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1.
The use of biofuels, such as bioethanol or biodiesel, has rapidly increased in the last few years. Near infrared (near-IR, NIR, or NIRS) spectroscopy (>4000 cm−1) has previously been reported as a cheap and fast alternative for biodiesel quality control when compared with infrared, Raman, or nuclear magnetic resonance (NMR) methods; in addition, NIR can easily be done in real time (on-line). In this proof-of-principle paper, we attempt to find a correlation between the near infrared spectrum of a biodiesel sample and its base stock. This correlation is used to classify fuel samples into 10 groups according to their origin (vegetable oil): sunflower, coconut, palm, soy/soya, cottonseed, castor, Jatropha, etc. Principal component analysis (PCA) is used for outlier detection and dimensionality reduction of the NIR spectral data. Four different multivariate data analysis techniques are used to solve the classification problem, including regularized discriminant analysis (RDA), partial least squares method/projection on latent structures (PLS-DA), K-nearest neighbors (KNN) technique, and support vector machines (SVMs). Classifying biodiesel by feedstock (base stock) type can be successfully solved with modern machine learning techniques and NIR spectroscopy data. KNN and SVM methods were found to be highly effective for biodiesel classification by feedstock oil type. A classification error (E) of less than 5% can be reached using an SVM-based approach. If computational time is an important consideration, the KNN technique (E = 6.2%) can be recommended for practical (industrial) implementation. Comparison with gasoline and motor oil data shows the relative simplicity of this methodology for biodiesel classification.  相似文献   

2.
Chen Y  Xie MY  Yan Y  Zhu SB  Nie SP  Li C  Wang YX  Gong XF 《Analytica chimica acta》2008,618(2):121-130
A rapid and nondestructive near infrared (NIR) method combined with chemometrics was used to discriminate Ganoderma lucidum according to cultivation area. Raw, first, and second derivative NIR spectra were compared to develop a robust classification rule. The chemical properties of G. lucidum samples were also investigated to find out the difference between samples from six varied origins. It could be found that the amount of polysaccharides and triterpenoid saponins in G. lucidum samples was considerably different based on cultivation area. These differences make NIR spectroscopic method viable. Principal component analysis (PCA), discriminant partial least-squares (DPLS) and discriminant analysis (DA) were applied to classify the geographical origins of those samples. The results showed that excellent classification could be obtained after optimizing spectral pre-treatment. For the discriminating of samples from three different provinces, DPLS provided 100% correct classifications. Moreover, for samples from six different locations, the correct classifications of the calibration as well as the validation data set were 96.6% using the DA method after the SNV first derivative spectral pre-treatment. Overall, NIR diffuse reflectance spectroscopy using pattern recognition was shown to have significant potential as a rapid and accurate method for the identification of herbal medicines.  相似文献   

3.
The potential of near infrared reflectance spectroscopy (NIR) was investigated for its ability to non-destructively discriminate the geographic origins of Scrophularia spp., Andong, Uisung and China. Application of principal component analysis to NIR spectra leads to a clear separation of Andong sample from the others. Moreover, the contents of two neuroprotective constituents of Scrophularia spp., 8-O-(E-p-methoxycinnamoyl)-harpagide (HG), and E-p-methoxycinnamic acid (MCA), were determined by HPLC-DAD. Partial least squares (PLS) regression of NIR spectra combined with these analytical reference data yield the development of calibration models for the contents of the two constituents. The correlation coefficients of prediction models for HG and MCA were > 0.87. These outcomes indicated that the NIRS could be useful for the discrimination of Scrophularia spp.  相似文献   

4.
Near infrared(NIR) spectroscopy technique has shown great power and gained wide acceptance for analyzing complicated samples.The present work is to distinguish different brands of tobacco products by using on-line NIR spectroscopy and pattern recognition techniques.Moreover,since each brand contains a large number of samples,an improved dendrogram was proposed to show the classification of different brands.The results suggest that NIR spectroscopy combined with principal component analysis (PCA) and hierarchical cluster analysis(HCA) performs well in discrimination of the different brands,and the improved dendrogram could provide more information about the difference of the brands.  相似文献   

5.
A novel compound Salvialactomine (1) along with two other unusual occurring natural products Pentatriacontanoic acid 1, 3-dihydroxypropyl ester (2) and 5-Methylflavone (3) were isolated from the callus of Salvia santolinifolia Boiss. Callus was initiated on MS medium containing NAA (0.5 mg/L) and further sub-cultured on MS medium supplemented with NAA with BA (0.5 + 1.5 mg/L). The structures of isolated compounds were determined by using mass spectrometry, 1D, and 2D–NMR techniques. Compounds 1, and 3 were tested for two different cancer cell lines, i.e. Hela (Cervical cancer cell) and PC-3 (Prostate cancer cells). IC50 was found as > 30 using Doxorobicin (0.912 ± 0.12 μmol L?1) as a standard.  相似文献   

6.
《Analytical letters》2012,45(2):322-342
Abstract

The isolation, identification and characterization of bacteria obtained from soil of Ergani Makam Mountain were performed and the results revealed that the bacteria were thermophilic Anoxybacillus caldiproteolyticus. The characterized bacteria and purchased Geobacillus stearothermophilus were immobilized on Amberlite XAD-16 in order to prepare two biosorbents for preconcentration experiments for the determination of cadmium (II) ions. The produced biosorbents were enriched separately using mini-columns and the analyte was determined by flame atomic absorption spectrometry. The effects of solution parameters were investigated for the separation and preconcentration yields. The recovery efficiencies of Amberlite XAD-16 immobilized separately with A. caldiproteolyticus and G. stearothermophilus were determined to be 98.23?±?2.40 and 98.93?±?1.3 (n?=?5) for the optimum working conditions, respectively. Moreover, the Cd (II) ion was recovered with 10?mL of 1?mol L?1 of HCl and 2?mL of 0.5?mol L?1 HNO3 solutions. The optimum working conditions were determined to be at pH 6.0 and a flow rate of 2?mL min?1 for both biosorbents. The recovery efficiencies of matrix ions were characterized to investigate the feasibility of the developed preconcentration methods. The accuracy of the proposed methods were controlled by analyzing a SCP Science EnviroMAT Waste Water, Low (EU-L-2) certified reference material. The obtained results were comparable to the certified values. These methods were also applied to the analysis of water samples from Dicle River, Hazar Lake and Diyarbak?r tap water for Cd (II).  相似文献   

7.
《Analytical letters》2012,45(18):2849-2859
ABSTRACT

A novel method was developed for the quality control of Ephedrae herba by near-infrared (NIR) spectroscopy. First, qualitative models established by discriminant analysis and support vector machine were used for the preliminary screening of unqualified samples of E. herba. Then quantitative models of ephedrine and the total alkali (ephedrine and pseudoephedrine) were established by partial least squares regression and particle swarm optimization based least square support vector machine. The contents of test samples were predicted by the established NIR quantitative models. As a result, the accuracies of unqualified identification were 98.9% by discriminant analysis and 100% by support vector machine. The performance of the particle swarm optimization based least square support vector machine models were better than the partial least squares regression models. The correlation coefficients were both more than 0.98 and relative standard errors of calibrations were less than 9% in the calibration sets of particle swarm optimization based least square support vector machine models. As for the test sets, the correlation coefficients were both more than 0.93 and the relative standard errors of prediction were less than 13%, indicating satisfactory predicted results. All of these results demonstrated that NIR spectroscopy may be a powerful tool for the quality control of E. herba.  相似文献   

8.
《Analytical letters》2012,45(2):290-307
Abstract

Distinguishing chemicals and improvement on analytical methods has a direct impact on modern chemical analysis. In this work, the dissociative ionization of xylene isomers was investigated using a femtosecond laser mass spectrometry (FLMS) method with a custom-built linear time-of-flight (TOF) instrument. Laser beams at 800?nm and 400?nm were used and intensity-dependent analysis of the obtained mass spectra was performed using principal component analysis (PCA) to distinguish the xylene isomers, which give identical mass spectra in appearance that cannot be distinguished using normal mass spectrometry methods. The results show that there is a statistically highly significant difference between the xylene isomers for two principal components (1 ? α?>?99.99%) and minimal information loss (<5%) took place during the PCA procedure. Also, the use of the k-medoid clustering method showed that the isomers may be distinguished in real-time for a wide range of ionization laser pulse powers with approximately 99% accuracy. The results suggest that real-time isomer analysis by the FLMS method is suitable for mass spectral identification applications. The FLMS method has been shown to be an important alternative to other mass spectrometric methods that use different ionization mechanisms.  相似文献   

9.
Abstract

Two new oxamate-containing manganese(II) complexes, [{Mn(H2edpba)(H2O)2}2]n (1) and [Mn(H2edpba)(dmso)2]?dmso?CH3COCH3?H2O (2) (H4edpba = N,N′-ethylenediphenylenebis(oxamic acid) and dmso = dimethylsulfoxide), have been synthesized and the structures of 1 and 2 were characterized by single crystal X-ray diffraction. The structure of 1 consists of neutral honeycomb networks in which each manganese(II) is six-coordinate by one H2edpba2? ligand and two carboxylate–oxygens from two other H2edpba2? ligands building the equatorial plane. Each manganese is connected to its nearest neighbor through two carboxylate(monoprotonated oxamate) bridges in an anti-syn conformation. A dmso solution of single crystals of 1 was placed under acetone atmosphere affording 2, whereas putting 2 in equimolar water:ethanol mixture results in 1. The molecular structure of 2 is made up of mononuclear manganese(II) units which are interlinked by weak C–H?π and edge-to-face π-stacking interactions leading to supramolecular chains along the crystallographic b axis. Magnetic measurements reveal the occurrence of an antiferromagnetic coupling between two manganese(II) ions through anti-syn carboxylate bridges for 1 [J = ?1.18 cm?1, the Hamiltonian being defined as H = ?J S1.S2] and very weak intrachain ferromagnetic interactions in 2 [J = + 0.046 cm?1, H = ?JiSi.Si + 1].  相似文献   

10.
Near-infrared (NIR) chemical imaging is an emerging technique with the potential for the detection of contaminants in the environmental field. In this study the potential of NIR chemical imaging (NIR-CI) to predict concentrations of nutrients (total nitrogen, total phosphorus) and indicator microorganisms (Escherichia coli) in surface water was investigated. Chemical images of multiple samples were obtained simultaneously using a pushbroom imaging system operating in the 950–1650 nm wavelength range with spectral resolution of 7 nm. Using partial least squares regression models, the relationship between these pollutants and NIR spectral data extracted from the chemical images in samples of aqueous surface water and filtered residue from surface water was assessed. When calibration models were tested on an independent data set, it was found that models developed on filtered residue spectra outperformed those developed on aqueous samples. For samples of filtered residue, the performance of the calibrations achieved for total nitrogen was reasonable (R2 > 0.75); however, performance for total phosphorus and E. coli was poor (R2 < 0.5). Lower concentrations of these parameters were detected in the surface water samples included in the study (<1 mg L?1 and <20 colony-forming units per 100 mL, respectively), a likely reason for the poor performance. The results indicate that NIR-CI has the potential for screening samples in which the contaminant concentration exceeds 1 mg L?1.  相似文献   

11.
A reaction-based strategy exploiting metal ion mediated oxidative C–O bond cleavage affords selective ‘switch-on’ near-infrared (NIR) emitting cyanine probe for Cu+ in aqueous media and live cells. Near-infrared fluorescence-ready probe TPACy readily reacts with Cu+ to release the quinone embedded heptamethine cyanine (Cy-quinone) with extended π-electron conjugation responsible for the switch-on NIR fluorescence in aqueous buffer solution (50 mM HEPES, pH 7.2). This probe can be conveniently used for monitoring Cu+ without the interference from pH dependent effects of physiological media. Utility of the probe has been demonstrated by its application in the detection of unbound copper species (Cu+) in live cells.  相似文献   

12.
Solid state stepwise nitro–nitrito linkage isomerization of trans-[dinitrobis(ethylenediamine)nickel(II)], [Ni(en)2(NO2)2] (N,N-en), trans-[dinitrobis(N,N′-dimethylethylenediamine)nickel(II)], [Ni(N,N′-dmen)2(NO2)2] (N,N-dmen), and trans-[dinitritobis(N,N-dimethylethylenediamine)nickel(II)], [Ni(N,N-dmen)2(ONO)2] (O,O-udmen) were investigated by performing non-isothermal differential scanning calorimetry (DSC) analyses and the thermodynamic and thermokinetic parameters of isomerization were determined using DSC curves. Both N,N-en and N,N-dmen DSC curves show an endothermic peak at elevated temperatures, attributed to dinitro-to-dinitrito linkage isomerization. Similar exothermic peaks were observed in the cooling cycle, assigned to the reverse dinitrito-to-dinitro isomerization. The O,O-udmen isomer is more stable than the corresponding dinitro one at ambient temperatures, but an exothermic dinitrito-to-dinitro isomerization occurs upon cooling down to ?70 °C and reverts endothermically to dinitrito isomer upon heating up to ambient temperature. The overlapping DSC peaks associated with stepwise linkage isomerization were resolved using nonlinear fitting method. The peak temperature and the enthalpy changes of linkage isomerization are inversely dependent on the steric hindrance provided by diamine ligands, which increases in the order udmen > dmen > en. The results showed that the steric factor of the co-ligands also influences the kinetic parameters of isomerization, so that more bulky ligand substituent leads to higher isomerization rate constants. A DFT and TD-DFT calculations have been carrid out on both dinitro complexes of this investigation .  相似文献   

13.
Trinuclear Ag(I) (1) and dinuclear and mononuclear Zn(II) isonicotinate (2 and 3) complexes were prepared and characterized by X-ray crystallography, elemental analysis, IR spectroscopy, and thermal analysis. Single-crystal analysis of the Ag(I) complex reveals two different monodentate carboxylate coordination modes, protonated and deprotonated, respectively. IR spectra showed correlations between isonicotinate coordination modes and Δ(νas???νs)IR values. In addition, the hydrogen bonds significantly influence a position of carboxylate absorption bands. Moreover, IC50 and MIC data for bacteria, yeasts, and filamentous fungi were determined and the binding of Ag(I) and Zn(II) complexes to calf thymus DNA was investigated using electronic absorption, fluorescence, and CD measurements. Biological tests showed that the Ag(I) complex is more active than commercially used Ag(I) sulfadiazine against Escherichia coli. The fluorescence spectral results indicate that the complexes can bind to DNA through an intercalative mode. The Stern–Volmer quenching constants for investigated complexes obtained from the linear quenching plot are in the range of 1.67 × 104–3.42 × 104 M?1.  相似文献   

14.
Abstract

Two iron(II)-rhenium(IV) compounds of general formula [FeII(dmf)6][ReIVX6] [X = Cl (1) and Br (2); dmf = N,N-dimethylformamide] have been prepared and characterized. X-ray powder diffraction measurements on samples of 1 and 2 support the same structure for both systems. The crystal structure of 1 was determined by single-crystal X-ray diffraction. 1 crystallizes in the triclinic system with space group Pī. Each iron(II) is six-coordinate and bonded to six oxygens from six dmf molecules building a distorted octahedral environment. Rhenium(IV) is six-coordinate by six halide anions in an almost regular octahedral geometry. The magnetic properties were investigated from variable-temperature magnetic susceptibility measurements performed on microcrystalline samples of 1 and 2, whose experimental data were reproduced by a model of two isolated paramagnetic centers [S = 2 (FeII) and S = 3/2 (ReIV)] with large values of zero-field splitting (zfs) parameter.  相似文献   

15.
Four new supramolecular compounds, (2-mimH)[Ca(pydcH)3][Ca(pydcH2)(pydc)(H2O)2]·4H2O (1), (1-mimH)2[Zr(pydc)3] (2), (2-mimH)2[Cd(pydc)2]·8H2O (3), and (2-mimH)2[Hg(pydc)2]·8H2O (4) [where pydcH2 = pyridine-2,6-dicarboxylic acid (dipicolinic acid), 1-mim = 1-methylimidazole, and 2-mim = 2-methylimidazole], have been synthesized and characterized by elemental analyses, spectroscopic techniques (IR, UV–vis, 1H NMR, and 13C NMR), thermal (TG/DTG/DTA) analysis as well as single-crystal X-ray diffraction. All four compounds are proton-transfer salts of the methylimidazolium cations and metal complex anions that crystallized from a solution of pyridine-2,6-dicarboxylic acid, methylimidazole, metal nitrates or chlorides as starting materials. The coordinating dicarboxylic acid is deprotonated at the carboxyl group and methylimidazole is protonated to balance the charge. In the crystal structures of 14, hydrogen bonding and ππ stacking play important roles. Water clusters are formed in 1, 3, and 4. The equilibrium constants of dipicolinic acid (pydc) and methylimidazole derivatives (1-mim and 2-mim), pydc-2-mim, pydc-1-mim proton-transfer systems as well as those of their complexes were investigated by a potentiometric pH titration method. The stoichiometries of most of the complex species in solution were very similar to the cited crystalline metal ion complexes.  相似文献   

16.
An automated spectrophotometric system is proposed for the determination of bismuth in well water samples, using multi-syringe flow injection analysis (MSFIA) and exploiting a liquid waveguide capillary cell (LWCC). This method is based on the colorimetric reaction of bismuth and methylthymol blue (MTB) in the presence of polyvinylpyrrolidone (PVP) in acid medium (0.1 mol L?1 HNO3). The Bi(III)–MTB complex was measured at 600 nm. The method was optimised by multivariate techniques. Some figures of merit of the proposed system are worth being highlighted, such as its wide linear working range (between 4.9 and 600 μg L?1), its low detection limit (1.5 μg L?1 of bismuth) and its high intra-day precision and inter-day precision (0.7% (n = 12) and 1.4% (n = 5), respectively, both expressed as RSD). Moreover, a high injection frequency of 30 h?1 is achieved, as the proposed analyser is a powerful tool for fast Bi(III) determination. The method developed was successfully validated by analysing reference samples (pharmaceutical samples) by comparing the results with those obtained by ICP-OES and it was satisfactorily applied to well water samples. Besides, the present system is miniaturised allowing in situ measurements in control processes and field analysis.  相似文献   

17.
ABSTRACT

In this approach, a new carbon paste electrode modified with N,N′-bis(5-bromo-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine Schiff base ligand (L) was synthesised for selective and effective determination of Hg2+ ions in aqueous environmental samples using cyclic and square wave anodic stripping voltammetric methods. First, the selective detection of mercury ion was confirmed by evaluating the stability constants of metal complexes formed between the Schiff base ligand (L) and some desired cations by conductometric measurements. Afterwards, by preparing an effective carbon paste electrode modified with L, the experimental and instrumental parameters affecting the performance of modified electrode were investigated. Square wave anodic stripping voltammograms were obtained after applying an accumulation potential ?0.5 V and accumulation time 150 s in Britton–Robinson buffer solution at pH 2.0. The optimal square wave parameters found are pulse amplitude 75 mV, frequency 50 Hz and step potential 6 mV. The procedure exhibited linear range from 0.4 to 120 μg L?1 Hg2+ with a limit of detection of 0.042 μg L?1. The proposed electrode was proved to be highly selective in the presence of various cations and anions and was successfully used for determination of mercury in tobacco and several water samples.  相似文献   

18.
《Analytical letters》2012,45(6):1209-1226
Abstract

A sensitive method for the simultaneous spectrophotometric determination of Fe(II), Cu(II), Zn(II), and Mn(II) in mixtures has been developed with the aid of multivariate calibration methods, such as classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS). The method is based on the spectral differences of the analytes in their complexation reaction with 4‐(2‐pyridylazo)‐resorcinol (PAR) and the use of full spectra with wavelengths in the range of 300–600 nm. It was found that both the spectral positive and negative bands obtained against the PAR blank, are proportional to the concentration for each metal complex. The obtained linear calibration concentration ranges are 0.025–0.6, 0.05–0.8, 0.025–0.8, and 0.05–0.8 µg ml?1 for Fe(II), Cu(II), Zn(II), and Mn(II), respectively, and the LODs for the four metal ions were found to be approximately 1–3×10?2 µg ml?1. The proposed method was applied to a verification set of synthetic mixtures of these four metal ions, with models built in three different wavelength ranges, i.e., 300–450, 450–600, and 300–600 nm, corresponding to the positive, negative bands and their combinations, respectively. It was shown that the PLS model for the 300–600 nm range gave the best results (RPET=6.9% and average recovery ~100%; cf. PCR: RPET=9.5% and average Recovery ~110%). This method was also successfully applied for the determination of the four metal ions in pharmaceutical preparations, chicken feedstuff, and water samples.  相似文献   

19.
《Analytical letters》2012,45(1):122-139
Abstract

Species of Garcinia (Guttiferae) are used for flavoring curries, as a supplement, and to treat various diseases. This study describes the comparison and discrimination of Garcinia cambogia, Garcinia indica, Garcinia mangostana and Garcinia atroviridis fruits by analyzing their major phytochemicals, elemental content, antioxidant, antidiabetic, and anticholinesterase enzymes activities. For phytochemical and elemental profiling, ultraviolet (UV), near infrared/infrared (NIR/IR), inductively coupled plasma-optical emission spectroscopy (ICP-OES) and ICP-mass spectrometric (ICP-MS) techniques were used. The chemometric multivariate tests of linear discriminant and principal component analyses (LDA, PCA) were used to discriminate the subject fruit samples. Spectroscopic data showed resonances of phenolics and flavonoidal constituents present in the fruits. G. mangostana exhibited the highest phenolics (721.6 to 2815.3?µM GAE/g), whereas G. cambogia was rich in flavonoids (51.9 to 2709.2?µM QE/g). Anthocyanin (cyanidin-3-O-glucoside) evaluated by high performance liquid chromatographic was 9.01?mg/kg in G. mangostana fruit. In the analyzed fruits, Ca, K and Na were high, trace essential elements were at appreciable contents, whereas the toxic elements As, Cd, Tl, and Pb were within the safe limits. G. mangostana contained potent free radicals and cholinesterase enzyme inhibitors, whereas G. cambogia inhibited α-amylase enzyme more significantly. PCA and LDA discriminated the fruit samples with distinct classification and variability indices. The analyzed fruits were shown to be good sources of free radicals, cholinesterase, and α-amylase enzymes inhibition, mineral and essential elements, and safe for human consumption.  相似文献   

20.
Four new manganese(III) Schiff base complexes (1–4) were synthesized and characterized. The complexes have general formula [MnClLx] in which L represents a Schiff base ligand derived from condensation of meso-1,2-diphenyl-1,2-ethylenediamine with salicylaldehyde or its 3-OMe-, 5-Br-, or 5-OMe-derivatives (x = 1–4, respectively). The crystal structure of [MnClL1] (1) was characterized by X-ray crystallography. The in vitro anticancer activity of these complexes was evaluated by MTT and apoptosis assays against human breast (MCF-7) and liver (Hep G2) cancer cells. The complexes exhibited considerable antiproliferative activity against both cell lines (IC50 = 10.8–21.02 μM) comparable to cis-platin, except 4 (MCF-7). The highest activity was found for 1 with IC50 values of 13.62 μM (MCF-7) and 10.8 μM (Hep G2). Flow cytometry experiments showed that 1 induced apoptosis on MCF-7 tumor cell line. Docking simulations using AUTODOCK were also carried out. The results showed that all complexes fitted into the minor groove region of DNA.  相似文献   

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