A rapid, reliable and accurate method for the determination of hexavalent chromium in Portland cement is developed. The proposed method includes direct spectrophotometric determination of Cr (VI) in Portland cement wi...A rapid, reliable and accurate method for the determination of hexavalent chromium in Portland cement is developed. The proposed method includes direct spectrophotometric determination of Cr (VI) in Portland cement with 1, 2, 5, 8 Tetrahydroxyanthraquinone, (Quinalizarin, QINZ) at pH 1.5. The European Directive (2003/53/EC) limits the use of cements so that it contains no more than 2 mg.Kg-1 of water-soluble Cr (VI). The absorbance at 565 nm due to Cr (VI)-QINZ complex is recommended for the determination of water-soluble Cr (VI) in Portland cement. The quantification of Cr (VI) released from cement when mixed with water is performed according to TRGS 613 (Technical Rules of Hazardous Substances). The validity of the method is thoroughly examined and the proposed method gives satisfactory results. A derivative spectrophotometric method has been developed for the determination of total Cr (VI) in Portland cement in the presence of Fe (III) and Ti (IV). The hexavalent chromium complex formed at pH 1.5 allows precise and accurate determination of chromium (VI) over the concentration range 0.05 to 3.0 mg.L-1of chromium (VI). The validity of the method was examined by analyzing several Standard Reference Material (SRM) Portland cement samples. The MDL (at 95% confidence level) was found to be 25 ng/mL for chromium (VI) in National Institute of Standards and Technology (NIST) cement samples using the proposed method.展开更多
Based on the premise that the addition of glass beads (GB) could hardly influence the linear viscoelasticity in low frequency (ω) region for homogeneous polymer systems, the dynamic rheological behaviors of unfil...Based on the premise that the addition of glass beads (GB) could hardly influence the linear viscoelasticity in low frequency (ω) region for homogeneous polymer systems, the dynamic rheological behaviors of unfilled and filled poly(methyl methyacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN) blends were studied in order to explore the effect of GB on the phase-separation of binary polymer matrix. Results show that GB has an induced effect on the phase-separation, which embodies that the phase-separation temperature (Ts) of PMMA/SAN blend filled with GB is lower than that of the unfilled system. The higher content of GB, the higher is the "secondary plateau" of ω in the terminal region of storage modulus (G') versus ω plot. The "secondary plateau" appearing in the terminal region is attributed to the phase-separation of PMMA/SAN blends and it becomes more fiat for filled polymer blends under the same conditions. However, it is suggested that this kind of "induced effect" is related to the GB content; the higher content of GB particles might enhance the interaction between the particles and polymer matrix. Moreover, it is found that the addition of GB also has an influence more or less on the morphology and domain size of polymer matrix. It is believed that the plot of dynamic viscosity (η') versus the loss viscosity (η") is sensitive to examine the effect induced by GB on the phase-separation of binary polymer matrix.展开更多
Aiming at the complex electromagnetic transient process of EMU passing by phase-separation with electric load in high-speed railway, mechanism of overvoltage caused by switching off, overvoltage caused by switching on...Aiming at the complex electromagnetic transient process of EMU passing by phase-separation with electric load in high-speed railway, mechanism of overvoltage caused by switching off, overvoltage caused by switching on and impact current is analyzed systematically in this article. π-type equivalent circuit of feeding section is put forward in the analysis of overvoltage mechanism. Overvoltage and overcurrent model of passing by phase-separation with electric load are also built. Correctness of mechanism was validated by simulation. In addition, the methods to solve the influence on substations, transformers and protection devices in this process are put forward, which provides a new idea on passing by phase-separation with electric load technology.展开更多
The current work imitates the trivial method which intricates the abstraction along with classification of caffeine accessible in variability of decoction shrubberies which are expended in two different states of Indi...The current work imitates the trivial method which intricates the abstraction along with classification of caffeine accessible in variability of decoction shrubberies which are expended in two different states of India (Telengana & Uttar Pradesh). As per observation individuals of both the states are identical tender of consumption of tea. Abstraction progression tangled variability of stages which are discoursed in the work. In addition, the outcome of drinking of caffeine or the permitted ingestion of caffeine over tea has also been conferred through the work and linked the data with the literature data. In this study, we used a UV-visible spectrophotometer as well as liquid-liquid extraction method to determine the caffeine content in various tea samples. The significance of this study lies in the fact that accurate determination of caffeine content is essential for quality control and labeling of tea products. The UV-visible spectrophotometer method was found to be simple, reliable, and sensitive for the detection of caffeine in tea samples.展开更多
DNA analysis is the core of biotechnology applied in petroleum resources and engineering. Traditionally accurate determination of DNA purity and concentration by spectrometer is the first and critical step for downstr...DNA analysis is the core of biotechnology applied in petroleum resources and engineering. Traditionally accurate determination of DNA purity and concentration by spectrometer is the first and critical step for downstream molecular biology research. In this study, three different spectrophotometry methods, BPM, NDTT and NPMTTZ were compared for their performance in determining DNA concentration and purity in 32 oil samples, and molecule methods like quantitative real-time PCR (qPCR) and high-throughput sequence were also performed to help assess the accuracy of the three methods in determining DNA concentration and purity. For ordinary heavy oil (OHO), extra heavy oil (EHO) and super heavy oil (SHO), the characteristics of high viscosity (η), density (ρ) and resin plus asphaltene content will affect the DNA extraction and UV determination. The DNA concentration was decreased as density increased: OHO (11.46 ± 18.34 ng/μL), EHO (6.68 ± 9.67 ng/μL) and SHO (6.20 ± 7.83 ng/μL), and the DNA purity was on the reverse: OHO (1.31 ± 0.27), EHO (1.54 ± 0.20), and SHO (1.83 ± 0.32). The results suggest that spectrophotometry such as BPM and NPMTTZ are qualitatively favorite methods as the quick non-consumable methods in determining DNA concentration and purity of medium oil and heavy oil.展开更多
[Objectives] To establish a determination method for the content of total lignanoids in Tangjiangshenkang granules. [Methods] Two-wavelength ultraviolet spectrophotometry (TWBS) was used to scan arctiin control soluti...[Objectives] To establish a determination method for the content of total lignanoids in Tangjiangshenkang granules. [Methods] Two-wavelength ultraviolet spectrophotometry (TWBS) was used to scan arctiin control solution, chlorogenic acid control solution and Tangjiangshenkang granule test solution in the range of 200-400 nm. In the ultraviolet scanning diagram of arctiin reference solution, the maximum absorption wavelength of 280 nm was determined as the determination wavelength λ 1, the detection wavelength in the ultraviolet scanning diagram of chlorogenic acid reference solution ( λ 1=280 nm) was determined, and 350 nm was the reference wavelength λ 2;the content of total lignosides in Tangjiangshenkang granules was determined with arctiin as the reference substance. [Results] The precision, accuracy, and durability of this method were fine. The concentration of arctiin was linearly correlated with the absorbance difference in the range of 0.007 95-0.071 55 mg/mL ( r =0. 999 9). The average recovery of arctiin was 100.8%, and the RSD value was 1.04% ( n =6). Calculated as arctiin, three batches of Tangjiangshenkang granules contain no less than 20% of total lignosides. [Conclusions] The method has the advantages of simple operation, good accuracy, precision and reliable stability. It can be used as the content determination and quality control method of total lignosides in Tangjiangshenkang granules.展开更多
文摘A rapid, reliable and accurate method for the determination of hexavalent chromium in Portland cement is developed. The proposed method includes direct spectrophotometric determination of Cr (VI) in Portland cement with 1, 2, 5, 8 Tetrahydroxyanthraquinone, (Quinalizarin, QINZ) at pH 1.5. The European Directive (2003/53/EC) limits the use of cements so that it contains no more than 2 mg.Kg-1 of water-soluble Cr (VI). The absorbance at 565 nm due to Cr (VI)-QINZ complex is recommended for the determination of water-soluble Cr (VI) in Portland cement. The quantification of Cr (VI) released from cement when mixed with water is performed according to TRGS 613 (Technical Rules of Hazardous Substances). The validity of the method is thoroughly examined and the proposed method gives satisfactory results. A derivative spectrophotometric method has been developed for the determination of total Cr (VI) in Portland cement in the presence of Fe (III) and Ti (IV). The hexavalent chromium complex formed at pH 1.5 allows precise and accurate determination of chromium (VI) over the concentration range 0.05 to 3.0 mg.L-1of chromium (VI). The validity of the method was examined by analyzing several Standard Reference Material (SRM) Portland cement samples. The MDL (at 95% confidence level) was found to be 25 ng/mL for chromium (VI) in National Institute of Standards and Technology (NIST) cement samples using the proposed method.
基金This project was supported by the National Natural Science Foundation of China(No.20304014)the Special Funds for National Science Funds for Distinguished Young Scholars(No.50125312).
文摘Based on the premise that the addition of glass beads (GB) could hardly influence the linear viscoelasticity in low frequency (ω) region for homogeneous polymer systems, the dynamic rheological behaviors of unfilled and filled poly(methyl methyacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN) blends were studied in order to explore the effect of GB on the phase-separation of binary polymer matrix. Results show that GB has an induced effect on the phase-separation, which embodies that the phase-separation temperature (Ts) of PMMA/SAN blend filled with GB is lower than that of the unfilled system. The higher content of GB, the higher is the "secondary plateau" of ω in the terminal region of storage modulus (G') versus ω plot. The "secondary plateau" appearing in the terminal region is attributed to the phase-separation of PMMA/SAN blends and it becomes more fiat for filled polymer blends under the same conditions. However, it is suggested that this kind of "induced effect" is related to the GB content; the higher content of GB particles might enhance the interaction between the particles and polymer matrix. Moreover, it is found that the addition of GB also has an influence more or less on the morphology and domain size of polymer matrix. It is believed that the plot of dynamic viscosity (η') versus the loss viscosity (η") is sensitive to examine the effect induced by GB on the phase-separation of binary polymer matrix.
文摘Aiming at the complex electromagnetic transient process of EMU passing by phase-separation with electric load in high-speed railway, mechanism of overvoltage caused by switching off, overvoltage caused by switching on and impact current is analyzed systematically in this article. π-type equivalent circuit of feeding section is put forward in the analysis of overvoltage mechanism. Overvoltage and overcurrent model of passing by phase-separation with electric load are also built. Correctness of mechanism was validated by simulation. In addition, the methods to solve the influence on substations, transformers and protection devices in this process are put forward, which provides a new idea on passing by phase-separation with electric load technology.
文摘The current work imitates the trivial method which intricates the abstraction along with classification of caffeine accessible in variability of decoction shrubberies which are expended in two different states of India (Telengana & Uttar Pradesh). As per observation individuals of both the states are identical tender of consumption of tea. Abstraction progression tangled variability of stages which are discoursed in the work. In addition, the outcome of drinking of caffeine or the permitted ingestion of caffeine over tea has also been conferred through the work and linked the data with the literature data. In this study, we used a UV-visible spectrophotometer as well as liquid-liquid extraction method to determine the caffeine content in various tea samples. The significance of this study lies in the fact that accurate determination of caffeine content is essential for quality control and labeling of tea products. The UV-visible spectrophotometer method was found to be simple, reliable, and sensitive for the detection of caffeine in tea samples.
基金supported by grants from the PetroChina-CUP Major Strategic Cooperation Projects(ZLZX2020010805,ZLZX2020020405)National Natural Science Foundation of China(41373086)+3 种基金National Science and Technology Major Project(No.2016ZX05050011,2016ZX05040002)Beijing Nova Program and Leading Talent Culturing Cooperative Projects(No.Z161100004916033)Beijing Higher Education Young Elite Teacher Project(No.YETP0670)Outstanding Young Excellent Teachers Foundation of China University of Petroleum(Beijing)(KYJJ2012-01-10).
文摘DNA analysis is the core of biotechnology applied in petroleum resources and engineering. Traditionally accurate determination of DNA purity and concentration by spectrometer is the first and critical step for downstream molecular biology research. In this study, three different spectrophotometry methods, BPM, NDTT and NPMTTZ were compared for their performance in determining DNA concentration and purity in 32 oil samples, and molecule methods like quantitative real-time PCR (qPCR) and high-throughput sequence were also performed to help assess the accuracy of the three methods in determining DNA concentration and purity. For ordinary heavy oil (OHO), extra heavy oil (EHO) and super heavy oil (SHO), the characteristics of high viscosity (η), density (ρ) and resin plus asphaltene content will affect the DNA extraction and UV determination. The DNA concentration was decreased as density increased: OHO (11.46 ± 18.34 ng/μL), EHO (6.68 ± 9.67 ng/μL) and SHO (6.20 ± 7.83 ng/μL), and the DNA purity was on the reverse: OHO (1.31 ± 0.27), EHO (1.54 ± 0.20), and SHO (1.83 ± 0.32). The results suggest that spectrophotometry such as BPM and NPMTTZ are qualitatively favorite methods as the quick non-consumable methods in determining DNA concentration and purity of medium oil and heavy oil.
基金Supported by Major Science and Technology Project"Major New Drug Innovation".
文摘[Objectives] To establish a determination method for the content of total lignanoids in Tangjiangshenkang granules. [Methods] Two-wavelength ultraviolet spectrophotometry (TWBS) was used to scan arctiin control solution, chlorogenic acid control solution and Tangjiangshenkang granule test solution in the range of 200-400 nm. In the ultraviolet scanning diagram of arctiin reference solution, the maximum absorption wavelength of 280 nm was determined as the determination wavelength λ 1, the detection wavelength in the ultraviolet scanning diagram of chlorogenic acid reference solution ( λ 1=280 nm) was determined, and 350 nm was the reference wavelength λ 2;the content of total lignosides in Tangjiangshenkang granules was determined with arctiin as the reference substance. [Results] The precision, accuracy, and durability of this method were fine. The concentration of arctiin was linearly correlated with the absorbance difference in the range of 0.007 95-0.071 55 mg/mL ( r =0. 999 9). The average recovery of arctiin was 100.8%, and the RSD value was 1.04% ( n =6). Calculated as arctiin, three batches of Tangjiangshenkang granules contain no less than 20% of total lignosides. [Conclusions] The method has the advantages of simple operation, good accuracy, precision and reliable stability. It can be used as the content determination and quality control method of total lignosides in Tangjiangshenkang granules.