Detection of heavy metals in water samples by laser-induced breakdown spectroscopy combined with annular groove graphite flakes

The use of laser-induced breakdown spectroscopy(LIBS) for the analysis of heavy metals in water samples is investigated. Some factors such as splashing, surface ripples, extinction of emitted intensity, and a shorter plasma lifetime will influence the results if the water sample is directly measured. In order to avoid these disadvantages and the ‘coffee-ring effect', hydrophilic graphite flakes with annular grooves were used for the first time to enrich and concentrate heavy metals in water samples before being analyzed by LIBS. The proposed method and procedure have been evaluated to concentrate and analyze cadmium, chromium, copper, nickel, lead,and zinc in a water sample. The correlation coefficients were all above 0.99. The detection limits of 0.029, 0.087, 0.012, 0.083, 0.125, and 0.049 mgl^(-1) for Cd, Cr, Cu, Ni, Pb, and Zn,respectively, were obtained in samples prepared in a laboratory. With this structure, the heavy metals homogeneously distribute in the annular groove and the relative standard deviations are all below 6%. This method is very convenient and suitable for online in situ analysis of heavy metals.

Online calibration of laser-induced breakdown spectroscopy for detection of heavy metals in water

In order to reduce the fluctuation of LIBS detection spectrum of liquid sample,the full-spectrum sum method and the internal standardization method is adopted,using an equal-RSD normalization algorithm to calibrate the detection spectrum.Experiment result shows that the full-spectrum sum method reduced the RSD of parallel samples of Cd and Cr to 9.4% and 11.06% from 28.32% and 31.93% respectively,yielded better overall calibration than the singleelement internal standardization approach,thereby suggesting that the former method is convenient and effective for online calibration of LIBS for detection of aqueous heavy metals.

Studies on Extracting Microcystin-Lr from Microcystis Aeruginosa by Water Bath

Different temperatures of water bath was used to extract the intracellular microcystin-LR(MC-LR) of Microcystis aeruginosa. Researching the extraction efficiency under the suitable temperature, so that it could find out the best temperature and time for extracting MC-LR from Microcystis aeruginosa cells. Five equal Microcystis aeruginosa was used to find out the best temperature, extracting at 60℃, 70℃, 80℃, 90℃ and 100℃ for 15 minutes, respectively. Results showed that the content of MC-LR extracted with the water under 100℃ was the highest. But meanwhile, the type and the content of impurities was the highest, too. In addition, another six equal Microcystis aeruginosa was extract with the water under 100℃ for 5min, 10 min, 15 min, 20 min, 25 min and 30 min respectively. It was proved that 20 minutes was enough for extracting MC-LR from Microcystis aeruginosa, no long time was needed.

Spectral characteristic of laser-induced plasma in soil

The spectral characteristic of laser-induced plasma in soil was studied in this work,laser-induced breakdown spectroscopy was used to analyze the spectral characteristic of plasma under the condition of different time delays and irradianccs.Moreover,the time evolution characteristics of plasma temperature and electron density were discussed.Within the time delay range of 0-5μs,the spectral intensity of the characteristic lines of Si I:288.158 nm,Ti I:336.126 nm.Al I:394.400 nm and Fe I:438.354 nm of the four main elements in two kinds of national standard soil decayed exponentially with time.The average lifetime of the spectral lines was nearly 1.56μs.Under the condition of different time delays,the spectral intensity of Pb I:405.78 nm in soil increased linearly with laser energy.However,the slope between the spectral intensity and laser energy decreased exponentially with the increase in time delay,from 4.91 to 0.99 during 0-5μs.The plasma temperature was calculated by the Boltzmann plot method and the electron density was obtained by inversion of the full width at half maximum of the spectrum.The plasma temperature decreased from 8900 K to 7800 K and the electron density decreased from 1.5 x 1Ol7cm-3 to 7.8 x lO16cm-3 in the range of 0-5μs.

Characteristics of optical emission during laser-induced damage events of fused silica

Spontaneous optical emission properties of laser-produced plasma during laser damage events at input and exit surfaces of fused silica were retrieved and compared.We show that plasma at the input surface is much larger in size and exhibits significantly higher electron number density and excitation temperature,even when smaller laser energy was used.This effect was attributed to the stronger laser–plasma coupling at the input surface.In addition,a strong continuum background containing three peaks at 1.3eV,1.9eV,and 2.2eV was observed at the exit surface,and possible origins for this effect are also discussed.