[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. The model is used to analyze the scattering light of Escherichia coli in the region of 400~900 nm. The average size of external structure and the internal structure can be obtained, and the ratio of the two parts is also obtained. According to the relationship of the optical density of single cell and the overall measurement, the concentration of bacterial can be obtained quickly. The maximum difference in all the concentrations of the bacteria repeated measurements is 1.83%; compared with the plate culture method, the measurement results were in the same order of magnitude, with relative error of 3.43%. The scattering light of Escherichia coli and Klebsiella pneumoniae are analyzed in different growth stages, the curves of the concentration and the size of the two species bacteria over time are obtained. The results can provide a quick way for the study of bacterial growth and technical support for rapid detection of bacteria in the water.

[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. The characteristic of excitation-emission three-dimensional spectra of carbaryl is studied. By changing the concentration of methanol in methanol-water binary solvent, the impact of methanol-water mixture on three-dimensional fluorescence spectra of carbaryl is discussed. The results show that the characteristic excitation-emission spectra of carbaryl is single peak, the range of the excitation wavelength and emission wavelength are: 244~304 and 300~350 nm respectively, the maximum excitation/emission peak located at 280 and 335 nm. With increasing the content of methanol in methanol-water binary solvent mixture, there is no obviously spectra shift of three dimensional fluorescence spectra of carbaryl. However, the intensity of fluorescence is nonlinear dependent on the content of methanol, mainly due to the specific properties of binary mixed solvent.

[Study of Rapid Species Identification of Bacteria in Water].

Multi-wavelength ultraviolet visible (UV-Vis) transmission spectra of bacteria combined the forward scattering and absorption properties of microbes, contains substantial information on size, shape, and the other chemical, physiological character of bacterial cells, has the bacterial species specificity, which can be applied to rapid species identification of bacterial microbes. Four different kinds of bacteria including Escherichia coli, Staphylococcus aureus, Salmonella typhimurium and Klebsiella pneumonia which were commonly existed in water were researched in this paper. Their multi-wavelength UV-Vis transmission spectra were measured and analyzed. The rapid identification method and model of bacteria were built which were based on support vector machine (SVM) and multi-wavelength UV-Vis transmission spectra of the bacteria. Using the internal cross validation based on grid search method of the training set for obtaining the best penalty factor C and the kernel parameter g, which the model needed. Established the bacteria fast identification model according to the optimal parameters and one-against-one classification method included in LibSVM. Using different experimental bacteria strains of transmission spectra as a test set of classification accuracy verification of the model, the analysis results showed that the bacterial rapid identification model built in this paper can identification the four kinds bacterial which chosen in this paper as the accuracy was 100%, and the model also can identified different subspecies of E. coli test set as the accuracy was 100%, proved the model had a good stability in identification bacterial species. In this paper, the research results of this study not only can provide a method for rapid identification and early warning of bacterial microbial in drinking water sources, but also can be used as the microbes identified in biomedical a simple, rapid and accurate means.

[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 > 0.95). Consequently, EC10 (10% effective concentration) after 48 h and 53 h inhibition in photosynthetic activity inhibition tests could be used to represented EC50 (50% effective concentration) in 96 h algal growth inhibition tests for evaluating the Cd2+ toxicity. Dose-response relationships between the algal photosynthetic activity inhibition rates after 48 h and 53 h inhibition and Cd2+ toxic equivalency quantity were further analyzed. The method provided a rapid and viable new thought to monitoring single Cd2+ toxicity in lab and early warn integrated toxicity of pollution in water.

[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, 0.8786 and 0.7953. This work provides a rapid and in-situ measurement method for phytoplankton photosynthesis activity.

[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. For one kind of heavy metals, synchronous scan fluorometry is a sensitive method for its toxicity assessment. Compared to 3DEEM fluorescence spectroscopy, synchronous scan fluorescence spectroscopy is less time consuming and of higher selectivity. It is suitable to assess the toxicity of pollutions in water.

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+). On the basis of this fact, a rapid, simple, highly sensitive and selective method based on fluorescence quenching principle for Ag(+) detection in aqueous solution was proposed. Under optimal conditions, the quenched fluorescence intensity (F(0)-F) increased linearly with the concentration of Ag(+) ranging from 4 × 10(-7) to 32 × 10(-7)mol L(-1). The limit of detection for Ag(+) was 4.106 × 10(-8)mol L(-1). The obtained plot of F(0)/F versus [Ag(+)] was an upward curvature, concave towards the y-axis, rather than a straight line. The modified form of the Stern-Volmer equation was third order in Ag(+) concentration. According to the modified Stern-Volmer equation, it can be inferred that dynamic quenching and static quenching simultaneously occurred when Ag(+) interacted with MPA capped CdTe QDs. At the same time other factors might also influence the quenching process. Based on this study, hydrothermal synthesized MPA capped CdTe QDs with particle size 3 nm may be used as a novel fluorescence probe to quantificationally and selectively detect Ag(+).