Computer Simulation of Insoluble Pr（Ⅲ） Speciation in Human Interstitial Fluid

A multi-phase model of Pr(Ⅲ） speciation in human interstitial fluid was constructed and insoluble Pr(Ⅲ）speciation was studied. When the total concentration of Pr(Ⅲ）is below 8.401E-10 mol/L, soluble Pr(Ⅲ） species are main species. With rising the total concentration of Pr(Ⅲ）, Pr（Ⅲ） is firstly bound to phosphate to form precipitate of PrPO4,then bound to carbonate and another precipitate of Pr2(CO3)3 was obtained. When the total concentration is between 1.583E-9 mol/L and 4.000E-3 mol/L, the insoluble species are predominant Pr(Ⅲ） species.     

Flow-injection Determination of Cysteine,N-Acetyl Cysteine and Glutathione in Pharmaceuticals via Potassium Ferricyanide-Fe(Ⅲ) Spectrophotometric System

A simple flow injection spectrophotometric method is reported for the determination of cysteine,N-acetyl cysteine and glutathione based on the reduction of Fe(Ⅲ)/ferricyanide,the in situ reduced ions are reacted with unreduced portion of ferricyanide/Fe(Ⅲ) to form soluble Prussian blue,which is monitored at 735 nm.The calibration graphs are linear in the concentration ranges of(1―100)×10-6 mol/L for cysteine and N-acetyl cysteine,and(1―50)×10-6 mol/L for glutathione.The relative standard deviations of 1.8%,2.5% and 1.9% were found for eleven replicate analyses of 5×10-6 mol/L cysteine,N-acetyl cysteine and glutathione.The limits of detection(3σ blank) at 5×10-7 mol/L for cysteine,and 3×10-7 mol/L for N-acetyl cysteine and glutathione were obtained.The proposed method allowed 60 injections/h.The effects of common substances present in pharmaceuticals and human physiological fluids were examined.The method was applied to determining cysteine in pharmaceutical formulations with the recoveries in a range of 97% to 106% and the results obtained are agreed well with labeled values.     

STUDIES ON THE POLAROGRAPHIC ADSORP-TIVE COMPLEX WAVE OF RARE EARTH-ERIOCHROME AZUROL B (Ⅱ)

The rare earth ions form complexes with ECAB in 0.1 mol/L NaAc-HAc supporting electrolyte at pH 6. The composition of the complex was determined by spectrophotometric method to be 1: 2. The decrease of SAC peak height of ECAB is proportional to the concentration of rare earth ions in the range of 1×10~(-6)-2×10~(-5) mol/L. The reduction mechanism of ECAB and RE-ECAB is proposed based on the experimental evidence. The complexing group of ECAB with RE ions iust is the redox group, so when RE ions are added, there is no new peak appearing in the polarograms:, the only phenomenon observed is that the peak current of ECAB decreases. The fast protonation of EGAB carbanion formed after the second electron transfer results in the formation of colourless tetrahedral molecules.     

Study on supported combined liquid membrane containing HEH（EH）P and HNO3 for trivalent gadolinium transfer

A novel kind of supported combined liquid membrane（SCLM） has been studied for the Gd（Ⅲ） transfer.SCLM contained polyvinylidene fluoride membrane（PVDF） as the liquid membrane support and renewal solution including HNO₃ solution as the stripping solution and 2-ethyl hexyl phosphonic acid-mono-2-ethyl hexyl ester（HEH（EH）P） as the carrier dissolved in kerosene. The mixed solution of carrier and kerosene was membrane solution.The optimum transport conditions of Gd（Ⅲ） were that concentration of HNO₃ solution was 4.00 mol/L,concentration of carrier was 0.16 mol/L,and volume ratio of membrane solution to stripping solution was 30:30 of the renewal phase,and pH value was 4.80 of the feed phase.Under the optimum condition studied, when initial concentration of Gd（Ⅲ） was 1.00×10^-4 mol/L,the transfer rate of Gd（Ⅲ） was 96.8%during 130 min.     

CRITICAL CONCENTRATIONS OF α(1→3)-D-GLUCAN FROM LENTINUS EDODES IN NaOH AQUEOUS SOLUTION

Critical concentrations of α-(1→3)-D-glucan L-FV-Ⅱ from Lentinus edodes were studied by viscometry andfluorescence probe techniques. The dependence of the reduced viscosity on concentration of the glucan in 0.5 mol/L NaOHaqueous solutions with or without urea showed two turning points corresponding to the dynamic contact concentration c_s andthe overlap concentration c~* of the polymer. The values of c_s and c~* were found to be 1×10~(-3) g cm~(-3) and 1.1×10~(-2) g cm~(-3),respectively, for L-FV-Ⅱ in 0.5 mol/L NaOH aqueous solutions. The two critical concentrations of L-FV-Ⅱ in 0.5 mol/LNaOH aqueous solutions were also found to be 1.2×10~(-3) g cm~(-3) fbr c_s and 9.2×10~(-3) g cm~(-3) for c~* from the concentrationdependence of phenanthrene fluorescence intensities. The overlap concentration c~* of L-FV-Ⅱ in 0.5 mol/L NaOH aqueoussolutions was lower than that of polystyrene with same molecular weight in benzene, owing to the fact that polysaccharidetends to undergo aggregation caused by intermolecular hydrogen bonding. A normal viscosity behavior of L-FV-Ⅱ in 0.5 mol/L urea/0.5 mol/L NaOH aqueous solutions can still be observed in an extremely low concentration range at 25℃.     

Amperometric Hydrogen Peroxide Biosensor Based on Multiwall Carbon Nanotubes and Cadmium Sulfide Quantum Dots

<正>A novel third-generation hydrogen peroxide(H_2O_2) biosensor(Hb/CdS/MWNTs/GCE) was fabricated through hemoglobin(Hb) adsorbed onto the mercaptoacetic acid modified CdS QDs/carboxyl multiwall carbon nanotubes'(MWNTs) films.Cyclic voltammogram of Hb/CdS/MWNTs/GCE showed a pair of well-defined and quasi-reversible redox peaks with a formal potential(E~0) of-0.230 V(vs.Ag/AgCl) in 0.1 mol/L pH=8.0 phosphate buffer solution(PBS),which was the characteristic of the Hb heme Fe(Ⅲ)/Fe(Ⅱ) redox couple.The biosensor shows an excellent electrocatalytic activity to the reduction of H_2O_2.The response time of the designed biosensor to H_2O_2 at a potential of -0.30 V was less than 2 s and linear relationships were obtained in the concentration ranges of 2.0×10~(-6)—2.7×10~(-3) mol/L and 2.7×10~(-3)—7.7×10~(-3) mol/L with a detection limit of 3.0×10~(-7)mol/L(S/N=3).The apparent Michaelis-Menten constant K_m was estimated to be 1.324 mmol/L that illustrated the excellent biological activity of the fixed Hb.     

用聚(L-蛋氨酸)/纳米金修饰玻碳电极同时灵敏检测多巴胺和尿酸(英文)

A novel electrochemical sensor was fabricated by electrodeposition of gold nanoparticles on a poly(L-methionine)(PMT)-modified glassy carbon electrode(GCE) to form a nano-Au/PMT composite-modified GCE(nano-Au/PMT/GCE).Scanning electron microscopy and electrochemical techniques were used to characterize the composite electrode.The modified electrode exhibited considerable electrocatalytic activity towards the oxidation of dopamine(DA) and uric acid(UA) in phosphate buffer solution(pH = 7.00).Differential pulse voltammetry revealed that the electrocatalytic oxidation currents of DA and UA were linearly related to concentration over the range of 5.0 ×10–8 to 10–6 mol/L for DA and 7.0 × 10–8 to 10–6 mol/L for UA.The detection limits were 3.7 × 10–8mol/L for DA and 4.5 × 10–8 mol/L for UA at a signal-to-noise ratio of 3.According to our experimental results,nano-Au/PMT/GCE can be used as a sensitive and selective sensor for simultaneous determination of DA and UA.     

The detection of bergenin based on the gold nanoparticles/chitosan/reduced graphene oxide modified electrodeEI北大核心CSCD

Gold nanoparticles (AuNPs)/chitosan (CS)/reduced graphene oxide (RGO) modified electrode was prepared. The electrochemical behaviors of bergenin on this modified electrode was investigated by cyclic voltammetry. The results showed that the proposed electrode exhibited an obvious electrocatalytic ability to the oxidation of bergenin. The differential pulse voltammetry was employed to detect bergenin in 0.1 mol/L phosphate buffer solution (pH 6.0). A good linear relationship between the oxidation peak current and the concentration of bergenin was found in the range of 2.0×10-7-1.2×10-6 mol/L with the detection limit of 6.0×10-8 mol/L (S/N=3).The prepared electrode had good anti-interference ability and potential application in the actual detection of bergenin. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

DISSOCIATION AND RECONSTITUTION OF IMMOBILIZED RIBULOSE-1, 5-BISPHOS PHATE CARBOXYLASE//OXYGENASE FROM TOBACCO

Ribulose-1,5-bisphosphate carboxylase/oxygenase from tobacco covalently coupled to CNBr-activated Sepharose 4B was treated with urea. Analysis by electrophoresis showed that the small subunit was dissociated at 2—2.5 mol/L urea, while the large subunit was still bound to matrix. The large subunit core, L_8, was further dissociated into monomer at 3 mol/L urea. It is suggested that RuBPCase is coupled to Sepharose by virtue of ε-NH_2 on a large subunit. The activity of the immobilized enzyme was inversely proportional to the amount of small subunit dissociated by urea. The dissociated small subunits were almost completely bound back to the S-depleted immobilized RuBPCase, if the urea concentration was diluted to 0.5 mol/L. The enzyme activity could be recovered nearly to 100％. The activity of the S-depleted enzyme was linearly correlated on the concentration of small subunits in solution. These results indicate that the small subunit plays an important role in the maintenance of RuBPCase activity.     

A reversible fluorescent chemosensor for Fe~(3+) and H_2PO_4~- with “on-off-on” switching in aqueous media

To realize highly selective relay recognition of Fe3+ and H2PO4- ions, a simple benzimidazole-based fluorescent chemosensor(L) was designed and synthesized. Sensor L displays rapid, highly selective, and sensitive recognition to Fe3+ in H2O/DMSO(1:1, v/v) solutions. The in situ-generated L-Fe3+ complex solution exhibits a fast response and high selectivity toward dihydrogen phosphate anion via the Fe3+ displacement approach. The detection limits of sensor L to Fe3+ and L-Fe3+complex to H2PO4- anion were estimated to be 1.0 × 10-9 mol/L. Notably, the sensor was retrievable to indicate dihydrogen phosphate anions with Fe3+, and H2PO4-, in turn, increased. This successive recognition feature of sensor L makes it a potential utility for Fe3+ and H2PO4- anion detection in aqueous media.     

Novel smart supramolecular metallo-hydrogel that could selectively recognize and effectively remove Pb2+ in aqueous solution

A series of novel and simple ligands based on a biscarboxyl-functionalized benzimidazole derivative were synthesized.The experiments showed that the ligand L2 as a low molecular weight(LMW) hydrogelator could form stable metallo-hydrogels in the presence of up to 0.3 equiv.of lead ions.The metallo-hydrogels were characterized using powder X-ray diffraction,scanning electron microscopy(SEM),and Fourier transform infrared(FT-IR) spectroscopic techniques.When the molar ratio of L2:Pb2+ was in the range of 1:0.3 to 1:0.5 a translucent gel was produced.When the L2:Pb2+ molar ratio was higher than 1:0.5 the resulting gel tended to be opaque.The morphologies of these metallo-hydrogels were L2/Pb ratio dependent,ranging from worm-like to rod-shaped and nanofibrous.The FT-IR and X-ray diffraction(XRD) studies revealed that L2-Pb complexation was the main driving force for the formation of the metallo-hydrogels.In addition,these metallo-hydrogels exhibited outstanding thermostability and thermoreversibility,and displayed a reversible sol-gel transition induced by changes in pH and EDTA concentration.Importantly,ligand L2 showed an excellent capacity for the removal of Pb 2+ in aqueous solution through the formation of metallo-hydrogels.At a L2:Pb molar ratio of 1:0.5 and below,the concentration of residual Pb2+ was as low as 7.6×10-5 mol/L in aqueous solution,and the removal ratio was as high as 95.4%.These results demonstrate that multi-channel responsive smart metallo-hydrogels have the potential to be widely applied in materials science,and might provide the basis for lead pollution capture and removal.     

Immobilization and hybridization of DNA based on magnesium ion modified 2,6-pyridinedicarboxylic acid polymer and its application for label-free PAT gene fragment detection by electrochemical impedance spectroscopy

A new approach for a simple electrochemical detection of PAT gene fragment is described. Poly(2,6-pyridinedicarboxylic acid) (PDC) modified glassy carbon electrode (GCE) was prepared by potential scan electropolymerization in an aqueous solution. Mg2 ions were incorporated by immer-sion of the modified electrode in 0.5 mol/L aqueous solution of MgCl2 to complete the preparation of a generic "activated" electrode ready for binding the probe DNA. The ssDNA was linked to the conduct-ing polymer by forming a bidentate complex between the carboxyl groups on the polymer and the phosphate groups of DNA via Mg2 . DNA immobilization and hybridization were characterized with dif-ferential pulse voltammetry (DPV) by using methylene blue (MB) as indicator and electrochemical im-pedance spectroscopy (EIS). The EIS was of higher sensitivity for DNA detection as compared with voltammetric methods in our strategy. The electron transfer resistance (Ret) of the electrode surface in EIS in [Fe(CN)6]3-/4- solution increased after the immobilization of the DNA probe on the Mg/PDC/GCE electrode. The hybridization of the DNA probe with complementary DNA (cDNA) made Ret increase further. The difference between the Ret at ssDNA/Mg/PDC/GCE and that at hybridization DNA modified electrode (dsDNA/Mg/PDC/GCE) was applied to determine the specific sequence related to the target PAT gene with the dynamic range comprised between 1.0 × 10-9 and 1.0 × 10_5 mol/L. A detection limit of 3.4 × 10-10 mol/L of oligonucleotides can be estimated.     

Celestine blue as a new indicator in electrochemical DNA biosensors

Celestine blue(CB)was introduced as a new electroactive indicator in DNA biosensors.The interaction of CB with DNA was investigated by electrochemical and spectroscopic methods.The effect of buffer kind and p H on the electrochemical behavior of CB was studied.The peak currents of CB were linearly related to DNA concentration in the range of 5.0×10~(-9) to 1.0×10~(-7)mol/L.The detection limit of this approach was 4.76×10~(-10) mol/L.Based on spectrometry data a hypochromic effect was observed in UV-Vis spectra of CB with increasing DNA concentration.The results illustrate the possible interaction mode between CB and DNA is electrostatic binding.     

Trace determination of cobalt ion by using malic acid-malonic acid double substrate oscillating chemical system

A novel kinetic method for determination of trace amounts of cobalt ion was proposed and validated. The method is based on adding malic acid into classical Belousov-Zhabotinskii （B-Z） oscillating chemical system to form a double substrate one. The results showed that when the concentration of cobalt ion was in the range of 5.27× 10^-8 to 5.37 × 10^-12 mol L^-1, the change of the oscillating period was directly proportional to the negative logarithm of cobalt ion concentration. The sensitivity and precision of the developed method were quite satisfactory. The limit of detection was down to 5.20 × 10^-13 mol L^-1 which was a highest sensitivity found for determination of metal ions using oscillating chemical reaction so far. Some factors influencing the determination were also examined. The method has been successfully used to determine cobalt ion in vitamin B12 injection.     

Electroanalysis and simultaneous determination of dopamine and epinephrine at poly(isonicotinic acid)-modified carbon paste electrode in the presence of ascorbic acid

A carbon paste electrode modified with electropolymerized fills of isonicotinic acid was developed.The modified electrode shows excellent electrocatalytic activity toward the oxidation of both dopamine(DA)and epinephrine(EP).Separation of the reduction peak potentials for dopamine and epinephrine was about 357 mV in pH 5.3 phosphate buffer solution(PBS)and the character was used for the detection DA and EP simultaneously.The peak currents increase linearly with DA and EP concentration over the range of 8.0×10-5 to 7.0×10-4 mol/L and 5.0×10-6 to 1.0×10-4 mol/L with detection limits of 2 × 10-5 and 1×10-6 mol/L,respectively.The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of ascorbic acid(AA).     

Electrochemical Determination of Alkaline Phosphatase in Human Serum by Differential Pulse Voltammetry

Differential pulse voltammetry(DPV) was applied to the determination of alkaline phosphatase(ALP) activity in human serum with phenyl phosphate as the substrate. Phenyl phosphate can enzymatically be hydrolyzed to produce phenol which is quantified by DPV at 660 mV(vs. Ag/AgCl) in the concentration rangeof 2.0--100 μmol/L. The standard curve for ALP is linear over the range from 0.06 to 1000U/L with a relative standard deviation of 3.0%. The conditions for the enzymatic reaction and voltammetric detection were optimized and the kinetic constants were also examined. The human serum samples were tested by this method and the results were in good agreement with those obtained by the routine p-nitrophenyl phosphate spectrophotometric method.     

Solubility Study of the MH Buffer Assemblage in HCl Solutions at 300℃ and 500 bar

Using a gold cell hydrothermal apparatus the solubility of the MH (magnetite + hematite)buffer assemblage in HCl aqueous solutions was determined at 300℃ and 500 bar. The activity of ions in hydrothermal solutions was estimated, and the experiment data were treated by ridge regression and iteration to fit to all possible Fe speciation schemes. The result showed that the dominant Fe species in solutions was FeOH~+ under the run conditions. The equilibrium constant for the dissolution reaction was obtained, K=57.161. △G_5~0,FeOH~+ value of -260.3 kJ/mol at 300℃ and 500 bar was calculated. Fe basically exists as Fe-OH species in hydrothermal solution under geologically reasonable conditions of pH and chloride concentration.     

Chromatographic separation of cerium(Ⅲ) in L-valine medium using poly[dibenzo-18-crown-6]

A column chromatographic method has been developed for the separation and determination of cerium(Ⅲ) using poly[dibenzo-18-crown-6]. The separation was carried out in L-valine medium. The adsorption of cerium(Ⅲ) was quantitative from 1×10-1 to 1×10-4 mol/L L-valine. Amongst the various eluents, 1.0-8.0 mol/L hydrochloric acid, 1.0-8.0 mol/L hydrobromic acid, 1.0-8.0 mol/L perchloric acid, 1.0-2.0 mol/L sulfuric acid and 4.0-5.0 mol/L acetic acid, were found to be the efficient eluents for cerium(Ⅲ). The capacity of poly[dibenzo-18-crown-6] for cerium(Ⅲ) was (0.428±0.01) mmol/g. The method was applied to the separation of cerium(Ⅲ) from associated elements link uranium(Ⅵ) and thorium(Ⅳ). It was also applied for the determination of cerium(Ⅲ) in geological samples. The method is simple, rapid and selective with good reproducibility (approximately±2% ).     

Measurements of HO2 uptake coefficient on aqueous (NH4)2SO4 aerosol using aerosol flow tube with LIF system

The γ(HO₂) was elevated with increase of Cu(II) concentrations in aqueous (NH₄)₂SO₄ aerosol. The threshold of Cu(II) concentration was 10^-3 mol/L for the dramatic increase of γ(HO₂) to 0.1, suggesting sensitive γ(HO₂) value to concentration of transition metal ions in aerosol.     

Determination of Metamizole Sodium by Cyclic Voltammetry Under Microwave Activation

<正>Microwave radiation was applied to the detection of metamizoie sodium by cyclic voltammetry.The electrochemical characteristics of metamizoie sodium were studied by cyclic voltammetry at GC electrode under microwave radiation and a considerable current enhancement was observed for metamizoie sodium in aqueous 0.05 mol/L H_2SO_4.Under the optional conditions,metamizoie sodium was determined in the absence and presence of microwave activation.In the absence of microwave activation cyclic voltammogram of metamizoie sodium shows good linear relationship in a concentration range of 8.0×10~(-5)—1.0×10~(-3) mol/L in aqueous 0.05 mol/L H_2SO_4 with a detection limit of 6.75×10~(-6) mol/L(S/N=3) and the equation of linear regression is I_p=12.973c-0.1905(R~2=0.9996,n=6);in the presence of 80 W microwave activation cyclic voltammogram of metamizoie sodiumin shows good linear relationship in a concentration range of 4.0×10~(-5)—1.0×10~(-3) mol/L in aqueous 0.05 mol/L H_2SO_4 with a detection limit of 4.41×10~(-6)mol/L(S/N=3) and the equation of linear regression is I_p=25.107c-0.1193(R~2=0.9973,n=7).The current in the presence of 80 W microwave activation increases to about 2 orders of magnitude compared with that in the absence of microwave activation.The proposed method in the presence of microwave activation showed high selectivity and sensitivity,and the sampling of the disposal method is simple.The method was verified by the determination of Metamizoie Sodium tablet with satisfactory results.