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: 15 mmol/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 1 mL/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 0.15 µmol/L and from 0.01 to 0.04 µmol/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.     

Rapid synthesis of DyFeO<Subscript>3</Subscript> nanopowders by auto-combustion of carboxylate-based gels

EDTA and citric acid as two typical chelating reagents with multi-carboxyl groups were used to prepare DyFeO₃ nanopowders, respectively. The experimental results show that all of the carboxylate-based gels exhibited auto-propagating combustion behaviors. The XRD results indicate that DyFeO₃ single phase can be formed directly with CA/MN (citric acid to metal nitrate mole ratio) = 1 when the calcination temperature was above 700 °C. The specimen with EA/MN (EDTA to metal nitrate mole ratio) = 1 had the minimum crystallite size of 33 nm. The SEM images show that the as-burnt powders prepared with EDTA had more excellent dispersibility feature and clearer grain boundaries than that of citric acid. The magnetic measurement results show that DyFeO₃ nanopowders displayed antiferromagnetism characteristics at low temperatures due to the strong exchange interaction between Fe sublattice. As the ambient temperature increased, there was a transition from antiferromagnetism to paramagnetism in DyFeO₃ nanopowders.     

Solubilization of Terfenadine,Riboflavin, and Sudan III by Aqueous Multi-basic Organic Acids

ABSTRACT

The aqueous solubility of terfenadine, riboflavin, and Sudan III (water-insoluble compounds) was enhanced by the addition of multi-basic organic acids, including citric, glutaric, malic, malonic, and tartaric acids. The variations of physical properties (density, viscosity, electrical conductivity, pH, and surface tension) against acid concentration (0–3.6 M at 25°C) were measured in order to explore possible mechanisms of solubility enhancement. Apart from the partial molar volumes, the measured physical properties varied nonlinearly with acid concentration. Glutaric acid contributes to solubility enhancement of terfenadine and Sudan III more than citric acid, with the latter slightly more effective towards riboflavin. Tartaric acid is the least effective, while malic and malonic acids occupy an intermediate position. Among the organic acids examined, only glutaric acid solutions exhibit significant surface activity, which lends itself to solubility enhancement of the three hydrophobic drugs (interfacial packing of 55 ± 3 Å² at the air–water interface, critical aggregate concentrations (CAC) at 1.8 ± 0.4 M). In contrast, all five organic acid solutions of terfenadine demonstrate more effective lowering of the surface tension of water, with the terfenadinium acid salts exhibiting interfacial packing of 108 ± 9 Å² at the air–water interface. On the other hand, organic acid solutions of riboflavin and Sudan III exhibited essentially no surface activity, aside from the intrinsic contribution of the organic acids themselves. Thus, self-association of glutaric acid contributes to the solubility enhancement of the three hydrophobic drugs. This combined with the surface activity of terfenadinium acid salts explains the higher tendency of glutaric acid to solubilize terfenadine. Mixed micellization of terfenadinium glutarate and glutaric acid occurs with an interfacial packing of 166 ± 18 Å² at the air–water interface. The corresponding CAC were estimated at 3.1 ± 0.2 mM for terfenadinium glutarate and 8.0 ± 0.4 mM for glutaric acid. Intermolecular hydrogen bonding with the extensive hydroxyl group network of riboflavin reflects the higher affinity of citric acid than glutaric acid towards riboflavin. The variability in solubility enhancement exhibited by tartaric, malic, and malonic acids appears to be a result of the interplay between several factors including intra- vs. inter-molecular hydrogen bonding, slight organic acid surface activity, and acid hydration.     

A series of stable,metastable and unstable salts of Imatinib with improved solubility

Pharmaceutical salt formation is the most preferred and effective method to enhance the physicochemical properties of APIs. The aim of the study was to design and synthesize a series of new salts to improve the solubility of Imatinib(IM). Two stable salts with malonic acid(S1) and citric acid(S5), one metastable salt with fumaric acid(S2), two unstable salts with citric acid(S3, S4) were obtained for the first time.Single crystal and powder X-ray diffraction, Fourier transform infrared, differen...     

Determination of hydroxycarboxylic acids in food products by capillary electrophoresis

A procedure for the capillary-electrophoretic determination of lactic, malic, tartaric, and citric acids in food products was developed. The use of 3-nitrobenzoic acid as a light-absorbing component of the running buffer was proposed for the indirect photometric detection of these substances. This considerably increased the determination sensitivity (up to n × 10 ??g/L), as compared with currently available analogs. The composition of the running buffer was optimized: 3-nitrobenzoic acid, 10 mM; cetyltrimethylammonium bromide, 0.5 mM; EDTA, 0.1 mM; and monoethanolamine, to pH 5.3. The procedure was tested with the samples of food products: fruits, juices, nectars, wines, beer, etc. The accuracy of the analytical results was confirmed by the standard addition method.     

Inclusion polymerization of isoprene in deoxycholic acid

The radiation-induced polymerization of isoprene was made on its inclusion (or clathrate) complex with deoxycholic acid (DOCA) at 150 and 300 kGy. The microstructure of the resulting polyisoprene (PIP) was studied by FTIR spectroscopy and found fully comparable to that of PIP prepared by emulsion polymerization by a free radical initiator. Thus, the 1,4-trans content was found to be 48% and that of 1,4-cis units was 28% of the polymer structure; the remaining are being 1,2 and 3,4 units. The PIP irregular microstructure was justified in terms of monomer dynamics inside the DOCA channels. PIP from inclusion polymerization is fully amorphous as studied by differential thermal analysis (DTA) in comparison to an authentic sample of trans-1,4-polyisoprene, which instead has a crystalline melting point of 71.5 °C. The inclusion complex of PIP with DOCA (PIP@DOCA) shows a DTA melting point of 194.4 °C, 12.4 °C higher than the melting point of pure DOCA. PIP isolated from inclusion polymerization from DOCA and its complex PIP@DOCA was studied also by thermogravimetry (TGA) and differential thermogravimetry (DTG).Isoprene does not form inclusion complexes with urea and thiourea. When irradiated with these two compounds it produces an oily PIP oligomer whose microstructure was found by FTIR spectroscopy analogous to that of PIP prepared by emulsion polymerization by a free radical initiator.     

Cornstarch/Poly(vinyl alcohol) Biocomposite Blend Films: Mechanical Properties,Thermal Behavior,Fire Retardancy,and Antibacterial Activity

In the present study, biocomposite films of starch/poly(vinyl alcohol) (St/PVA) reinforced with delignified Grewia optiva fiber and methyl methacrylate (MMA) grafted fibers were prepared using citric acid as a plasticizer and glutaraldehyde as the cross-linker. The biocomposite films were subjected to evaluation of mechanical properties, biodegradability, and antibacterial properties. The biocomposite films were characterized by using Fourier transform-infrared (FT-IR) spectrophotometry, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA/DTA/DTG). SEM showed good adhesion between St/PVA blend matrix and fibers. The antimicrobial activity of biocomposite films against pathogenic bacteria such as Staphylococcus aureus and Escherichia coli was also explored. The results confirmed that the biocomposite films may be used for food packaging.     

Creep study of high-esterified pectin gels

A creep study has been made of 2% pectin gels in the 1∶1 water-glycerol mixture in the temperature interval 284.7 to 321.7 °K, and also of water-glycerol pectin gels concentrated to 2–5% at 290.7 °K. Water-glycerol pectin gels by their thermorheological properties are close to water-sucrose gels studied earlier. It is shown that the rate of the relaxation processes is independent of the concentration. The standard break-down enthalpy of the 2% gel cross-links in the temperature interval where rheological properties are measured, is 17–39 kJ · mole^?1.     

Investigation on the coacervation of fish scale gelatin hydrogel with seafood waste hydrolysates for the development of artificial fish bait: Physico-chemical,thermodynamic, and morpho-structural properties

The study dealt with the development of biopolymer based hydrogel artificial fish bait with hydrolysates derived from fish processing wastes. Fish scale gelatin (FSG) was used for the development of a hydrogel to which bioattractants extracted from seafood processing wastes of fish, squid and shrimp were added to prepare composite gels such as FSG-FH, FSG-SH and FSG-SPH, respectively. To understand the homogenesity and cross linking complexation of composite gels, the study aimed at investigating physico-chemical, thermodynamic, molecular and structural properties were analysed. The gel strength, melting point and thermal stability of the composite hydrogels were found to decrease marginally compared to the control gel, FSG. It could be understood that the crystalline structure at 2θ = 23° of the FSG-SH, and FSG-FH were not much altered compared to FSG gel. However, alteration in the crystalline structure in FSG-SPH was evident at 2θ = 27.3°. The TGA and DSC analysis revealed the reduction in the thermal stability of FSG on the addition of protein hydrolysates in the process of coacervation to get hydrogel based fish bait. Further, FESEM and AFM analysis indicated FSG-SH as the composite hydrogel with most compact and smooth surface was evident by Ra and Rq values. Among the composite gels, FSG-SH was found to have higher hydrophobicity due to enhanced gel structure. FTIR spectra of FSG and composite gels exhibitted similarity corresponding to amide-A, B, I, II and III bands. However, NMR analysis revealed the existence of notable difference with respect to chemical shift in the range of 7.0–7.75 ppm expressing the presence of aromatic protons of the amino acid phe and N–H protons of amide in all the composite gels. Further, NMR analysis confirmed the role of imino acids (δ CH₂ & β CH₂ protons) and hydrophobic amino acids (α-CH₂ protons) in decrease the physical and thermal properties of the composite gels. The addition of protein hydrolysates with FSG was found to decrease the physical, thermal and structural properties, however improve the aromatic compounds of the composite gels.     

Water stability of a cheap sol-gel-based adhesive

The humidity and water tolerance of a sol-gel derived binder prepared using a cheap, multicomponent precursor has been studied. The sol was prepared by dissolving the precursor in water under acidic conditions using either formic acid or a mixture of formic acid and citric acid for pH adjustments. It is shown that a post-treatment temperature of 400 °C or higher is needed in order to achieve full binder stability under excess water conditions, as thermal decomposition of metal carboxylates leads to a pronounced decrease in water solubility of the gels. The mesoporous gel can be made hydrophobic by post-treatments with either a silane or an organophosphonate, showing that both silica and metal oxides are exposed on the surface of the binder. Surface functionalization is especially effective for gels heat-treated at higher temperatures where the metal carboxylates have decomposed to the corresponding oxides or carbonates. The results are expected to be of great importance for the use of this cheap binder in large scale industrial applications. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

LC–MS analysis of low molecular weight organic acids derived from root exudation

A sensitive method for quantification of citric, fumaric, malic, malonic, oxalic, trans aconitic, and succinic acid in soil- and root-related samples is presented. The method is based on a novel, fast, and simple esterification procedure and subsequent analysis via liquid chromatography–mass spectrometry. Derivatization comprises in situ generation of HCl, which catalyzes the Fischer esterification with benzyl alcohol. As a key advance, the esterification with the aromate allows reversed-phase separation and improves electrospray ionization efficiency. The method provided procedural detection limits of 1 nM for citric, 47 nM for fumaric, 10 nM for malic, 10 nM for malonic, 16 nM for oxalic, 15 nM for succinic, and 2 nM for aconitic acid utilizing 500 μL of liquid sample. The working range was 3 nM to 10 μM for citric acid, 158 nM to 10 μM for fumaric acid, 34 nM to 10 μM for malic acid, 33 nM to 10 μM for malonic acid, 53 nM to 10 μM for oxalic acid, 48 nM to 10 μM for succinic acid, and 6 nM to 10 μM for aconitic acid. Quantification of the analytes in soil-related samples was performed via external calibration of the entire procedure utilizing ¹³C-labeled oxalic and citric acid as internal standards. The robustness of the method was tested with soil extracts and samples from hydroponic experiments. The latter concerned the regulation of phosphorus solubilization via plant root exudation of citric, malic, and oxalic acid.     

超积累植物体内的小分子螯合物质及其生理作用

螯合效应是超积累植物忍耐重金属的重要机理之一,不同的超积累植物对不同的重金属胁迫其体内产生的螯合物质不同。目前在超积累植物中发现的螯合物质以其分子量大小可分为两大类,即：草酸、组氨酸、苹果硫、柠檬酸及谷胱甘肽等小分子物质和金属硫蛋白、植物络合素、金属结合体及金属结合蛋白等大分子物质。本文就超积累植物体内的小分子螯合物质及其生理作用作一概述。     

Architecture of intracellular networks in plant matrices

Pectin is an integral component of plant cell walls. It is believed to form an interconnected network structure independent of the cellulose–xyloglucan network structure. Pectin gels are often used as a model for the pectin network structure within the plant cell wall. The middle lamella pectin can be extracted with chelating agents and is believed to be associated through cooperative binding of calcium ions in the so-called egg-box junction zones. Although a great deal is known about the nature of the junction zones in pectin gels, less is known about the long-range structure within calcium-set gels. Two plausible alternative models for long-range order in these gels are a pseudo rubber-like structure and a fibrous network structure. Atomic force microscopy studies of calcium-induced gel precursors, and fragments released from gels, suggest that association leads to a branched fibrous structure within the gels. Enzymatic de-esterification of high methoxy pectin in the presence of calcium ions can induce gelation of the pectin. Thus pectin gel networks may provide a model for a self-assembled network structure within the middle lamella region of the plant cell wall.     

Bi<Subscript>3.25</Subscript>La<Subscript>0.75</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> powders by the complex polymerization method: synthesis,characterization and morphology

Lanthanum-modified bismuth titanate (Bi_3.25La_0.75Ti₃O₁₂, BLTO) powders were prepared by the complex polymerization method. The structure and morphology of BLTO powders were investigated by X-ray diffraction and scanning electron microscopy. The complexation of citric acid with the metallic cations was detected by Fourier transformed infrared (FT-IR). The thermal analyses of obtained gels were investigated by differential thermal gravimetric (DTG). The pure and normally stoichiometric phase of BLTO powders could be obtained at relatively low temperature of 550–700 °C even if the bismuth content is not excess in the starting precursors, while the secondary phase could be detected at lower and higher calcination temperatures. The shape of the BLTO grains is similarly to platelet in Bi-layer structure and stoichiometry BLTO was detected by the analysis of energy dispersive spectrometry.     

Preparation and characterization of high-rate and long-cycle LiFePO4/C nanocomposite as cathode material for lithium-ion battery

Olivine LiFePO₄/C nanocomposite cathode materials with small-sized particles and a unique electrochemical performance were successfully prepared by a simple solid-state reaction using oxalic acid and citric acid as the chelating reagent and carbon source. The structure and electrochemical properties of the samples were investigated. The results show that LiFePO₄/C nanocomposite with oxalic acid (oxalic acid: Fe²⁺= 0.75:1) and a small quantity of citric acid are single phase and deliver initial discharge capacity of 122.1 mAh/g at 1 C with little capacity loss up to 500 cycles at room temperature. The rate capability and cyclability are also outstanding at elevated temperature. When charged/discharged at 60 °C, this materials present excellent initial discharge capacity of 148.8 mAh/g at 1 C, 128.6 mAh/g at 5 C, and 115.0 mAh/g at 10 C, respectively. The extraordinarily high performance of LiFePO₄/C cathode materials can be exploited suitably for practical lithium-ion batteries.     

负载于HZSM-5上的CuO-ZnO-Al2O3纳米粒子：尿素－硝酸盐燃烧合成和理化表征

用尿素-硝酸盐燃烧法制备了一系列的负载于HZSM-5上的CuO-ZnO-Al2O3纳米复合材料(CZA/HZSM-5)。研究了燃料与氧化物的比率对所合成的复合材料的理化性质的影响。用TGA/DTG,FTIR和XRD等研究了尿素-硝酸盐凝胶的热分解和煅烧粉体的相演变过程。FESEM结果表明在燃烧过程中燃料的用量对CZA/HZSM-5的性质有重大影响。CuO和ZnO的晶粒首先随尿素量的增加而增大,然后随尿素量的增加而减小。CuO和ZnO的相对结晶度随燃料量的增加表现为非单调趋势。随着燃料与硝酸盐的比率的增加,CZA/HZSM-5不仅形貌变得超细和均一,而且表面孔隙率也显著增加。FTIR结果表明HZSM-5的结构甚至在负载了CuO-ZnO-Al2O3纳米粒子后也未被破坏,而且在CuO和ZnO与HZSM-5之间还有表面的键合。TGA/DTG结果指出燃烧合成法是一种由若干过程组合起来的方法,例如前驱体的热分解和前驱体间的放热反应等。另外,提出了CuO-ZnO-Al2O3负载在HZSM-5上的生成机理。     

Synthesis,characterization, and in vitro degradation of liquid‐crystalline terpolyesters of 4‐hydroxyphenylacetic acid/3‐(4‐hydroxyphenyl)propionic acid with terephthalic acid and 2,6‐naphthalene diol

Melt‐processable liquid‐crystalline terpolyesters of 4‐hydroxyphenylacetic acid (HPAA) and 3‐(4‐hydroxyphenyl)propionic acid (HPPA) with terephthalic acid and 2,6‐naphthalene diol were synthesized by one‐step acidolysis melt polycondensation followed by postpolymerization and were characterized with viscosity studies, Fourier transform infrared (FTIR) and NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarized light microscopy, and wide‐angle X‐ray diffraction. The melting behaviors and liquid‐crystalline transition temperatures of the terpolyesters were dependent on the composition of the HPAA/HPPA content. The transition temperatures of the polyesters could be effectively reduced by the introduction of an even number of built‐in short methylene spacers in combination with the 2,6‐naphthalene offset structure. A terpolyester with an HPPA content of 33% (NTP33) showed optimum properties for the glass‐transition temperature, around 71 °C, and the melting temperature, near 240 °C, with a Schlieren nematic texture. The polymer showed excellent flow behavior in a Brabender plasticorder. It was also thermally stable up to 400 °C. NTP33 showed 2.5% in vitro hydrolytic degradation in buffer solutions of pH 10 at 60 °C after 540 h. Considerable enzymatic degradation was also observed with porcine pancreas lipase/buffer solutions in comparison with Candida rugosa lipase after 60 days. The degradation was also followed with FTIR, DSC, and TGA. Apart from the temperature and pH of the buffer solution, several structural parameters, such as the aromatic content, crystallinity percentage, and composition of the polymer, affected the degradation behavior. FTIR studies indicated the involvement of chain scission during degradation. Scanning electron microscopy studies further showed that surface erosion also played a major role in the degradation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1845–1857, 2002     

Synthesis of Smart Food Packaging from Poly (Gelatin-co-Dimethyl Acrylamide) / Citric Acid-Red Apple peel Extract

ABSTRACT

A novel and smart hydrogel was synthesized from N, N dimethyl acrylamide (DMAAm), gelatin, and citric acid (CA) red apple peel extract (RApE) to be utilized as a multi-functional food packaging material. The p(Gelatin-co-DMAAm)/CA-RApE was prepared through a redox polymerization technique in film form in petri dishes. Mechanical and water resistance of the p(Gelatin-co-DMAAm)/CA-RApE was improved by the addition of citric acid and N, N, methylenebisacrylamide (MBA) as cross linker. The characterization of p(Gelatin-co-DMAAm)/CA-RApE was carried out by Fourier transform infrared spectroscopy (FT-IR), thermo gravimetric analyzer (TGA), scanning electron microscopy (SEM), and dynamic and mechanical analyzer (DMA). FT-IR revealed the existence of bonding interactions between the functional group of RApE and gelatin, carbonyl groups of DMAAm, and carboxylic acid groups of CA. TGA results found that p(Gelatin-co-DMAAm)/CA-RApE was stable up to 565°C. It was observed that RApE improved thermal stability and decreased the elasticity of the p(Gelatin-co-DMAAm)/CA-RApE. When tested against Escherichia coli, Bacillus subtilis and Staphylococcus aureus, p(Gelatin-co-DMAAm)/CA-RApE was observed to have antimicrobial activity. Total antioxidant and anthocyanin effect of p(Gelatin-co-DMAAm)/CA-RApE was analyzed. Additionally, to monitor the color changes of p(Gelatin-co-DMAAm)/CA-RApE, it was studied at different pH values. Furthermore, p(Gelatin-co-DMAAm)/CA-RApE was applied to real samples such as whole pasteurized milk and cheese. It was found to have a good color indicator and antimicrobial activity for pasteurized whole milk and cheese. It was concluded that p(Gelatin-co-DMAAm)/CA-RApE is a very good candidate to be used in food packaging and biomedical materials, along with other potential applications.     

HPLC determination of antioxidant synergists and ascorbic acid in some fatty pharmaceuticals,cosmetics and food

Summary A specific and sensitive reverse-phase HPLC method for the quantitative determination of ascorbic acid and antioxidant synergists (1-tartaric acid, citric acid, lactic acid as lithium lactate and EDTA) in fatty pharmaceuticals, cosmetics and food has been developed. Two extraction procedures were used; treatment with hot water, and extraction with water from a hexane dilution of the product. No significant differences between the two procedures were found (p<0.05), except for ascorbic acid. Quantitative determinations were performed using a C-18 column and sulfuric acid (pH 1.95) mobile phase. With detection, at 210 nm, lactic acid overlapped with ascorbic acid, but the former could be readily identified by TLC. Ascorbic acid was detected at 254 nm, when lactic acid (as lithium lactate) did not interfere in the analysis. Mean recoveries for tartaric, citric and lactic acids were in the range 96–101%.     

Characterization of crosslinked Macrotyloma uniflorum(Horsegram) protein films for packaging and medical applications

Natural polymers such as proteins and polysaccharides are of great demand in packaging and medical applications. Horse gram (Macrotyloma uniflorum) is a good source of protein and possess excellent antioxidant properties. The present study investigates the development and potential applications of transparent and water-resistant horse gram protein-based films crosslinked with citric acid. Films prepared were further characterized for their physical, chemical and biological properties. Films crosslinked at higher concentrations (15%) of citric acid exhibited 50% reduction in water sorption and reduced water vapor permeability. At 15% citric acid concentration, the films showed excellent free radical scavenging of up to 96%. Also, maximum antimicrobial activity against clinical isolates were observed for the 15% citric acid crosslinked films. Increase in thermal stability and decrease in water vapor permeability was obtained at higher levels of crosslinking. The crosslinked films were cytocompatible and showed potential to be used as substrates for cell culture. Citric acid crosslinked horse gram protein films have good physicochemical properties along with biological activities and could be suitable for applications in the packaging and medical fields.