The impact of vertical fiscal asymmetry on carbon emissions in China.

Facing the double pressure of promoting economic growth and achieving the goal of "emission peak" by 2030, China must cut down the carbon emission intensity. Focusing on the typical characteristics of China's financial system arrangement, we theoretically analyze the mechanism of vertical fiscal asymmetry affecting carbon emission intensity and use a panel data from 30 Chinese provinces to conduct an empirical examination. The results show that (1) vertical fiscal asymmetry significantly increases the local carbon emission intensity. After a series of robust tests, such as replacement variables and sample data, the conclusion is still valid. (2) The analysis of regional heterogeneity shows that the influence of vertical fiscal asymmetry in carbon emission intensity is the largest in the central area of China, followed by the eastern provinces, and not evident in the western area. The rise in carbon emission intensity brought on by vertical fiscal asymmetry can be successfully reduced by the central transfer payment. The impact of vertical fiscal asymmetry on carbon emission intensity will be greatly lessened when the central transfer payment surpasses the threshold. (3) The mechanism test shows that vertical fiscal asymmetry increases the carbon emissions intensity by three paths: reducing the intensity of environmental regulation, strengthening local governments' dependence on land finance, and local government competition. The above analysis further enriches the relevant research on how China's vertical fiscal asymmetry system affects carbon emission intensity through land finance and local government competition while pointing out the role of transfer payment, and it can help to provide new ideas and empirical evidence for further improving the financial system and promoting the green development of the economy.

Clinical Observation of Reduning Combined with Recombinant Human Interferon α-2b in the Treatment of Children with Viral Pneumonia.

Purpose: To observe the clinical efficacy of Reduning injection combined with recombinant human interferon α-2b spray in the treatment of children with viral pneumonia. Methods: A total of 200 children with viral pneumonia over 2 years old who were admitted to the Pediatrics Department of the Cangzhou Central Hospital from September 2018 to November 2020 were recruited and randomized into the control group and observation group at a ratio of 1 : 1, with 100 cases in each group. The children in the control group were given recombinant human interferon α-2b spray, and the children in the observation group were given Reduning injection on the basis of the control group. The clinical symptoms and signs, clinical efficacy, levels of inflammatory mediators, and drug safety were compared between the two groups. Results: The t-test results showed that the disappearance time of body temperature, respiratory rate, pulmonary rales, and cough in the observation group was significantly shorter than that in the control group. The chi-square revealed a significantly higher total effective rate in the observation group vs. the control group. After treatment, the levels of IL-1, IL-6, TNF-α, and CRP in the two groups were lower than the corresponding values before treatment, and greater reduction was observed in the observation group in relative to the control group (both p < 0.05). The two groups have a similar safety profile. Conclusion: Reduning combined with recombinant human interferon α-2b produces a remarkable effect in the treatment of children with viral pneumonia, and it ameliorates clinical symptoms and reduces inflammatory response with a good safety profile.

The effects of acute hypervolemic hemodilution and conventional infusion in laparoscopic radical prostatectomy patients.

OBJECTIVE: To compare the effect of acute hypervolemic hemodilution and conventional infusion in prostate cancer patients undergoing laparoscopic radical prostatectomies. METHODS: A total of 87 patients with prostate cancer who underwent laparoscopic radical prostatectomies in our hospital were retrospectively analyzed. The patients were randomly divided into a control group (the CNG, n=43, conventional infusion) and an observation group (the OG, n=44, acute hypervolemic hemodilution). Blood gas analyses were performed at different time points, and the patients' cognitive dysfunction was evaluated. RESULTS: The intraoperative blood transfusion rates of the OG and the CNG were 11.36% and 30.23%. The average intraoperative blood transfusions in the OG and the CNG were (315.46±24.49) ml and (486.95±42.17) ml (P < 0.05). The CVP and JVP levels in the OG and the CNG at T2 and T3 were significantly higher than the levels at T0 (P < 0.05). The Hb levels of the CNG at T3 and T4 were lower than they were at T0 (P < 0.05), and the Hb level in the OG at T4 was lower than it was at T1 (P < 0.05). The Hb levels in the CNG at T3 and T4 were lower than they were at T1 (P < 0.05), and the Hb levels in the OG at T1 and T2 were lower than they were in the CNG (P < 0.05). The MMSE cognitive function scores were lower than the scores recorded on the day before the operations (P < 0.05). CONCLUSION: Acute hypervolemic hemodilution in laparoscopic radical prostatectomy patients can maintain their hemodynamics in a stable state, help reduce blood transfusion, improve the oxygen supply to the brain tissue to maintain the supply and demand balance, and reduce the impact on the patients' cognitive function.

Unexpected Deprotonation from a Chemically Inert OH Group Promoted by Metal Ions in Lanthanide-Erythritol Complexes.

Single-crystal structures of five lanthanide-erythritol complexes are reported. The analysis of the chemical compositions and scrutinization of structural features in the single-crystal data of the complexes led us to find that unexpected deprotonation occurs on the OH group of erythritol of three complexes. Considering these complexes were prepared in acidic environments, where spontaneous ionization on an OH group is suppressed, we suggest metal ions play an important role in promoting the proton transfer. To find out why the chemically inert OH is activated, the single-crystal structures of 63 rare-earth complexes containing organic ligands with multiple hydroxyl groups (OLMHs) were surveyed. The formation of µ2-bridges turns out to be directly relevant to the occurrence of deprotonation. When an OH group from an OLMH molecule participates in the formation of a µ2-bridge, the polarization ability of the metal ions becomes strong enough to promote the deprotonation on the OH group. The above structural characteristics may be useful in the rational design of catalysts that can activate the chemically inert OH group and promote the relevant chemical conversions.

Fourier Transform Infrared Spectroscopy: An Innovative Method for the Diagnosis of Ovarian Cancer.

Ovarian cancer is the most lethal gynecologic malignancy due to the late diagnoses at advanced stages, drug resistance and the high recurrence rate. Thus, there is an urgent need to develop new techniques to diagnose and monitor ovarian cancer patients. Fourier transform infrared (FTIR) spectroscopy has great potential in the diagnosis of this disease, as well as the real-time monitoring of cancer development and chemoresistance. As a noninvasive, simple and convenient technique, it can not only distinguish the molecular differences between normal and malignant tissues, but also be used to identify the characteristics of different types of ovarian cancer. FTIR spectroscopy is also widely used in monitoring cancer cells in response to antitumor drugs, distinguishing cells in different growth states, and identifying new synthetic drugs. In this paper, the applications of FTIR spectroscopy for ovarian cancer diagnosis and other works carried out so far are described in detail.

Intensity Enhancement of a Two-Dimensional Asynchronous Spectrum Without Noise Level Fluctuation Escalation Using a One-Dimensional Spectra Sequence Change.

Previously, we demonstrated that the intensities of cross-peaks in a two-dimensional asynchronous spectrum could be enhanced using sequence change of the corresponding one-dimensional spectra. This unusual approach becomes useful when the determination of the sequential order of physicochemical events is not essential. However, it was not known whether the level of noise in the two-dimensional asynchronous spectrum was also escalated as the sequence of one-dimensional spectra changed. We first investigated the noise behavior in a two-dimensional asynchronous spectrum upon changing the sequence of the corresponding one-dimensional spectra on a model system. In the model system, bilinear data from a chromatographic-spectroscopic experiment on a mixture containing two components were analyzed using a two-dimensional asynchronous spectrum. The computer simulation results confirm that the cross-peak intensities in the resultant a two-dimensional asynchronous spectrum were indeed enhanced by more than 100 times as the sequence of one-dimensional spectra changed, whereas the fluctuation level of noise, reflected by the standard deviation of the value of a two-dimensional asynchronous spectrum at a given point, was almost invariant. Further analysis on the model system demonstrated that the special mathematical property of the Hilbert-Noda matrix (the modules of all column vectors of the Hilbert-Noda matrix being a near constant) accounts for the moderate variation of the noise level during the changes of the sequence of one-dimensional spectra. Next, a realistic example from a thermogravimetry-Fourier transform infrared spectroscopy experiment with added artificial noise in seven one-dimensional spectra was studied. As we altered the sequence of the seven FT-IR spectra, the variation of the cross-peak intensities covered four orders of magnitude in the two-dimensional asynchronous spectra. In contrast, the fluctuation of noise in the two-dimensional asynchronous spectra was within two times. The above results clearly demonstrate that a change in the sequence of one-dimensional spectra is an effective way to improve the signal-to-noise level of the two-dimensional asynchronous spectra.

Exciton diffusion in solid solutions of luminescent lanthanide ß-diketonates.

In this article, a series of luminescent lanthanide ß-diketonate solid solutions, with the formula of TBAEuxM1-x(TTA)4 (TBA = tetrabutylammonium; M = La or Gd; TTA = 2-thenoyltrifluoroacetonate), are synthesized by co-precipitation. In the solid solutions, the emission efficiency of Eu3+ is significantly increased with the presence of non-luminescent chelates TBALa(TTA)4 and TBAGd(TTA)4. Low temperature luminescence spectroscopy studies indicate that the TTA- ligands in these non-luminescent chelates do emit phosphorescence with long lifetime. However, the ligand phosphorescence is strongly quenched in solid solutions with the luminescent chelate TBAEu(TTA)4, providing strong evidence for intermolecular energy transfer through the triplet excited states of the ligands. A quantitative analysis of Eu3+ emission enhancement and TTA- phosphorescence quenching reveals that each Eu3+ center may receive excitation energy from about 30 TTA- ligands, suggesting that the excitation energy has become exciton-like in the solid solutions. Based on the crystallography analysis of TBALn(TTA)4, it is discovered that TTA- ligands in neighboring Ln(TTA)4- units may form π-π stacks with intermolecular distance ≤3.5 Å, thus enabling efficient triplet exciton diffusion via exchange interaction.

The effects of emission trading system on corporate innovation and productivity-empirical evidence from China's SO2 emission trading system.

Emission trading system is a significant market-based environmental regulation tool worldwide. This study fills existing knowledge gap on whether ETSs have "weak" and "strong" version of Porter hypothesis effects in China, by examining the effects of the Chinese SO2 emission trading on corporate innovation and productivity. Using the micro-data of domestic-listed manufacturing companies from 2004 to 2015, this study regarded China's SO2 emission trading system as a quasi-natural experiment by applying a difference-in-difference framework to eliminate endogenous problems. It was found that the SO2 emission trading system significantly promoted corporate innovation but did not have a significant effect on corporate productivity. The cause analysis showed that suboptimal institutional context and lack of corporate dynamic response led to the failure of strong Porter hypothesis effect. In addition, small- and medium-sized enterprises and non-state-owned enterprises gained greater innovation compensation effects of the emission trading system. This research believed that, the design, institutional context, and market incentives of emission trading systems need to be improved from the top down, to achieve the dual goal of environmental sustainability and economic growth.

Fourier Transform Infrared Spectroscopy Monitoring of Dihydroartemisinin-Induced Growth Inhibition in Ovarian Cancer Cells and Normal Ovarian Surface Epithelial Cells.

PURPOSE: Ovarian cancer is the most lethal of gynecological malignancies. Dihydroartemisinin (DHA), a derivative of artemisinin (ARS), has profound effects against human tumors. The aim of this study was to provide a convenient, cost-efficient technique, Fourier transform infrared (FTIR) spectroscopy, to monitor and evaluate responses to DHA-induced growth inhibition of ovarian cancer cells. METHODS: Cell growth and viability and the 50% inhibitory concentration (IC50) of DHA were assessed by the MTT assay. FTIR spectroscopy was used to monitor cells following DHA treatment, and data were analyzed by OMNIC 8.0 software. RESULTS: DHA can decrease the viability of ovarian cancer cells and normal cells, but cancer cells were more sensitive to this drug than normal cells. Spectral differences were observed between cells with or without DHA treatment. In particular, an increase in the amount of lipids and nucleic acids was observed. The band intensity ratio of 1454/1400, and the intensity of the band 1741 cm-1 increased, indicating stronger absorption after DHA treatment. Moreover, the differences were larger for the cell lines that were more sensitive to DHA. CONCLUSION: The spectral features provided information about important molecular characteristics of the cells in response to chemicals. These findings demonstrated the possible use of FTIR spectroscopy to evaluate DHA-induced growth inhibition effects in ovarian cancer cells and provided a promising new tool for monitoring cell growth and the effects of antitumor drugs in the clinic in the future.

Sample-Sample Correlation Asynchronous Spectroscopic Method Coupled with Multivariate Curve Resolution-Alternating Least Squares To Analyze Challenging Bilinear Data.

An approach to construct a secondary asynchronous spectrum via sample-sample correlation (SASS) is proposed to analyze bilinear data from hyphenated spectroscopic experiments. In SASS, bilinear data is used to construct a series of two-dimensional (2D) sample-sample correlation spectra. Then a vertical slice is extracted from each 2D sample-sample correlation spectrum so that a secondary 2D asynchronous spectrum is constructed via these slices. The advantage of SASS is demonstrated by a model system with the following challenging situations: (1) Temporal profiles of different components severely overlap, making spectra of pure components difficult to directly obtain from either original bilinear data or multivariate curve resolution-alternating least squares (MCR-ALS) with non-negativity and unimodality constraints. (2) Every peak in the spectra of the eluted samples contains contributions from at least two components. Hence, two-dimensional correlation spectroscopy (2D-COS) and n-dimensional (nD) asynchronous spectroscopic method developed in our previous work, which previously worked so well, are now invalid. SASS managed to reveal different groups of systematic absences of cross peaks (SACPs) that reflect the lack of spectral contributions of different components at different regions in the second asynchronous spectrum. Spectra of different components can still be faithfully retrieved via MCR-ALS calculation using constraints revealed by different groups of SACPs. The results demonstrate that implicit but intrinsic information revealed by SASS is indispensable in solving challenging bilinear data as the model system. We applied SASS on two real-world examples from thermogravimetry-Fourier transform infrared spectroscopy (TG-FT-IR) experiments of mixtures (H2O/HOD/D2O and H2O/isopropanol/pyridine). FT-IR spectra of different components were successfully recovered. Moreover, FT-IR spectrum of HOD, which is difficult to obtain, was successfully extracted. SASS can be applied in the analysis of gaseous mixtures from TG-FT-IR experiment and a combination of quantum cascade lasers with substrate-integrated hollow waveguides in environmental monitoring and biomedical diagnosis. Furthermore, SASS is also useful in various advanced hyphenated spectroscopic experiments.

A novel systematic absence of cross peaks-based 2D-COS approach for bilinear data.

A novel approach to use two-dimensional correlation spectroscopy (2D-COS) to analyze bilinear data is proposed. A phenomenon called Systematic Absence of Cross Peaks (SACPs) is observed in a 2D asynchronous spectrum. Two theorems relevant to SACPs have been derived. The SACP-based 2D-COS method has been successfully applied on analyzing bilinear data from mixed samples (including one model system and two real systems). Implicit isolated peaks can be identified and assigned to different components based on characteristic pattern of SACPs even if the time-related profiles of different components are severely overlapped. Based on the results of SACPs, spectra of pure components can be retrieved. Identification of SACPs can still be achieved in the presence of artifacts. Thus, neither noise nor baseline drift can produce significant influence on the results obtained from the approach described in this paper. We have used several well-established chemometric methods, including N-Findr, VCA, and MCR with various initial settings, on two systems that can be successfully solved using the 2D-COS method. The chemometric methods mentioned above cannot provide correct spectra of pure components because of severe problem of rotational ambiguity derived from severe overlapping of the time-related profiles. Only when the information from SACPs in 2D-COS is used as additional constraints in MCR calculation, correct spectra can be obtained. That is to say, the SACP-based 2D-COS method provides intrinsic information which is crucial in the analysis of chromatographic-spectroscopic and analogous data even if the time-related profiles of different components overlap severely.

A Novel Approach Based on Two-Dimensional Correlation Spectroscopy to Determine the Stoichiometric Ratio of Two Substances Involved in Intermolecular Interactions.

A novel technique called AOSD@Job's, combining asynchronous orthogonal sample design scheme (AOSD) with Job's method, is proposed to estimate the stoichiometric ratio of two substances that form a supramolecular aggregate under intermolecular interactions. First, a mathematical analysis was performed along with the procedure of the AOSD@Job's method. Then, the validity of the AOSD@Job's method was manifested by computer simulation on two model systems. Finally, the AOSD@Job's method was applied on two real chemical systems. The stoichiometric ratio between the coordination complex of Ni2+ and ethylenediaminetetraacetic acid disodium salt (EDTA) was estimated to be 1.0. Benzyl alcohol (BA) and ß-cyclodextrin (ß-CD) were determined to form a 1 : 1 host-guest complex. These values were consistent with the values reported in the literature. Compared with the traditional Job's method, the AOSD@Job's method has an evident advantage since it is still valid even if all the peaks of the supramolecular aggregate severely overlap with the peaks of the substances that form the aggregate.

Characterization of ovarian cancer cells and tissues by Fourier transform infrared spectroscopy.

BACKGROUND: Ovarian cancer is the most lethal of gynecological malignancies. Fourier Transform Infrared (FTIR) spectroscopy has gradually developed as a convenient, inexpensive and non-destructive technique for the study of many diseases. In this study, FTIR spectra of normal and several heterogeneous ovarian cancer cell lines as well as ovarian cancer tissue samples were compared in the spectral region of 4000 cm- 1 - 600 cm- 1. METHODS: Cell samples were collected from human ovarian surface epithelial cell line (HOSEpiC) and five ovarian cancer cell lines (ES2, A2780, OVCAR3, SKOV3 and IGROV1). Validation spectra were performed on normal and cancerous tissue samples from 12 ovarian cancer patients. FTIR spectra were collected from a NICOLET iN10 MX spectrometer and the spectral data were analyzed by OMNIC 8.0 software. RESULTS: Spectral features discriminating malignant tissues from normal tissues were integrated by cell line data and tissue data. In particular changes in cancerous tissues, the decrease in the amount of lipids and nucleic acids were observed. Protein conformation and composition were also altered in some cancer cells. The band intensity ratio of 1454/1400 was higher in normal cells/tissues and lower in cancer cells/tissues. CONCLUSION: The spectral features revealed the important molecular characteristics about ovarian cancer cells/tissues. These findings demonstrate the possible diagnostic use of FTIR spectroscopy, providing the research model and evidences, and supporting the future study on more tissue samples to establish a data bank of spectra features for the possible discrimination of ovarian cancers.

Design of a Novel Apparatus to Enrich Analytes via a Diffuse-Evaporation Process for HPLC-FTIR Analysis.

HPLC-FTIR analysis using a novel apparatus with CuO powder as an interface is reported. This apparatus initially serves as a reservoir for the dilute eluted solution of HPLC, and then acts as an enrichment device by combining diffusion and evaporation processes. It can be used not only to effectively remove the mobile phase of the eluted solution, but also to enrich the analyte within a tiny spatially resolved separated sample spot whose size is suitable for obtaining spectra using an FTIR microscope. An experimental demonstration using benzamide and sodium dodecyl benzene sulfonate shows that this apparatus is readily applicable in the analysis of real-world mixture samples.

Two-dimensional correlation spectroscopic studies on coordination between organic ligands and Ni2+ ions.

3A2g→3T1g(P) transition band of Ni2+ is used to probe the coordination of Ni2+. Two-dimensional asynchronous spectra (2DCOS) are generated using the Double Asynchronous Orthogonal Sample Design (DAOSD), Asynchronous Spectrum with Auxiliary Peaks (ASAP) and Two-Trace Two-Dimensional (2T2D) approaches. Cross peaks relevant to the 3A2g→3T1g(P) transition band of Ni2+ are utilized to probe coordination between Ni2+ and various ligands. We studied the spectral behavior of the 3A2g→3T1g(P) transition band when Ni2+ is coordinated with ethylenediaminetetraacetic acid disodium salt (EDTA). The pattern of cross peaks in 2D asynchronous spectrum demonstrates that coordination brings about significant blue shift of the band. In addition, the absorptivity of the band increases remarkably. The interaction between Ni2+ and galactitol is also investigated. Although no clearly observable change is found on the 3A2g→3T1g(P) transition band when galactitol is introduced, the appearance of cross peak in 2D asynchronous spectrum demonstrates that coordination indeed occurs between Ni2+ and galactitol. Furthermore, the pattern of cross peak indicates that peak position, bandwidth and absorptivity of the 3A2g→3T1g(P) transition band of Ni(galactitol)x2+ is considerably different from those of Ni(H2O)62+. Thus, 2DCOS is helpful to reveal subtle spectral variation, which might be helpful in shedding light on the physical-chemical nature of coordination.

Novel Method of Constructing Two-Dimensional Correlation Spectroscopy without Subtracting a Reference Spectrum.

In this study, we propose a new approach to generate two-dimension spectra to enhance the intensity of cross peaks relevant to intermolecular interaction. We investigate intermolecular interaction between two solutes (denoted as P and Q, where P has a characteristic peak at XP) dissolved in the same solvent via the near diagonal cross peaks around the coordinate (XP, XP) in a two-dimensional (2D) asynchronous spectrum of generalized spectroscopy. Because of physical constrains in many cases, the variation ranges of the initial concentrations of P or Q must be kept very narrow, leading to very weak cross peak intensities. The weak cross peaks vulnerable to noise bring about difficulty in the investigation of subtle intermolecular interaction. Herein, we propose a new of way constructing a 2D asynchronous spectrum without the subtraction of the average spectrum often used as a reference spectrum. Mathematical analysis and computer simulation demonstrate that the near diagonal cross peaks around the coordinate (XP, XP) in the 2D asynchronous spectrum using the new approach possess two characteristics: (1) they can still reflect an intermolecular interaction reliably; 2) the absolute intensities of the cross peaks are significantly stronger than those generated by the conventional method. We incorporate the novel method with the DAOSD (double asynchronous orthogonal sample design scheme) approach and applied the modified DAOSD approach to study hydrogen bonding behavior in diethyl either/methanol/THF system. The new approach made the weak cross peaks, which are not observable in 2D asynchronous spectrum generated using conventional approach, become observable. The appearance of the cross peak demonstrate that When a small amount of THF is introduced into diethyl solution containing low amount of methanol, THF breaks the methanol-diethyl ether complex and forms methanol-THF complex via new hydrogen bond. This process takes place in spite of the fact that the content of diethyl ether is overwhelmingly larger than that of THF. The above result demonstrates that the new approach described in this article is applicable to enhance intensity of cross peaks in real chemical systems.

Investigation on the Behavior of Noise in Asynchronous Spectra in Generalized Two-Dimensional (2D) Correlation Spectroscopy and Application of Butterworth Filter in the Improvement of Signal-to-Noise Ratio of 2D Asynchronous Spectra.

The behavior of noise in asynchronous spectrum in generalized two-dimensional (2D) correlation spectroscopy is investigated. Mathematical analysis on the noise of 2D spectra and computer simulation on a model system show that the fluctuation of noise in a 2D asynchronous spectrum can be characterized by the standard deviation of noise in 1D spectra. Furthermore, a new approach to improve a signal-to-noise ratio of 2D asynchronous spectrum by a Butterworth filter is developed. A strategy to determine the optimal conditions is proposed. Computer simulation on a model system indicates that the noise of 2D asynchronous spectrum can be significantly suppressed using the Butterworth filtering. In addition, we have tested the approach to a real chemical system where interaction between berberine and ß-cyclodextrin is investigated using 2D UV-vis asynchronous spectra. When artificial noise is added, cross peaks that reflect intermolecular interaction between berberine and ß-cyclodextrin are completely masked by noise. After the method described in this article is utilized, noise is effectively suppressed, and cross peaks are faithfully recovered. The above result demonstrates that the approach described in this article is applicable in real chemical systems.

Investigation on intermolecular interaction between berberine and ß-cyclodextrin by 2D UV-Vis asynchronous spectra.

The interaction between berberine chloride and ß-cyclodextrin (ß-CyD) is investigated via 2D asynchronous UV-Vis spectrum. The occurrence of cross peaks around (420nm, 420nm) in 2D asynchronous spectrum reveals that specific intermolecular interaction indeed exists between berberine chloride and ß-CyD. In spite of the difficulty caused by overlapping of cross peaks, we manage to confirm that the 420nm band of berberine undergoes a red-shift, and its bandwidth decreases under the interaction with ß-CyD. The red-shift of the 420nm band that can be assigned to n-π* transition indicates the environment of berberine becomes more hydrophobic. The above spectral behavior is helpful in understanding why the solubility of berberine is enhanced by ß-CyD.

Investigation on the relationship between solubility of artemisinin and polyvinylpyrroli done addition by using DAOSD approach.

In this work, we investigated the influence of polyvinylpyrrolidone (PVP) on the solubility of artemisinin in aqueous solution by using quantitative 1H NMR. Experimental results demonstrate that about 4 times of incremental increase occurs on the solubility of artemisinin upon introducing PVP. In addition, dipole-dipole interaction between the ester group of artemisinin and the amide group of N-methylpyrrolidone (NMP), a model compound of PVP, is characterized by two-dimensional (2D) correlation FTIR spectroscopy with the DAOSD (Double Asynchronous Orthogonal Sample Design) approach developed in our previous work. The observation of cross peaks in a pair of 2D asynchronous spectra suggests that dipole-dipole interaction indeed occurs between the ester group of artemisinin and amide group of NMP. Moreover, the pattern of cross peaks indicates that the carbonyl band of artemisinin undergoes blue-shift while the bandwidth and absorptivity increases via interaction with NMP, and the amide band of NMP undergoes blue-shift while the absorptivity increases via interaction with artemisinin. Dipole-dipole interaction, as one of the strongest intermolecular interaction between artemisinin and excipient, may play an important role in the enhancement of the solubility of artemisinin in aqueous solution.

Use of CuO Particles as an Interface in LC-FTIR Analysis.

In this study, the feasibility of using copper oxide (CuO) as an interface for the coupling of liquid chromatography (LC) and Fourier-transform infrared (FTIR) spectroscopy was investigated. CuO exhibits low absorption in the 4000 to 1000 cm-1 FTIR spectral region. In addition, LC-FTIR using CuO as the interface was extended to the analysis of sample mixtures containing benzamide and dioctyl sebacate; both analytes were successfully separated. After complete removal of the mobile phase, benzamide and dioctyl sebacate were successfully identified from the FTIR spectrum. Surprisingly, the interference from adsorbed water or conventionally used LC solvents in the FTIR spectrum was completely eliminated by using CuO particles as the interface in the off-line hyphenation of LC-FTIR. Based on these results, CuO demonstrates potential as an ideal interface for LC-FTIR analysis.