Quantitative detection on metabolites of Haematococcus pluvialis by terahertz spectroscopy

Study on infrared radiation spectrum characteristics of new smokeless moxibustion and traditional moxibustion

Dynamic Detection of Thiol Oxidation/Reduction Status During the Conversion of Cysteine/Cystine

Investigations were initiated for developing a rapid and nondestructive detection method to measure the illegal additive of melamine into milk powder by using terahertz (THz) spectroscopy and the correlation analysis algorithm. The absorption coefficients exhibited a maximum absorption peak at 2.04 THz, which would normally increase along with the concentration of melamine additive. In the current study, correlation analysis was carried out to select a pair-variable at 2.04 and 2.34 THz for improving the predictive ability of the multiple linear regression (MLR) model. Compared with the partial least square (PLS) model in full spectrum, the MLR model for powder samples could be considered successful in terms of quality control of milk powder with correlation coefficient R2 of 0.97 and root mean square error of prediction (RMSEP) of 1.38%. At the same time, the MLR model was simple and easier to interpret than the PLS one. The results of the research suggested that THz spectroscopy in combination with the correlation analysis algorithm has a significant potential in the quantitative analysis of the illegal additive of melamine in milk powder.

The intensity of signals in polarization-resolved laser-induced breakdown spectroscopy (PRLIBS) is affected by laser-induced energy. To reduce the interference of laser energy fluctuations on plasma signal intensity and improve the stability of spectral line identification of fertilizer in paddy soil, the intensity equation for the characteristic peaks of PRLIBS was derived. Based on the Boltzmann distribution, Malus' law, and the dependence of polarization degree on laser energy, combined with the anisotropic characteristics of plasma, the mechanism by which induced energy affects signal intensity during plasma radiation is explained. In this study, the potassium (K) element was selected as the research object. The characteristic spectral lines generated under five different reference laser-induced energies were collected using the measurement models of laser-induced breakdown spectroscopy and PRLIBS, and seven soil samples with varying K contents were measured. The characteristic peak intensities at K I 766.34nm and K I 769.79nm were taken as the analysis targets. Through linear fitting analysis, a linear correlation between spectral line intensity and induced energy was established to characterize the stability of spectral line identification. The results indicate that the intensities of the characteristic peak obtained by the PRLIBS exhibited a superior linear relationship with laser energy. After the induced energy correction, the linear correlation coefficients of the two characteristic peaks have been improved by an average of 4.76% and 5.64%, respectively. Based on the original measurement optical path system, the model demonstrates nice feasibility and reliability without modifying the hardware structure.

In the study, a new correction method was applied to reduce error during Raman spectral detection on mixed pesticide residue in apples. Combined with self-built pesticide residues detection system by Raman spectroscopy and the application of surface enhancement technology, rapid real-time qualitative and quantitative analysis of deltamethrin and acetamiprid residues in apples could be applied effectively. In quantitative analysis, compared with the intensity value of characteristic peaks of single pesticide with same concentration, the intensity value of characteristic peaks of the two pesticides decreased after mixing the pesticides, which affected the results severely. By comparing the difference in the intensity of characteristic peaks of single and mixed pesticides, a correction method was proposed to eliminate the influence of pesticides mixture. Characteristic peak intensity values of gradient concentration pesticide from 100 mg·kg−1 to 10−3 mg·kg−1 and Lagrangian interpolation were applied in the correction method. And a smooth surface was applied to describe the correction coefficient of characteristic peak intensity. Through detecting the characteristic peak intensity values of the mixed pesticide, correction coefficient would be obtained. Then real values of the peak intensity of pesticides and the content of each component of the mixed pesticide would be acquired by the correction method. Correlation coefficient of model validation exceeded 0.88 generally and Root Mean Square Error also decreased obviously after correction, which proved the reliability of the method.

Development of calibration models for the evaluation of pomegranate aril quality by Fourier-transform near infrared spectroscopy combined with chemometrics

Armand clematis stem (Clematidis Armandii Caulis, Chuanmutong) is a widely used Chinese herb to disinhibit urine and relieve stranguria. It is difficult to be identified owing to its various macroscopic feature and unknown characteristic compounds. Thus, total of 24 Chuanmutong samples and 7 related herbs including four manshurian aristolochia stem (Aristolochiae Manshuriensis Caulis, Guanmutong) and three akebia stem (Akebiae Caulis, Mutong) samples were collected and analyzed in the range of 4 000 - 400 cm⁻¹ by Fourier Transform Infrared (FTIR) and two-dimensional infrared correlation spectroscopy (2D-FTIR) techniques. The FTIR spectra of 24 Chuanmutong samples are consistent in the spectrum profiles, position and intensity of characteristic peaks. 20 of the 24 Chuanmutong samples were randomly selected as calibration samples to calculate and simulate mean spectrum. This mean spectrum is named as FTIR fingerprint of Chuanmutong with characteristic peaks at 3 412, 2 932, 1 739, 1 639, 1 509, 1 456, 1 426, 1 376, 1 332, 1 261, 1 159, 1 035, 897 ,609 cm⁻¹. Meanwhile, the limited level (Mean-3σ=0.992 6) to identify true or false Chuanmutong by correlation coefficient of FTIR spectra was calculated based on the 20 Chuanmutong calibration samples. Then, the rest 4 Chuanmutong, 4 Guanmutong and 3 Mutong samples were used as validation samples to evaluate the identification efficacy. The result shows that the FTIR spectra of 4 Chuanmutong validation samples were similar to the fingerprint. Their correlation coefficients of FTIR spectra were over the limited level and accepted as Chuanmutong. However, the spectra of Guanmutong and Mutong were significantly different from Chuanmutong fingerprint. The correlation coefficients of Guanmutong (0.902 1-0.940 4, n=4) and Mutong (0.954 9-0.978 9, n=3) FTIR spectra were less than the limited level and rejected from Chuanmutong. Furthermore, the number, position and intensity of auto-peaks on the 2D-FTIR were drastically different among the three herbs. It is concluded that the developed FTIR fingerprinting can be rapidly and accurately identify Chuanmutong and differentiate from related herbs.

Study of the relationship among biomarkers, cell and tissue of glioma through Raman spectroscopy

Removing dissolved organic matter (DOM) from sedimentation sludge water (SSW) before recycling is an effective method to reduce the impact on drinking water. The pH of SSW was adjusted from 5 to 9, followed by mixing, sedimentation, and filtration to simulate SSW treatment process. The concentration of dissolved organic carbon (DOC), value of UV254 and specific UV254 absorbance all increased with the increase of pH. The hydrophilicity fractionation and fluorescence excitation–emission matrix spectra showed that the hydrophilic, fulvic and humic acid-like compounds were the primary DOM in SSW at different pH conditions. These compounds were removed at acidic conditions, while adding alkali caused the release of these compounds. Fourier transform infrared spectroscopy showed that the characteristic peaks were not shifted at different pH conditions, however, the intensity of characteristic peaks related to Al and organic matter, such as Al–OH, Al–O, C = C, C = O, and COO-, were enhanced at acidic conditions. The contents of Al and C in sludge at acidic condition were also higher than that in the unadjusted sludge sample. These results suggested that the incidental coagulation reaction was enhanced at acidic conditions, promoting the removal of DOM from SSW. Nevertheless, the intensity of characteristic peaks and contents of Al and C in sludge at alkaline conditions showed the opposite trend to that at acidic conditions, illustrating that the sludge flocs in SSW were destroyed, causing the release of DOM. Therefore, maintaining a slightly acidic pH is an effective approach for treating DOM in the recycling of SSW.

Magnesium Phthalocyanine (MgPc) was deposited on a glass substrate by pulsed laser deposition (PLD) using Q-Switching Nd: YAG laser with wavelength 1064(nm), (6Hz) Repetition rate, in addition to different laser energies (200,300,400 and 500 mJ) at room temperature under vacuum condition with (10-3torr). All films were annealed at (298K) for 1hour to attain crystallinity. X-ray diffraction of MgPc powder indicated the fact that MgPc crystallizes in polycrystalline with a monoclinic structure While comparing the MgPc of films, it’s found the intensity of characteristic peak is high as the number and energy of laser pulses increase and the crystallize is monoclinic form is observed in β-form. Miller indices, hkl, values for every one of the diffraction peaks in the spectrum of the XRD have been computed. The characteristic peak of Phthalocyanine (MgPc) is found at 2θ value 6.9137o with the hkl value of {100} for both MgPc powder and deposited thin film. The surface morphology of the films showed more uniform sized grains. EDX and FESEM analysis has shown that there has been an enhancement in the crystallinity and surface morphology as a result of the increase of laser energies and for finding the optimum parameters for which film provides more efficient structural characteristics.

The Ag-doped nanostructured CdS thin films are grown by simple, cost effective chemical ion exchange technique at room temperature on ITO-coated glass substrate. These as grown thin films are annealed at 100, 200, 300, and 400°C in air atmosphere for 1 hour. To study the effect of annealing on physicochemical and optoelectronic properties, these as grown and annealed thin films are characterized for structural, compositional, morphological, optical, and electrical properties. X-ray diffraction (XRD) pattern reveals polycrystalline nature of these thin films with increase in crystallite size from 6.4 to 11.2 nm, from XRD the direct identification of Ag doping in CdS thin films cannot be judged, while shift in characteristics peak position of CdS is observed. The Raman spectrum represents increase in full width at half maxima and intensity of characteristic peak, confirming the material modification upon annealing treatment. Presence of Cd, Ag, and S in energy dispersive X-ray analysis spectra (EDAX) confirms expected elemental composition in thin films. Scanning electron microscopy (SEM) images represent grain growth and agglomeration upon annealing. Red shift in optical absorbance strength and energy band gap values from 2.28 to 2.14 eV is obtained.I-Vresponse obtained from as grown and annealed thin films shows an enhancement in photosensitivity from 72% to 96% upon illumination to 100 mW/cm2light source.

Objective To establish an infrared spectroscopic method for the rapid qualitative and quantitative analysis of caffeine and sodium benzoate in Annaka samples. Methods Qualitative and quantitative modeling samples were prepared by mixing high-purity caffeine and sodium benzoate. The characteristic absorption peaks of caffeine and sodium benzoate in Annaka samples were determined by analyzing the infrared spectra of the mixed samples. The quantitative model of infrared spectra was established by partial least squares （PLS）. Results By analyzing the infrared spectra of 17 mixed samples of caffeine and sodium benzoate （the purity of caffeine ranges from 10% to 80%）, the characteristic absorption peaks for caffeine were determined to be 1 698, 1 650, 1 237, 972, 743, and 609 cm-1. The characteristic absorption peaks for sodium benzoate were 1 596, 1 548, 1 406, 845, 708 and 679 cm-1. When the detection of all characteristic absorption peaks was the positive identification criteria, the positive detection rate of caffeine and sodium benzoate in 48 seized Annaka samples was 100%. The linear range of PLS quantitative model for caffeine was 10%-80%, the coefficient of determination （ R2） was 99.9%, the root mean square error of cross validation （RMSECV） was 0.68%, and the root mean square error of prediction （RMSEP） was 0.91%; the linear range of PLS quantitative model for sodium benzoate was 20%-90%, the R2 was 99.9%, the RMSECV was 0.91% and the RMSEP was 1.11%. The results of paired sample t test showed that the differences between the results of high performance liquid chromatography method and infrared spectroscopy method had no statistical significance. The established infrared quantitative method was used to analyze 48 seized Annaka samples, the purity of caffeine was 27.6%-63.1%, and that of sodium benzoate was 36.9%-72.3%. Conclusion The rapid qualitative and quantitative analysis of caffeine and sodium benzoate in Annaka samples by infrared spectroscopy method could improve identification efficiency and reduce determination cost.

Determination of aflatoxin B1 level in rice (Oryza sativa L.) through near-infrared spectroscopy and an improved simulated annealing variable selection method

Phenolic resin–trisilanolphenyl polyhedral oligomeric silsesquioxane (POSS) hybrid nanocomposites: Structure and properties

The potential applicability of time‐of‐flight secondary ion mass spectrometry (ToF SIMS) as an independent quantitative technique has been studied using a more complicated copolymer system: styrene‐butadiene copolymer. The complication of this system is that the characteristic SIMS peaks are not unique to each monomer. It has been found that quantitative information can be obtained from the relative SIMS intensities of certain characteristic peaks, i.e. m / z = 63, 89, 103 and 115 for styrene and 53, 67 and 79 for butadiene. In particular, the intensity ratios A /( A + B ), where A and B represent, respectively, the above characteristic peaks of styrene and butadiene, have been found to be linearly related to the bulk styrene molar concentration. These results suggest that a sensitivity factor that is constant and independent of the copolymer composition can be defined for these peaks. However, this conclusion cannot be generalized for other SIMS peaks, such as m / z = 77, 91 and 105.