Phosphate Ratio Research Articles

Dielectric breakdown strength of alumina ceramics reinforced by fractal dendritic Ca9Al(PO4)7 as the second crystalline phase

Abstract In polycrystalline ceramics, charge trapping property has important impact on the dielectric breakdown strength (DBS). In this work, alumina ceramics with Ca9Al(PO4)7(CAP) as the second crystalline phase were synthesized using coarse alumina as main raw materials, and the CAP crystal being dendritic or granular depends on the mass ratio of calcium phosphate to kaolin in the raw material composition. Microstructure and impedance spectrum indicated that dendritic CAP with typical fractal features greatly increases the charge trapping sites and charge spreading barrier. The AC DBS of ceramics with 70 wt% alumina and fractal dendritic CAP achieved a competitive value of 16.1 kV/mm. The results indicate that growing fractal dendritic CAP between the main crystalline grains is a very feasible way to enhance the DBS of alumina ceramic.

Effect of Ag concentration on structure and wear behaviour of coatings formed by micro-arc oxidation on Ti6Al4 V Alloy

ABSTRACT Micro-arc oxidation (MAO) coating was prepared on Ti6Al4 V alloy in the electrolyte based on different ratios of calcium acetate and a fixed ratio of sodium phosphate with/without Ag additive. The surface, elemental and phase compositions, and dry wear tests of the MAO coating were analysed. The X-ray diffraction results presented that the MAO coating formed rutile, anatase and hydroxyapatite. The results show that the coating performance was improved when Ag additives were included. The wear resistance of the MAO coatings was increased by the addition of Ag.

Silicon nitride laser cladding: A feasible technique to improve the biological response of zirconia

Zirconia is the most common ceramic used in dental implants. Even if it possesses both mechanical strength and esthetics, its intrinsic bio-inertness often results in a lack of biological integration. On the other hand, Si3N4 has been proved to be bio-active and to be able to easily osteointegrate. In this work, a Si3N4 powder-based laser-cladding process has been developed in order to improve the biological response to biomedical zirconia. The process resulted in the formation of a composite coating with Si3N4 particles dispersed in nano-crystalline/amorphous silicon. Microscopic observation showed that the layer is adherent to the substrate. The application of the laser cladding treatment resulted in an increase of the roughness, further enhancing the probability of interaction with biological tissues and consequently the bioactivity. Testing with human osteosarcoma cell lines resulted in the formation of bone tissue with high collagen maturity, high carbonate to phosphate ratios and good tissue mineralization, but lower cell proliferation when compared to stoichiometric Si3N4. The bone tissue quality parameters, as measured by Raman spectroscopy, resulted to be comparable to healthy human bone tissue and suggest that laser-cladded Si3N4 treatments might be able to improve the stability of zirconia implants.

Translation Approach for Dentine Regeneration Using GSK-3 Antagonists

The canonical Wnt/β-catenin signaling pathway is crucial for reparative dentinogenesis following tooth damage, and the modulation of this pathway affects the rate and extent of reparative dentine formation in damaged mice molars by triggering the natural process of dentinogenesis. Pharmacological stimulation of Wnt/β-catenin signaling activity by small-molecule GSK-3 inhibitor drugs following pulp exposure in mouse molars results in reparative dentinogenesis. The creation of similar but larger lesions in rat molars shows that the adenosine triphosphate (ATP)–competitive GSK-3 inhibitor, CHIR99021 (CHIR), and the ATP noncompetitive inhibitor, Tideglusib (TG), can equally enhance reparative dentine formation to fully repair an area of dentine damage up to 10 times larger, mimicking the size of small lesions in humans. To assess the chemical composition of this newly formed dentine and to compare its structure with surrounding native dentine and alveolar bone, Raman microspectroscopy analysis is used. We show that the newly formed dentine comprises equal carbonate to phosphate ratios and mineral to matrix ratios to that of native dentine, both being significantly different from bone. For an effective dentine repair, the activity of the drugs needs to be restricted to the region of damage. To investigate the range of drug-induced Wnt-activity within the dental pulp, RNA of short-term induced (24-h) molars is extracted from separated roots and crowns, and quantitative Axin2 expression is assayed. We show that the activation of Wnt/β-catenin signaling is highly restricted to pulp cells in the immediate location of the damage in the coronal pulp tissue with no drug action detected in the root pulp. These results provide further evidence that this simple method of enhancement of natural reparative dentinogenesis has the potential to be translated into a clinical direct capping approach.

Strontium-substituted biphasic calcium phosphate scaffold for orthopedic applications

Strontium ion-substituted calcium phosphate-based ceramic scaffolds enhance osteogenesis. The objective of the present study was to optimize the strontium hydroxyapatite (Sr-HA) and beta tricalcium phosphate (β-TCP) ratio in the fabricated scaffolds to enhance their mechanical strength and bioactivity with controlled biodegradability. Porous polyurethane sponge scaffolds containing Sr-HA and β-TCP in varying concentration were developed by dipping 3D sponge pieces into a slurry containing 10% gelatin, proper concentration of biphasic calcium phosphate (BCP) and 3% poly vinyl alcohol. Four different samples [Sr-BCP, Sr-BCP (20/80), Sr-BCP (30/70), Sr-BCP (40/60)] were prepared and were characterized for biodegradability, water uptake capability and cytotoxicity using various techniques. Pure, crystalline, cytocompatible Sr-BCP Scaffolds possessing both micropores and macropores with porosity greater than 80% and water uptake capability above 100% were obtained. Thus, the effective substitution of Sr-HA and β-TCP in varying proportion makes the composite scaffold a distinctive material of bone tissue engineering.

ABAT and ALDH6A1, regulated by transcription factor HNF4A, suppress tumorigenic capability in clear cell renal cell carcinoma

BackgroundClear cell renal cell carcinoma (ccRCC) is a malignancy characterized by metabolic reprogramming. ABAT and ALDH6A1 are metabolic enzymes. In this study, we aim to investigate the associations of ABAT and ALDH6A1 with the malignancy of ccRCC cells.MethodsThe gene expression levels of ABAT and ALDH6A1 in ccRCC were analyzed from gene expression microarray datasets and RNA sequencing data. Clinical information was analyzed from The Cancer Genome Atlas (TCGA) data. The distributions of ABAT and ALDH6A1 in ccRCC clinical tissues were screened by reverse transcription-quantitative polymerase chain reaction (RT-QPCR) and immunohistochemical assays. The effect of overexpression of ABAT or ALDH6A1 was measured by detecting the cell viability, migration ability, and the ratio of lactate and nicotinamide adenine dinucleotide phosphate (NADPH). Chromatin immunoprecipitation (ChIP) and luciferase reporter assays were carried out to investigate the transcript regulation of HNF4A in ABAT and ALDH6A1.ResultsRemarkable downregulated ABAT and ALDH6A1 expression levels were observed in ccRCC patients and low expression of ABAT and ALDH6A1 was correlated with poor survival. Overexpression of ABAT or ALDH6A1 significantly attenuated cell proliferation and migration, and impaired lactate production. In ABAT increased ccRCC cells, the ratio of NADPH/NADP+ was reduced. Finally, we demonstrated that ABAT and ALDH6A1 were directly regulated by a tumor suppressor, HNF4A.ConclusionsThese observations identified HNF4A-regulated low-expressed ABAT and ALDH6A1 as promising diagnostic and prognostic biomarkers for ccRCC.

Effects of spacers within a series of novel folate-containing lipoconjugates on the targeted delivery of nucleic acids

Limitations regarding the targeted delivery of therapeutic nucleic acids into cancer cells can be overcome by developing a non-viral delivery system equipped with folate-containing conjugates. Here, we report the synthesis of novel folate-containing lipoconjugates (FLs), which differ by spacers between the hydrophobic domain and ligand (folic acid). FLs were incorporated into a liposome composed of the polycationic amphiphile 1,26-bis(cholest-5-en-3β-yloxycarbonylamino)-7,11,16,20-tetraazahexacosan tetrahydrochloride (2X3) and helper lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). At low (2/1) nitrogen to phosphate (N/P) ratio, liposomes containing 0.5 mol% FL with a short hydrophobic spacer and 2 mol% FL with medium hydrophilic spacer were compared with control liposomes containing 2 mol% FL with a polyethylene glycol spacer and showed higher transfection efficiency than non-targeted liposomal formulations and the commercial agent Lipofectamine 2000. At an N/P ratio of 4/1, the transfection efficiency of FL-containing liposomes were correlated neither with FL content within the liposomes nor FL structure.

Effect of smear layer deproteinization with chemo-mechanical caries removal agents on sealing performances of self-etch adhesives

ObjectivesTo evaluate the sealing performance of self-etch adhesives (SEA) after smear layer deproteinization with chemo-mechanical caries removal agents (CRA) to enamel and dentin cavity walls in comparison with 6% NaOCl smear layer deproteinizing. MethodsEighty extracted bovine incisors with tapered cylindrical cavities (2.5 mm upper diameter, 1.5 mm lower diameter, 2 mm depth) at the cemento-enamel junction were randomly divided into four pre-treatment groups; no treatment (control), Papacarie (papain enzyme-based CRA), Carisolv (NaOCl-based CRA), and 6% NaOCl. After pretreatment, G-Bond Plus (GBP, one-step SEA) or Clearfil SE Bond 2 (CSE, two-step SEA) was applied to the pre-treated cavity, and then filled with a flowable resin composite (Clearfil Majesty ES Flow). Gap formations at the enamel and dentin lateral walls, and on the dentin cavity floor were investigated using swept-source optical coherence tomography (SS-OCT) after 24-h water storage at 37 °C. Deproteinizing effects of the tested agents on smear layer-covered enamel and dentin were quantified by changes in the amide:phosphate ratio using ATR-FTIR analysis. ResultsPapacarie significantly reduced gap formation with both self-etch adhesives at all locations, compared to the control group (p < 0.05). In contrast, increased gap formation was observed with Carisolv and NaOCl. In most groups, CSE exhibited significantly lower gap formation than GBP (p < 0.05). ATR-FTIR revealed a significant decrease in the amide:phosphate ratio for all the deproteinizing agents (p < 0.05). ConclusionsChemo-mechanical CRAs could effectively remove the organic phase of enamel and dentin smear layer. The papain enzyme-based gel Papacarie could improve the sealing performance of the self-etch adhesives to both enamel and dentin.

Changes of oxygen isotope values of soil P pools associated with changes in soil pH

Field data about the effect of soil pH on phosphorus (P) cycling is limited. A promising tool to study P cycling under field conditions is the 18O:16O ratio of phosphate (δ18OP). In this study we investigate whether the δ18OP can be used to elucidate the effect of soil pH on P cycling in grasslands. Soils and plants were sampled from different fertilisation and lime treatments of the Park Grass long term experiment at Rothamsted Research, UK. The soils were sequentially extracted to isolate different soil P pools, including available P and corresponding δ18OP values were determined. We did not observe changes in plant δ18OP value, but soil P δ18OP values changed, and lower δ18OP values were associated with higher soil pH values. At sites where P was not limiting, available P δ18OP increased by up to 3‰ when lime was applied. We show that the δ18OP method is a useful tool to investigate the effect of pH on soil P cycling under field conditions as it highlights that different soil processes must govern P availability as pH shifts. The next challenge is now to identify these underlying processes, enabling better management of soil P at different pH.

Study on the Lubrication Performances of Rolling Oil for Cold Rolled Laminated Cu/Al Composite Sheet

Three kinds of ester base oils (D85, D100, D115), dodecyl alcohol, dodecyl acid, butyl stearate as oiliness agents, and thiophosphate, fatty alcohol phosphates and dibutyl phosphate as extreme pressure agents were used to prepare and investigate the tribological properties of rolling oils for cold rolled laminated Cu/Al composite sheet by an orthogonal experiment, and lubrication performances of the rolling oils were studied through rolling experiments. Surface roughness and the interface of Cu/Al composite sheet were analyzed. The results show that the optimum tribological properties of the rolling oil is compose of D100 as basic oil, butyl stearate as oiliness agent and the compound ratio of fatty alcohol phosphates and thiophosphate of 3:1 as extreme pressure antiwar agent. The PB value reaches 1020 N, the coefficient of friction is 0.0795. Basic oil is the main factor of rolling capacity. The rolling oil contented D115, showed the best rolling capacity while the minimum thickness was only 0.045mm. The addition of butyl stearate improved the surface quality of both copper and aluminum side of the rolled stripes and make the sheet surface roughness decreased. After cold rolling, new composite interface, which is clear and tightly bound replaced the brittle mesophase.

Optimization of ATP Synthase c-Rings for Oxygenic Photosynthesis.

The conversion of sunlight into useable cellular energy occurs via the proton–coupled electron transfer reactions of photosynthesis. Light is absorbed by photosynthetic pigments and transferred to photochemical reaction centers to initiate electron and proton transfer reactions to store energy in a redox gradient and an electrochemical proton gradient (proton motive force, pmf), composed of a concentration gradient (ΔpH) and an electric field (Δψ), which drives the synthesis of ATP through the thylakoid FoF1-ATP synthase. Although ATP synthase structure and function are conserved across biological kingdoms, the number of membrane–embedded ion–binding c subunits varies between organisms, ranging from 8 to 17, theoretically altering the H+/ATP ratio for different ATP synthase complexes, with profound implications for the bioenergetic processes of cellular metabolism. Of the known c–ring stoichiometries, photosynthetic c–rings are among the largest identified stoichiometries, and it has been proposed that decreasing the c-stoichiometry could increase the energy conversion efficiency of photosynthesis. Indeed, there is strong evidence that the high H+/ATP of the chloroplast ATP synthase results in a low ATP/nicotinamide adenine dinucleotide phosphate (NADPH) ratio produced by photosynthetic linear electron flow, requiring secondary processes such as cyclic electron flow to support downstream metabolism. We hypothesize that the larger c subunit stoichiometry observed in photosynthetic ATP synthases was selected for because it allows the thylakoid to maintain pmf in a range where ATP synthesis is supported, but avoids excess Δψ and ΔpH, both of which can lead to production of reactive oxygen species and subsequent photodamage. Numerical kinetic simulations of the energetics of chloroplast photosynthetic reactions with altered c–ring size predicts the energy storage of pmf and its effects on the photochemical reaction centers strongly support this hypothesis, suggesting that, despite the low efficiency and suboptimal ATP/NADPH ratio, a high H+/ATP is favored to avoid photodamage. This has important implications for the evolution and regulation of photosynthesis as well as for synthetic biology efforts to alter photosynthetic efficiency by engineering the ATP synthase.

Physical Barrier Type Abuse-Deterrent Formulations: Mechanistic Understanding of Sintering-Induced Microstructural Changes in Polyethylene Oxide Placebo Tablets.

The main goal of the presented work was to understand changes in the microstructure of tablets, as well as the properties of its main component viz. polyethylene oxide (PEO) as a function of sintering. Key polymer variables and sintering conditions were investigated, and sintering-induced increase in tablet tensile strength was evaluated. For the current study, binary-component placebo tablets comprised of varying ratios of PEO and anhydrous dibasic calcium phosphate (DCP) were prepared at two levels of tablet solid fraction. The prepared tablets were sintered in an oven at 80°C at different time points ranging from 10 to 900min and were evaluated for pore size, tablet expansion (%), and PEO crystallinity. The results showed that for efficient sintering and a significant increase in the tablet tensile strength, a minimum of 50% w/w PEO was required. Moreover, all microstructural changes in tablets were found to occur within 60min of sintering, with no significant changes occurring thereafter. Sintering also resulted in a decrease in PEO crystallinity, causing changes in polymer ductility. These changes in PEO ductility resulted in tablets with higher tensile strength. Formulation variables such as PEO level and PEO particle size distribution were found to be important influencers of the sintering process. Additionally, tablets with high initial solid fraction and sintering duration of 60min were found to be optimal conditions for efficient sintering of PEO-based compacts. Finally, prolonged sintering times were not found to provide any additional benefits in terms of abuse-deterrent properties.

Five Constituents in Psoralea corylifolia L. Attenuate Palmitic Acid-Induced Hepatocyte Injury via Inhibiting the Protein Kinase C-α/Nicotinamide-Adenine Dinucleotide Phosphate Oxidase Pathway.

Psoralea corylifolia L. (PC) is a traditional Chinese herb used to treat yang deficiency of the spleen and kidney in pediatric disease. Our previous studies have found that PC can alleviate the liver oxidative stress of juvenile mice with nonalcoholic steatohepatitis (NASH), and its mechanism is related to the inhibition of the protein kinase C-α (PKC-α)/nicotinamide-adenine dinucleotide phosphate oxidase (NOX) signaling pathway. The aim of this study was to confirm the aforementioned drug target in vitro and to conduct preliminary screening for some effective compounds of PC on the treatment of NASH. A primary hepatocyte model of non alcoholic fatty liver disease was established by palmitic acid. The existence of Psoralen, Isopsoralen, Neobavaisoflavone, Isobavachalcone, and Bakuchiol were identified by ultra-performance liquid chromatography. Then, five PC compounds were administered. Intracellular triglyceride and total cholesterol content, the cell supernatant alanine aminotransferase and aspartate aminotransferase, and hepatocellular superoxide anion were examined. The changes of PKC-α/NOX signaling pathways in hepatocytes were also determined. Furthermore, PKC-α activator phorbol 12-myristate 13-acetate was administered for 4 h before Psoralen intervention was conducted again to detect the changes of PKC-α/NOX signaling pathways. Our data demonstrated that Psoralen, Isopsoralen, and Isobavachalcone decreased intracellular content of triglyceride while all five PC compounds improved hepatocellular total cholesterol accumulation and hepatocyte damage in palmitic acid-induced primary hepatocyte model of non alcoholic fatty liver disease. All five PC compounds could also reduce hepatocytic superoxide anion levels, nicotinamide-adenine dinucleotide phosphate/reduced nicotinamide-adenine dinucleotide phosphate ratio, NOX activity as well as p47phox protein expression and PKCα activation in hepatocytes. Psoralen exhibited the best efficacy but the effectiveness was lost when pre-stimulated by phorbol 12-myristate 13-acetate. The results suggest that Psoralen, Isopsoralen, and Isobavachalcone could improve hepatocyte steatosis; five PC compounds could ameliorate hepatocyte injury, relieve oxidative stress, and downregulate the PKC-α/NOX signaling pathway of hepatocytes. In addition, Psoralen exhibits the best efficacy and a prospective PKC-α inhibitor pharmaceutical activity.

Characterization of Simultaneous Aerobic Denitrification and Dephosphorization Strain Cupriavidus sp. H29 and Its Application on Cadmium-Removing

A cadmium tolerant strain Cupriavidus sp. H29 could be applied on simultaneous removal of nitrate, phosphorus and cadmium. Response surface methodology (RSM) experiments showed that optimal removal ratios of nitrate, phosphate and Cd(II), which reached 98.89%, 75.23% and 85.01%, occurred at Cd(II) initial concentration of 30.00 mg/L, nitrate initial concentration of 55.20 mg/L, phosphate initial concentration of 50.00 mg/L, initial pH of 7.0 and C/N ratio of 6.0. Studies on gaseous product, precipitations and extracellular polymeric substances (EPS) indicated that the removal of Cd(II) occurred in the extracellular place. Through the coordinated complexation of EPS, strain H29 can achieve the bio-induced phosphate-cadmium removal. Moreover, studies on heated cells, resting cells, permeable cells, cells membrane and cytoplasm demonstrated that the removal of Cd(II) mainly taken place on the cells membrane. This study provided the theoretical basis for the subsequent research of synchronous removal of heavy metals and other pollutants.

The Connectivity of Nutrient Ratios on The Abundance of Phytoplankton Population In Jakarta Bay

The frequency of algal bloom’s event has been increased in Jakarta Bay, recently. Most of the bloom events were tend to be reoccurred after the rainy season. The research was conducted from 2008 until 2015 to study the linkage of nutrients and the ratios on the growth of the phytoplankton population. Collecting samples were conducted using a canonical plankton net of 20 µm mesh size, 125 cm length and 30 cm diameter of the opening mouth. The results of the study showed that the concentration of phosphate in the waters ranged from 0.01-12.5 µg/l (average 4.58 µg/l) and nitrate ranged from 0.01-15.89 µg/l (average 0.72 µg/l). The N/P ratio during the study ranging from 0.2 up to 45.4. High ratios of nutrients were mostly recorded in 2010 where the overall abundance of phytoplankton is very high. There is a strong correlation of N/P ratio with the community structure or composition of the phytoplankton population. The variability of phytoplankton abundance appears to be related to nutrient ratios of nitrate and phosphate.

Ageing of TotalFill BC Sealer and MTA Fillapex in Simulated Body Fluid.

Objective:The bioactivities of TotalFill BC and the MTA Fillapex sealers were evaluated.Methods:Sixty horizontal root sections were enlarged to size 5 Gates Glidden and randomly divided into six groups (n=10 in each group). In Groups 1–3, sections were filled with TFBCS, while sections in groups 4–6 were filled with MTAFS. Specimens from groups 1 and 4 were soaked in simulated body fluid (SBF) for one day, those from groups 2 and 5 for one week, and those from groups 3 and 6 for two months. All specimens were processed for scanning electron microscope (SEM) examination. Apatite precipitation on sealer and sealer–dentine interfaces was quantified using image analysis software (ImageJ). Energy dispersive X-ray (EDX) was used to analyse calcium (Ca) and phosphate (P) contents of surface precipitation on which calculation of the calcium phosphate (Ca/P) ratio was based.Results:TFBCS samples, regardless of the duration of SBF soaking, yielded a significantly higher surface area of precipitation compared to MTAFS (P<0.05); such precipitation increased over time, and the differences among the three time-points were also statistically significant. Following one day of SBF soaking, MTAFS samples showed only limited precipitation that started to appear after one week. EDX showed that Ca content and the Ca/P ratio of surface deposits on TFBCS samples increased over time with no difference between one week and two months of SBF soaking. The Ca content and Ca/P ratio of surface deposits on MTAFS were significantly lower than that of TFBCS samples regardless of the SBF soaking time.Conclusion:Ageing TotalFill BC sealer in SPF can induce considerable apatite formation. In addition, the TotalFill BC sealer surface showed high Ca2+ ion release as reflected by the formation of apatite with a high Ca/P ratio. These bioactivity features increased over time. In comparison, the MTAFS appears to have lower and delayed bioactivity.

A dynamic control system for aerobic granular sludge reactors treating high COD/P wastewater, using pH and DO sensors

This study developed a control system using pH and DO sensors to dynamically control an aerobic granular sludge (AGS) reactor while varying the influent chemical oxygen demand (COD) with a high COD to phosphate ratio (COD/P ratio). The AGS reactor was operated in an anaerobic/aerobic sequence. The pH profile was used to control the anaerobic step and the oxygen uptake rate (OUR) was applied to control the aerobic step. AGS was successfully formed and retained for 220 days. The sludge volume index, SVI5 and SVI30 remained below 50 ml/g and the average granule size (DV50) increased to approximately 500 μm. The anaerobic and aerobic step durations were effectively controlled guaranteeing (1) an optimal anaerobic COD uptake, which is key to granulation and (2) a good effluent quality.

Effects of lemon essential oil and limonene on the progress of early caries: An in vitro study

ObjectiveThe purpose of this study was to investigate the effects of Lemon essential oil (LEO) and Limonene (LIM) in the progress of early caries. DesignLEO and LIM were selected as experimental medicine, while sodium fluoride (NaF) and deionized water (DW) were positive and blank controls, respectively. Bovine incisors were used to establish enamel and dentin early caries models by demineralization method in vitro. Then specimens were subjected to pH cycling. Calcium and phosphate release of demineralizing solution were measured by an automatic biochemical analyzer; Surface microhardness tester and energy dispersive X-ray spectrometer were used to detect the surface microhardness recovery and calcium- phosphate ratio on tooth surface; Degraded collagen matrix by collagenase was investigated by assaying hydroxyproline. ResultsCalcium release of dentin demineralizing solution of LEO group was lower than DW group’s and higher than NaF group’s. Both of LEO and LIM groups, the surface microhardness recovery were significantly lower than those of NaF group, which were similar to DW group. Dentin surface calcium- phosphate ratio of LEO and LIM groups were lower than those of NaF group and higher than those of DW group. Hydroxyproline concentration in the remineralizing solution of LEO and LIM groups were lower than DW groups’ and higher than NaF groups’. ConclusionsLEO and LIM have influence on the progress of dentin early caries, which can stabilize its structure by inhibiting collagen degradation. Meanwhile, these medicines may provide a new drug choice for the prevention and treatment of early root caries.

Simultaneous separation and determination of seven chelating agents using high-performance liquid chromatography based on statistics design.

We describe an optimization approach to determine simultaneously occurring chelating agents (glycine, malonic acid, citric acid, glycolic acid, lactic acid, DL-malic acid, and ethylenediaminetetraacetic acid) in an electroplating effluent using high-performance liquid chromatography. With chromatography signal area and overall resolution considered as responses, detection conditions were optimized via multiple functions combined with response surface methodology and Plackett-Burman design. Optimized detection conditions were as follows: 15mmol/L ammonium phosphate buffer (pH 2.5), a 94:6 v/v ratio of ammonium phosphate buffer/acetonitrile, a column temperature of 23.3°C, and a mobile phase flow rate of 1mL/min. The experimental values conformed to the predicted values and were repeatable (relative standard deviation<6.4%) and linear (r2 >0.991) over concentration ranges of 1-100 µmol/L. Moreover, the quantification limit (signal-to-noise ratio=10) and the detection limit (signal-to-noise ratio=3) ranged from 0.03 to 0.15µmol/L and from 0.01 to 0.04µmol/L, respectively. These results indicate that high-performance liquid chromatography coupled with statistical design may be a simple and rapid method for simultaneously determining multiple chelating agents in electroplating wastewater effectively.

The efficiency of sequential extraction of phosphorus in soil and sediment: insights from the oxygen isotope ratio of phosphate

Phosphorus (P) occurs in different chemical forms in soil and sediment, and they play different ecological and environmental roles. Thus, separation and quantification of different P pools are essential to the understanding of P dynamics in the environment. Over the past decades, different sequential extraction methods have been used concurrently. However, systematic evaluation of different extraction methods is lacking, making choice of methods and comparisons between results difficult. We compared the oxygen isotope compositions (δ18OP) of different phosphate pools that were extracted by two major extraction methods, Hedley (Hedley et al., Soil Sci Soc Am J 46:970-976, 1982) and SEDEX methods (Ruttenberg, Limnol Oceanogr 37:1460-1482, 1992), for both a soil and an estuarine sediment sample. Additionally, Ag3PO4 and KH2PO4 standards were used to test the fidelity of the extraction and purification procedure. The purity of the precipitated Ag3PO4 was also examined. The δ18OP values have large differences among phosphate pools for the soil extracted by the Hedley method and for the sediment extracted by the SEDEX method. The δ18OP values of Ag3PO4 and KH2PO4 standards after extraction, purification, and/or re-precipitation are similar to their original δ18OP values. The XRD patterns of the precipitated Ag3PO4 are identical to that of Ag3PO4 standard. The residual carbon and nitrogen contents in the precipitated Ag3PO4 are low. The Hedley method has good efficiency for separating isotopically distinct Pi pools (different sources/bioavailability) in the soil samples, while the SEDEX method has good efficiency for separating isotopically distinct Pi pools (different sources/bioavailability) in sediments that are more marine in character such as for the estuarine sample. The extraction and purification processes do not alter δ18OP, and the precipitated Ag3PO4 has high purity.