Simultaneous measurement of phenols by three-way fluorescence spectroscopy: A comparison of N-PLS/RBL, U-PLS/RBL and PARAFAC.

Phenol, o-cresol, p-cresol, catechol and resorcinol are five phenolic compounds with extremely similar structure. Their fluorescence spectra are hard to be analyzed because of the serious spectral overlaps between any two of the five phenolic components in the mixture system. In this experiment, multi-dimensional partial least-squares (N-PLS), unfolded partial least-squares (U-PLS) with residual bilinearization (RBL) and parallel factor analysis (PARAFAC) are employed to analyze the three-way fluorescence spectra aiming to achieve quantitative results.

[Rapid Quantitative Detection of Bacterial in Water Based on Multi-Wavelength Scattering Spectra].

The structures of bacterial cells are analyzed in this paper. The scattering components of individual cell were divided into two parts including external structure and internal structure. The interpretation model of bacteria about scattering light is established.

[Study of the Impact of Sample Thickness on Thin Film Method X-Ray Fluorescence Spectrum Measurement].

The mixed samples of nylon film enrichment of Cr, Pb and Cd three elements and glass fiber membrane filter were as the research object. With the method of superposition of membrane filter, the XRF spectra were measured under different thin film samples thicknesses. According the changes of characteristic XRF of Cr, Pb and Cd elements in the mixed sample and Ca, As and Sr elements in glass fiber membranes, the effects of sample thickness on thin film method XRF spectrum measurement were studied.

[Effect of Methanol-Water Mixture on Three-Dimensional Fluorescence Spectra of Carbaryl].

Extensive use of pesticides has a significant impact on the environment. Carbaryl, whose residues stay in the surface water, is one of the most widely used broad spectrum insecticides in agriculture. It is important to understand carbaryl spectral characteristics and detection methods.

[Photosynthetic Parameters Inversion Algorithm Study Based on Chlorophyll Fluorescence Induction Kinetics Curve].

The fast chlorophyll fluorescence induction curve contains rich information of photosynthesis. It can reflect various information of vegetation, such as, the survival status, the pathological condition and the physiology trends under the stress state. Through the acquisition of algae fluorescence and induced optical signal, the fast phase of chlorophyll fluorescence kinetics curve was fitted.

[The study of selecting sample detecting position and lead plate inner material in thin film method X-ray fluorescence measurement].

(1) In this paper type 316 stainless steel metal plate as the research object, the selection of sample detecting position was studied when thin film method X-ray fluorescence measurement was conducted. The study showed that the optimal location for the sample detection was sample distance X-ray tube and detector baseline 1cm with the baseline into a 16°angle. (2) Heavy metal pollutants of Pb, Cd and Cr in industrial ambient air as the main analysis object, when thin film method X-ray fluorescence conducted with lead plate protection, X-rays will penetrate the membrane and continuely stimulate the protective lead plate.

[Determination of chemical rank of three-dimensional fluorescence spectra using mathematical morphology method].

The present paper firstly denoises the signal with morphological method, selecting sine-shaped structure element, using the morphological difference in waveform between the three-dimensional fluorescence and noise signal, then singular value decomposition is applied to the denoised data, and finally the chemical rank is determinated jointing eigenvalues and eigenvectors form singular value decomposition. This paper principally discusses the theory basis of morphological filtering method, firstly simulated data is analysed by morphological filtering method to confirm the necessity and effectiveness of proposed method, then the feasibility and practicability of the proposed method is verified by the determination of components number of phenols mixture three-dimensional fluorescence spectra compared with traditional Monte Carlo method. The experiments demonstrate that the proposed method is able to estimate the chemical rank correctly.

[Analysis of three-dimensional fluorescence overlapping spectra using nonnegative matrix factorization].

The present paper primarily tests and verifies the effect of NMF in blind source separation of three-dimensional simulative fluorescence spectra, and then four different computational algorithms (multiplicative iterative; alternating least square; second order method; projected gradient algorithm) were used in three practical phenolic compounds (cresol, phenol, thymol) overlapping fluorescence spectra to find out which nonnegatively constrained algorithms is the most efficient for fluorescence spectra unmixing. The experiments demonstrate that four ways have the normalized residuals below 0.06%, and alternating least square (ALS) is the best at both convergence behavior and robustness.

[Study on a new method of fast monitoring toxicity of Cd2+ by algal in water].

Chlorophyll concentration and photosynthesis activity fluorescence parameters of Chlorella pyrenoidosa stressed by different concentrations of Cd2+ were measured based on algal growth inhibition tests and photosynthetic activity inhibition tests. The relationship between the algal photosynthetic activity inhibition rate and 96 h inhibition rate of specific growth rate at different Cd2+ stress times was studied by sigmoidal curve fitting and one-way ANOVA analysis. The result shows that S function relevance exists between the algal photosynthetic activity inhibition rates for 48 h, 53 h, 72 h, 77 h and 96 h respectively and 96 h inhibition rate of specific growth rate (R2 > 0.

[The method of phytoplankton photosynthesis activity in-situ measurement based on light induced fluorescence].

According to the phytoplankton fluorescence induction characteristics under different light conditions, chlorophyll fluorescence as a probe for analysis of phytoplankton photosynthesis was studied. The present paper proposed a in-situ measurement method based on the chlorophyll fluorescence values Ft and Fm to get phytoplankton photosynthesis activity, Chlorella vulgaris, microcystis aeruginosa and Cyclotella meneghiniana Kiits were selected as experimental subjects, a comparison test was done between self-developed in-situ measurement system and Water PAM in lab, and the results showed that coefficients between the two methods were 0.9778, 0.

[Studies on toxicity of four kinds of heavy metals in water by synchronous-scan fluorescence].

Spectrofluorometry of chlorella pyrenoidosa was studied by three dimensional excitation-emission (3DEEM) fluorescence spectroscopy and synchronous scan fluorescence spectroscopy with Delta gamma = 20 nm in the stress of Hg+, Cd2+, Cu2+ and Zn2+. The conclusion from two kinds of Spectrofluorometry was the same: after 96h stress by heavy metals, the maximum fluorescence values reduced obviously, chlorophyll-a and chlorophyll-b in the photosynthetic system were seriously damaged by heavy metal. Further analysis of the correlations between heavy metal concentration and fluorescence quenching efficiency I0/I can conclude that the toxicity of heavy metal and the fluorescence quenching efficiency I0/I were positively correlated, and they all increased with the heavy metal concentration and stress time.

[Analysis of three-dimensional fluorescence overlapping spectra using differential spectra and independent component analysis].

The analysis of multi-component three-dimensional fluorescence overlapping spectra is always very difficult. In view of the advantage of differential spectra and based on the calculation principle of two-dimensional differential spectra, the three-dimensional fluorescence spectra with both excitation and emission spectra is fully utilized. Firstly, the excitation differential spectra and emission differential spectra are respectively computed after unfolding the three-dimensional fluorescence spectra.

Hydrothermal synthetic mercaptopropionic acid stabled CdTe quantum dots as fluorescent probes for detection of Ag⁺.

Mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs) with particle size 3 nm have been successfully synthesized in aqueous medium by hydrothermal synthesis method. And the effects of different metal ions on MPA capped CdTe QDs fluorescence were studied using fluorescence spectrometry. The results demonstrated that at the same concentration level, Ag(+) could strongly quench CdTe QDs fluorescence, and the other metal ions had little effect on CdTe QDs fluorescence except Cu(2+).

[Experimental studies on three-dimensional fluorescence spectral of mineral oil in ethanol].

Three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy was applied to characterize the mineral oil in ethanol. In the paper, a simple way of treating the first-order Rayleigh, Raman and second-order Rayleigh scatter is used involving subtracting an EEM of a solvent blank, and removing and replacing the values with zeros. The corrected results showed that the characteristic three-dimensional fluorescence spectra of mineral oil were as follows: there was one mainly peak in the fluorescence spectrum of the kerosene, and the peak was identified at excitation/emission wavelengths (Ex/Em) of 270/290 nm; there were two intense fluorescence peaks in the fluorescence spectrum of 0 # diesel, located at (Ex/Em) of 240/344 nm and 270/362 nm respectively; there were several fluorescence peaks in the fluorescence spectrum of lubricating oil, with the two intense peaks located at (Ex/Em) of 240/348 nm and 258/358 nm respectively.

[Excitation-emission fluorescence characterization study of the three phenolic compounds].

The fluorescence intensity information was collected by scanning its fluorescence spectra at different excitation wavelengths. Based on its high sensitivity and selectivity, excitation-emission fluorescence can be widely used for detection of pollutants in the environment. The characterizations of the three phenolic compounds were investigated by this method, and the fluorescence peaks of phenol, m-cresol and thymol were confirmed at 272/300 nm, 274/300 nm and 276/304 nm when the excitation and emission wavelength were set in the range of 240-360 nm and 260-500 nm respectively.

[Quantitative analysis of phenanthrene and humic acid in solution based on fluorescence method].

Polycyclic aromatic hydrocarbons as a universal concern in the monitoring of priority pollutants have low content in the water environment and are interfered with the coexistence of humic acid. The spectra of humic acid and polycyclic aromatic hydrocarbons overlap seriously, so it was difficult to use the conventional methods for rapid quantitative detection. As a model compound of polycyclic aromatic hydrocarbons, Phenanthrene (PHE) was chosen in the experiment.

[Study on three-dimensional fluorescence spectra of phenanthrene].

According to the high fluorescence quantum yields of polycyclic aromatic hydrocarbons (PAHs), the fluorescence spectra of phenanthrene were investigated by three dimensional fluorescence excitation-emission matrix (3DEEM). The results show that the three-dimensional fluorescence spectra of phenanthrene in aqueous solution mainly have two fluorescence peaks. On the basis of three-dimensional fluorescence spectrometry analysis of phenanthrene, the excitation wavelength of 255 nm and emission wavelength of 273 nm were chosen for the quantitative analysis of phenanthrene.