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Analytica Chimica Acta (v.650, #1)
Metabonomics study of liver cancer based on ultra performance liquid chromatography coupled to mass spectrometry with HILIC and RPLC separations by Jing Chen; Wenzhao Wang; Shen Lv; Peiyuan Yin; Xinjie Zhao; Xin Lu; Fengxia Zhang; Guowang Xu (pp. 3-9).
In this study, urinary metabolites from liver cancer patients and healthy volunteers were studied by a metabonomic method based on ultra performance liquid chromatography coupled to mass spectrometry. Both hydrophilic interaction chromatography (HILIC) and reversed-phase liquid chromatography (RPLC) were used to separate the urinary metabolites. Principle component analysis (PCA) and partial least squares to latent structure-discriminant analysis (PLS-DA) models were built to separate the healthy volunteers from the liver cancer patients and to find compounds that are expressed in significantly different amounts between the two populations. 21 metabolite ions were considered as potential biomarkers according to the Variable importance in the Project (VIP) value and S-plot. Compared with RPLC, a more sensitive and stable response can be recorded in HILIC mode due to the high content of organic solvent used. Moreover, the liver cancer group and the healthy volunteers can be better separated based on the data from the HILIC separation, which indicates that HILIC is suitable for urinary metabonomic analysis. In HILIC mode, several polar compounds related to arginine and proline metabolism, alanine and aspartate metabolism, lysine degradation, nicotinate and nicotinamide metabolism were found to be significantly changed in the concentrations of the two different populations: healthy and cancer. In contrast, in RPLC mode, these changed compounds are related to fatty acids oxidation.
Keywords: Metabonomics; Metabolomics; Hydrophilic interaction chromatography; Ultra performance liquid chromatography–mass spectrometry; Liver cancer; Biomarker
Analysis of highly polar metabolites in human plasma by ultra-performance hydrophilic interaction liquid chromatography coupled with quadrupole-time of flight mass spectrometry by Xiaoming Cai; Lijuan Zou; Jun Dong; Lili Zhao; Yuanyuan Wang; Qing Xu; Xingya Xue; Xiuli Zhang; Xinmiao Liang (pp. 10-15).
Highly polar metabolites are abundant in human plasma. Analysis of these compounds by standard reverse-phase chromatography is difficult. Highly polar metabolites were extracted by a two-step method. They were analyzed by ultra-performance hydrophilic interaction chromatography (HILIC) coupled to quadrupole-time of flight mass spectrometer detection technology. The middle and low polar fraction were also analyzed using a standard C18 column. Data were extracted by Markerlynx, and analyzed by multivariate statistical methods to discriminate human plasma samples by sex and age. The results not only showed good classification of samples by sex and age, but also revealed new potential biomarkers not revealed by standard RPLC/MS analysis. This study showed that HILIC is an effective technique to analyze highly polar metabolites for metabonomic studies.
Keywords: Hydrophilic interaction liquid chromatography; Plasma; Metabonomics; Highly polar metabolites
Metabonomics research of diabetic nephropathy and type 2 diabetes mellitus based on UPLC–oaTOF-MS system by Jie Zhang; Lijuan Yan; Wengui Chen; Lin Lin; Xiuyu Song; Xiaomei Yan; Wei Hang; Benli Huang (pp. 16-22).
Ultra performance liquid chromatography (UPLC) coupled with orthogonal acceleration time-of-flight (oaTOF) mass spectrometry has showed great potential in diabetes research. In this paper, a UPLC–oaTOF-MS system was employed to distinguish the global serum profiles of 8 diabetic nephropathy (DN) patients, 33 type 2 diabetes mellitus (T2DM) patients and 25 healthy volunteers, and tried to find potential biomarkers. The UPLC system produced information-rich chromatograms with typical measured peak widths of 4s, generating peak capacities of 225 in 15min. Furthermore, principal component analysis (PCA) was used for group differentiation and marker selection. As shown in the scores plot, the distinct clustering between the patients and controls was observed, and DN and T2DM patients were also separated into two individual groups. Several compounds were tentatively identified based on accurate mass, isotopic pattern and MS/MS information. In addition, significant changes in the serum level of leucine, dihydrosphingosine and phytoshpingosine were noted, indicating the perturbations of amino acid metabolism and phospholipid metabolism in diabetic diseases, which having implications in clinical diagnosis and treatment.
Keywords: Diabetic nephropathy; Diabetes mellitus; Metabonomics; Ultra performance liquid chromatography; Time-of-flight mass spectrometry
Capillary microextraction (CME) and its application to trace elements analysis and their speciation by Bin Hu; Fei Zheng; Man He; Nan Zhang (pp. 23-32).
As a solvent-free miniaturized sample preparation technique, capillary microextraction (CME) has been hyphenated with different analytical instruments for trace elements analysis of environmental, biological, food and pharmaceutical samples. This review discusses the fundamentals and recent development of CME, including the theoretical basis, extraction modes (packed, open-tubular and monolithic CME) and capillary materials for CME. The emphasis is placed on the application of CME to trace/ultra-trace elements analysis and their speciation. Existing coating/monolithic materials used for CME are summarized together with a detailed overview of their preparation methods.
Keywords: Capillary microextraction; Trace elements analysis; Inductively coupled plasma mass spectrometry; Review
Determination of cadmium in rice and water by tungsten coil electrothermal vaporization-atomic fluorescence spectrometry and tungsten coil electrothermal atomic absorption spectrometry after cloud point extraction by Xiaodong Wen; Peng Wu; Li Chen; Xiandeng Hou (pp. 33-38).
In this work, the microsampling nature of tungsten coil electrothermal vaporization Ar/H2 flame atomic fluorescence spectrometry (W-coil ETV-AFS) as well as tungsten coil electrothermal atomic absorption spectrometry (W-coil ET-AAS) was used with cloud point extraction (CPE) for the ultrasensitive determination of cadmium in rice and water samples. When the temperature of the extraction system is higher than the cloud point temperature of the selected surfactant Triton X-114, the complex of cadmium with dithizone can be quantitatively extracted into the surfactant-rich phase and subsequently separated from the bulk aqueous phase by centrifugation. The main factors affecting the CPE, such as concentration of Triton X-114 and dithizone, pH, equilibration temperature and incubation time, were optimized for the best extract efficiency. Under the optimal conditions, the limits of detection for cadmium by W-coil ETV-AFS and W-coil ET-AAS were 0.01 and 0.03μgL−1, with sensitivity enhancement factors of 152 and 93, respectively. The proposed methods were applied to the determination of cadmium in certified reference rice and water samples with analytical results in good agreement with certified values.
Keywords: Cloud point extraction; Cadmium; Tungsten-coil; Electrothermal atomization; Atomic absorption spectrometry; Atomic fluorescence spectrometry
Direct determination of melamine in dairy products by gas chromatography/mass spectrometry with coupled column separation by Xiao-min Xu; Yi-ping Ren; Yun Zhu; Zeng-xuan Cai; Jian-long Han; Bai-fen Huang; Yan Zhu (pp. 39-43).
A coupled capillary column system was developed for the qualitative and quantitative determination of melamine with isotope internal standard in dairy products by gas chromatography/mass spectrometry (GC/MS) without derivatization. A 30m of DB-5ms ((5%-phenyl)-methylpolysiloxane, 0.25mm i.d., 0.25μm df) coupled with a 1.5m of Innowax (polyethylene glycol, 0.32mm i.d., 0.25μm df) by a quartz capillary column connector was introduced as separation column. Three advantages were discussed for the coupled system. The sample was fortified with a ring-labeled13C315N3-melamine as an isotope internal standard and extracted by 1% of trichloroacetic acid aqueous solution. 2.2% of lead acetate solution was then added to deposit protein in the sample matrix. After purification by cation exchange cartridge, the sample solution was directly injected and detected by GC/MS. A six-point calibration curve ranging from 0.05 to 2mgkg−1 of melamine in sample was used to establish instrument response. The recovery was 93.9–102% with relative standard deviation from 3.1 to 8.7% when isotope internal standard used. The calculated method detection limit was 0.01mgkg−1.
Keywords: Melamine; Isotope internal standard; Gas chromatography/mass spectrometry (GC/MS); Coupled column; Direct determination; Dairy products
Label-free and sequence-specific DNA detection down to a picomolar level with carbon nanotubes as support for probe DNA by Ningning Zhu; Yuqing Lin; Ping Yu; Lei Su; Lanqun Mao (pp. 44-48).
This study describes a simple and label-free electrochemical impedance spectroscopic (EIS) method for sequence-specific detection of DNA by using single-walled carbon nanotubes (SWNTs) as the support for probe DNA. SWNTs are confined onto gold electrodes with mixed self-assembly monolayers of thioethanol and cysteamine. Single-stranded DNA (ssDNA) probe is anchored onto the SWNT support through covalent binding between carboxyl groups at the nanotubes and amino groups at 5′ ends of ssDNA. Hybridization of target DNA with the anchored probe DNA greatly increases the interfacial electron-transfer resistance ( Ret) at the double-stranded DNA (dsDNA)-modified electrodes for the redox couple of Fe(CN)63−/4−, which could be used for label-free and sequence-specific DNA detection. EIS results demonstrate that the utilization of SWNTs as the support for probe DNA substantially increases the surface loading of probe DNA onto electrode surface and thus remarkably lowers the detection limit for target DNA. Under the conditions employed here, Ret is linear with the concentration of target DNA within a concentration range from 1 to 10pM with a detection limit down to 0.8pM ( S/ N=3). This study may offer a novel and label-free electrochemical approach to sensitive sequence-specific DNA detection.
Keywords: Single-walled carbon nanotubes; Electrochemical impedance spectroscopy; Sequence-specific DNA detection
A carbon nanotubes assisted strategy for insulin detection and insulin proteolysis assay by Ying Wang; Jinghong Li (pp. 49-53).
The carbon nanotubes (CNTs) assisted strategy has been proposed for insulin sensing and insulin proteolysis analysis. Experiments demonstrated that this strategy could be used for trace insulin determination with a low detection limit 7.75ngmL−1 (S/N=3) and a detection range from 20ngmL−1 to 400ngmL−1. Both biocompatibility and intrinsic conductivity of pristine CNTs enabled them to act an excellent biosensing platform for the realization of direct electrochemistry and electrocatalysis of insulin. Compared with the present methods, the proposed strategy could realize the trace insulin detection without electrode modifications. It is more convenient and simpler than those based on the chemically modified electrodes. This method also made the CNTs as the indicator for insulin proteolysis analysis so that the biological process could be studied by electron microscope, electrochemical methods and digital camera. CNTs obtained after the proteolysis showed the same capabilities as the pristine ones in electrochemical signal enhancement and could participate in the bio-circle repeatedly.
Keywords: Insulin; Carbon nanotubes; Electrocatalysis; Proteolysis
A facile synthesis of palladium nanoparticles supported on functional carbon nanotubes and its novel catalysis for ethanol electrooxidation by Xiao-mei Chen; Zhi-jie Lin; Tian-tian Jia; Zhi-min Cai; Xiao-li Huang; Ya-qi Jiang; Xi Chen; Guo-nan Chen (pp. 54-58).
In this study, a novel material, palladium nanoparticles–carboxylic functional carbon nanotubes (PdNPs–CFCNTs), based on PdNPs supported on CFCNTs was synthesized by a facile spontaneous redox method. The material reveals high electrochemical activity and excellent catalytic characteristic for alcohol electrooxidation on a glassy carbon electrode (GCE) in an alkaline medium. The preparation mechanism was studied by the galvanic cell effect between PdCl42− and functional defect sites on CFCNTs. Results from UV–visible absorption spectroscopy and electrochemical impedance spectroscopy revealed that the reduction of PdCl42− to metallic Pd was successfully achieved. Morphologies of PdNPs supporting on CFCNTs (PdNPs–CFCNTs) were also characterized by transmission electron micrograph. PdNPs–CFCNTs with the best electrocatalytic characteristics were obtained under the condition as: the weight ratio of Pd to CFCNTs was kept at 2:1, the temperature was kept at 70°C in the synthesis, and the scan rate of the applied potential was selected at 60mVs−1. The results indicate that PdNPs–CFCNTs could be a great potential material in direct ethanol fuel cells and ethanol sensors.
Keywords: Electrocatalyst; Palladium nanoparticles; Carbon nanotubes; Ethanol; Alkaline solution
Effects of room-temperature ionic liquids on the chemical vapor generation of gold: Mechanism and analytical application by Chuan Zhang; Yan Li; Peng Wu; Yan Jiang; Qian Liu; Xiu-Ping Yan (pp. 59-64).
To get insight into the mechanism of the effect of room-temperature ionic liquids (RTILs) on the chemical vapor generation (CVG) of noble metals, gold was taken as a model element, and eight RTILs were examined. All the RTILs resulted in 3–24 times improvement in sensitivity for Au, depending on their nature. For the RTILs with identical anion, the RTILs with the cations of short chain exhibited better enhancement effect than those with long alkyl chain length or complex branch chain. For the RTILs with identical cation, the RTILs with Br− gave the best enhancement effect. The formation of ion pairs between the cation of RTILs and the anion species of gold via electrostatic interaction, and/or the substitution of the Cl− in the anion species of gold by the anion of RTILs likely enabled a more effective CVG reaction to occur. The RTILs also facilitated the generation of small bubbles and provided an electrostatic stabilization to protect the unstable volatile gold species and to help fast isolation of volatile gold species from the reaction mixture. 1-Butyl-3-methylimidazolium tetrafluoroborate [C4mim]Br gave the best improvement in the sensitivity (24 times) among the RTILs studied, and also reduced the interferences from common transition and other noble metals. Based on the enhancement effect of [C4mim]Br, a novel flow injection–CVG–atomic fluorescence spectrometric method with a detection limit (3 s) of 1.9μgL−1 and a precision of 3.1% (50μgL−1, RSD, n=11) was developed for the determination of trace gold in geological samples.
Keywords: Chemical vapor generation; Room-temperature ionic liquids; Atomic fluorescence spectrometry; Flow injection; Gold
Ionic liquids extraction of Para Red and Sudan dyes from chilli powder, chilli oil and food additive combined with high performance liquid chromatography by Yunchang Fan; Meilan Chen; Chao Shentu; Fawzi El-Sepai; Kaixiong Wang; Yan Zhu; Mingli Ye (pp. 65-69).
A simple analytical method, based on the coupling of ionic liquid-based extraction with high performance liquid chromatography (HPLC), is developed for the determination of Sudan dyes (I, II, III and IV) and Para Red in chilli powder, chilli oil and food additive samples. Two ionic liquids (ILs), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]), were compared as extraction solvents; experiments indicated that the latter possesses higher recoveries for each analyte. Parameters related to extraction of Sudan dyes and Para Red were also optimized. Under the optimal conditions, good reproducibility of extraction performance was obtained, with the relative standard deviation (RSD) values ranging from 2.0% to 3.5%. The detection limits of Sudan dyes and Para Red (LOD, S/N=3) were in the range of 7.0–8.2μgkg−1 for chilli powder and 11.2–13.2μgL−1 for chilli oil and food additive. The recoveries were in the range of 76.8–109.5% for chilli powder samples and 70.7–107.8% for chilli oil and food additive samples.
Keywords: Ionic liquid (IL); Sudan dyes; Para Red; Extraction; High performance liquid chromatography (HPLC)
Molecularly imprinted polymer as micro-solid phase extraction combined with high performance liquid chromatography to determine phenolic compounds in environmental water samples by Qinzhong Feng; Lixia Zhao; Jin-Ming Lin (pp. 70-76).
The molecularly imprinted polymer with 2,4,6-trichlorophenol (2,4,6-TCP) as the template molecule and methylacrylic acid (MAA), divinylbenzene (DVB) as functional monomer and the crosslinker, respectively, has been prepared and used as molecularly imprinted micro-solid phase extraction (MIMSPE) procedure for the selectively preconcentration of phenolic compounds from environmental water samples. Various parameters for the extraction efficiency of the MIMSPE have been evaluated. The optimized MIMSPE method allowed the extraction of the analytes from the sample matrix followed by a selective washing step using acetonitrile containing 0.3% (v/v) acetic acid. The characteristics of the MIMSPE method were valid by high performance liquid chromatography. The recoveries ranged between 88.9% and 102.5% for tap water, between 80.0% and 94.0% for river water, between 80.0% and 90.5% for sewage water fortified with 0.4mgL−1 of phenol, 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-TCP, pentachlorophenol (PCP) were obtained. This method has been successfully applied to preconcentrate and determine of phenolic compounds in environmental water samples directly.
Keywords: Molecularly imprinted polymer; Micro-solid phase extraction; Precipitation polymerization; 2,4,6-Trichlorophenol; Phenolic compounds; High performance liquid chromatography
Microchip-based ELISA strategy for the detection of low-level disease biomarker in serum by Yun Liu; Huixiang Wang; Jingyu Huang; Jie Yang; Baohong Liu; Pengyuan Yang (pp. 77-82).
A simple and sensitive method has been proposed to determine a trace level of α-fetoprotein (AFP), hepatocellular carcinoma biomarker, using poly(methyl methacrylate) (PMMA) microfluidic chips coupled with electrochemical detection system. The PMMA microchannels have been modified with poly(ethyleneimine) (PEI) containing abundant NH2 groups to covalently immobilize AFP monoclonal antibody. Afterward, the antigen AFP and horseradish peroxidase (HRP)-conjugated AFP antibody can sequentially bind through antigen–antibody specific interaction. Atomic force microscopy (AFM) and confocal fluorescence microscope (CFFM) were utilized to characterize the surface topography and protein immobilization after modification. Coupled with three-electrode electrochemical detection system, the immunochip can perform the detection limit of AFP down to 1pgmL−1, and achieve a detectable linear concentration range of 1–500pgmL−1 by differential pulse voltammetry (DPV). The on-chip immunoassay platform can not only provide rapid and sensitive detection for target proteins but also be resistant to non-specific adsorption of proteins, which contributes to the detection of low-level protein in real sample. Finally, AFP existing in healthy human serum was detected to demonstrate the utility of the immunochip. The result shows that the proposed approach is feasible and has the potential application in clinical analysis and diagnosis.
Keywords: Microchip; Immunoassays; α-Fetoprotein; Electrochemical detection
Microfluidic chip: Next-generation platform for systems biology by Xiaojun Feng; Wei Du; Qingming Luo; Bi-Feng Liu (pp. 83-97).
Systems biology advocates the understanding of biology at the systems-level, which requires massive information of correlations among individual components in complex biological systems. Such comprehensive investigation entails the use of high-throughput analytical tools. Microfluidic technology holds high promise to facilitate the progress of biology by enabling miniaturization and upgrading of current biological research tools due to its advantages such as low sample consumption, reduced analysis time, high-throughput and compatible sizes with most biological samples. In this article, we documented the recent applications of microfluidic chips in biological researches at the molecular level, cellular level and organism level, serving the purpose for systems-level understanding of biology.
Keywords: Microfluidic chip; Systems biology; Omics; Cell; C. elegans
Combining nanosurface chemistry and microfluidics for molecular analysis and cell biology by Yi Sun; Yingyi Liu; Weisi Qu; Xingyu Jiang (pp. 98-105).
Development of new tools catalyzes progress in biochemical sciences [G.M. Whitesides, E. Ostuni, S. Takayama, X.Y. Jiang, D.E. Ingber, Annual Review of Biomedical Engineering 3 (2001) 335]. Recent advances in micro-/nano-technology have resulted in an explosion of the number of new tools available for biochemical sciences. We have used surface chemistry, nano-structures and microfluidics to create a set of tools applicable for problems ranging from molecular to cellular analysis. These tools will promote the understanding of fundamental problems in cell biology, development and neurobiology, and become useful for real-world applications such as molecular diagnostics, food analysis and environmental monitoring.
Keywords: Self-assembled monolayer; Microfluidics; Microcontact printing; Soft lithography; Cell patterning
Study on a hidden protein-DNA binding in salmon sperm DNA sample by dynamic kinetic capillary isoelectric focusing by Liang Liang; Peng Dou; Mingming Dong; Xiaokang Ke; Ningsheng Bian; Zhen Liu (pp. 106-110).
Nuclease P1 is an important enzyme that hydrolyzes RNA or single-stranded DNA into nucleotides, and complete digestion is an essential basis for assays based on this enzyme. To digest a doubled-stranded DNA, the enzyme is usually combined with heat denaturing, which breaks doubled-stranded DNA into single strands. This paper presents an un-expected phenomenon that nuclease P1, in combination with heat denaturing, fails to completely digest a DNA sample extracted from salmon sperm. Under the experimental conditions used, at which nuclease P1 can completely digest calf thymus DNA, the digestion yield of salmon sperm DNA was only 89.5%. Spectrometric measurement indicated that a total protein of 4.7% is present in the DNA sample. To explain the reason for this phenomenon, the dynamic kinetic capillary isoelectric focusing (DK-CIEF) approach proposed previously, which allows for the discrimination of different types of protein-DNA interactions and the measurement of the individual dissociation rate constants, was modified and applied to examine possible protein-DNA interactions involved. It was found that a non-specific DNA-protein binding occurs in the sample, the dissociation rate constant for which was measured to be 7.05±0.83×10−3s−1. The formation of DNA-protein complex was suggested to be the main reason for the incomplete digestion of the DNA sample. The modified DK-CIEF approach can be applied as general DNA samples, with the advantages of fast speed and low sample consumption.
Keywords: Protein-DNA interaction; Capillary isoelectric focusing; Whole column imaging detection; DNA; Salmon sperm
Experiments on moving interaction boundaries and their characteristics of focusing and probing of both guest and host target molecules by Liuyin Fan; Wei Yan; Chengxi Cao; Wei Zhang; Qian Chen (pp. 111-117).
In this paper, the concept of a moving interaction boundary (MIB) is proposed with regard to guest and host molecules. With 2-naphthalene-sulfonate (2-NS) and β-cyclodextrin (CD) as the model guest and host compounds, respectively, the relevant experiments were carried out on the MIB in capillary electrophoresis (CE). The experiments show that (1) there are a MIB and a complex boundary (CB) if proper guest and host molecules are used; (2) the MIB system has the characteristic of selective focusing and probing of the target 2-NS; (3) the system also has the characteristic of selective probing of the target host molecule β-CD without UV-absorbance, making the direct UV determination of β-CD from other CDs possible; (4) interestingly, the focusing of the guest molecule is a kind of leaky-sample stacking rather than a collection of analytes in sample sweeping; (5) the mechanism of MIB-induced separation of target analyte from unwanted ones is similar to but different from that of an affinity chromatography. In addition, the utility of MIB was briefly tested for a real sample of wastewater spiked with 2-NS.
Keywords: Cyclodextrin; Focusing; Guest molecule; Host molecule; Moving interaction boundary; Sweeping
Study of the contact charge transfer behavior between cryptophanes ( A and E) and fullerene by absorption, fluorescence and1H NMR spectroscopy by Caihong Zhang; Weili Shen; Ruying Fan; Guomei Zhang; Lingzhi Shangguan; Jianbin Chao; Shaomin Shuang; Chuan Dong; Martin M.F. Choi (pp. 118-123).
A group of novel cage-like compounds cryptophanes A and E were synthesized from vanillin by a three-step method. The intermolecular interaction between cryptophanes ( A and E) and fullerene (C60) was investigated in detail by absorption, fluorescence and1H NMR spectroscopy. The absorption of C60 at 410–650nm decreased in the presence of cryptophanes A or E. The decrease in absorption intensity was proportional to the concentration of cryptophanes A or E. On the other hand, the fluorescence intensity of cryptophanes A or E decreased and the emission maxima were blue-shifted with the increase in C60 concentration. These results suggest that contact charge transfer (CCT) complexes can be formed from C60 with cryptophanes A or E. In addition, the electrochemical behavior of cryptophanes ( A and E) and C60 was studied by cyclic voltammetry. The redox currents of cryptophanes ( A and E) decreased and the peak potentials were shifted on addition of C60. The changes in the chemical shifts (Δ δ) of aromatic protons of cryptophanes ( A and E) in their NMR spectra further support that CCT complexes were formed with cryptophanes as the electron donors and C60 as the electron acceptor.
Keywords: Cryptophane; Fullerene; Absorption; Contact-pair charge transfer
Study on the complexation of isoquercitrin with β-cyclodextrin and its derivatives by spectroscopy by Yunlong Wang; Xiaona Qiao; Wenchao Li; Yehong Zhou; Yong Jiao; Cheng Yang; Chuan Dong; Yoshihisa Inoue; Shaomin Shuang (pp. 124-130).
The inclusion complexes of isoquercitrin (IQ) with cyclodextrins (CDs) including β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD) and dimethyl-β-cyclodextrin (DM-β-CD) have been investigated using the methods of steady-state fluorescence, UV–vis absorption and induced circular dichroism. The stoichiometric ratio of the three complexes was found to be 1:1 and the stability constants ( K) were estimated from spectrofluorometric titrations, as well as the thermodynamic parameters. Maximum inclusion ability was measured in the case of DM-β-CD due to the increased hydrophobicity of the host cavity, followed by HP-β-CD and β-CD. The effect of pH on the complexation process was also quantitatively assessed. IQ exists in different molecular forms depending on pH and β-CDs were most suitable for inclusion of the neutral form of IQ. The phase-solubility diagrams obtained with β-CD, HP-β-CD and DM-β-CD were all classical AL type. And DM-β-CD provided the best solubility enhancement, 12.3-fold increase compared to 2.8- and 7.5-fold increase for β-CD and HP-β-CD. The apparent stability constants obtained from the solubility data at 25°C were comparable with those obtained from the fluorescence assays. Moreover,1H NMR was carried out, which revealed that the IQ favorably inserted into the inner cavity from the chromone part instead of the phenyl part, which was in agreement with molecular modeling studies.
Keywords: Isoquercitrin; β-Cyclodextrins; Stability constants; Inclusion complexation
Multi-way chemometric methodologies and applications: A central summary of our research work by Hai-Long Wu; Jin-Fang Nie; Yong-Jie Yu; Ru-Qin Yu (pp. 131-142).
Multi-way data analysis and tensorial calibration are gaining widespread acceptance with the rapid development of modern analytical instruments. In recent years, our group working in State Key Laboratory of Chemo/Biosensing and Chemometrics in Hunan University has carried out exhaustive scientific research work in this area, such as building more canonical symbol systems, seeking the inner mathematical cyclic symmetry property for trilinear or multilinear decomposition, suggesting a series of multi-way calibration algorithms, exploring the rank estimation of three-way trilinear data array and analyzing different application systems. In this present paper, an overview from second-order data to third-order data covering about theories and applications in analytical chemistry has been presented.
Keywords: Multi-way data analysis; Tensorial calibration; Second-order advantage; Rank estimation; Chemometrics
Fluorescent quantification of terazosin hydrochloride content in human plasma and tablets using second-order calibration based on both parallel factor analysis and alternating penalty trilinear decomposition by Hong-Yan Zou; Hai-Long Wu; Li-Qun OuYang; Yan Zhang; Jin-Fang Nie; Hai-Yan Fu; Ru-Qin Yu (pp. 143-149).
Two second-order calibration methods based on the parallel factor analysis (PARAFAC) and the alternating penalty trilinear decomposition (APTLD) method, have been utilized for the direct determination of terazosin hydrochloride (THD) in human plasma samples, coupled with the excitation–emission matrix fluorescence spectroscopy. Meanwhile, the two algorithms combing with the standard addition procedures have been applied for the determination of terazosin hydrochloride in tablets and the results were validated by the high-performance liquid chromatography with fluorescence detection. These second-order calibrations all adequately exploited the second-order advantages. For human plasma samples, the average recoveries by the PARAFAC and APTLD algorithms with the factor number of 2 ( N=2) were 100.4±2.7% and 99.2±2.4%, respectively. The accuracy of two algorithms was also evaluated through elliptical joint confidence region (EJCR) tests and t-test. It was found that both algorithms could give accurate results, and only the performance of APTLD was slightly better than that of PARAFAC. Figures of merit, such as sensitivity (SEN), selectivity (SEL) and limit of detection (LOD) were also calculated to compare the performances of the two strategies. For tablets, the average concentrations of THD in tablet were 63.5 and 63.2ngmL−1 by using the PARAFAC and APTLD algorithms, respectively. The accuracy was evaluated by t-test and both algorithms could give accurate results, too.
Keywords: Parallel factor analysis; Alternating penalty trilinear decomposition; Terazosin hydrochloride; Standard addition method; Figures of merit