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2016 Volume 33 Issue 7
2016, 33(7): 733-741
doi: 10.11944/j.issn.1000-0518.2016.07.150394
Abstract:
Cataluminescence as a kind of important chemical analysis method has been widely used in pharmaceutical analysis, food analysis, immunological analysis, environmental monitoring and so on. Herein, we reviewed the progress in applications of cataluminescence in three aspects:the rapid quantitative detection of volatile organic compounds, the identification and discrimination of the analytes and the evaluation of catalytic activity. Moreover, the expectations of the study on cataluminescence are discussed.
Cataluminescence as a kind of important chemical analysis method has been widely used in pharmaceutical analysis, food analysis, immunological analysis, environmental monitoring and so on. Herein, we reviewed the progress in applications of cataluminescence in three aspects:the rapid quantitative detection of volatile organic compounds, the identification and discrimination of the analytes and the evaluation of catalytic activity. Moreover, the expectations of the study on cataluminescence are discussed.
2016, 33(7): 742-755
doi: 10.11944/j.issn.1000-0518.2016.07.150393
Abstract:
Carbon quantum dots(CQDs) as a new member of the family of carbon nanomaterials, have excellent fluorescence properties, biocompatibility and weak cytotoxicity, and have attracted wide interests of scientists. In this paper, the preparation methods of CQDs were introduced. The advantages and disadvantages of these methods and their effect on the composition, structure and properties of CQDs were discussed. In view of optical and electrochemical properties of CQDs, the application of CQDs in the field of energy and environment was summarized. In addition, some challenges in the process of CQDs research were analyzed. Several recommendations and opinions were provided for the further research in CQDs, which will provide important reference for the development of CQDs applications.
Carbon quantum dots(CQDs) as a new member of the family of carbon nanomaterials, have excellent fluorescence properties, biocompatibility and weak cytotoxicity, and have attracted wide interests of scientists. In this paper, the preparation methods of CQDs were introduced. The advantages and disadvantages of these methods and their effect on the composition, structure and properties of CQDs were discussed. In view of optical and electrochemical properties of CQDs, the application of CQDs in the field of energy and environment was summarized. In addition, some challenges in the process of CQDs research were analyzed. Several recommendations and opinions were provided for the further research in CQDs, which will provide important reference for the development of CQDs applications.
2016, 33(7): 756-765
doi: 10.11944/j.issn.1000-0518.2016.07.160155
Abstract:
Polyethylene-g-polystyrene(PE-g-PS) copolymers, which were synthesized by the combination of ring-opening metathesis polymerization(ROMP), hydrogenation and atom transfer radical polymerization(ATRP) method, were utilized to compatibilize linear low density polyethylene/polystyrene(LLDPE/PS) blends. Using the LLDPE/PS blend in mass ratio of 70:30 as example, the effect of introduction of PE-g-PS on the mechanical properties was investigated. Compared to binary blends, elongation at break, tensile strength and yield strength are improved when the PE-g-PS is introduced. Utilizing PE-g-PS0.34k(the subscript 0.34k represents a relative molecular mass of PS is 340) and PE-g-PS1.59k as compatibilizers, the influence of PS branch length on foaming behavior of LLDPE/PS blends was investigated in a batch foaming process with supercritical carbon dioxide as physical foaming agent. Compared to the case containing PE-g-PS0.34k, the cellular structure of the foamed blends becomes much more uniform and no large gap appeares with the addition of PE-g-PS1.59k. When the foaming temperature is lowered to 80 ℃, confined effect of LLDPE solid around exists, much more uniform cellular structure also appears as PE-g-PS1.59k is introduced.
Polyethylene-g-polystyrene(PE-g-PS) copolymers, which were synthesized by the combination of ring-opening metathesis polymerization(ROMP), hydrogenation and atom transfer radical polymerization(ATRP) method, were utilized to compatibilize linear low density polyethylene/polystyrene(LLDPE/PS) blends. Using the LLDPE/PS blend in mass ratio of 70:30 as example, the effect of introduction of PE-g-PS on the mechanical properties was investigated. Compared to binary blends, elongation at break, tensile strength and yield strength are improved when the PE-g-PS is introduced. Utilizing PE-g-PS0.34k(the subscript 0.34k represents a relative molecular mass of PS is 340) and PE-g-PS1.59k as compatibilizers, the influence of PS branch length on foaming behavior of LLDPE/PS blends was investigated in a batch foaming process with supercritical carbon dioxide as physical foaming agent. Compared to the case containing PE-g-PS0.34k, the cellular structure of the foamed blends becomes much more uniform and no large gap appeares with the addition of PE-g-PS1.59k. When the foaming temperature is lowered to 80 ℃, confined effect of LLDPE solid around exists, much more uniform cellular structure also appears as PE-g-PS1.59k is introduced.
2016, 33(7): 766-773
doi: 10.11944/j.issn.1000-0518.2016.07.150384
Abstract:
The non-isothermal crystallization behavior of polylactide(PLA) was investigated by differential scanning calorimetry(DSC), including heating from glass state and cooling from melted state for the PLA polymer. Crystallization kinetic parameters were calculated using Ozawa equation, Mo method, Khanna law and Kissinger method. These methods are all suitable for handling non-isothermal crystallization process of PLA.The crystallization rate coefficient(CRC) proposed by Khanna can easily evaluate the relative crystallization rate of PLA. In contrast to the cooling process from melted state, the heating process of PLA from glass state stimulates crystal nucleus generation, while cooling process is conducive to the growth of crystals. When the heating rate is at 2.0 ℃/min, crystallization enthalpy(ΔHc) reaches the maximum of 27.1 J/g. When the crystallization starts from the melted state, ΔHc increases with the decreasing cooling rate. The cooling rate is lowered to 0.25 ℃/min, and ΔHc is increased to 28.3 J/g. At a lower temperature, the process of crystallization from the glass state, is mainly heterogeneous nucleation of two-dimensional crystal growth pattern. At higher temperature, crystallization from the glass state and melted polymer largely attributes to the homogeneous nucleation for three-dimensional growth pattern. Compared with the heating process, the cooling process is not conducive to the formation of crystal nucleus, so that in the cooling process ΔHc is much lower, and the diffusion activation energy is a little higher than that in the heating process.
The non-isothermal crystallization behavior of polylactide(PLA) was investigated by differential scanning calorimetry(DSC), including heating from glass state and cooling from melted state for the PLA polymer. Crystallization kinetic parameters were calculated using Ozawa equation, Mo method, Khanna law and Kissinger method. These methods are all suitable for handling non-isothermal crystallization process of PLA.The crystallization rate coefficient(CRC) proposed by Khanna can easily evaluate the relative crystallization rate of PLA. In contrast to the cooling process from melted state, the heating process of PLA from glass state stimulates crystal nucleus generation, while cooling process is conducive to the growth of crystals. When the heating rate is at 2.0 ℃/min, crystallization enthalpy(ΔHc) reaches the maximum of 27.1 J/g. When the crystallization starts from the melted state, ΔHc increases with the decreasing cooling rate. The cooling rate is lowered to 0.25 ℃/min, and ΔHc is increased to 28.3 J/g. At a lower temperature, the process of crystallization from the glass state, is mainly heterogeneous nucleation of two-dimensional crystal growth pattern. At higher temperature, crystallization from the glass state and melted polymer largely attributes to the homogeneous nucleation for three-dimensional growth pattern. Compared with the heating process, the cooling process is not conducive to the formation of crystal nucleus, so that in the cooling process ΔHc is much lower, and the diffusion activation energy is a little higher than that in the heating process.
2016, 33(7): 774-779
doi: 10.11944/j.issn.1000-0518.2016.07.150462
Abstract:
Absolute calibration of small-angle X-ray scattering data is necessary for determining quantitative parameters of microstructure of the samples. This work details the absolute calibration method by the measurement of incident beam directly with Pilatus detector. Absolute calibration of standard sample(water) was carried out to verify this method. Application of this method to a poly(methyl methacrylate) colloidal dispersion and a high density polyethylene were performed to obtain the volume fraction and specific surface of scatters. The volume fraction of polymethylmethacrylate(PMMA) is close to the result calculated by density. The specific surface of quenched high density polyethylene is larger than slow cooled sample.
Absolute calibration of small-angle X-ray scattering data is necessary for determining quantitative parameters of microstructure of the samples. This work details the absolute calibration method by the measurement of incident beam directly with Pilatus detector. Absolute calibration of standard sample(water) was carried out to verify this method. Application of this method to a poly(methyl methacrylate) colloidal dispersion and a high density polyethylene were performed to obtain the volume fraction and specific surface of scatters. The volume fraction of polymethylmethacrylate(PMMA) is close to the result calculated by density. The specific surface of quenched high density polyethylene is larger than slow cooled sample.
2016, 33(7): 780-791
doi: 10.11944/j.issn.1000-0518.2016.07.160031
Abstract:
Three alcohol intermediates were synthesized through protection of one side phenolic hydroxyl group, coupling with methyl bromoacetate, and reduction using p-dihydroxybenzene, m-dihydroxybenzene and o-dihydroxybenzene as lead compounds. These three intermediates coupled with three different glycogens to get nine targeting compounds. Similarly, we protected phenolic hydroxyl of 3-(4-hydroxyphenyl)-1-propanol, and then coupled it with three different glycogens to yield three target compounds. The twelve target compounds were characterized by IR, 1H NMR, 13C NMR and HRMS. The study of whitening activity of these conjugates shows that compounds p-HQ-6a, m-HQ-7a, p-HQ-6b, m-HQ-6b, o-HQ-6b, p-HQ-6c, m-HQ-7c, L-3a and L-4b have significant inhibition to tyrosinase, among of them compounds o-HQ-6b and p-HQ-6c against tyrosinase are obviously better than the positive control of α-Abutin.
Three alcohol intermediates were synthesized through protection of one side phenolic hydroxyl group, coupling with methyl bromoacetate, and reduction using p-dihydroxybenzene, m-dihydroxybenzene and o-dihydroxybenzene as lead compounds. These three intermediates coupled with three different glycogens to get nine targeting compounds. Similarly, we protected phenolic hydroxyl of 3-(4-hydroxyphenyl)-1-propanol, and then coupled it with three different glycogens to yield three target compounds. The twelve target compounds were characterized by IR, 1H NMR, 13C NMR and HRMS. The study of whitening activity of these conjugates shows that compounds p-HQ-6a, m-HQ-7a, p-HQ-6b, m-HQ-6b, o-HQ-6b, p-HQ-6c, m-HQ-7c, L-3a and L-4b have significant inhibition to tyrosinase, among of them compounds o-HQ-6b and p-HQ-6c against tyrosinase are obviously better than the positive control of α-Abutin.
2016, 33(7): 792-797
doi: 10.11944/j.issn.1000-0518.2016.07.150353
Abstract:
6-Aryl-6'-bromo-2,2'-bipyridine derivatives 2b~2d were synthesized efficiently from aryl-ethanone by the Krhnke method in one-pot. Then, four chiral 6-[3-((R)-2,2'-diethoxyl-1,1'-binaphthyl)]-2,2'-bipyridine ligands (R)-3a~3d were synthesized by Suzuki coupling of (R)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)-2,2' -diethoxyl-1,1'-binaphthyl (R)-1 with 6-bromo-2,2'-bipyridine derivatives 2a~2d. These ligands were applied to asymmetric transfer hydrogenation of acetophenone. The ligand (R)-3a affords 92% of conversion and 4% enantiomeric excess(ee).
6-Aryl-6'-bromo-2,2'-bipyridine derivatives 2b~2d were synthesized efficiently from aryl-ethanone by the Krhnke method in one-pot. Then, four chiral 6-[3-((R)-2,2'-diethoxyl-1,1'-binaphthyl)]-2,2'-bipyridine ligands (R)-3a~3d were synthesized by Suzuki coupling of (R)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)-2,2' -diethoxyl-1,1'-binaphthyl (R)-1 with 6-bromo-2,2'-bipyridine derivatives 2a~2d. These ligands were applied to asymmetric transfer hydrogenation of acetophenone. The ligand (R)-3a affords 92% of conversion and 4% enantiomeric excess(ee).
2016, 33(7): 798-803
doi: 10.11944/j.issn.1000-0518.2016.07.150361
Abstract:
Bio-based surfactants are the one using renewable biomass as the main starting material. Bio-based surfactants, different from petroleum-based surfactants, have attracted more attentions from scientific and industrial fields due to the renewable resource and outstanding surface/interfacial properties. Interfacial tension and dynamic light scattering measurement were utilized to evaluate the interfacial properties and aggregation behavior of bio-based zwitterionic surfactants derived from waste cooking oils in aqueous solution. The bio-based surfactants show excellent interfacial properties in the absence of alkali and remain ultra-low oil-water interfacial tensions at temperatures 50~70 ℃ and pH 7 to 12; the bio-based surfactants solution exhibits good interfacial properties in different simulated oil-water samples; the interfacial properties are not effected by the storage temperature of 50 ℃, -20 ℃ and 4 ℃; the hydrodynamic diameters of the aggregates in different water samples are in the range of 10 to 30 nm and inorganic salt ions have little effect on the size of the aggregates. The bio-based surfactants derived from waste cooking oils are potentital substitutes to petroleum-based surfactants for many applications, especially in enhanced oil recovery.
Bio-based surfactants are the one using renewable biomass as the main starting material. Bio-based surfactants, different from petroleum-based surfactants, have attracted more attentions from scientific and industrial fields due to the renewable resource and outstanding surface/interfacial properties. Interfacial tension and dynamic light scattering measurement were utilized to evaluate the interfacial properties and aggregation behavior of bio-based zwitterionic surfactants derived from waste cooking oils in aqueous solution. The bio-based surfactants show excellent interfacial properties in the absence of alkali and remain ultra-low oil-water interfacial tensions at temperatures 50~70 ℃ and pH 7 to 12; the bio-based surfactants solution exhibits good interfacial properties in different simulated oil-water samples; the interfacial properties are not effected by the storage temperature of 50 ℃, -20 ℃ and 4 ℃; the hydrodynamic diameters of the aggregates in different water samples are in the range of 10 to 30 nm and inorganic salt ions have little effect on the size of the aggregates. The bio-based surfactants derived from waste cooking oils are potentital substitutes to petroleum-based surfactants for many applications, especially in enhanced oil recovery.
2016, 33(7): 804-812
doi: 10.11944/j.issn.1000-0518.2016.07.150382
Abstract:
Three Schiff base ligands containing two pyridine rings, isophthalaldehyde-bis(4-pyridine formyl hydrazone)(S1), isophthalaldehyde-bis(3-pyridine formyl hydrazone)(S2) and isophthalaldehyde-bis(2-pyridine formyl hydrazone) (S3), have been synthesized with isophthalaldehyde and one of isonicotinyl hydrazine, nicotinic hydrazine and 2-pyridine-carboxylic acid hydrazine as raw materials. The gelation behaviors of the three Schiff base ligands with Cu(Ac)2 in different solvents were tested, and three Cu(Ⅱ)-metallogels were obtained. The gelation test results show that a slight variation in ligand structures can lead to dramatic changes in gelation abilities of ligands. The microstructures of metallogels observed by SEM reveal that the morphology of a metallogel depends on the structure of the ligand. FT-IR and UV/Vis spectroscopy studies reveal that the coordination interaction between Schiff base ligands and Cu(Ⅱ) plays an important role for the formation and maintenance of metallogels. The XRD analysis demonstrates that two metallogels formed by ligand S1 and Cu(Ac)2 in two mixed solvents take the same tetragonal packing mode.
Three Schiff base ligands containing two pyridine rings, isophthalaldehyde-bis(4-pyridine formyl hydrazone)(S1), isophthalaldehyde-bis(3-pyridine formyl hydrazone)(S2) and isophthalaldehyde-bis(2-pyridine formyl hydrazone) (S3), have been synthesized with isophthalaldehyde and one of isonicotinyl hydrazine, nicotinic hydrazine and 2-pyridine-carboxylic acid hydrazine as raw materials. The gelation behaviors of the three Schiff base ligands with Cu(Ac)2 in different solvents were tested, and three Cu(Ⅱ)-metallogels were obtained. The gelation test results show that a slight variation in ligand structures can lead to dramatic changes in gelation abilities of ligands. The microstructures of metallogels observed by SEM reveal that the morphology of a metallogel depends on the structure of the ligand. FT-IR and UV/Vis spectroscopy studies reveal that the coordination interaction between Schiff base ligands and Cu(Ⅱ) plays an important role for the formation and maintenance of metallogels. The XRD analysis demonstrates that two metallogels formed by ligand S1 and Cu(Ac)2 in two mixed solvents take the same tetragonal packing mode.
2016, 33(7): 813-819
doi: 10.11944/j.issn.1000-0518.2016.07.150363
Abstract:
To improve the electrochemical properties of La-Mg-Ni-based hydrogen storage alloy La0.73Ce0.18Mg0.09Ni3.20Al0.21Mn0.10Co0.60, a kind of Schiff base was synthesized and added to the alloy as a surface modifier. According to the results of UV and infrared spectroscopies, the phase structure of the alloy does not change after adding this Schiff base. Compared with the original alloy, the maximum discharge capacity decreases somewaht. The cycle stability of the alloy electrodes with 5% addition of Schiff base is improved from original 63% to 75% after 50 cycles, and the high rate discharge performance is improved also. After surface treatment, the exchange current density I0 and the limiting current density IL increases obviously. The potentiodynamic polarization curves of the alloy electrodes indicate that the corrosion resistance is increased. The results above suggest that the addition of small amount of Schiff base contributes to improving the electrochemical properties of the hydrogen storage alloy.
To improve the electrochemical properties of La-Mg-Ni-based hydrogen storage alloy La0.73Ce0.18Mg0.09Ni3.20Al0.21Mn0.10Co0.60, a kind of Schiff base was synthesized and added to the alloy as a surface modifier. According to the results of UV and infrared spectroscopies, the phase structure of the alloy does not change after adding this Schiff base. Compared with the original alloy, the maximum discharge capacity decreases somewaht. The cycle stability of the alloy electrodes with 5% addition of Schiff base is improved from original 63% to 75% after 50 cycles, and the high rate discharge performance is improved also. After surface treatment, the exchange current density I0 and the limiting current density IL increases obviously. The potentiodynamic polarization curves of the alloy electrodes indicate that the corrosion resistance is increased. The results above suggest that the addition of small amount of Schiff base contributes to improving the electrochemical properties of the hydrogen storage alloy.
2016, 33(7): 820-826
doi: 10.11944/j.issn.1000-0518.2016.07.150356
Abstract:
A graphitic carbon nitride/cyanuric chloride(g-C3N4/C3Cl3N3) composite photocatalyst was developed. The obtained catalyst effectively expands π-conjugated system of g-C3N4. Moreover, the band gap is significantly shifted, and the reduction ability of the photo generated charge is improved because of the introduction of a chlorine atom. The catalyst can effectively degrade organic pollutants under visible light. The result shows that the degradation ratio of reactive red-dye is 94.7% and is still kept at 94% after using 5 times. The mechanism on the degradation of organic pollutants under visible light was studied.
A graphitic carbon nitride/cyanuric chloride(g-C3N4/C3Cl3N3) composite photocatalyst was developed. The obtained catalyst effectively expands π-conjugated system of g-C3N4. Moreover, the band gap is significantly shifted, and the reduction ability of the photo generated charge is improved because of the introduction of a chlorine atom. The catalyst can effectively degrade organic pollutants under visible light. The result shows that the degradation ratio of reactive red-dye is 94.7% and is still kept at 94% after using 5 times. The mechanism on the degradation of organic pollutants under visible light was studied.
2016, 33(7): 827-833
doi: 10.11944/j.issn.1000-0518.2016.07.150352
Abstract:
The solid inclusion complexes of β-carotene with β-cyclodextrin, 2-hydroxypropyl-β-cyclodextrin and sulfobutylether-β-cyclodextrin were prepared in order to improve physicochemical properties of β-carotene, such as solubility and stability. The inclusion complexes of β-carotene with β-cyclodextrin and its derivatives were characterized by UV-Vis absorption spectroscopy, Fourier-transform infrared spectroscopy and 1H NMR spectroscopy. The physicochemical properties of inclusion complexes indicate that the heat stability, light stability and antioxidant activity of β-carotene are evidently improved by the formation of inclusion complexes of β-carotene with β-cyclodextrin, 2-hydroxypropyl-β-cyclodextrin and sulfobutylether-β-cyclodextrin, respectively. The solubility of β-carotene increases 12 times and 18 times by the formation of inclusion complexes of β-carotene with 2-hydroxypropyl-β-cyclodextrin and sulfobutylether-β-cyclodextrin, respectively.
The solid inclusion complexes of β-carotene with β-cyclodextrin, 2-hydroxypropyl-β-cyclodextrin and sulfobutylether-β-cyclodextrin were prepared in order to improve physicochemical properties of β-carotene, such as solubility and stability. The inclusion complexes of β-carotene with β-cyclodextrin and its derivatives were characterized by UV-Vis absorption spectroscopy, Fourier-transform infrared spectroscopy and 1H NMR spectroscopy. The physicochemical properties of inclusion complexes indicate that the heat stability, light stability and antioxidant activity of β-carotene are evidently improved by the formation of inclusion complexes of β-carotene with β-cyclodextrin, 2-hydroxypropyl-β-cyclodextrin and sulfobutylether-β-cyclodextrin, respectively. The solubility of β-carotene increases 12 times and 18 times by the formation of inclusion complexes of β-carotene with 2-hydroxypropyl-β-cyclodextrin and sulfobutylether-β-cyclodextrin, respectively.
2016, 33(7): 834-840
doi: 10.11944/j.issn.1000-0518.2016.07.150375
Abstract:
It is very important to develop efficient drugs for the cure of Alzheimer's disease. Here, gold nanoparticle probes were utilized to acquire the ability of 13 kinds of compounds to inhibit the Cu2+ induced β-amyloid peptide aggregation. Ten of then were screened as the effective inhibitors. The relationships between the chemical structures and their inhibitory efficiencies were also studied as well. We also used the screened molecules to regulate the morphology changes of Cu2+-β-amyloid aggregates and to decrease the production of H2O2 formed by the interaction of Cu2+ and β-amyloid peptide. This research is significant to the study of Alzheimer's disease.
It is very important to develop efficient drugs for the cure of Alzheimer's disease. Here, gold nanoparticle probes were utilized to acquire the ability of 13 kinds of compounds to inhibit the Cu2+ induced β-amyloid peptide aggregation. Ten of then were screened as the effective inhibitors. The relationships between the chemical structures and their inhibitory efficiencies were also studied as well. We also used the screened molecules to regulate the morphology changes of Cu2+-β-amyloid aggregates and to decrease the production of H2O2 formed by the interaction of Cu2+ and β-amyloid peptide. This research is significant to the study of Alzheimer's disease.
2016, 33(7): 841-847
doi: 10.11944/j.issn.1000-0518.2016.07.150348
Abstract:
The probe, Coumarin 343-SO2, was readily synthesized from Coumarin 343 and 2-benzothiazole acetonitrile. The structure of this probe was fully characterized by 1H NMR, 13C NMR, MS, and HRMS. The mechanism of this fluorescent probes for SO32- is based on blocking conjugated structure of the benzothiazole and coumarin upon SO32- nucleophilic addition. The probe exhibits excellent water solubility, fast response, high sensitivity, and high selectivity over other biological related species, with the low detection limit at 0.08 μmol/L. In addition, the probe has good cell membrane permeability, and is suitable for fluorescence imaging of SO32- in living cells.
The probe, Coumarin 343-SO2, was readily synthesized from Coumarin 343 and 2-benzothiazole acetonitrile. The structure of this probe was fully characterized by 1H NMR, 13C NMR, MS, and HRMS. The mechanism of this fluorescent probes for SO32- is based on blocking conjugated structure of the benzothiazole and coumarin upon SO32- nucleophilic addition. The probe exhibits excellent water solubility, fast response, high sensitivity, and high selectivity over other biological related species, with the low detection limit at 0.08 μmol/L. In addition, the probe has good cell membrane permeability, and is suitable for fluorescence imaging of SO32- in living cells.
2016, 33(7): 848-854
doi: 10.11944/j.issn.1000-0518.2016.07.150354
Abstract:
The species and equilibrium constants were assigned for F--Al3+ system in Visual MINTEQ software. The similarity between the simulated titration curves and experimental ones, and the accordance confirms this assignment. The masking effect of sodium hydroxide and masking mechanism was investigated according to the equilibrium distribution simulation of F-(0.01/0.1 mol/L)-Al3+(0.02 mol/L)-OH- system. Although the species and aluminum masking mechanism are different in these two systems, aluminum can be masked efficiently at pH 11~12. The larger discrepancy between the simulated titration curve and the experimental curve in the latter system is due to the slower reaction rate of the latter system. Furthermore, the permissible aluminum concentration at pH 11~12 was obtained by simulation. Considering the interference of OH- to fluoride ion selective electrode, pH is limited to 11.5±0.2 for the determination of fluoride at 0.01~0.1 mol/L, and the maximum aluminum concentration masked at pH 11.5 is 0.02 mol/L. This method suits for the determination of high F concentration in the F-Al system. The error analysis indicates that the standard calibration curve method is more accurate than standard addition method if the potential error is larger than the error of electrode slope constant.
The species and equilibrium constants were assigned for F--Al3+ system in Visual MINTEQ software. The similarity between the simulated titration curves and experimental ones, and the accordance confirms this assignment. The masking effect of sodium hydroxide and masking mechanism was investigated according to the equilibrium distribution simulation of F-(0.01/0.1 mol/L)-Al3+(0.02 mol/L)-OH- system. Although the species and aluminum masking mechanism are different in these two systems, aluminum can be masked efficiently at pH 11~12. The larger discrepancy between the simulated titration curve and the experimental curve in the latter system is due to the slower reaction rate of the latter system. Furthermore, the permissible aluminum concentration at pH 11~12 was obtained by simulation. Considering the interference of OH- to fluoride ion selective electrode, pH is limited to 11.5±0.2 for the determination of fluoride at 0.01~0.1 mol/L, and the maximum aluminum concentration masked at pH 11.5 is 0.02 mol/L. This method suits for the determination of high F concentration in the F-Al system. The error analysis indicates that the standard calibration curve method is more accurate than standard addition method if the potential error is larger than the error of electrode slope constant.
