Ion-selective Electrode Measurements Research Articles

Hydrothermal Destruction and Defluorination of Trifluoroacetic Acid (TFA).

Per- and polyfluoroalkyl substances (PFAS) have received increased attention due to their environmental prevalence and threat to public health. Trifluoroacetic acid (TFA) is an ultrashort-chain PFAS and the simplest perfluorocarboxylic acid (PFCA). While the US EPA does not currently regulate TFA, its chemical similarity to other PFCAs and its simple molecular structure make it a suitable model compound for studying the transformation of PFAS. We show that hydrothermal processing in compressed liquid water transforms TFA at relatively mild conditions (T = 150-250 °C, P < 30 MPa), initially yielding gaseous products, such as CHF3 and CO2, that naturally aspirate from the solution. Alkali amendment (e.g., NaOH) promotes the mineralization of CHF3, yielding dissolved fluoride, formate, and carbonate species as final products. Fluorine and carbon balances are closed using Raman spectroscopy and fluoride ion selective electrode measurements for experiments performed at alkaline conditions, where gas yields are negligible. Qualitative FTIR gas analysis allows for establishing the transformation pathways; however, the F-balance could not be quantitatively closed for experiments without NaOH amendment. The kinetics of TFA transformation under hydrothermal conditions are measured, showing little to no dependency on NaOH concentration, indicating that the thermal decarboxylation is a rate-limiting step. A proposed TFA transformation mechanism motivates additional work to generalize the hydrothermal reaction pathways to other PFCAs.

Fluoride Determination in Milk, Soy, and Water-Based Products Using Ion-Selective Electrode and Direct Measurement Technique: Single-Laboratory Validation, First Action 2022.05.

The AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals issued a call for methods for the determination of fluoride in infant formula. Standard Method Performance Requirement (SMPR®) 2014.016 was approved. A single-laboratory validation (SLV) of a fluoride ion-selective electrode (F-ISE) method was completed. Five powder samples were reconstituted, and hydrochloric acid was added to dissolve and release any bound fluoride. Samples included infant and adult nutritional products made from milk, whey, or soy, containing intact, partially hydrolyzed, or hydrolyzed proteins. Sodium citrate buffer was added to complex any interfering ions and adjust pH and ionic strength. Samples were analyzed in duplicate over 6 days using F-ISE. Results were calculated based on one of two least-squares (log fit) standard curves (0.02 to 0.1 µg/100 g or 0.1 to 2.0 µg/100 g). The LOQ for the method was determined to be 3.3 µg/100 g, which was far below the minimum analytical value of 30 µg/100 g required in the SMPR. The fluoride concentrations ranged from approximately 3 to 14 µg/100 g reconstituted powder and the intermediate precision, RSDr, ranged from 0.7 to 12.4%. Although all of these results are out of scope for the SMPR due to their low fluoride, it should be noted that the RSDr for formulas with fluoride concentrations ranging from approximately 9 to 14 µg/100 g ranged from 0.7 to 4.3%, and the RSDr for the two formulas with fluoride concentrations at or below the theoretical detection limit of the method were only approximately10 and 12.4%. Recoveries ranged from 94 to 98% for samples spiked at three levels with NIST-traceable standard solutions, meeting the SMPR. The F-ISE method meets the SMPR and was adopted as a First Action Official MethodSM. The fluoride ion-selective electrode method presented here is affordable and easy to run. The addition of acid to the samples dissolves any minerals which may bind the fluoride.

Laying the foundation for enhancing safety of desmopressin in older people: Validation of capillary blood sodium levels.

We aim to make desmopressin a safe treatment option for (older) patients at risk for hyponatremia, by introducing a new way of sodium monitoring. The goal is to reduce the risk of hyponatremia, enhance patient safety and ultimately introduce self-monitoring of sodium levels. The first step in the aforementioned is to validate capillary sodium. 100 randomly selected patients admitted to the urology department received a single finger prick to collect capillary blood (250 µl) in a lithium-heparin tube. Each patient acted as its own control for the capillary and venous blood sample. Venous and capillary plasma sodium were analyzed by indirect ion-selective electrodemeasurement. The primary outcome was the agreement between capillary and venous sodium measurements, measured by the intra-class correlation coefficient (ICC). One hundred paired blood samples were obtained of which four were excluded. There was no significant statistical difference observed between venous and capillary sodium (-0.23 mmol/L, p = 0.374). The ICCfor single measures between capillary and venous sodium was 0.82 (95% confidence interval 0.75-0.88). Inter-method differences analyzed by a Bland-Altman plot and a Passing-Bablock regression did not reveal a statistically significant difference between both groups. We demonstrated that venous and capillary sodium levels are interchangeable, taken into account the inter- and intravariability between analyses. We provided the first step towards a simple and safe solution for frequent sodium monitoring through a minimal invasive capillary blood collection. The results are of direct clinical relevance to safely use desmopressin in (older) patients at risk.

Comparison of i-STAT Point of Care vs. Indirect Ion Selective Electrode Measurements of Sodium in Severe Hyponatremia

Comparison of i-STAT Point of Care vs. Indirect Ion Selective Electrode Measurements of Sodium in Severe Hyponatremia

CYANanobot: Miniaturized Boat-Assisted Data Acquisition for Automated Cyanide Monitoring in Wastewater Using Optical Nano-Sensors

Cyanide contamination in water and wastewater is ubiquitous, particularly in gold mining industries, where cyanide is commonly used to extract gold. It is constantly being monitored by collecting samples which are analyzed in the laboratory using traditional cyanide analysis, which requires complicated instrumentation, skilled analysts, and expensive equipment. Using the gold nanoparticle (AuNP)-decorated paper-based sensor employing Whatman Filter Paper (WFP) as a substrate, an automated process for cyanide monitoring with the aid of an assembled and improvised remotely controlled miniature boat was developed. The technology is equipped with a filtration system with automated water sample collection and preparation with an automatic paper sensor dispenser. Images of the collected wastewater samples are taken at different time intervals and are analyzed on their respective color spaces based on 8 mathematical models, each predicting the cyanide level of the water sample. The predictions are compared to the actual Ion-Selective Electrode (ISE) measurement, and Root Mean Square Error (RMSE) values were calculated. The predictions at 165s using the Hue, Saturation, Value (HSV) color space exhibited the highest R2 of 0.85 and the lowest RMSE of 3.80 parts per million (ppm) with an average error of 3.40ppm. The predictions are sent to a database using Global System for Mobile Communications (GSM). The results suggest that the CYANanobot technology facilitates fast analysis time, circumvents the frequent instrument calibration, reduces operating costs, minimizes exposure to toxic cyanide-containing samples, and reduces person-to-person interaction.

Optimizing Colloidal Stability and Transport of Polysaccharide-Coated Magnetic Nanoparticles for Reservoir Management: Effects of Ion Specificity

In this work we explore the mechanisms of ion-specific stabilization of a polysaccharide-based coating for colloidal nanomaterials used within the oil &amp;amp; gas industry. While nanotechnology has wide prevalence across multiple industries, its utility within this sector is largely undeveloped but has potential applications in areas including (but not limited to) exploration, drilling and production processes. For example, reservoir contrast agents in the form of superparamagnetic nanoparticles could be used to accurately determine the residual oil saturation distribution in a reservoir and thus advise enhanced oil recovery (EOR) efforts. However, deployment of such materials in oil reservoirs proves challenging in cases where high salinity subsurface environments induce nanoparticle aggregation, leading to loss of mobility. Here, we report the synthesis and characterization of dextran-coated superparamagnetic iron oxide nanoparticles (Dex-SPIONs), the colloidal stability of which was evaluated in various brine formulations at elevated temperatures. Initial dynamic light scattering (DLS) measurements reveal a lack of contingency between particle stability and total electrolyte concentration for samples comprised of synthetic seawater and low-salinity brine, the latter fluid of which possesses higher ionic strength yet preserves colloidal integrity to a much greater extent than its seawater counterpart. Further experiments point to a calcium (Ca2+) ion-specific stabilization effect wherein surface complexation of Ca2+ ions to the dextran periphery improves carbohydrate hydration and thus enhances colloidal stability. Ion selective electrode (ISE) measurements provide additional evidence of the Ca2+ - dextran binding interaction, the role of which also factors significantly into mitigation of polysaccharide degradation [as demonstrated through gel permeation chromatography (GPC)]. Finally, we assess the transport of Dex-SPIONs through porous media, including examination of retention properties with respect to variances in ionic composition.

Reliability of an Ion-Selective Electrode as a Simple Diagnostic Tool for Mastitis.

Developing a simple quantitative tool for mastitis diagnosis is essential. The Ion-Selective Electrode for sodium has been reported to reliably measure sodium concentrations in human milk. To determine whether an Ion-Selective Electrode measurement of sodium:potassium ratios could serve as a diagnostic tool for mastitis and, if so, to determine the diagnostic cut-off value. A total of 107 milk samples, including 55 from milk bank donors and 52 from participants with mastitis, were studied. The sodium:potassium ratios were determined in 33 samples (without mastitis n = 15; with mastitis n = 18) by the Ion-Selective Electrode and ion chromatography. The remaining 74 samples (donor milk n = 40; participants with mastitis n = 34) were analyzed by Ion-Selective Electrode only. Values were averaged over three measurements for each method. The median postpartum months of donors and participants with mastitis were 2 and 3 months, respectively. The mean (SD) sodium:potassium ratios without and with mastitis were 0.5 (0.1) and 1.7 (1.2), respectively. A positive correlation existed between sodium:potassium ratios obtained from the two methods (r = 0.98). Area under the curve values were 0.951 (95% CI [0.904, 0.986]) for the Ion-Selective Electrode (N = 107) and 0.978 (95% CI [0.926, 1.000]) for the ion chromatography (n = 33) methods. The optimal cut-off value for the Ion-Selective Electrode method was 0.60, with 86.5% sensitivity and 92.7% specificity. The Ion-Selective Electrode was sufficiently accurate for the diagnosis of mastitis. Cohort studies are needed to explore the relationship between sodium:potassium ratios and clinical outcomes.

The effect of haemolysis on the direct and indirect ion selective electrode measurement of sodium.

We compared the effect of haemolysis in sodium measurement using indirect and direct ion-selective electrodes to test the hypothesis that haemolytic effect on sodium would be greater with indirect ion-selective electrode due to electrolyte exclusion effect from released intracellular proteins. Plasma lithium heparin samples (n = 36) from four volunteers were prepared to give a range of haemolytic indices (H-indices). Samples were analysed for sodium by indirect ion-selective electrode, H-index and total protein on an Abbott Architect c16000 and sodium by direct ion-selective electrode on a Siemens RAPIDPoint 500. Percentage changes in sodium in paired direct and indirect ion-selective electrode values were compared. Abbott H-index, which represents haemoglobin concentration in g/L, correlated with percentage negative change in sodium by direct ion-selective electrode (ρ 0.995, P < 0.001) and indirect ion-selective electrode (ρ 0.991, P < 0.001). Percentage negative change was less when sodium was measured by direct ion-selective electrode compared to indirect ion-selective electrode (Wilcoxon signed-rank Z = 3.46, P = 0.01). The difference in percentage change in sodium between direct ion-selective electrode and indirect ion-selective electrode correlated with total protein (ρ 0.751, P < 0.001). The negative bias in sodium results exceeded the reference change value of 2.2% at an H-index of 8.31 for indirect ion-selective electrode and 9.26 for direct ion-selective electrode. Haemolysis causes negative influence with sodium measured by both indirect and direct ion-selective electrode due to a dilutional hyponatremia. The additional interference in indirect ion-selective electrode is due to the electrolyte exclusion effect but this is unlikely to be clinically significant as it is small in magnitude.

Depletion Forces Induced by Mixed Micelles of Nonionic Block Copolymers and Anionic Surfactants.

Depletion forces were measured between a silica sphere and a silica plate in solutions containing nonionic Pluronic P123 poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymers and anionic sodium dodecyl sulfate (SDS) surfactants using colloidal probe atomic force microscopy. Prior research established synergistic depletion force enhancement in solutions containing SDS and unimeric Pluronic F108 block copolymers via formation of large pseudo-polyelectrolyte complexes. The current work addresses a more complex system where the polymer is above its critical micelle concentration, and surfactant binding alters not only the size and charge of the micelles but also the number of polymers per micelle. Force profiles were measured in 10 000 ppm P123 (1 wt %, corresponding to 1.72 mM based on average molar mass) solutions containing SDS at concentrations up to 64 mM and compared to micellar P123 solutions and to P123-free SDS solutions. Whereas force profiles in the SDS-free micellar P123 solutions were purely repulsive, P123/SDS complexation produced synergistic depletion force enhancement for SDS concentrations between 2 and 32 mM. The synergism that occurred within a finite SDS concentration range was explained by comparing the hydrodynamic size, molar mass, charge, and concentration of depletants in P123/SDS mixtures and their respective single-component solutions obtained with the aid of dynamic light scattering, static light scattering, and dodecyl sulfate ion-selective electrode measurements. These measurements showed that complexation produced effects that would be mutually counteracting with respect to depletion forces: decreasing the mixed micelle hydrodynamic diameter relative to SDS-free P123 micelles would tend to weaken depletion forces, while adding charge and decreasing the aggregation number of polymers per micelle (thereby increasing the number concentration of micellar depletants) would tend to strengthen depletion forces.

Thermal water chemistry of Yellowstone National Park after 24 years of research

The collection, analysis, and interpretation of 24 years of thermal water chemistry data from Yellowstone National Park have led to substantial insights into the water-rock interactions here and implications for other geothermal areas. New sampling and analytical methods have been developed and tested for trace elements. Quantitative measurements were obtained for changes in redox species of S, Fe, As, Sb, and Hg during outflow of thermal waters in which biotic and abiotic reactions play important roles. Fluoride speciation calculations were confirmed with ion-selective electrode measurements. The fate of contaminants, especially As and F, from thermal features in major rivers revealed no significant attenuation during downstream transport. Continuous monitoring for heat flux using year-round conductivity measurements was established. Testing of the “Multiple Equilibria Geothermometer” was achieved with high-quality, long-term data from Ojo Caliente, a continuously flowing hot spring. Yellowstone continues to be an outstanding field laboratory for expanding our knowledge of thermal water-rock interactions.

Influence of Preparation and Isolation Methods on Calcium Content Measurements in the Sea Water Shrimp (Metapenaeus sp.)

Ebi are small, dried shrimp consumed as a whole. Although they are assumed to have high calcium content, the actual calcium content of this genus has not been determined. This study aimed to determine the calcium content in Metapenaeus sp. and to investigate the effects of preparation (oven and non-oven) and isolation (dilution, acid digestion, and dry ashing) methods on ion selective electrode and atomic absorption spectrometry measurements. Our results showed that the highest calcium content [6.769 ppm (oven) and 7.785 ppm (non-oven)] was obtained in samples treated with acid digestion. The calcium content differed according to the preparation and isolation methods, indicating that both methods influence the calcium content measurements.

Validation of a Real-Time ISE Methodology to Quantify the Influence of Inhibitors of Demineralization Kinetics in vitro Using a Hydroxyapatite Model System

The aim was to validate a novel protocol to measure the cariostatic efficacies of demineralization inhibitors by repeating previous SMR (scanning microradiography) studies investigating the dose response of Zn²⁺ and F^– on demineralization kinetics in vitro using real-time Ca²⁺ ion selective electrodes (ISEs). In this study, Ca²⁺ release was used as a proxy for the extent of demineralization. Forty-eight hydroxyapatite (HAP) discs were allocated into 16 groups (n = 3) and adding either increasing [Zn²⁺], or [F^–], similar to those used in the previous SMR studies. Each HAP disc was immersed in 50 mL, pH 4.0, buffered acetic acid for 1 h, and real-time ISE methodology was used to monitor the rate of increase in [Ca²⁺] in the demineralization solution. Next, either zinc acetate or sodium fluoride was added into each demineralization solution accordingly. Then after each [Zn²⁺] or [F^–] addition, the HAP disc was further demineralized for 1 h, and ISE measurements were continued. The percentage reduction in the rate of calcium loss from hydroxyapatite (PRCL_HAP) at each [Zn²⁺] or [F^–] was calculated from the decrease in Ca²⁺ release rate, similar to that used in the previous SMR studies. A log-linear relationship between mean PRCL_HAP and inhibitor concentration was found for both Zn²⁺ and F^–, similar to that reported for each ion in the previous SMR studies. In conclusion, real-time Ca²⁺ ISE systems can be used to measure the cariostatic efficacies of demineralization inhibitors.

A Simple and Accurate Measurement Procedure for Serum Chloride by Ion Chromatography and Bias Evaluation of Six Ion Selective Electrode Measurements in China.

Chloride is the main anion in human body. A simple and accurate method for serum chloride measurement was developed using ion chromatography (IC) in China. In the measurement, serum samples were diluted 500 times with water, filtered and injected into ion chromatography column. A mixed eluent (2 mmol/L CO32- + 12 mmol/L OH-) was used and peak area signal was collected. Five calibrators made from Standard Reference Material (SRM) 919b were used in the bracketing method. The IC method was applied as the comparative method and six ion selective electrode (ISE) measurement systems were evaluated using 60 individual patient serums. The IC method was proven to be accurate. The precision was 0.18% - 0.30%, the recovery was 99.66% - 100.60%, the bias was 0.19% to -0.06%, and the related expanded uncertainty was 0.775% (k = 2). The precisions of the ISE systems were smaller than the 0.9% tolerable CV except for the Beckman DXC (0.91% - 1.16%). In comparison, the results of linear regression analysis showed that the correlation coefficients were 0.9876 to 0.9979. For all systems, the range of mean biases was -5.96 - 1.48 mmol/L (-5.57% - 1.36%); the expected biases at the medical decision levels were -4.97% - 0.84% at 90 mmol/L and -6.02% - 1.76% at 120 mmol/L. All biases of the Beckman AU met the requirement of within ± 1.5%. The IC measurement method is proven to be of high precision and trueness, and the quality of routine ISE measurement of serum chloride still needs significant improvement. The establishment of the IC method can improve the measurement quality and promote its standardization process in China.

Comparing sulfidation kinetics of silver nanoparticles in simulated media using direct and indirect measurement methods.

Reported reaction kinetics of metal nanoparticles in natural and engineered systems commonly have used proxy measurements to infer chemical transformations, but extension of these methods to complex media has proven difficult. Here, we compare the sulfidation rate of AgNPs using two ion selective electrode (ISE)-based methods, which rely on either (i) direct measurement of free sulfide, or (ii) monitor the free Ag+ available in solution over time in the presence of sulfide species. Most experiments were carried out in moderately hard reconstituted water at pH 7 containing fulvic acid or humic acid, which represented a broad set of known interferences in ISE. Distinct differences in the measured rates were observed between the two proxy-based methods and details of the divergent results are discussed. The two ISE based methods were then compared to direct monitoring of AgNP chemical conversion to Ag2S using synchrotron-based in situ X-ray diffraction (XRD). Using XRD, distinct rates from both ISE-based technique were observed, which demonstrated that ISE measurements alone are inadequate to discriminate both the rate and extent of AgNP sulfidation. XRD rate data elucidated previously unidentified reaction regimes that were associated with AgNP coating (PVP and citrate acid) and NOM components, which provided new mechanistic insight into metallic NP processing. In general, the extent of Ag2S formation was inversely proportional to surface coverage of the initial AgNP. Overall, methods to determine reaction kinetics of nanomaterials in increasingly complex media and heterogeneous size distributions to improve NP-based design and performance will require similar approaches.

Performance and mechanism of free nitrous acid on the solubilization of waste activated sludge.

Free nitrous acid (FNA) is a promising chemical reagent for excess sludge reduction. The distinctive properties of FNA treatment on waste activated sludge (WAS) disposal have previously been demonstrated, however, the cellular response, permeabilization, and disruption caused by low-concentration FNA and the direct cell solubilization of WAS using concentrated FNA should be better understood. In this study, the parameters that influence the sludge solubilization efficiency were optimized over a wide range of FNA concentrations. The sludge solubilization efficiency was found to be superior when the sludge was exposed to FNA (when the dosage of NaNO2 was 0.12 g g−1 TSS and the pH was 3.0, FNA = 20.94 mg L−1) for 10 h at 25 °C, and the TSS removal and COD dissolution efficiencies were found to be prominent at 38% and 7%, respectively. In the FNA treatment of WAS, some FNA-tolerable cells increased the K+, Ca2+, and H+ effluxes under low concentrations of FNA, and finally achieved ion homeostasis based on the results using a scanning ion-selective electrode measurement technique. This could cause the cells in WAS to maintain cytoactivity and integrity under a low-concentration FNA treatment. Furthermore, flow cytometry was used to assess the permeabilization and disruption of sludge cells toward a concentration gradient of FNA. Flow cytometry results indicated that cells in sludge flocs were disrupted within 30 minutes when the FNA concentration was above 8 mg L−1.

Prevalence of pseudonatremia in a clinical laboratory - role of the water content.

Sodium concentration is a frequently used marker to discriminate between differential diagnoses or for clinical follow-up. Pseudonatremia, as a result of indirect ion-selective electrode (ISE) measurements in automated chemistry analyzers, can lead to incorrect diagnosis and treatment. We investigated whether the estimated water content, based on total protein and lipid concentrations, can be used to reduce diagnoses of pseudonatremia. Indirect and direct ISE measurements of sodium were compared in blood samples from intensive care unit (ICU) (n = 98) and random non-ICU patients (n = 100). Differences between direct measurements using whole blood and lithium-heparin plasma were also determined. Water content, estimated by a linear combination of total protein and lipid concentrations, was used to correct indirectly measured sodium concentrations. The prevalence of pseudonatremia was evaluated in the ICU patient group. An absolute difference of 3 mmol/L was observed between direct measurements using lithium-heparin plasma and whole blood, with higher concentrations in plasma. Additionally, we observed that differences between indirect and direct measurements displayed a linear relationship with the estimated water content. The prevalence of pseudohypernatremia after indirect measurements (32%) was reduced when measurements were corrected for water content (19%). In critically ill patients, sodium concentrations should be preferably measured by direct measurements. Whole blood is the preferred material for these measurements. For routine sodium analyses in other patients, correction using the estimated water content appears promising in reducing the prevalence of pseudohypernatremia by indirect measurements.

Fusion of Spectral and Electrochemical Sensor Data for Estimating Soil Macronutrients

Abstract. Rapid and efficient quantification of plant-available soil phosphorus (P) and potassium (K) is needed to support variable-rate fertilization strategies. Two methods that have been used for estimating these soil macronutrients are diffuse reflectance spectroscopy in visible and near-infrared (VNIR) wavelength ranges and electrochemical sensing using an automated ion-selective electrode (ISE) system. The goal of this research was to compare P and K estimates with VNIR spectroscopy, ISE analysis, and a data fusion approach that combined the two methods. Diffuse reflectance spectra of air-dried, sieved samples were obtained in the laboratory. Estimates of P and K based on ISE measurements and standard laboratory analysis methods were available for the same samples from a previous study. Calibrations relating spectra to P, K, and other soil properties determined by standard laboratory methods were developed using partial least squares regression with leave-one-out cross-validation. Although good models (R 2 = 0.83 to 0.92, residual prediction deviation (RPD) = 2.45 to 3.60) for soil texture fractions, organic matter, and CEC were obtained using the spectral data, models for pH, P, and K were not good (R 2 ≤ 0.7, RPD ≤ 1.81). Models for P and K based on ISE data fit better (R 2 ≥ 0.88, RPD ≥ 2.96), but both P and K were systematically underestimated by over 40% due to a large slope bias in both models. Including both spectral and ISE information in P and K calibrations improved model fits (R 2 ≥ 0.90, RPD ≥ 3.19) and reduced the systematic slope bias underestimation to less than 10%, resulting in a considerable improvement in accuracy over ISE data alone. In P and K models including ISE data and spectrally estimated soil properties, significant variables included texture and cation exchange capacity, suggesting that these soil properties might affect the relationship of ISE-measured P and K to values determined by standard laboratory methods. These improved results obtained with a data fusion approach using laboratory-collected data are promising and warrant further investigation with additional datasets.

The Fate of Trace Elements in Yanshan Coal during Fast Pyrolysis

In this study, a high-sulfur and high-ash yield coal sample obtained from the Yanshan coalfield in Yunnan, China was analyzed. A series of char samples was obtained by pyrolysis at various temperatures (300, 400, 500, 600, 700, 800, and 900 °C) and at a fast heating rate (1000 °C/min). A comprehensive investigation using inductively coupled plasma mass spectrometry (ICP-MS), a mercury analyzer, ion-selective electrode (ISE) measurements, X-ray diffraction (XRD) analysis, and Fourier transform infrared (FTIR) spectroscopy was performed to reveal the effects of the pyrolysis temperature on the transformation behavior of trace elements (TEs) and the change in the mineralogical characteristics and functional groups in the samples. The results show that the TE concentrations in the raw coal are higher than the average contents of Chinese coal. The concentrations of Be, Li, and U in the char samples are higher than those in raw coal, while the opposite was observed for As, Ga, Hg, and Rb. The F and Se concentrations are initially higher but decrease with pyrolysis temperature, which is likely caused by associated fracturing with fluoride and selenide minerals. Uranium shows the highest enrichment degree, and Hg shows the highest volatilization degree compared to the other studied TEs. As the temperature increases, the number of OH groups decreases, and the mineral composition changes; for example, pyrite decomposes, while oldhamite and hematite occur in the chars. It is suggested that the behavior and fate of TEs in coal during fast pyrolysis are synergistically influenced by self-characteristic modes of occurrence and mineralogical characteristics.

The effect of polyaspartate chain length on in vitro remineralization of dental tissues

Event Abstract Back to Event The effect of polyaspartate chain length on in vitro remineralization of dental tissues Bryan Quan1 and Eli D. Sone1, 2, 3 1 University of Toronto, Institute of Biomaterials and Biomedical Engineering, Canada 2 University of Toronto, Faculty of Dentistry, Canada 3 University of Toronto, Department of Materials Science & Engineering, Canada Introduction: Most mineralized mammalian tissues are composites of hydroxyapatite (HAP) and collagen fibrils, with between 10 % and 80 % of bone and dentin HAP estimated to be intrafibrillar. Though intrafibrillar HAP is essential to the mechanical properties of bony tissues, the mechanism of intrafibrillar mineralization is not well known. However, it is thought that mineralizing proteins are involved in directing the process. These proteins are typically enriched in aspartate or glutamate residues[1], which is important for their mineralization-regulating properties[2]. Recently polyaspartate (pAsp) and polyacrylate, used as analogs of mineralizing proteins, have been shown to mediate intrafibrillar HAP formation in spontaneously precipitating calcium-phosphate (CaP) solutions[3]. Currently, the roles of these polycarboxylate additives and the parameters which govern their effectiveness are not well described. Here, we investigate the effect of pAsp chain length on remineralization of dental tissues and characterize the remineralizing solutions to gain insight into the mechanisms of intrafibrillar mineralization. These studies will lead to improved materials for fixation, replacement, and repair of bony tissues. Materials and Methods: We remineralize ultrathin sections of demineralized mouse dental tissues directly on TEM grids in spontaneously precipitating solutions of calcium and phosphate ions[4], using either no pAsp as a control, or low polydispersity pAsp additives with nominal degrees of polymerization (DP) of 6, 10, and 100 to mediate intrafibrillar remineralization. Remineralization outcomes are characterized by conventional transmission electron microscopy (TEM), while the remineralizing solutions are characterized by a combination of Ca2+-ion selective electrode (ISE) measurements, dynamic light scattering (DLS), and TEM. Results and Discussion: Remineralization experiments (Figure 1) show that with no pAsp, or with pAsp hexapeptide, superficial HAP forms quickly and without selectivity, while selected area electron diffraction (SAED) indicates no preferential HAP orientation. Conversely, pAsp with DP 10 or 100 induces selective remineralization of only the natively mineralizing tissues dentin and cementum, and SAED of shows that the c-axes of HAP crystals orient with the long axes of collagen fibrils. This demonstrates a role for both pAsp and tissue-specific mineralization factors in determining mineralization selectivity. Though the affinity of pAsp for Ca2+ is relatively insensitive to DP, ISE measurements show that higher DP pAsp better inhibits crystallization, while DLS suggests that a higher DP pAsp better inhibits the formation of amorphous CaP precursors (not shown). These results suggest that pAsp inhibits CaP precipitation in the solution compartment, thereby maintaining a high supersaturation and supporting intrafibrillar mineralization. Conclusion: We show that while higher DP pAsp is an effective mediator of intrafibrillar mineralization, pAsp with DP 6 is not. However, pAsp with DP as low as 10 does mediate intrafibrillar mineralization. This demonstrates a lower size limit for the effective inhibition of amorphous CaP formation and CaP crystallization in solution by aspartate repeats in mineralizing proteins. Figure 1 - TEM micrographs and SAED of sections remineralized in solution control (a) or with 25μg/mL pAsp6 (b), pAsp10 (c), or pAsp100 (d).

Influence of dissolved organic matter (DOM) source on copper speciation and toxicity to Brachionus plicatilis

Environmental context Organic matter dissolved in water can mitigate toxic effects of copper, which should be taken into account when estimating risks of copper pollution. The composition of this organic matter, however, can vary widely, and these variations might also need to be taken into account. This work addresses the question of organic matter quality and demonstrates that only the amount and not the source influences copper toxicity – good news for risk analysis because it simplifies predictions of the effects of copper in specific receiving waters. Abstract The toxicity of copper in marine systems is dependent on its speciation and bioavailability. Dissolved organic matter (DOM) can complex copper, resulting in decreased bioavailability and hence decreased toxicity. The purpose of this study was to measure acute copper LC50 values (concentration lethal to 50% of the organisms) in natural marine waters in a sensitive organism, and identify the relationships between DOM quality and copper toxicity and speciation. Static acute copper toxicity tests (48-h LC50) were performed using the euryhaline rotifer Brachionus plicatilis. Ion-selective electrode measurements of free copper were performed at the LC50 concentrations to determine the influence of DOM source on copper speciation. LC50 values ranged from 333 to 980nM (21.1 to 62.3µgL–1) with DOC concentrations ranging from 0.55 to 7.57mgCL–1. DOC was found to be protective (R2 = 0.72, P = 0.016); however, the degree of protection decreased as DOC increased. This suggests salt-induced colloid formation could be occurring, resulting in a decrease of binding sites available to complex free copper. Free copper remained fairly constant between each sample site, with an average pCu of 10.14. Overall, this study is consistent with other studies that suggest free copper is the best species for predicting toxicity. Additionally, no significant correlation between DOM source and copper toxicity was observed as compared with total DOC concentration and copper toxicity, suggesting that DOM quality does not need to be taken into account for copper toxicity modelling in salt water.