Gran Plot Research Articles

AN ELECTROMETRIC METHOD FOR THE DETERMINATION OF IMPACT OF DMSO-WATER MIXTURES ON pKa VALUES OF SALICYLIC ACID DERIVATIVES

Objective: The main objective of this present study is to conduct an experiment to analyze the variation of protonation-deprotonation equilibria with regards to the dielectric constants of an organic medium, influence of errors on protonation constants and effect of pH on the percentage of species. Methods: The present investigation was carried out by using pH meter at a temperature of 303 K and ionic strength of 0.16 mol dm-3 in Dimethyl sulfoxide (DMSO)-water mixtures. The processing of data was done by using Gran plot titration. The advanced principles of mathematics and fuzzy logic have been employed to correlate chemical problems, known as chemometrics. To obtain best-fit chemical models, a modelling strategy such as SCPHD is used and a computer program MINIQUAD 75 is also employed for the refinement of results. Results: In the present study, we found the influence of dielectric constants of a medium Dimethyl sulfoxide (DMSO)-water on protonation constants of 5-Sulfosalicylic acid and 5-Hydroxysalicylic acid has been studied. The species distribution diagrams were presented and understood the effect of pH on the percentage of species. The obtained skewness values are ranging from 0.11-0.36 and–0.56-0.38, for 5-Sulfosalicylic acid (5-SSA) and 5-Hydroxysalicylic acid (5-HSA), respectively, which describes the distribution curves are right skewed and left skewed. The kurtosis values are ranging from 2.12-3.56, which indicates the peak of the distribution curve exhibits both platykurtic and leptokurtic pattern. The changes in the concentrations of some influential parameters such as log F, acid, alkali, volume of titrands, ligand causes variation of stability constants and the order of the effect of influential parameters on stability constants are as alkali>acid>ligand>volume of titrand>log F. Conclusion: It is observed that the significant influence of co-solvent Dimethyl sulfoxide (DMSO)-Water mixtures on the protonation constants of ligands also studied how some factors such as changes in concentrations of ligand, acid, base log F and volume of the solution have influence on the protonation constants.

Autonomous high-frequency time-series observations of total alkalinity in dynamic estuarine waters

Total alkalinity (TA) is a variable that reflects the acid buffering capacity of seawater, and is key to studies of the global carbon cycle. Daily and seasonal TA variations are poorly constrained due to limitations in observational techniques, and this hampers our understanding of the carbonate system. High quality and high temporal resolution TA observations are required to constrain the controlling factors on TA. Estuarine and coastal waters usually have low TA values and may experience enhanced remineralization of organic matter in response to processes such as eutrophication and terrestrial organic matter input. Therefore, these waters are considered vulnerable to acidification as a consequence of ongoing atmospheric anthropogenic carbon dioxide uptake. An In Situ Analyzer for seawater Total Alkalinity (ISA-TA) was deployed for the first time in low salinity, dynamic estuarine waters (Kiel Fjord, southwestern Baltic Sea). The ISA-TA and a range of additional sensors (for pH, pCO2, nitrate and temperature, salinity, dissolved oxygen) used to obtain ancillary data to interpret the TA variability, were deployed on a pontoon in the inner Kiel Fjord for approximately four months. Discrete samples (for TA, nutrients including NO3−, soluble reactive phosphorus (SRP) and H4SiO4, chlorophyll a) were collected regularly to validate the ISA-TA and to interpret the TA data. The effects on TA in the study area of nitrate uptake and of other processes such as precipitation, run-off and mixing of different waters were observed. The difference between the TA values measured with the ISA-TA and TA of discretely collected samples measured with the Gran titration method was −2.6 ± 0.9 μmol kg−1 (n = 106), demonstrating that the ISA-TA provides stable and accurate TA measurements in dynamic, low salinity (13.2–20.8), estuarine waters. The TA and ancillary data recorded by the sensor suite revealed that physical mixing was the main factor determining the variability in TA in Kiel Fjord during the study period.

Effect of Antifibrotic Therapy on Survival in Patients With Idiopathic Pulmonary Fibrosis

Real-world studies have reported reduced mortality in patients with idiopathic pulmonary fibrosis (IPF) treated with antifibrotic therapy; however, the initiation or discontinuation of therapy during these studies may have introduced bias. This study investigated the effect of antifibrotic therapy on mortality and other outcomes in patients with IPF using causal inference methodology. Data from a multicenter US registry of patients with IPF were used to assess the effect of antifibrotic therapy (nintedanib or pirfenidone) on death, death or lung transplant, respiratory-related hospitalization, and acute worsening of IPF (defined as any health care encounter deemed due to acute worsening of IPF). This study used the Gran method, which accounts for differences in patient characteristics and for treatment initiations and discontinuations during follow-up. The analysis cohort was limited to patients who started antifibrotic therapy on or after the day of enrollment or had never taken it. Among the 499 patients analyzed, 352 (70.5%) received antifibrotic therapy. Estimated event rates of death at 1 year were 6.6% (95% CI, 6.1-7.1) for treated patients and 10.2% (95% CI, 9.5-10.9) for control patients. There was a numerical reduction in the risk of death (hazard ratio [HR], 0.53; 95% CI, 0.28-1.03; P=0.060) but numerical increases in risks of respiratory-related hospitalization (HR, 1.88; 95% CI, 0.90-3.92; P=0.091) and acute worsening of IPF (HR, 1.71; 95% CI, 0.36-8.09; P=0.496) in treated versus control patients. Analyses based on causal inference methodology suggest that patients with IPF who receive antifibrotic therapy have improved survival.

Development of the New Sensor Based on Functionalized Carbon Nanomaterials for Promethazine Hydrochloride Determination

Promethazine hydrochloride (PM) is a widely used drug so its determination is important. Solid-contact potentiometric sensors could be an appropriate solution for that purpose due to their analytical properties. The aim of this research was to develop solid-contact sensor for potentiometric determination of PM. It had a liquid membrane containing hybrid sensing material based on functionalized carbon nanomaterials and PM ions. The membrane composition for the new PM sensor was optimized by varying different membrane plasticizers and the content of the sensing material. The plasticizer was selected based on calculations of Hansen solubility parameters (HSP) and experimental data. The best analytical performances were obtained using a sensor with 2-nitrophenyl phenyl ether (NPPE) as the plasticizer and 4% of the sensing material. It had a Nernstian slope (59.4 mV/decade of activity), a wide working range (6.2 × 10-7 M-5.0 × 10-3 M), a low limit of detection (1.5 × 10-7 M), fast response time (6 s), low signal drift (-1.2 mV/h), and good selectivity. The working pH range of the sensor was between 2 and 7. The new PM sensor was successfully used for accurate PM determination in a pure aqueous PM solution and pharmaceutical products. For that purpose, the Gran method and potentiometric titration were used.

Developing Metal Complexes for Captopril Quantification in Tablets Using Potentiometric and Conductometric Methods.

Potentiometric and conductometric methods were successfully applied to elucidate the interaction of 10 ions, viz., Cr3+, Fe3+, La2+, Th4+, Co2+, Mn2+, Pd2+, Sr2+, Ti2+, and Zr2+, with the antihypertensive drug captopril (CAP) and its role to determine CAP in pure powder and tablet forms. The ionization constant of CAP and the generated complexes' stability constants (log K) were evaluated using potentiometric and conductometric methods at 25 ± 0.1 °C and 0.05 M ionic strength (I) of NaNO3 aqueous solution, and CAP was then determined in pure powder and tablet forms. Complexes having metal:ligand ratios of 1:1, 1:2, and/or 1:3 were produced, regardless of the type of the ligand or metal ions. Both the suggested potentiometric and conductometric procedures were utilized to confirm the stoichiometry of the M-CAP binary complexes formed. These two different techniques were utilized successfully to determine CAP in pure powder and tablet forms. Using the standard addition method (SAM) based on the Gran plot, CAP was satisfactorily determined throughout the concentration range of 0.83-13.04 mg/mL (SD = 0.20, R = 0.9986 (n = 5)), with a detection limit of 0.64 mg/mL (SD = 0.20, R = 0.9986 (n = 5)). In the presence of common tablet excipients, no interferences were observed. The percentage of CAP recovered from various dosage formulations (tablets) varied from 95.88 to 99.92%.

A new sensor for direct potentiometric determination of thiabendazole in fruit peels using the Gran method

A new sensor for direct potentiometric determination of thiabendazole (TBZ) was prepared. The ionic pair of TBZ cation and the 5-sulfosalicylate anion was used as the new sensor material incorporated in liquid type of ion-selective electrode membrane for TBZ determination. For optimization of the membrane of the sensor for TBZ determination, six different plasticizers and the content of the sensor material in the membrane were varied. The chosen sensor with dibutyl sebacate (DS) as plasticizer and 1% of sensor material in the membrane was characterized with Nernstian response towards TBZ (62.2 mV/decade of activity), a wide working range (8.6∙10−7–1.0∙10−3 M), and a low limit of detection (3.2·10−7 M). Also, it proved to be an accurate and reliable sensor for TBZ determination in pure and real samples (peel of oranges, lemons and bananas) where it was determined using direct potentiometry and Gran method.

Morphometric Analysis of Permanent Canines: Preliminary Findings on Odontometric Sex Dimorphism.

Aim: This study aims to investigate the morphometrics of permanent canines in establishing sexual dimorphism in the native Arabian population. Methods: Thirty (male = 12; female = 18) native Arabian subjects, with ages ranging between 20–45 years. The mesiodistal (MD), cericoincisal (CI) and labiolingual (LL) widths of the teeth 13, 23, 33, and 43 and the inter-canine distance in maxillary (MaxICW) and mandibular (ManICW) arches were measured using a digital caliper. The gran method was used for establishing sex dimorphism among the study subjects. Descriptive statistics were employed using SPSS version 20.0 (Armonk, NY, USA, IBM Corp.). Results: The comparison of either of the measurements (MD, CI, LL, MaxICW and ManICW) were shown to be statistically significant (p > 0.05). The overall mean values of teeth 13, 23, 33, and 43 for CI, LL, MaxICW, and ManICW were lower for females than males (p > 0.05). The MD width was higher in females than that of males (p > 0.05). The sex dimorphism value for teeth 13, 23, 33, and 43 were 0.98, 0.99, 1, and 0.99, respectively. The standard canine index was high for mandibular teeth and lower for mandibular teeth, and SCI values for teeth 13, 23, 33, and 43 were 0.219, 0.218, 0.257 and 0.256, respectively. Conclusion: The morphometrics of permanent canines are helpful in sex determination with the aid of odontometric analysis.

Gradual back-projection residual attention network for magnetic resonance image super-resolution

Background and objectiveMagnetic Resonance Image (MRI) analysis can provide anatomical examination of internal organs, which is helpful for diagnosis of the disease. Aiming at the problems of insufficient feature information mining in the process of MRI super-resolution (SR) reconstruction, the difficulty of determining the interdependence between the channels of the feature map, and the reconstruction error when reconstructing high-resolution (HR) images, we propose a SR method to solve these problems. MethodsIn this work, we propose a gradual back-projection residual attention network for MRI super-resolution (GRAN), which outperforms most of the state-of-the-art methods. Firstly, we use the gradual upsampling method to gradually scale the low-resolution (LR) image to a given magnification to alleviate the high-frequency information loss caused by the upsampling process. Secondly, we merge the idea of iterative back-projection at each stage of gradual upsampling, learn the mapping relationship between HR and LR feature maps and reduce the noise introduced during the upsampling process. Finally, we use the attention mechanism to dynamically allocate attention resources to the feature maps generated at different stages of the gradual back-projection network, so that the network model can learn the interdependence between each feature map. ResultsFor the 2 × and 4 × enlargement, the proposed GRAN method shows the superiority over the state-of-the-art methods on the Set5, Set14, and Urban100 benchmark datasets, extensive benchmark experiment and analysis show that the superiority of the GRAN algorithm in terms of peak signal-to-noise ratio and structural similarity index indicators. ConclusionThe MRI results reconstructed by gradual back-projection residual attention network on the public dataset IDI have good image sharpness, rich texture details and good visual experience. In addition, the reconstructed image is the closest to the real image, enabling the medical expert to see the biological tissue structure and its early pathological changes more clearly, providing assistance and support to the medical expert in the diagnosis and treatment of the disease.

Potentiometric studies on bioactive material species of ternary complexes in SLS-Water mixtures

Chemical speciation plays key role in understanding the physiological and biological aspects of metal ions and ligands in human body. The complexation of essential metal ions with Glycylglycine (GG) and Histamine (Him) in Sodium Lauryl Sulphate (SLS) has been presented in this study. The complexes formed in the present study are M L X H 2 , M L 2 X H 2 and M L X 2 H 3 . The Skewness values in the present study are from 0.05 to 0.84 for Ca(II), 0.03 to 0.93 for Mg(II) and 0.45 to 1.34 for Zn(II) and the χ2 values obtained the present study are ranging from 7.8250.37 for Ca(II), 6.1837.45 for Mg (II) and15.69143.67 for Zn(II). A very low standard deviation in log β values indicates the precision of the parameters. The advanced principles of mathematics and fuzzy logic have been employed to correlate chemical problems, which is called chemo metrics. In the present investigation potentiometer is used for analysis and the results obtained in the study have been processed through Gran plot method, SCPHD is used for best fit chemical model and MINIQUAD75 is used for refinement of results. An experiment has been conducted to understand the distribution of species, effect of surfactant on stability constants of ternary complexes, effect of influential parameters like concentration of alkali, acid, ligands and metal ions on the stability constants.

Potentiometric Studies on Bioactive Material Species of Ternary Complexes

Complexation of essential metal ions with glycylglycine and histamine in cetyltrimethylammonium bromide (CTAB) has been presented in this study, which targets insight in the distribution of species, effect of surfactants on stability constants of ternary complexes, and effect of concentration of alkali, acids, ligands, and metal ions on the stability constants. The studied complexes are MLXH2, ML2XH2, and MLX2H3. The advanced principles of mathematics and fuzzy logic have been employed to correlate chemical problems, known as chemo metrics. A potentiometer has been used for analysis, and the results obtained have been processed through gran plot method, SCPHD used for best fit chemical model. MINIQUAD75 has been used for refinement of the results.

Determination of surface protonation-deprotonation behavior, surface charge, and total surface site concentration for natural, pillared and porous nano bentonite heterostructure

In this paper, the physicochemical properties of natural, pillared and porous nano bentonite heterostructure in the points of view of surface protonation–deprotonation behaviors were studied. Moreover, the structural heterogeneity in each sample based on three-dimensional field-emission scanning electron microscopy (FESEM) plots were investigated to obtain its effect on the formation of surface active sites. To better understand the surface protonation properties and adsorptive capability of natural, pillared and porous clays, it is essential to investigate the surface charge, surface active sites, pH at point of zero charge (pHzpc), and surface acid-base equilibrium constants. Since the information about amphoteric acid-base groups especially in porous clays is still lacking, our main purpose is to obtain the best estimates to compare the surface properties of natural, pillared and porous clays by means of Gran method and surface complexation model from titration data. The 2 pK-diffusion layer model (DLM) was applied to evaluate the contribution and concentration of the various surface site species (such as SOH, SOH2+, and SO−) in the different pH and ionic strengths. This paper indicates considerable new information about surface acid-base reactions, total surface site concentrations, pHzpc measurement, which provides basic knowledge of the underlying adsorption mechanisms. The maximum value of total surface sites concentration (8.84 mmol/L) in ionic strengths of 0.05 M NaCl belonged to porous nano bentonite heterostructure (PBH) with the highest pHzpc at 9.73.

Dissolved inorganic carbon export by mountainous tropical rivers of the Western Ghats, India

Large rivers that are known for carrying huge fluxes are few in numbers; nevertheless, the contributions of thousands of small mountainous coastal rivers to global biogeochemical cycles is also measured to be equally important. Small catchment sizes, high channel gradients yet high water discharge are prominent characters of the coastal rivers draining the Western Ghats (WG) of India. Three geo-tectonic divisions, namely, Southern Granulite Terrain (SGT) in southern, Western Darwar Craton (WDC) in central and Deccan Traps (DT) in the north constitute the entire Western Ghats. Based on the seasonal sampling of 70 coastal rivers draining into the Arabian Sea, this study provides a comprehensive discharge-weighted estimate of DIC for the Western Ghats (WG) region. The concentration of bicarbonate measured in-situ using gran plot method. Fluxes and yields were calculated using seasonal discharge and area of respective rivers. The discharge-weighted DIC concentration of WG region is 629 μM, which is slightly higher than the average global DIC concentration for the low latitude (< 30°) rivers. Despite, covering 113×103km2 area, this region yearly exports 175×109 mol DIC to the Arabian Sea. The DIC flux contributed by the WG region is among the highest in peninsular rivers and comparable with several large global rivers. DIC export rates suggest that within the region, the chemical weathering rate of DT is ∼4 times and WDC is ∼2.5 times higher than that of SGT region. The DIC flux of the WG region (covering 0.076% of global land area) is approximately 0.55% of the global riverine DIC flux to the ocean. Thus, in terms of global DIC export to seas, this region is the 28th largest contributor. Due to high annual DIC yield (1547×103 mol km−2) WG region ranks as the 9th most active region of the world. DIC yields of rivers draining granite-dominated (SGT and WDC) and basalt-dominate (DT) regions of WG are remarkably higher than the global rivers draining similar lithology from temperate and arctic regions. The WG rivers display a latitudinal gradient in DIC transport. Type of silicate rocks, rainfall-runoff, temperature range, and sediment yields control the variability in DIC fluxes and export rates of Western Ghats region.

Surface complexation model of Cd in paddy soil and its validation with bioavailability

In southern China, the paddy soils are mainly variable-charge soils, which have undergone high weathering processes and leaching processes. Due to deficiencies of carbonate and base cations, the variable-charge soil pH is normally less than 6.5, and decrease of soil pH can substantially enhance the mobility and bioavailability of heavy metals. Cadmium (Cd) is one of the most important pollutant influencing human health and environmental safety. Cd contamination is a serious problem in paddy soils, and the acidic condition could further aggravate the mobility and bioavailability of Cd. There is an urgent need to establish a model to investigate the adsorption characteristics of Cd and accurately assess the bioavailability of Cd in variable-charge paddy soils. In this study, the paddy soil was selected from agricultural regions in southern China. Batch experiments were conducted to investigate the Cd adsorption characteristics of the soils from pH 3 to 10. The results showed that Cd mainly existed in dissolved forms at pH 5.5, almost all Cd was adsorbed on the soil surface. Based on the potentiometric titration, the point of zero charge (pHpzc) was obtained when the surface charge density ( σ ) was equal to zero. The pHpzc of the paddy soil was 5.91. The 1-site/2-p K surface complexation model (SCM) was applied to further examine the acid-base properties of the soils by assuming the acid-base buffering system as a protonation-deprotonation process. The surface site concentration ( H s) and the surface site density ( D s) were obtained by Gran plot. The two acid equilibrium constants (p K a1 and p K a2) were determined by extrapolation and the calculated pHpzc were obtained by the average values of the p K a1 and p K a2. The value of pHpzc calculated from the model was 6.10, which was well matched with those from the potentiometric titration, indicating that it is feasible for the application of SCM to the variable-charge soils. The intrinsic equilibrium constants (lg K SOCd) was estimated from the Cd adsorption experimental data and acid-base parameters (p K a1, p K a2 and D s) using Visual MINTEQ software. The results showed that the adsorption of Cd on the paddy soil could be successfully modeled by the SCM. Based on the previous study, the pH was significantly negatively correlated with grain Cd content in paddy soil when pH was below 5.5 ( P 1 mol L−1 MgCl2 (exchangeable fraction) and 1 mol L−1 NaOAc/HOAc (bound to carbonate). Although the extracted Cd was positively correlated with Cd content in grain, the P value was much higher than 0.05, indicating the insignificant correlation. Compared with the extraction method, the dissolved Cd calculated from the SCM was significantly correlated with the grain Cd content (P

Simulated calculation of surface acid-base equilibrium constants and surface species distribution of the nanoceria suspension

As artificial nano-enzymes and effective adsorbents, CeO2 nanomaterials have been extensively studied for their potential applications in biomedicine and environmental protection. However, the surface acid-base properties of nanoceria suspensions have not been fully studied. In this work, the ceria nanoparticles were synthesized by hydrothermal reaction and calcination. They have a BET specific surface area of 52.01 m2/g. FTIR and XPS showed that there are two amphoteric sites (≡Ce(IV)-OH and ≡Ce(III)-OH) and a trace acidic site (≡Ce(III)-OCOOH) which can act as a site probe. The pH range of the acid-base reaction of surface hydroxyl groups of the CeO2 nanomaterials was determined by Gran plot method. The acidic ionization constants (log K1, log K2), site concentration (log C) of two amphoteric surface hydroxyl sites and pHpzc in three KNO3 supported electrolytes were simultaneously optimized by ProtoFit GUI v2.1 free software using Donnan Shell Model (DSM) and same initial parameters. Their surface species distribution was calculated by PHREEQCI 3.4.0 free software using Donnan model and database (phreeqc.dat). The results show that the proton transfer reaction occurred between ≡Ce(IV)-OH and ≡Ce(III)-OH sites. Therefore, this study reveals the surface acid-base properties, proton transfer behavior and pHpzc of the CeO2 suspension.

Valorization of manganese-containing groundwater treatment sludge by preparing magnetic adsorbent for Cu(II) adsorption

Mn-containing sludge from groundwater treatment was converted to magnetic particles (MPs) via a one-step hydrothermal method using sodium ascorbate (SA) as the reductant. The MPs were characterized by X-ray diffraction spectroscopy, Mössbauer spectroscopy, X-ray fluorescence spectroscopy, magnetometry and Gran titration and the results showed that magnetic jacobsite was obtained as an intermediate product in transformation of Fe/Mn oxides to siderite and rhodochrosite. When the molar ratio of SA to Mn in the sludge was two, the produced MPs-2 contained a mixture of ferrihdyrite, hematite, jacobsite and Si/Al oxides, and could magnetize at 2.4 emu/g. Ferrihydrite content in MPs decreased with increase of the SA/Mn molar ratio, leading to decrease of the surface sites concentration (Hs). Thus, MPs-2 contained optimized Hs of 6.7 mmoL/g and a desirable adsorption capacity of Cu(II) (73.1 mg/g). The adsorption isotherms of MPs-2 on Cu(II) complied with the Langmuir model and the adsorption kinetics fitted well with the pseudo-second-order model. The major mechanism of adsorption was cationic exchange of the coordinated H and Na ions on MPs-2 surface sites with the Cu(II) ions. This study was the first time to report preparation of MPs by recycling Mn-containing sludge, which could be used as a high-capacity and low-cost adsorbent in treatment of heavy metal-containing wastewater.

Chemical composition of rainwater in an urban area of the southeast of Brazil

In the city of Limeira, located in the State of São Paulo, Brazil, the major ions of 30 rainwater samples, collected from Sep/2013 to Mar/2014, were quantified by ionic chromatography (ICS 90); and HCO3− was determined via Gran titration. Three source apportionment methods, namely Principal Component Analysis (PCA), air mass trajectory clustering and enrichment factor (EF), were used to identify the main sources of pollutants dissolved in rainwater samples. The concentration of ions (μeq L−1), of the samples was: Ca2+ > NH4+ > Na+ > HCO3− > Mg2+ > SO42− > NO3− > Cl− > K+ > H+, and pH = 5.6 in VWM. The first three components obtained via PCA explained 75% of the total variance correlation and indicated a strong contribution of pollutants from agricultural emissions in the studied region, possibly due to the proximity of rural areas. The generated trajectory clusters indicated a 70% contribution from continental sources in the studied area. EF showed that SO42−, NO3−, Cl−, K+, Mg2+ and HCO3− are from anthropogenic sources whereas Ca2+ is from crust and Na+ is from crust and anthropogenic sources. The anthropogenic sources, possibly associated with the region's agricultural activities, mining, industries and heavy vehicle traffic. In addition, it was verified the negative impact the fire outbreaks in the State of São Paulo had on the quality of the air in Limeira. Finally, the ionic concentrations in rainwater samples collected in the urban area of Limeira were compared with data from monitored cities in Brazil and throughout the world.

Monitoring the Chloride Concentration in International Scheldt River Basin District Water Using a Low-Cost Multifunction Data Acquisition Board

In analytical chemistry laboratories, to gather in the shortest time as many data as possible with the utmost accuracy and precision, high throughput automated setups are indispensable. In the present study, to determine the chloride concentration in the international Scheldt river basin district, experiments are carried out utilizing a thermostatically controlled semi-automated setup. A novel ICT-based method is developed using a low-cost multifunction Data Acquisition Board (DAQ) controlled by a homebuilt LabVIEW™ program. Specifically, this approach enables a correlation between different parameters i.e., droplet volume, temperature, A/D voltage conversions. Here, processing experimental data of a potentiometric precipitation titration utilizing a silver nitrate standard solution as titrant in a manual burette equipped with a controllable electronic valve allows for a preliminary indication of the titration end point via the Virtual Instrument (VI) numerical first derivative tool in the LabVIEW software. The LabVIEW tool is compared with the well-known Gran method implemented in the LabVIEW program, emphasizing an accurate performance of the setup to determine the chloride concentration in fresh river water. We are confident that our findings are evidence of the versatile and powerful features of the LabVIEW controlled DAQ in the analytical chemistry laboratory.

The modified Gran methods in potentiometric redox titrations derived according to GATES/GEB principles

The modified Gran methods in potentiometric redox titrations derived according to GATES/GEB principles

Chemical composition of polluted mist droplets

Mist events occur frequently worldwide, but the chemical characteristics of the mist droplets has never been investigated because of very low liquid water contents of them. We estimated the concentrations of the mist water, the average concentration of the mist droplets, via the determination of water-soluble components of the coarse aerosol and the observation of the imprints of the droplets on a MgO-coated glass slide. The pH of the mist water was estimated from the equilibrium calculation with the data of the Gran plot of the solution of the dissolved coarse particles, the inorganic ion concentrations of aerosol larger than 10 μm, and the estimated volume of mist water. The mist water was measured as about 1 eq/L total concentration for typical inorganic ions and about pH 4.5 in Yokohama. Such highly concentrated mist droplets may have intense environmental effects.

A Precise Method for Processing Data to Determine the Dissociation Constants of Polyhydroxy Carboxylic Acids via Potentiometric Titration.

The thermodynamic dissociation constants of xylonic acid and gluconic acid were studied via potentiometric methods, and the results were verified using lactic acid, which has a known pKa value, as a model compound. Solutions of xylonic acid and gluconic acid were titrated with a standard solution of sodium hydroxide. The determined pKa data were processed via the method of derivative plots using computer software, and the accuracy was validated using the Gran method. The dissociation constants associated with the carboxylic acid group of xylonic and gluconic acids were determined to be pKa1=3.56±0.07 and pKa1=3.74±0.06, respectively. Further, the experimental data showed that the second deprotonation constants associated with a hydroxyl group of each of the two acids were pKa2=8.58±0.12 and pKa2=7.06±0.08, respectively. The deprotonation behavior of polyhydroxy carboxylic acids was altered using various ratios with Cu(II) to form complexes in solution, and this led to proposing a hypothesis for further study.