeneous nucleation in gelatin leads to Liesegang bands, as opposed to surface nucleation in agar yielding crystallites. We use viscosity, pH measurements, and notably scanning electron microscopy (SEM) in this endeavor.

Along with the repaid growth of aquaculture production and high density in China, the Water quality real-time monitoring has become more and more important that influence the development of aquaculture. The pH is an important parameter for measuring the water quality, and the pH affects the growth and reproduction of aquatic animals. However, the traditional pH measurement methods have several disadvantages, such as low stability, heavy drift, short service life, poor anti-interference ability, long response time and low accuracy. To solve these problems, this paper proposed an intelligent pH sensor based on IEEE1451.2 mechanism. The intelligent pH sensor includes light detection module, signal processing module and intelligent calibration module. The light detection module adopts fluorescent absorption methods to obtain the pH signal. The optical fibre is been selected as the transmission element. The signal processing module is responsible for processing pH signals, which convert the output of pH probe from mV to V. It adopts the IEEE 1451.2 standard to achieve the intelligent compensation of turbidity, light source, temperature and ionic strength. The experiments results have shown that the intelligent pH sensor is stable, accurate and suitable for online monitoring in aquaculture.

The phosphate glasses of composition Na2O-CaO-P2O5 are widely accepted glass material for biomedical applications. The glass samples with composition (26-x)Na2O-xBaO-29CaO-45P2O5 (x = 0,5,10,15) are prepared at 1100°C by melt-quenching technique. In order to reduce the fast dissolution rate, which limits their application, BaO is added by reducing Na2O composition. The dissolution studies have been carried out in deionized water under semi-dynamic conditions at 37°C for 14 days. The properties are studied based on Barium composition and time of immersion. The samples are taken out at 24 hrs. intervals to carry out weight loss and pH measurements. The rates of cation (Na+ and Ca2+) release from the glass to the solution were found out using flame photometer. The release of orthophosphate (PO43-) anions is measured by UV-Visible spectrometer using phospho-molybdenum blue method. The weight losses linearly increase with time for all the compositions. The addition of barium decreases the weight loss in deionized water. The pH of the solutions varies with dissolution of ions. The dissolution rate has been found out from the slope of the weight loss vs time graph and it decreased with increase in barium content

A chairside tool for quantitative analysis of dental caries would improve clinical dental inspections. The wireless caries sensing tool with dental-explorer size has been developed comparing two sensing methods, Raman reading and pH reading for evaluating dental caries. The Raman spectra at 575 cm−1 and 960 cm−1 for in inorganic compounds, as well as 1450 cm−1 and 2940 cm−1 for organic compounds reinforced and supported the pH results. An Iridium/Iridium oxide (Ir/IrOx) pH sensing probe and wireless pH sensor (comprising an ESP8266 ESP-01 wireless module and ADS1115 analog digital converter) has been developed to quantitatively evaluate dental caries. All the operations of the wireless pH sensor were performed with a developed LabVIEW-based real-time data monitoring program. The slope and the linear fitting regression value (R2) of the wireless pH sensor using seven standards were −54.9 mV/pH and 0.999, respectively, showing high accuracy and stability for the pH measurements. The pH on the dental caries surface was measured with the wireless pH sensor, and the pH mapping results in the non-caries and caries areas were 6.9 and 5.7, respectively. The developed wireless pH sensor would be useful to understand the condition of dental caries and support dentists’ inspection to remove only the caries part while keeping the non-caries structure.

The indicator meta-cresol purple (mCP) has been widely used for spectrophotometric pH measurements in seawater and has been recently used in freshwater as well. Previous works have not, however, provided the comprehensive characterization of purified mCP (equilibrium and spectral behavior) required for pH measurements across the full ranges of temperature ( T ) and salinity ( S ) found in temperate estuaries. This work provides, for the first time, a comprehensive S - and T -dependent model for spectrophotometric pH measurements appropriate to freshwater, estuarine water, and seawater. Our model combines previous characterizations of the behavior of (a) purified mCP in pure water ( S = 0), (b) purified mCP in seawater (20 ≤ S ≤ 40), and (c) unpurified mCP at 298.15 K and 0 ≤ S ≤ 40, herein corrected for the effects of impurities. Using the ratio ( R ) of mCP absorbances at 578 nm and 434 nm, the summary equations for calculations of pH on the total proton concentration scale for the conditions of 0 ≤ S ≤ 40 and 278.15 ≤ T ≤ 308.15 K are as follows: p H T = p K I e 2 + log R − e 1 1 − R e 3 e 2 where e 1 = - 0.007762 + 4.5174 x 10 - 5 T e 3 e 2 = − 0.020813 + 2.60262 × 10 − 4 T + 1.0436 × 10 − 4 S - 35 p K I e 2 = 5.561224 − 0.547716 S 0.5 + 0.123791 S − 0.0280156 S 1.5 + 0.00344940 S 2 − 0.000167297 S 2.5 + 52.640726 S 0.5 T − 1 + 815.984591 T − 1 This new model, appropriate for use with purified mCP, produces pH values that are within ± 0.004 of those obtained using previously published data and purified-mCP models for pure water and seawater.

The measurement of arterial oxygen saturations, end-tidal carbon dioxide and pH are all key to modern anaesthetic practice. They can all be measured in a variety of ways but with the most common being discussed in the article. The understanding of the underlying physical principles and how the anaesthetist monitors function to measure these variables is discussed in this article, including limitations and inaccuracies of each technique.

A novel micro-structured bubble column reactor (MSBC) is studied by a combined experimental and simulation approach, for the chemisorption of CO 2 into NaOH. To understand the reactor behavior different reactor configurations are tested for chemisorption by varying the internals (single wire mesh, staged wire meshes, Sulzer packing). Bubble size distribution, pH and holdup data are obtained from chemisorption experiments using an advanced digital image analysis technique. The effect of superficial gas velocities ranging from 5 to 25 mm/s and varying number of wire mesh stages (1, 6 and 10) is deduced from the experiments. The experimental results are used for the validation of the detailed VoF-DBM simulations.

We investigated the possibility to grow molecularly porous amino-silane layers on glass-like substrates. The goal of this work is to show that it is possible to substantially increase the sensitivity of a fluorescence sensor by adjusting the functionalization strategy. Two methods are studied, one using APTMS only and another one using both APTMS and APDMS. We show that, using the second method, sensor sensitivity is improved by a factor of about 5. In order to demonstrate this, we applied the technique to the grafting of fluorescein in order to build a fluorescence pH sensor.

This study was performed to determine the consistency of exhaled breath condensate (EBC) hydrogen peroxide (H2O2), pH and leukotriene B4 (LTB4) measurements in asymptomatic horses and to define the influence of environmental and animal factors on these variables. Intra- and inter-day consistency for both H2O2 and pH measurements were adequate, with intraclass correlation coefficients ≥0.8, whereas the consistency for LTB4 was poor. H2O2 was influenced by ambient temperature (TA), humidity, time of day and collection location (all P

For best accuracy, spectrophotometric characterizations of seawater pH are obtained using a purified pH-sensitive dye—usually meta-cresol purple (mCP) for typical ranges of seawater pH. In recognition of practical limitations, though, a straightforward method is here proposed to improve measurements made using unpurified mCP. The user first determines, for a particular lot of unpurified mCP, the absorbance contribution of indicator impurities at 434 nm (434Aimp). Correction for this contribution is then mathematically applied to the measurements of seawater pH. We tested this approach using six unpurified lots of mCP and, for comparison, purified mCP in a synthetic experimental solution over the pH range 7.25–8.25. The 434Aimp correction yielded substantial improvements in pH accuracy: on the order of 0.005 at low pH (~ 7.25) and 0.01 or more at higher pH (~ 8.25). The pH accuracy achieved by the corrective model was also examined relative to the Global Ocean Acidification Observing Network (GOA-ON) “weather” and “climate” goals for pH measurements (uncertainties of ± 0.02 and ± 0.003, respectively). When previously published algorithms (appropriate for purified mCP) were used, none of the unpurified dyes met the more stringent “climate” goal in waters of pH > 7.6. With the algorithms proposed here (i.e., incorporating the lot-specific 434Aimp correction), three of the six lots came into “climate” compliance over the full experimental pHT range and two additional lots achieved “climate” compliance up to pH ~ 8.0. This protocol offers a simple, user-determined correction to significantly improve the accuracy of pH measurements made with unpurified mCP.

Calcium oxy fluoro borophosphate glasses doped with fixed concentration of Fe2O3 and mixed with different important modifier oxides (viz., BaO, SrO, ZnO and MgO) that play a crucial role in healing bone fractures and in improving osteointegration etc., were synthesized. In vitro bioactivity studies were carried out by immersing the samples in simulated body fluid (SBF) solution for about one month. The formation of HAp layer on the surface of the samples was confirmed by recording XRD and SEM photographs and also IR spectra before and after immersion in SBF. The magnitude growth of HAp layer was evaluated by measuring weight loss of the samples along with pH measurements of the residual solutions at specific intervals of time. The analysis of the results of degradability together with spectroscopic studies viz., IR and optical absorption spectra have revealed that BaO is an effective modifier in improving the bioactivity of the host glass, among all the modifiers investigated.

A non-contact real time pH measurement using fully modular optical parts is described for phenol-red medium cell cultures. The modular parts can be sterilized, and once the measurement is started at the beginning of culture, no recalibration or maintenance is needed till the end of the culture. Measurements can be carried out without any special manual attention. The modular assembly of LED and sensor cassettes is unique, robust, reusable and reproducible. pH is measured in an intact closed flow system, without wasting any culture medium. A special pump encapsulation enables the system to be effortlessly functional in extremely humid incubator environments. This avoids lengthy sample tubings in and out of the incubator, associated large temperature changes and CO 2 buffering issues. A new correction model to compensate errors caused e.g. by biolayers in spectrometric pH measurement is put-forward, which improves the accuracy of pH estimation significantly. The method provides resolution down to 0.1 pH unit in physiological pH range with mean absolute error 0.02.

Canastra cheese is an artisanal product from the Serra da Canastra region in Brazil. It is produced with raw milk and an endogenous culture called pingo. Brazilian legislation requires 22 days of ripening to ensure microbiological safety. This study evaluated the microbiological characteristics of samples collected in two settings. In the first, samples were harvested along the manufacturing process (including milk, pingo, curd and cheese at different ripening times) from three producers registered in the state's quality program. In the second setting, cheese samples were collected from 78 local producers, after ripening. All samples were assessed for total coliforms, Escherichia coli, coagulase positive Staphylococcus and submitted to pH measurement. Enterobacteriaceae, Salmonella spp., and Listeria monocytogenes were tested in cheeses from the second setting, in addition to aw measurement. Results collected during cheese production indicated that the regulatory microbiological limits related to counts of total coliforms, E. coli and Staphylococcus could be reached before 22 days. Conversely, the study with cheeses collected from a larger pool of producers (samples with 22 days of ripening) showed a high number of non-compliances to the Brazilian regulation, regardless of registration in the quality program. Counts of coagulase positive Staphylococcus were above the legal limits in many samples, one was positive for L. monocytogenes, while Salmonella was not detected. The pH and aw were not good indicators of safety, as none of these parameters correlated with microbial counts. There is a need for improvements in the good manufacturing practices in the Canastra cheese production chain.

A method based on Digital Image Analysis (DIA) is described to quantify pH and phosphates simultaneously in eye drops for the treatment of glaucoma and dry eye syndrome. In this work, images acquired with a smartphone were used. For phosphate determination, the colorimetric reaction that uses ammonium molybdate and antimony potassium tartrate was used. The formed blue complex was quantified using the R channel of the RGB color space. The pH was measured using bromothymol blue indicator, which gives a color between yellow and blue. The information of the pH measurement was extracted from histograms of the pictures and a PLS model was performed to quantify the values. All solutions were placed in microtitration wells in which less than 400 μL of sample are necessary and up to 92 samples can be measured in a single image. The method shows good linearity (R2 = 0.9962) for phosphates between 5.0·10−6 and 3.0·10−5 mol L−1. Inter and intra-day precision were less than %12.8 (RSD) and LOD and LOQ were between 1.8·10−6 mol L−1and 5.6·10−6 mol L−1respectively. For pH, the color change of the indicator gives good results between 4.99 and 9.02 values. The RMSEC and REMSEP values of the PLS models were between 0.103 and 0.462 respectively with four components. Inter and intraday precision were less than %12.2 in terms of RSD. Phosphates and pH were determined simultaneously in different eye drops and the results were validated using reference method such as potentiometry (pHmeter) and ion chromatography.

Scale formation from calcium carbonate deposition is a major drawback in many industrial facilities, including oil and gas industry, leading to obstruction problems then causing productivity reduction and economic loss. Several anti-scalant formulations, known as inhibitors, are used to control CaCO 3 deposition. The evaluation of inhibitors performance is a time-consuming challenge. In the present work a fast approach for evaluation of inhibitor towards calcium carbonate scale controlling is proposed based on continuous pH measurement under jar test condition. Two commercial inhibitors, phosphino polycarboxylic acid (PPCA), usually regarded as a nucleation inhibitor, and diethylenetriamine pentamethylene phosphonic acid (DETPMP), normally considered a growth inhibitor, were evaluated. It was possible to assess their efficiency at same concentration level (5.0 ppm), and DETPMP was the one presenting a better performance at the investigated conditions. The main mechanism of action of each inhibitor was also recognized by this methodology.

The aim of this research was to apply color parameters determined with the computer vision systems (CVS) in detection of PSE (pale, soft, exudative) porcine semimembranosus muscles. Based on pH measurements taken 24 h post mortem , meat were classified into two quality groups: RFN (red, firm, normal, non-exudative) and PSE. The color parameters were evaluated using the CVS and in CIE L*a*b* scale. In order to confirm or deny incidence of PSE the selected characteristics of technological quality of meat were also determined. Using CVS and CIE L*a*b* the considerable differences in color lightness for PSE were observed when compared to normal meat. The obtained correlation and determination coefficients between color parameters characterized by lightness reached low values 0.44 and 19.4%, respectively. Considerable dispersion of results and overlapping ranges of color parameters obtained for selected meat quality groups have proven the possibility of CVS application for m. semimembranosus classification to be limited.

pH colorimetric sensors with prediction error comparable to the potentiometric measurements in the working range of the indicator employed, were prepared. Bromothymol Blue (BB), Tetrabromophenol Blue (TBB), Cresol Red (CR) and Brilliant Yellow (BY) in PVDF (Polyvinylidene Fluoride)-supported OrMoSil (organically modified silicate) matrix, were used. Sensor preparation was reproducible. Signal was based on a suitably modified Hue coordinate from HSV (Hue, Saturation, Value) color space, H. Although H profile was not influenced by the indicator concentrations, the prediction error depended on the product of saturation and luminance, Δ. By using H, the response of every spot was less affected by shape and optical inhomogeneity. The H calibration held for all the spots of the same lot and remained identical in time giving an advantage with respect to a glass electrode requiring calibration before each set of measurements. The prediction errors both in solution and in the OrMoSil matrix were similar: for BB, s p H i = 0.03 in both environments; for TBB, s p H i = 0.02 in the sensing spot and 0.05 in solution; for CR, s p H i = 0.11 in the sensing spot and 0.04 in solution; for BY, s p H i = 0.17 in the sensing spot and 0.07 in solution. Indeed, H values of TBB and BB increased their variances near the inflection point where Δ has the minimum value (heteroscedastic behavior).

An in-depth study was conducted to determine the influence of some important parameters to produce a pH colorimetric sensor characterized by long-term stability, lack of leaching, high reversibility, repeatability and extended working range. Bromothymol Blue (BB) was used as pH sensitive molecule. Its performance was monitored while tailoring the concentration of some added cationic surfactants, together with the organic fraction of the sol-gel composition to avoid leaching phenomena, low homogeneity and to increase reversibility. Five cationic surfactants with different linear alkyl chain length (from C8 to C18) were added to a sol-gel containing BB. The C16 was chosen as optimal. The effect of the surfactant counterion was also investigated. The C16 surfactant had a pH working interval of 3 pH unit by using chloride, 1.5 with bromide and 1 pH unit with p-toluenesulfonate as counterions, respectively. Chloride was characterized by a larger inhomogeneity while p-toluenesulfonate gave homogeneity and high repeatability. The hexadecyltrimethylammonium p-toluenesulfonate was therefore chosen as the best surfactant. Leaching in alkaline medium was avoided by using the dodecyl moiety among three organic groups linked to the OrMoSil matrix (dodecyl, phenyl and methyl). Colorimetric sensor arrays made with these specifications remained stable and reversible for months.

Accurate determination of pH values is fundamentally important for understanding and predicting geochemical processes in surface and subsurface environments. However, conducting in situ pH measurements of fluids from geological formations exposed to high CO 2 pressures and elevated temperatures is technically and logistically challenging. Here we introduce a proxy-method for determining in situ pH values based on stable carbon equilibrium isotope fractionation (10 3 lnα 13 C) between dissolved inorganic carbon (DIC) and headspace CO 2 , which is valid for a DIC system composed of a mixture of H 2 CO 3 ⁎ (CO 2(aq) + H 2 CO 3 ) and HCO 3 − . The method is based on determination of DIC speciation and δ 13 C measurements of DIC and headspace CO 2 on de-pressurised fluid samples in the laboratory. Since 10 3 lnα 13 C DIC–CO 2 values vary predictably dependent upon temperature and pH, DIC speciation and carbon isotope ratio measurements on two carbon species (CO 2 and DIC) enable the determination of in-situ pH values if temperatures are known. This approach was verified in a series of laboratory experiments with water samples equilibrated with gaseous CO 2 at 55 bars for various temperatures and time periods. Concentration and carbon isotope measurements upon opening of the reaction vessels yielded 10 3 lnα 13 C DIC–CO 2(g) values between − 1.3 ± 0.1 and + 1.4 ± 0.2‰ corresponding to reconstructed in situ pH values ranging from 5.5 to 7.4 at temperatures between 20 and 120 °C. Measurements with a pH-metre immediately after opening the reaction vessels were on average 1.4 pH units higher than those determined by the proxy method due to CO 2 outgassing that increased the measured pH. This CO 2 degassing effect does not impact the here presented carbon isotope-based pH reconstruction method, which constitutes a viable alternative to direct pH measurements.

The present study addresses the use of spectrophotometric analysis to measure the change in absorbance of Hank’s balanced salt solution modified with phenol red as a function of immersion time to monitor the corrosion behaviour of Mg. The study confirms the existence of an good correlation between the pH and the absorbance of HBSS measured at any given point of immersion time for up to 1440 min and suggests that absorbance of HBSS at 559 nm can be used as an alternative method to monitor the change in pH of the medium with immersion time.

Fecal pH is a commonly used response variable in equine nutrition studies focused on evaluating gastrointestinal health. Although a relatively simple measurement, there is a lack of standardization in fecal-pH measurement protocols and a potential to improve precision of detection of differences between treatment groups. The objectives of this study were to measure fecal pH in collected feces using a range of different ratios with distilled water and allowing for different periods of time for equilibration, and to describe a simple fecal-pH measurement protocol to improve the knowledge gained from measuring fecal pH by decreasing measurement variation and standardizing the protocol across studies. Results indicate that addition of distilled water and the amount of time allowed for equilibration influence both measured pH and variation around the mean (P < 0.05). A protocol is described using fecal liquid without the addition of distilled water to measure fecal pH. Use of this approach results in less variation and a decrease in the number of animals needed per treatment group to detect small significant differences in fecal pH.

Both reactive MgO and CaO are alternative activators for ground granulated blast furnace slag (GGBS). In this study natural dolomite, as a source of MgO and CaO, was calcined at 800 °C (D800) and 1000 °C (D1000) in air. The activation of GGBS with the calcined dolomites was investigated using compressive tests, pH measurement of pore solutions, powder X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results indicated that both calcined dolomites can effectively activate GGBS. D800 showed a relatively slower acceleration to GGBS than D1000 and both were slower than CaO. The use of D800 produced similar compressive strengths as did D1000 after 7 days curing but lower strengths at later ages. By increasing the dosage of activators, significantly higher strengths were obtained using D800 while only small increases were observed using D1000. The detected hydration products by XRD and TGA were mainly C–S–H and hydrotalcite-like phases, similar to those from other alkali-activated slags. The comparison to other activators indicated that using calcined dolomite can induce faster hydration of slag than using reactive MgO in the early age while slower than Portland cement in this study.

The increasing uptake of anthropogenic CO 2 by the oceans has raised an interest in precise and accurate pH measurement in order to assess the impact on the marine CO 2 -system. Spectrophotometric pH measurements were refined during the last decade yielding a precision and accuracy that cannot be achieved with the conventional potentiometric method. However, until now the method was only tested in oceanic systems with a relative stable and high salinity and a small pH range. This paper describes the first application of such a pH measurement system at conditions in the Baltic Sea which is characterized by a wide salinity and pH range. The performance of the spectrophotometric system at pH values as low as 7.0 (“total” scale) and salinities between 0 and 35 was examined using TRIS-buffer solutions, certified reference materials, and tests of consistency with measurements of other parameters of the marine CO 2 system. Using m-cresol purple as indicator dye and a spectrophotometric measurement system designed at Scripps Institution of Oceanography (B. Carter, A. Dickson), a precision better than ±0.001 and an accuracy between ±0.01 and ±0.02 was achieved within the observed pH and salinity ranges in the Baltic Sea. The influence of the indicator dye on the pH of the sample was determined theoretically and is presented as a pH correction term for the different alkalinity regimes in the Baltic Sea. Because of the encouraging tests, the ease of operation and the fact that the measurements refer to the internationally accepted “total” pH scale, it is recommended to use the spectrophotometric method also for pH monitoring and trend detection in the Baltic Sea.

pH measurements taken from anaerobic digestion (AD) processes show fluctuations with an apparent random behavior that is usually associated to noise. However, it is well-known that the AD process is carried out on the basis of electron interchange from donors to acceptors. Therefore, such a random behavior could be associated to the current conditions governing the process behavior and then, a suitable analysis can provide important insights into the dynamical behavior and operational stability of AD processes. In this work, fractal scaling properties of pH signals from different continuous anaerobic bioreactors (applied to the treatment of tequila vinasses) are analyzed by using R/S analysis. Results indicated that fractal dimension is directly related to key process variables (influent COD, VFA and biogas production). This findings are helpful to achieve better insight into the operational aspects of continuous anaerobic digesters.

A portable light-emitting-diode (LED) photometer has been developed to provide low-cost seawater pH measurements. The benefits of the new system include a simple “do-it-yourself” construction design, a hundredfold reduction in cost relative to benchtop spectrophotometric systems, routine calibration-free operation in the field, and precision and accuracy well suited to applications such as education, coastal zone monitoring (including citizen science programs), and aquaculture and aquarium management. The photometer uses a high-sensitivity light-to-voltage integrated circuit as a detector, two LED light sources, and an open-source Arduino microcontroller for system control and data processing. Measurements are based on observations of absorbances of a pH-sensitive indicator. With meta-cresol purple, a sulfonephthalein indicator appropriate to natural seawater, the photometer system produces pHT measurements within 0.01 units of state-of-the-art spectrophotometric measurements (7.6 ≤ pH ≤ 8.2, 30 ≤ S ≤ 36.2, and 15 °C ≤ t ≤ 30 °C) and has a pH precision of ± 0.002. Measurement accuracy is achieved with a one-time calibration that relates absorbance ratios measured by the broadband photometer (RB) to absorbance ratios measured by a high-quality (narrowband) spectrophotometer (RN). Calculation of RN from RB allows the use of published algorithms that yield seawater pH as a function of RN, temperature, and salinity.

Two 6-hydroxyindole-based boron-dipyrromethenes (BODIPYs) have poor solubility and remain essentially nonemissive in water. In this paper, they were physically trapped inside the hydrophobic core of cetyltrimethylammonium bromide (CTAB) micelles, while ensuring solubility of the assembly in water. Due to the hydrophobic character of the micelles core, the two BODIPYs become fluorescent in water as they behave in organic solvents. More importantly, these BODIPY-CTAB assembles display distinct ratiometric optical change within the pH window of 4–9 in complete water system, indicating the capability as ratiometric fluorescent pH indicators. Furthermore, the pH dependent red/blue optical switch is reversible and can be repeated for many cycles by alternative exposure to acidic and basic media.

A fluorescence-based pH sensor based on a microfluidic chip is described. The indicator dye, 8-hydroxypyrene- 1,3,6-trisulfonic acid trisodium salt (HPTS) and the test solution are mixed in the microfluidic chip. Light fluorescing from this mixture is collected by a multi-mode optical fibre and its intensity is measured with a photodiode. The sensor is calibrated using a range of HPTS concentrations The highest sensitivity is achieved for a 500 mg L−1 solution of HPTS. Using this concentration of HPTS, the pH of test solutions, with pH ranging from 2.5 to 9.0, are measured. Results show a linear relationship between fluorescence intensity and pH within three pH ranges (i.e. 5.7–9.0; 4.2–5.7; 3.4–4.2) and a polynomial relationship within the pH range 2.5–3.3. Within the linear regions, the regression coefficients are greater than 0.99. Within the non-linear region the regression coefficient is 0.98.

In this study, a novel solid-state pH sensor based on an untreated platinum sheet was investigated. Chronopotentiometry using positive and negative currents was applied to effect the interconversion of Pt and PtO. To eliminate the influence of concentration polarization, a galvanostatic double-pulse method was applied for pH measurement. The consecutively applied currents were +100, +3, −100, and −3 μA for excitation times of 0.5, 1, 0.5, and 1 s, respectively. Stable potentials under the small currents were obtained which could be used to determine pH. The platinum sheet electrode exhibited near-Nernstian behavior in the pH range 2–12, with fitted lines having slopes of −44.2 and −51.1 mV/pH unit under the positive and negative currents, respectively. Overall, excellent linearity and reproducibility could be achieved. Moreover, the temperature responses for the method in pH 4, 6.86, and 9.18 buffer solutions obeyed the Nernst equation, and further supported the proposed mechanism for pH determination. In conclusion, this new detection method provides a solid-state, long-lived, and adaptable solution for pH measurement.

The coating of substrate materials with different geometry (gauze, plate, foam) and composition (Pt and FeCrAlloy) with Layered Double Hydroxides (Ni/Al, Mg/Al) was performed using the base electrogeneration method. The pH established by the cathodic reduction of nitrates in the proximity of a Pt gauze was measured with a glass electrode. In order to study the morphology, composition, and structure of the electrodeposited solids, at first Pt plates were used as substrates; the characterization was performed by SEM/EDS and XRD. Lastly, the study was focused on the FeCrAlloy foam more complex substrate. The more negative the applied potential was, the higher the pH values measured were; however, very negative potentials (-1.1 to -1.3 V vs SCE) promoted the formation of H2 bubbles. Optimum potential for precipitating Layered Double Hydroxides depended on their chemical composition and even if the potential applied was adequate for the formation of pure phases, SEM/EDS analyses revealed that a sequential precipitation occurred at long synthesis times. © 2013 Published by Elsevier Ltd.

The use of impure cresol red in spectrophotometric seawater pH measurements can introduce systematic inaccuracies greater than 0.1. Cresol red has been purified on a bulk scale to address this problem, but a characterization of the dye's physical–chemical properties has not been provided to date. This work reports the physical–chemical characteristics of purified cresol red for use in spectrophotometric seawater pH measurements over a range of temperatures and salinities. Seawater pH is expressed on the total hydrogen ion concentration scale (pHT) in terms of the ratio (R) of cresol red absorbances (A) at 433 and 573 nm (RCR = 573A/433A): pH T = − log K 2 T e 2 + log R CR − e 1 1 − R CR e 3 e 2 where − log(K2Te2) = a + b/T + c ln T − dT a = − 859.326051 + 0.14616 S + 7.81164 × 10 − 4 S 2 b = 22969.9366 + 8.04468 S − 0.20512 S 2 c = 152.209523 − 0.0317821 S d = 0.259915 and cresol red molar absorptivity ratios are expressed as: e 1 = − 0.00413 + 1.814 × 10 − 5 T e 3 / e 2 = − 0.021683 + 1.8107 × 10 − 4 T + 3.163 × 10 − 5 S − 35 for 278.15 ≤ T ≤ 308.15 K and 20 ≤ S ≤ 40. We recommend using cresol red to measure the acidity of seawater that has (at 298.15 K) a pHT of 6.8–7.8. This range might be encountered in ocean areas such as oxygen minimum zones or, hydrothermal vent fields, or it might be imposed in controlled laboratory studies. Ocean acidification will make cresol red an increasingly important indicator in coming decades as waters within ever larger ocean areas shift into its optimal indicating range.

Many studies have shown that metal ions may lead to oxidative stress in biological systems. Accordingly, DNA damage, protein modification, enzyme inhibition and activation, lipid peroxidation and many other effects may occur in living organisms. Many different formations of metal ions may enter human cells along with water, air, and various foods, and humans are negatively affected by these conditions, either directly or indirectly. These effects may cause irreversible damage to human metabolism. In this study, the toxicological effects of heavy metals on carbonic anhydrase enzyme activity from the gilthead sea bream liver were investigated. The carbonic anhydrase enzyme was purified via affinity chromatography and had a specific activity of 6775.5EUmg-1. The kinetics and characteristic properties, such as optimum pH, stable pH, optimum temperature, activation energy (Ea), activation enthalpy (?H), Q10, Km, and Vmax, were determined for the purified enzyme SDS-polyacrylamide gel electrophoresis showed a single band and molecular weight of the subunit was approximately 25kDa. Cd(II), Cu(II), Ni(II) and Ag(I) inhibited the enzyme activity in vitro. The type of inhibition and Ki values for these metals were calculated from Lineweaver-Burk plots as 17.74mM, 36.20mM, 12.85mM and 0.025mM for Cd(II), Cu(II), Ni(II) and Ag(I), respectively. All the metals were noncompetitive inhibitors. © 2013 The Authors.

Current anthropogenic carbon dioxide emissions generate besides global warming unprecedented acidification rates of the oceans. Recent evidence indicates the possibility that ocean acidification and low oceanic pH may be a major reason for several mass extinctions in the past. However, a major bottleneck for research on ocean acidification is long-term monitoring and the collection of consistent high-resolution pH measurements. This study presents a low-power (1 W) small sample volume (25 μL) semiconductor based fluorescence method for real-time ship-board pH measurements at high temporal and spatial resolution (approximately 15 s and 100 m between samples). A 405 nm light emitting diode and the blue and green channels from a digital camera was used for swift detection of fluorescence from the pH sensitive dye 6,8-Dihydroxypyrene-1,3-disulfonic acid in real-time. Main principles were demonstrated by automated continuous measurements of pH in the surface water across the Baltic Sea and the Kattegat region with a large range in salinity (~3-30) and temperature (~0-25°C). Ship-board precision of salinity and temperature adjusted pH measurements were estimated as low as 0.0001 pH units.

The Internet of Things (IoT) envisions a future based on billions of smart connected devices. Devices that sense their surroundings and which when combined with cloud computing services will provide information on scales ranging from the microscopic to global. We demonstrate here for the first time the development and characterisation of an ultra low-power radio-frequency identification (RFID) wireless sensor tag with potentiometric input for use with pH and ion-selective electrodes. Tags such as this will be critical to the practical realisation of the Internet of Things. The tag is able to autonomously measure and store electrode potential in its internal memory, and then transfer logged data wirelessly by RFID to a nearby reader or by near field communication (NFC) to a smart phone. The unique features of the sensor tag include its ultra low-power consumption, potentiometric sensing ability, autonomous data logging, and RFID/NFC compatible air interface. These features make the tag suitable for use where pH or ion-selective electrodes are deployed as stand-alone chemical sensors or as part of larger chemical sensor networks that will underpin the IoT. pH determination in solution is used as an experimental example for illustrating measurement capability of the tag, and its analytical performance is compared to a standard laboratory pH meter.

The determination of pH is the most commonly made analytical measurement throughout the world and the vast majority of these measurements are made to fulfil quality assurance and control requirements where traceability is required. Therefore, primary measurements of pH are essential to establish traceability to the agreed definition of this important quantity and disseminate this traceability to end users. The extrapolation of the acidity function to zero added ionic strength is an essential step in the Harned cell methodology for primary pH measurement. This approach relies on a number of solution chemistry approximations. Potential limitations of the current extrapolation method including possible non-linearity, and the validity of some approximations derived from solution chemistry, are reviewed and explored. Implications for the uncertainty of pH measurements using the Harned cell are discussed.

Impurities in sulphonephthalein indicator salts can result in significant errors in seawater pH determinations. To ensure suitable measurement accuracy and intercomparability on a global basis, impurities must be removed from all indicators used for oceanographic CO 2 system analyses. Previous work has described an effective HPLC (high-performance liquid chromatography) procedure for purification of meta-cresol purple, but the technique is labor-intensive, with each HPLC run producing only a small batch of purified indicator. This work describes the use of flash chromatography to more efficiently produce large batches of purified meta-cresol purple (mCP) and cresol red (CR), the preferred indicators for direct water column determinations of seawater pH. Several batches of unrefined mCP and CR of independent origin were prepared by flash chromatography. Indicator purity was then assessed in two ways: by (a) HPLC verification and (b) pH measurements of highly buffered solutions. HPLC chromatograms of the various flash-prepared mCPs indicated that the process did not always result in a completely pure product. In terms of performance, however – i.e., pH measurements of highly buffered solutions – no differences were observed between an HPLC-purified reference mCP and the flash-purified mCPs. HPLC examination of the flash-purified CRs indicated that every product was free of detectable impurities. No differences were seen in comparative pH measurements made with the purified CRs. The flash chromatography procedures outlined in this work are suitable for producing bulk quantities of mCP and CR for use in high-precision spectrophotometric pH measurements in seawater.

The efficacy of high pressure treatments in food processing is often attributed to the pressure induced pH change. However, knowledge of in-situ pH values of foods subjected to high pressure is scarce, because of obvious limitations of existing pH measurement methods. In this work, pH (25 °C) of some select liquid foods was measured in-situ under high hydrostatic pressure up to 800 MPa using our previously validated high pressure pH sensor. Our measurements show an increase of acidity in all tested food and water samples with increasing pressure. In general, food samples exhibit a buffering action under pressure resisting changes in pH. Furthermore, the pressure-dependent pH change is apparently independent of the concentration of added antimicrobial acids. Thus, any potential strategy of increasing the level of antimicrobial acid addition for enhancement of process pH effects is of dubious efficacy. Industrial relevance High pressure treatments in food processing require better understanding of in-situ pH values of foods subjected to high pressure. This paper describes in-situ pH measurement of some select liquid foods under high pressure using our high pressure pH sensor (Sastry & Samaranayake, 2009). The results of this study will assist product and process development in the food industry.

Polycations such as polyethylenimine (PEI) are used in many novel nonviral vector designs and there are continuous efforts to increase our mechanistic understanding of their interactions with cells. Even so, the mechanism of polyplex escape from the endosomal/lysosomal pathway after internalization is still elusive. The "proton sponge " hypothesis remains the most generally accepted mechanism, although it is heavily debated. This hypothesis is associated with the large buffering capacity of PEI and other polycations, which has been interpreted to cause an increase in lysosomal pH even though no conclusive proof has been provided. In the present study, we have used a nanoparticle pH sensor that was developed for pH measurements in the endosomal/lysosomal pathway. We have carried out quantitative measurements of lysosomal pH as a function of PEI content and correlate the results to the "proton sponge " hypothesis. Our measurements show that PEI does not induce change in lysosomal pH as previously suggested and quantification of PEI concentrations in lysosomes makes it uncertain that the "proton sponge " effect is the dominant mechanism of polyplex escape.Molecular Therapy (2012); doi:10.1038/mt.2012.185.

A real-time CO(2) evolution rate (CER) method together with conventional cultural and sensory techniques were utilized to determine the microbial quality and shelf life of several types of shrimp products: chloramphenicol (CAP) treated, imported farm raised, and domestic wild caught. Treatment with CAP was used to create different bacterial loads in shrimp samples to demonstrate the ability and sensitivity of the CER method for differentiating the bacterial activity in samples. Samples were divided into control (nontreated) and 0, 10, and 30 ppm of CAP treatment groups and stored at 4°C. The CER was recorded with a microrespirometer, and aerobic plate counts (APCs), olfactory sensory analyses, and pH measurements were recorded daily until spoilage occurred. The real-time CER results were highly correlated with the APCs (R(2) = 0.93) and readily distinguished the onset of spoilage in each of the treatment groups. CAP treatment at 10 and 30 ppm increased the sample shelf life by 2 and 3 days, respectively, compared with the nontreated samples. Untreated domestic wild-caught shrimp had a shelf life 1 day longer than that of the untreated imported farm-raised shrimp. No pattern of change in pH was noted throughout the storage period. When the olfactory sensory scores reached the marginally acceptable level, the mean CER was 27.23 μl/h/g and the mean APC was 5.78 log CFU/g. A cutoff CER of 25.0 μl/h/g was therefore selected to define acceptable raw shrimp. The CER method was a highly effective and sensitive real-time method for determining the microbial quality of raw shrimp.