The interactions of 4-aminosalicylic acid （4-ASA） and surfactants in aqueous solutions were investigated by using UV-Vis spectra and steady-state fluorescence spectroscopy.The results showed that the strongest peak ...The interactions of 4-aminosalicylic acid （4-ASA） and surfactants in aqueous solutions were investigated by using UV-Vis spectra and steady-state fluorescence spectroscopy.The results showed that the strongest peak at UV-vis spectra of 4-ASA aqueous solution in the presence of cationic surfactant and cetyltrimethyl ammonium bromide （CTAB） appeared at 206 nm and took a red shift from 206 nm to 221 nm with the increase of 4-ASA concentrations from 0.8×10-5 to 4.4×10-4 mol/L.Similarly,the strongest peak at UV-vis spectra of 4-ASA aqueous solution in the presence of nonionic surfactant and polyvinylpyrrolidone （PVP） appeared at 206 nm and took a red shift from 206 nm to 219 nm with the increase of 4-ASA concentrations from 0.8×10-5 to 4.4×10-4 mol/L.However,the similar phenomena did not appeared in the presence of anion surfactant,sodium dodecyl sulfate （SDS）,the UV-vis spectra of 4-ASA aqueous solution remained the same peak position and the peak value increased with the 4-ASA concentration increase.The results could be attributed to the electrostatic attraction between 4-ASA and CTAB or PVP,as well as the electrostatic repulsion between 4-ASA and SDS.Furthermore,the value of critical micelle concentration （CMC） of surfactants in the presence of 4-ASA was determined with Fluorescence method.The first and second CMC of CTAB was 1.2×10-4 M and 2.4×10-4 M,respectively.The first and second CMC of PVP was 1.2×10-4 M and 2.8×10-4 M.SDS realized the multiple micellizations to form multiple CMC.展开更多
[Objective] The aim was to develop a rapid, simple method for determina- tion of arsenic and mercury in soil samples by atomic fluorescence spectrometry. [Method] The method for determination of As and Hg in soil by c...[Objective] The aim was to develop a rapid, simple method for determina- tion of arsenic and mercury in soil samples by atomic fluorescence spectrometry. [Method] The method for determination of As and Hg in soil by combined atomic fluorescence spectrometry and microwave digestion was used. [Result] The concentration curve was linear within the range of 0-80.0μg/L of As and 0-8.0 μg/L of Hg, and the detection limits of As and Hg was 0.036 μg/L and 0.015 μg/L, respectively. The precision for elevenfold determination of As at 40.0 ug/L level and Hg at 4.0μg/L level were 1.1% and 2.2%（RSD）, respectively. Recoveries of 103.0%-106.6% for As and 90.0%-95.0% for Hg were obtained for there soil samples. [Conclusion] The proposed method has the advantages of simple operation, high sensitivity, and high efficiency; it was successfully used for determination of As and Hg in soil samples.展开更多
A method was developed for content determination of Na, Mg, A1, Si, P,S, C1, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Nb, Zr, Y, Sr, Rb, Ba, La and Ce etc. covering 26 major, minor, and trace elements in marine sedim...A method was developed for content determination of Na, Mg, A1, Si, P,S, C1, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Nb, Zr, Y, Sr, Rb, Ba, La and Ce etc. covering 26 major, minor, and trace elements in marine sediment samples using fused glass disc by X-ray Fluorescence spectrometry. Calibration was made using marine sediment certified reference materials and the synthetic standard samples prepared by mixing several marine sediments with stream sediment and carbonate standard samples in different proportions. The matrix effect was corrected using theoretical alpha coefficients, experience coefficients and the scattered radiation as the internal standard （for the trace elements）. The accuracy of the method was evaluated by analysis of certified reference materials GBW07314, GBW07334 and GSMS6. The results are in good agreement with the certified values of the standards with RSD less than 2.60%, except for Y, Cr, Ga, Ce, La, Nb, Rb, and V with RSD less than 9.0% （n=12）.展开更多
Ion chromatography-ultra violet-hydride generation-Atomic Florescence Spectrometry was applied to detect 5 arsenic species in seafoods. The arsenic species studied include arsenobetaine(As B), arsenite(As(III)), dimet...Ion chromatography-ultra violet-hydride generation-Atomic Florescence Spectrometry was applied to detect 5 arsenic species in seafoods. The arsenic species studied include arsenobetaine(As B), arsenite(As(III)), dimethylarsinic acid(DMA), monomethylarsonic acid(MMA), and arsenate(As(V)), which were extracted from samples using 2% formic acid. Gradient elution using 33 mmol L^(-1) CH_3COONH_4 and 15 mmol L^(-1) Na_2CO_3 with 10 mL CH_3CH_2OH at pH 8.4 allowed the chromatographic separation of all the species on a Hamilton PRP-X100 anion-exchange column in less than 8 min. In this study, an ultrasound extraction method was used to extract arsenic species from seafood. The extraction efficiency was good and the recoveries from spiked samples were in the range of 72.6%–109%; the precision between sample replicates was higher than 3.6% for all determinations. The detection limits were 3.543 μg L^(-1) for As B, 0.4261 μg L^(-1) for As(III), 0.216 μg L^(-1) for DMA, 0.211 μg L^(-1) for MMA, and 0.709 μg L^(-1) for As(V), and the linear coefficients were greater than 0.999. We also developed an application of this method for the determination of arsenic species in bonito, Euphausia superba, and Enteromorpha with satisfactory results. Therefore, it was confirmed that this method was appropriate for the detection of arsenic species in seafood.展开更多
A method for the analysis of trace germanium in marine sediments by HG-AFS has been investigated. The experimental conditions such as the acidity of reduction reaction, the amount of sodium boro-hydride, the carrier g...A method for the analysis of trace germanium in marine sediments by HG-AFS has been investigated. The experimental conditions such as the acidity of reduction reaction, the amount of sodium boro-hydride, the carrier gas flow rate, etc., were tested and optimized by using a kind of orthogonal design. The detection limit of the presented method is 0.95 μg L -1 for germanium. The calibration curve shows a satisfactory line in the concentration range 0-320 μg L -1 Ge with a variation coefficient of ±2.1%.展开更多
BACKGROUND Hepatitis C virus genotype 3a(HCV G3a)is highly prevalent in Pakistan.Due to the elevated cost of available Food and Drug Administration-approved drugs against HCV,medicinal natural products of potent antiv...BACKGROUND Hepatitis C virus genotype 3a(HCV G3a)is highly prevalent in Pakistan.Due to the elevated cost of available Food and Drug Administration-approved drugs against HCV,medicinal natural products of potent antiviral activity should be screened for the cost-effective treatment of the disease.Furthermore,from natural products,active compounds against vital HCV proteins like non-structural protein 3(NS3)protease could be identified to prevent viral proliferation in the host.AIM To develop cost-effective HCV genotype 3a NS3 protease inhibitors from citrus fruit extracts.METHODS Full-length NS3 without co-factor non-structural protein 4A(NS4A)and codon optimized NS3 protease in fusion with NS4A were expressed in Escherichia coli.The expressed protein was purified by metal ion affinity chromatography and gel filtration.Citrus fruit extracts were screened using fluorescence resonance energy transfer(FRET)assay against the protease and polyphenols were identified as potential inhibitors using electrospray ionization-mass spectrometry(MS)/MS technique.Among different polyphenols,highly potent compounds were screened using molecular modeling approaches and consequently the most active compound was further evaluated against HCV NS4A-NS3 protease domain using FRET assay.RESULTS NS4A fused with NS3 protease domain gene was overexpressed and the purified protein yield was high in comparison to the lower yield of the full-length NS3 protein.Furthermore,in enzyme kinetic studies,NS4A fused with NS3 protease proved to be functionally active compared to full-length NS3.So it was concluded that co-factor NS4A fusion is essential for the purification of functionally active protease.FRET assay was developed and validated by the half maximal inhibitory concentration(IC50)values of commercially available inhibitors.Screening of citrus fruit extracts against the native purified fused NS4A-NS3 protease domain showed that the grapefruit mesocarp extract exhibits the highest percentage inhibition 91%of protease activity.Among the compounds identified by LCMS analysis,hesperidin showed strong binding affinity with the protease catalytic triad having S-score value of-10.98.CONCLUSION Fused NS4A-NS3 protease is functionally more active,which is effectively inhibited by hesperidin from the grapefruit mesocarp extract with an IC50 value of 23.32μmol/L.展开更多
Although scientific and policy bodies have stated that nanomaterials are not intrinsically toxic, there is interest in evaluating if and how many engineered nanomaterials may do harm to the health of mankind and the e...Although scientific and policy bodies have stated that nanomaterials are not intrinsically toxic, there is interest in evaluating if and how many engineered nanomaterials may do harm to the health of mankind and the ecological environment. The interaction between nano-TiO2 and bovine serum albumin (BSA) was studied by using TDFS and UV methods in this research.展开更多
The Microwave-Induced Plasma (MIP) has received considerable attention during the past decade since theintroduction of the Becnakker Cavity. It has been commonly used as an atomization cell for atomic emission spectro...The Microwave-Induced Plasma (MIP) has received considerable attention during the past decade since theintroduction of the Becnakker Cavity. It has been commonly used as an atomization cell for atomic emission spectrometry (AES) and atomic absorption spectrometry (AAS), and a great success was achieved for both techniques. More展开更多
X-ray fluorescence spectrometry was used to detect the content of eight elements in metal coating smeared on waste plastics,and effects of sample cups,elements in plastic substrate,and interaction of elements in metal...X-ray fluorescence spectrometry was used to detect the content of eight elements in metal coating smeared on waste plastics,and effects of sample cups,elements in plastic substrate,and interaction of elements in metal coating on detection results were analyzed. The results show that the RSD of the method used to detect element content in the metal coating smeared on the waste plastics ranged from 0.008% to 0.044%; the determination range of the eight elements was 0.002%-52.0%,and their detection limit ranged from 0.0002% to 0.0008%. The determination results of X-ray fluorescence spectrometry were consistent with that of ICP-AES. The method can provide technical support for the determination of damage and pollution caused by metal coating smeared on waste plastics.展开更多
A rapid analysis method of determining content of eight compounds of open-hearth furnace slag was developed using X-ray fluorescence spectrometry and pressed powder briquettes. Matrix effect was corrected using theore...A rapid analysis method of determining content of eight compounds of open-hearth furnace slag was developed using X-ray fluorescence spectrometry and pressed powder briquettes. Matrix effect was corrected using theoretical alpha coefficient. Grains-size effect was eliminated by optimized sample preparation technique parameters. Mineral effect was corrected with standard curve of specially made standard samples. The analysis results of TiO2, TFe, SiO2, MgO, Al2O3, CaO, MnO and P2O5 in slag samples showed that both precision and accuracy are comparable with that of chemical method.展开更多
A quantitative analysis method of molybdenum in FeMo alloys by X-ray spectrometry using borate fusion technique was compared with that with pressed pellet. The complete pre-oxidation of FeMo alloys for the preparation...A quantitative analysis method of molybdenum in FeMo alloys by X-ray spectrometry using borate fusion technique was compared with that with pressed pellet. The complete pre-oxidation of FeMo alloys for the preparation of homogeneous fused discs was achieved by employing an automated fusion machine equipped with specially designed O2-blowing nozzles, which used lithium tetra-borate as flux with the addition of lithium nitrate (LiNO3) as oxidizer. The calibration curves of Mo and Fe were used in the quantitative analysis of standard materials and unknown plant samples with satisfactory accuracy and precision, utilizing the corrections of the matrix effects and line overlap. It was confirmed that the newly proposed method of preparing fused glass discs of FeMo alloys can replace the conventional wet chemical analyses requiring the labor intensive and time consuming procedure.展开更多
A method for the analysis of selenium in marine aquatic products by HG-AFS has been investigated. The method is based on the reduction of inorganic selenium to volatile SeH2 which is bubbled out by carrier gas of pure...A method for the analysis of selenium in marine aquatic products by HG-AFS has been investigated. The method is based on the reduction of inorganic selenium to volatile SeH2 which is bubbled out by carrier gas of pure argon, and then swept to Ar-H2 flame quarts atomizer to measure its fluorescence intensity. The hydride generation, transportation, atomization and some instrumental parameters were studied by a kind of orthogonal design. The optimum conditions selected are as follows： reactive acidity, 20% HC1; the amount of NaBH4, 4.9mL; gas flow of argon, 600mLmin^-1; atomizing temperature, 200 ℃ ; negative high voltage, - 300V; light current, 100 mA; integral time, 7s. The detection limit of the presented method is 0.072μgL^-1 for selenium. The calibration curve shows a satisfactory line inthe concentration range from 0.000 to 1.000μgL^-1 Se. The recovery is 95.8%-102.2%.展开更多
Using ultra high purity NaF-NaKCO3 in the Fluorescence spectrometry, determination of sub ppb levels of Uranium in the electronic materials has been achieved. The method could be applied to determination of Uranium in...Using ultra high purity NaF-NaKCO3 in the Fluorescence spectrometry, determination of sub ppb levels of Uranium in the electronic materials has been achieved. The method could be applied to determination of Uranium in any electronic materials.展开更多
In this paper, a new MPT(microwave plasma torch) device has been used as a atomizer for atomic fluorescence spectrometry. Spme elements, such as Zn, Cd, Hg, Pb, As, Co, Mg, Cu, Ag, Mn, Fe have been investigated in det...In this paper, a new MPT(microwave plasma torch) device has been used as a atomizer for atomic fluorescence spectrometry. Spme elements, such as Zn, Cd, Hg, Pb, As, Co, Mg, Cu, Ag, Mn, Fe have been investigated in detail.展开更多
A new method for determination of trace lead and mercury by hydride generation atomic fluorescence spectrometry （HG-AFS） was established. Lead was determined in the medium of citric acid using potassium ferricyanide...A new method for determination of trace lead and mercury by hydride generation atomic fluorescence spectrometry （HG-AFS） was established. Lead was determined in the medium of citric acid using potassium ferricyanide （K3Fe（CN）6） as oxidant. Ni enhanced the fluorescence signals in this system. Mercury was determined in the medium of nitric acid using mixture of thiourea and ascorbic acid as masking reagent, sodium dioctylsulphosuccinate （SDSS） as enhancing reagent. The working mechanism of the hydride generation of lead and mercury was discussed. Interferences of some coexisting ions were studied systematically and the determination conditions were optimized. Under the optimized conditions, the detection limits of the method were 0.31μg.L^-1 for lead and 0.023 μg·L^-1 for mercury, and the relative standard deviations based on eleven determinations of 5.00 μg·L^-1 standard of Pb and Hg, were 2.6% for Pb and 2.2 % for Hg. This method was applied to the analysis of lead and mercury in four different diameter airborne particles after microwave digestion. Results suggested heavy metal elements easily concentrated in smaller particles.展开更多
In this paper, two different diameter particles （TSP, PM10） were collected by TH-16A four-channels classification air sampler. The samples were treated by HNO3. Analysis of cadmium was carried out by hydride generat...In this paper, two different diameter particles （TSP, PM10） were collected by TH-16A four-channels classification air sampler. The samples were treated by HNO3. Analysis of cadmium was carried out by hydride generation atomic fluorescence spectrometry （HG-AFS） method, and distribution proportions of elements in four phases were calculated. This method was based on the reaction of cadmium with 1.5% （m/v） KBH4 solution and 0.5% KOH（m/v） solution to form the hydride gas in medium of 2% （v/v） HCl. The detection limit for cadmium as low as 0.008μg/L was obtained. The lineally correlation coefficient was 0.99992. The relative standard deviation （n=5, C=1.00μg/L） was 3.26%. The proposed method was applied for the determination of cadmium in atmosphere aerosol samples and the recoveries in the range of 95-102.2% were obtained. This method was simple, rapid, less matrix interference and high sensitivity.展开更多
Ultrasonic aided slurry sampling hydride generation atomic fluorescence spectrometry （USS-HG-AFS） was developed for the determination of Hg in soil samples from a sewage-irrigated farm. 500 mg grounded soil was susp...Ultrasonic aided slurry sampling hydride generation atomic fluorescence spectrometry （USS-HG-AFS） was developed for the determination of Hg in soil samples from a sewage-irrigated farm. 500 mg grounded soil was suspended in agar solution by an ultrasound water bath before the HG-AFS determination. The results for the reference material of soil （serial number GBW-07411） agreed satisfactorily with the certified values. Results obtained by the developed procedure compared well with those after traditional acid digestion of samples. The detection limit are 6.7ngL-1 for Hg respectively, with average relative standard deviation values of 6.4% for analysis of a series of soil samples of different origin. The recoveries of the anatytes varied in the range from 95 to 107%. This observation has stimulated interest in fast, accurate and sensitive analytical methods for determination of metals in soil.展开更多
0.2000g mogroside sample is digested by 7.0ml nitric acid and 3.0ml hydrogen peroxide, and generated by coprecipitation enrichment hydride - atomic fluorescence spectrometry determines trace selenium in it. Under opti...0.2000g mogroside sample is digested by 7.0ml nitric acid and 3.0ml hydrogen peroxide, and generated by coprecipitation enrichment hydride - atomic fluorescence spectrometry determines trace selenium in it. Under optimum experiment conditions, a standard curve was produced using selenium standard solution, the linear equation is Ise=2890.6c＋0.0012,compared wish the linear relaticnship is not by coprecipitation direct determination of standard series Ise=82.56c＋0.0018 Selenium detection sensitivity was increased by 35.01 times,the correlation coefficient of obtained linear regression equation is 0.9996, the detection limit is 0.0012~tg/L and the relative standard deviation is 0.76% （n=5）. Containing 0.1808pg.g-1 Se Luo Han Shen samples. Based on mogroside sample, add a certain of standard solution to do recovery experiment, the obtained recovery rate is in 95.8%-103.6% and the result is satisfactory.展开更多
Although laser-induced breakdown spectroscopy(LIBS),as a fast on-line analysis technology,has great potential and competitiveness in the analysis of chemical composition and proximate analysis results of coal in therm...Although laser-induced breakdown spectroscopy(LIBS),as a fast on-line analysis technology,has great potential and competitiveness in the analysis of chemical composition and proximate analysis results of coal in thermal power plants,the measurement repeatability of LIBS needs to be further improved due to the difficulty in controlling the stability of the generated plasmas at present.In this paper,we propose a novel x-ray fluorescence(XRF) assisted LIBS method for high repeatability analysis of coal quality,which not only inherits the ability of LIBS to directly analyze organic elements such as C and H in coal,but also uses XRF to make up for the lack of stability of LIBS in determining other inorganic ash-forming elements.With the combination of elemental lines in LIBS and XRF spectra,the principal component analysis and the partial least squares are used to establish the prediction model and perform multi-elemental and proximate analysis of coal.Quantitative analysis results show that the relative standard deviation(RSD) of C is 0.15%,the RSDs of other elements are less than 4%,and the standard deviations of calorific value,ash content,sulfur content and volatile matter are 0.11 MJ kg,0.17%,0.79% and 0.41%respectively,indicating that the method has good repeatability in determination of coal quality.This work is helpful to accelerate the development of LIBS in the field of rapid measurement of coal entering the power plant and on-line monitoring of coal entering the furnace.展开更多
基金Funded by the Foundation of Key Laboratory of Cellulose and Lignocellulosics Chemistry,Guangzhou Institute of Chemistry,Chinese Academy of Sciences (No.LCLC-2010-08)
文摘The interactions of 4-aminosalicylic acid （4-ASA） and surfactants in aqueous solutions were investigated by using UV-Vis spectra and steady-state fluorescence spectroscopy.The results showed that the strongest peak at UV-vis spectra of 4-ASA aqueous solution in the presence of cationic surfactant and cetyltrimethyl ammonium bromide （CTAB） appeared at 206 nm and took a red shift from 206 nm to 221 nm with the increase of 4-ASA concentrations from 0.8×10-5 to 4.4×10-4 mol/L.Similarly,the strongest peak at UV-vis spectra of 4-ASA aqueous solution in the presence of nonionic surfactant and polyvinylpyrrolidone （PVP） appeared at 206 nm and took a red shift from 206 nm to 219 nm with the increase of 4-ASA concentrations from 0.8×10-5 to 4.4×10-4 mol/L.However,the similar phenomena did not appeared in the presence of anion surfactant,sodium dodecyl sulfate （SDS）,the UV-vis spectra of 4-ASA aqueous solution remained the same peak position and the peak value increased with the 4-ASA concentration increase.The results could be attributed to the electrostatic attraction between 4-ASA and CTAB or PVP,as well as the electrostatic repulsion between 4-ASA and SDS.Furthermore,the value of critical micelle concentration （CMC） of surfactants in the presence of 4-ASA was determined with Fluorescence method.The first and second CMC of CTAB was 1.2×10-4 M and 2.4×10-4 M,respectively.The first and second CMC of PVP was 1.2×10-4 M and 2.8×10-4 M.SDS realized the multiple micellizations to form multiple CMC.
基金Supported by Key Fund of Guangxi Academy of Agricultural Sciences(2013YZ07)~~
文摘[Objective] The aim was to develop a rapid, simple method for determina- tion of arsenic and mercury in soil samples by atomic fluorescence spectrometry. [Method] The method for determination of As and Hg in soil by combined atomic fluorescence spectrometry and microwave digestion was used. [Result] The concentration curve was linear within the range of 0-80.0μg/L of As and 0-8.0 μg/L of Hg, and the detection limits of As and Hg was 0.036 μg/L and 0.015 μg/L, respectively. The precision for elevenfold determination of As at 40.0 ug/L level and Hg at 4.0μg/L level were 1.1% and 2.2%（RSD）, respectively. Recoveries of 103.0%-106.6% for As and 90.0%-95.0% for Hg were obtained for there soil samples. [Conclusion] The proposed method has the advantages of simple operation, high sensitivity, and high efficiency; it was successfully used for determination of As and Hg in soil samples.
基金Supported by China Ministry of Science and Technology (2000DEB20081)China Ocean Mineral Resources R&D Association (COMRA) (No.DY105-05-01-05)+1 种基金China Ministry of Education(No.205089)China National Natural Science Foundation (No.40076015)
文摘A method was developed for content determination of Na, Mg, A1, Si, P,S, C1, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Nb, Zr, Y, Sr, Rb, Ba, La and Ce etc. covering 26 major, minor, and trace elements in marine sediment samples using fused glass disc by X-ray Fluorescence spectrometry. Calibration was made using marine sediment certified reference materials and the synthetic standard samples prepared by mixing several marine sediments with stream sediment and carbonate standard samples in different proportions. The matrix effect was corrected using theoretical alpha coefficients, experience coefficients and the scattered radiation as the internal standard （for the trace elements）. The accuracy of the method was evaluated by analysis of certified reference materials GBW07314, GBW07334 and GSMS6. The results are in good agreement with the certified values of the standards with RSD less than 2.60%, except for Y, Cr, Ga, Ce, La, Nb, Rb, and V with RSD less than 9.0% （n=12）.
基金funded by the National Major ScientificInstrument and Equipment Development Project of China (No.2012YQ090229)
文摘Ion chromatography-ultra violet-hydride generation-Atomic Florescence Spectrometry was applied to detect 5 arsenic species in seafoods. The arsenic species studied include arsenobetaine(As B), arsenite(As(III)), dimethylarsinic acid(DMA), monomethylarsonic acid(MMA), and arsenate(As(V)), which were extracted from samples using 2% formic acid. Gradient elution using 33 mmol L^(-1) CH_3COONH_4 and 15 mmol L^(-1) Na_2CO_3 with 10 mL CH_3CH_2OH at pH 8.4 allowed the chromatographic separation of all the species on a Hamilton PRP-X100 anion-exchange column in less than 8 min. In this study, an ultrasound extraction method was used to extract arsenic species from seafood. The extraction efficiency was good and the recoveries from spiked samples were in the range of 72.6%–109%; the precision between sample replicates was higher than 3.6% for all determinations. The detection limits were 3.543 μg L^(-1) for As B, 0.4261 μg L^(-1) for As(III), 0.216 μg L^(-1) for DMA, 0.211 μg L^(-1) for MMA, and 0.709 μg L^(-1) for As(V), and the linear coefficients were greater than 0.999. We also developed an application of this method for the determination of arsenic species in bonito, Euphausia superba, and Enteromorpha with satisfactory results. Therefore, it was confirmed that this method was appropriate for the detection of arsenic species in seafood.
基金supported by the Key Science and Technology pnasp Minsty of Educaton umder contr act(N0.200010-0079).
文摘A method for the analysis of trace germanium in marine sediments by HG-AFS has been investigated. The experimental conditions such as the acidity of reduction reaction, the amount of sodium boro-hydride, the carrier gas flow rate, etc., were tested and optimized by using a kind of orthogonal design. The detection limit of the presented method is 0.95 μg L -1 for germanium. The calibration curve shows a satisfactory line in the concentration range 0-320 μg L -1 Ge with a variation coefficient of ±2.1%.
文摘BACKGROUND Hepatitis C virus genotype 3a(HCV G3a)is highly prevalent in Pakistan.Due to the elevated cost of available Food and Drug Administration-approved drugs against HCV,medicinal natural products of potent antiviral activity should be screened for the cost-effective treatment of the disease.Furthermore,from natural products,active compounds against vital HCV proteins like non-structural protein 3(NS3)protease could be identified to prevent viral proliferation in the host.AIM To develop cost-effective HCV genotype 3a NS3 protease inhibitors from citrus fruit extracts.METHODS Full-length NS3 without co-factor non-structural protein 4A(NS4A)and codon optimized NS3 protease in fusion with NS4A were expressed in Escherichia coli.The expressed protein was purified by metal ion affinity chromatography and gel filtration.Citrus fruit extracts were screened using fluorescence resonance energy transfer(FRET)assay against the protease and polyphenols were identified as potential inhibitors using electrospray ionization-mass spectrometry(MS)/MS technique.Among different polyphenols,highly potent compounds were screened using molecular modeling approaches and consequently the most active compound was further evaluated against HCV NS4A-NS3 protease domain using FRET assay.RESULTS NS4A fused with NS3 protease domain gene was overexpressed and the purified protein yield was high in comparison to the lower yield of the full-length NS3 protein.Furthermore,in enzyme kinetic studies,NS4A fused with NS3 protease proved to be functionally active compared to full-length NS3.So it was concluded that co-factor NS4A fusion is essential for the purification of functionally active protease.FRET assay was developed and validated by the half maximal inhibitory concentration(IC50)values of commercially available inhibitors.Screening of citrus fruit extracts against the native purified fused NS4A-NS3 protease domain showed that the grapefruit mesocarp extract exhibits the highest percentage inhibition 91%of protease activity.Among the compounds identified by LCMS analysis,hesperidin showed strong binding affinity with the protease catalytic triad having S-score value of-10.98.CONCLUSION Fused NS4A-NS3 protease is functionally more active,which is effectively inhibited by hesperidin from the grapefruit mesocarp extract with an IC50 value of 23.32μmol/L.
基金Suppoted by National Nature Science Foundation of China (Grant Nos. 41130746, 41272371)the Doctor Foundation of SWUST of China (Grant No. 11zx7139)
文摘Although scientific and policy bodies have stated that nanomaterials are not intrinsically toxic, there is interest in evaluating if and how many engineered nanomaterials may do harm to the health of mankind and the ecological environment. The interaction between nano-TiO2 and bovine serum albumin (BSA) was studied by using TDFS and UV methods in this research.
文摘The Microwave-Induced Plasma (MIP) has received considerable attention during the past decade since theintroduction of the Becnakker Cavity. It has been commonly used as an atomization cell for atomic emission spectrometry (AES) and atomic absorption spectrometry (AAS), and a great success was achieved for both techniques. More
基金Supported by Project of Ningbo Entry-Exit Inspection and Quarantine Bureau(K21-2013)
文摘X-ray fluorescence spectrometry was used to detect the content of eight elements in metal coating smeared on waste plastics,and effects of sample cups,elements in plastic substrate,and interaction of elements in metal coating on detection results were analyzed. The results show that the RSD of the method used to detect element content in the metal coating smeared on the waste plastics ranged from 0.008% to 0.044%; the determination range of the eight elements was 0.002%-52.0%,and their detection limit ranged from 0.0002% to 0.0008%. The determination results of X-ray fluorescence spectrometry were consistent with that of ICP-AES. The method can provide technical support for the determination of damage and pollution caused by metal coating smeared on waste plastics.
文摘A rapid analysis method of determining content of eight compounds of open-hearth furnace slag was developed using X-ray fluorescence spectrometry and pressed powder briquettes. Matrix effect was corrected using theoretical alpha coefficient. Grains-size effect was eliminated by optimized sample preparation technique parameters. Mineral effect was corrected with standard curve of specially made standard samples. The analysis results of TiO2, TFe, SiO2, MgO, Al2O3, CaO, MnO and P2O5 in slag samples showed that both precision and accuracy are comparable with that of chemical method.
文摘A quantitative analysis method of molybdenum in FeMo alloys by X-ray spectrometry using borate fusion technique was compared with that with pressed pellet. The complete pre-oxidation of FeMo alloys for the preparation of homogeneous fused discs was achieved by employing an automated fusion machine equipped with specially designed O2-blowing nozzles, which used lithium tetra-borate as flux with the addition of lithium nitrate (LiNO3) as oxidizer. The calibration curves of Mo and Fe were used in the quantitative analysis of standard materials and unknown plant samples with satisfactory accuracy and precision, utilizing the corrections of the matrix effects and line overlap. It was confirmed that the newly proposed method of preparing fused glass discs of FeMo alloys can replace the conventional wet chemical analyses requiring the labor intensive and time consuming procedure.
文摘A method for the analysis of selenium in marine aquatic products by HG-AFS has been investigated. The method is based on the reduction of inorganic selenium to volatile SeH2 which is bubbled out by carrier gas of pure argon, and then swept to Ar-H2 flame quarts atomizer to measure its fluorescence intensity. The hydride generation, transportation, atomization and some instrumental parameters were studied by a kind of orthogonal design. The optimum conditions selected are as follows： reactive acidity, 20% HC1; the amount of NaBH4, 4.9mL; gas flow of argon, 600mLmin^-1; atomizing temperature, 200 ℃ ; negative high voltage, - 300V; light current, 100 mA; integral time, 7s. The detection limit of the presented method is 0.072μgL^-1 for selenium. The calibration curve shows a satisfactory line inthe concentration range from 0.000 to 1.000μgL^-1 Se. The recovery is 95.8%-102.2%.
文摘Using ultra high purity NaF-NaKCO3 in the Fluorescence spectrometry, determination of sub ppb levels of Uranium in the electronic materials has been achieved. The method could be applied to determination of Uranium in any electronic materials.
文摘In this paper, a new MPT(microwave plasma torch) device has been used as a atomizer for atomic fluorescence spectrometry. Spme elements, such as Zn, Cd, Hg, Pb, As, Co, Mg, Cu, Ag, Mn, Fe have been investigated in detail.
文摘A new method for determination of trace lead and mercury by hydride generation atomic fluorescence spectrometry （HG-AFS） was established. Lead was determined in the medium of citric acid using potassium ferricyanide （K3Fe（CN）6） as oxidant. Ni enhanced the fluorescence signals in this system. Mercury was determined in the medium of nitric acid using mixture of thiourea and ascorbic acid as masking reagent, sodium dioctylsulphosuccinate （SDSS） as enhancing reagent. The working mechanism of the hydride generation of lead and mercury was discussed. Interferences of some coexisting ions were studied systematically and the determination conditions were optimized. Under the optimized conditions, the detection limits of the method were 0.31μg.L^-1 for lead and 0.023 μg·L^-1 for mercury, and the relative standard deviations based on eleven determinations of 5.00 μg·L^-1 standard of Pb and Hg, were 2.6% for Pb and 2.2 % for Hg. This method was applied to the analysis of lead and mercury in four different diameter airborne particles after microwave digestion. Results suggested heavy metal elements easily concentrated in smaller particles.
文摘In this paper, two different diameter particles （TSP, PM10） were collected by TH-16A four-channels classification air sampler. The samples were treated by HNO3. Analysis of cadmium was carried out by hydride generation atomic fluorescence spectrometry （HG-AFS） method, and distribution proportions of elements in four phases were calculated. This method was based on the reaction of cadmium with 1.5% （m/v） KBH4 solution and 0.5% KOH（m/v） solution to form the hydride gas in medium of 2% （v/v） HCl. The detection limit for cadmium as low as 0.008μg/L was obtained. The lineally correlation coefficient was 0.99992. The relative standard deviation （n=5, C=1.00μg/L） was 3.26%. The proposed method was applied for the determination of cadmium in atmosphere aerosol samples and the recoveries in the range of 95-102.2% were obtained. This method was simple, rapid, less matrix interference and high sensitivity.
文摘Ultrasonic aided slurry sampling hydride generation atomic fluorescence spectrometry （USS-HG-AFS） was developed for the determination of Hg in soil samples from a sewage-irrigated farm. 500 mg grounded soil was suspended in agar solution by an ultrasound water bath before the HG-AFS determination. The results for the reference material of soil （serial number GBW-07411） agreed satisfactorily with the certified values. Results obtained by the developed procedure compared well with those after traditional acid digestion of samples. The detection limit are 6.7ngL-1 for Hg respectively, with average relative standard deviation values of 6.4% for analysis of a series of soil samples of different origin. The recoveries of the anatytes varied in the range from 95 to 107%. This observation has stimulated interest in fast, accurate and sensitive analytical methods for determination of metals in soil.
文摘0.2000g mogroside sample is digested by 7.0ml nitric acid and 3.0ml hydrogen peroxide, and generated by coprecipitation enrichment hydride - atomic fluorescence spectrometry determines trace selenium in it. Under optimum experiment conditions, a standard curve was produced using selenium standard solution, the linear equation is Ise=2890.6c＋0.0012,compared wish the linear relaticnship is not by coprecipitation direct determination of standard series Ise=82.56c＋0.0018 Selenium detection sensitivity was increased by 35.01 times,the correlation coefficient of obtained linear regression equation is 0.9996, the detection limit is 0.0012~tg/L and the relative standard deviation is 0.76% （n=5）. Containing 0.1808pg.g-1 Se Luo Han Shen samples. Based on mogroside sample, add a certain of standard solution to do recovery experiment, the obtained recovery rate is in 95.8%-103.6% and the result is satisfactory.
基金supported by National Energy R&D Center of Petroleum Refining Technology of China(RIPP,SINOPEC)National Key Research and Development Program of China(No.2017YFA0304203)+5 种基金Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(No.IRT_17R70)National Natural Science Foundation of China(Nos.61975103,61875108,61775125 and 11434007)Industrial Application Innovation Project(No.627010407)Scientific and Technological Innovation Project of Shanxi Gemeng US-China Clean Energy R&D Center Co.,Ltd111 Project(D18001)Fund for Shanxi‘1331KSC’。
文摘Although laser-induced breakdown spectroscopy(LIBS),as a fast on-line analysis technology,has great potential and competitiveness in the analysis of chemical composition and proximate analysis results of coal in thermal power plants,the measurement repeatability of LIBS needs to be further improved due to the difficulty in controlling the stability of the generated plasmas at present.In this paper,we propose a novel x-ray fluorescence(XRF) assisted LIBS method for high repeatability analysis of coal quality,which not only inherits the ability of LIBS to directly analyze organic elements such as C and H in coal,but also uses XRF to make up for the lack of stability of LIBS in determining other inorganic ash-forming elements.With the combination of elemental lines in LIBS and XRF spectra,the principal component analysis and the partial least squares are used to establish the prediction model and perform multi-elemental and proximate analysis of coal.Quantitative analysis results show that the relative standard deviation(RSD) of C is 0.15%,the RSDs of other elements are less than 4%,and the standard deviations of calorific value,ash content,sulfur content and volatile matter are 0.11 MJ kg,0.17%,0.79% and 0.41%respectively,indicating that the method has good repeatability in determination of coal quality.This work is helpful to accelerate the development of LIBS in the field of rapid measurement of coal entering the power plant and on-line monitoring of coal entering the furnace.
