Search

A collinear dual-pulse laser induced breakdown spectroscopy (DP-LIBS) method was employed to analyze Chinese traditional medicine Artemisia annua. The spectral intensities and signal-to-background ratios of magnesium (II) 279.54 nm, CN 388.29 nm, calcium (II) 393.37 nm, and iron (II) 404.27 nm were used to evaluate the optical emission characteristics of A. annua induced by DP-LIBS. The temporal evolution characteristics, inter-pulse time, and laser energy values were optimized. In particular, the electron density and the temperatures of the plasma were reported as functions of the delay time. The results showed that the DP-LIBS had stronger intensity and better accuracy compared to single-pulse (SP) LIBS. The enhancement factors obtained using DP-LIBS for Mg, CN, Ca, and Fe were 7.2, 8.9, 13.8, and 3.4, respectively. This study provides important information about A. annua. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of laser wavelength on the detection of the metals in Artemisia annua, pulsed lasers operating at wavelengths of 1064 nm and 532 nm for laser induced breakdown spectroscopy (LIBS) have been employed to generate the plasma. The spectral lines of Mg (II) at 279.54 nm, CN at 388.29 nm, Ca (II) at 393.37 nm and Fe (II) at 404.27 nm were used to evaluate the optical emission at various delay times for the 532 nm and the 1064 nm laser. The effects of the data acquisition delay time on the line intensity, signal-to-background ratio and the characteristic parameters of laser plasma have been investigated as well. The results show that the 1064 nm beam induced plasmas with higher signal-to-background ratios and temperatures than the 532 nm beam. However, the 532 nm laser beam produced plasma with higher electron densities than the 1064 nm laser beam. In addition, a significant influence has been found: the spectral intensities of the ions were stronger than the spectral intensities of the atoms independent of whether the laser was operated at 532 nm or 1064 nm. [ABSTRACT FROM AUTHOR]

Chinese herbal medicine has attracted increasing attention because of the unique and significant efficacy in various diseases. In this paper, three types of Chinese herbal medicine, the roots of Angelica pubescens, Codonopsis pilosula, and Ligusticum wallichii with different places of origin or parts, are analyzed and identified using laser-induced breakdown spectroscopy (LIBS) combined with principal component analysis (PCA) and artificial neural network (ANN). The study of the roots of A. pubescens was performed. The score matrix is obtained by principal component analysis, and the backpropagation artificial neural network (BP-ANN) model is established to identify the origin of the medicine based on LIBS spectroscopy of the roots of A. pubescens with three places of origin. The results show that the average classification accuracy is 99.89%, which exhibits better prediction of classification than linear discriminant analysis or support vector machine learning methods. To verify the effectiveness of PCA combined with the BP-ANN model, this method is used to identify the origin of C. pilosula. Meanwhile, the root and stem of L. wallichii are analyzed by the same method to distinguish the medicinal materials accurately. The recognition rate of C. pilosula is 95.83%, and that of L. wallichii is 99.85%. The results present that LIBS combined with PCA and BP-ANN is a useful tool for identification of Chinese herbal medicine and is expected to achieve automatic real-time, fast, and powerful measurements. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy was used for the analysis of the Chinese traditional medicine,Ligusticum wallichii. The laser energy and delay time were optimized to obtain best spectral quality. The limits of detection for lead and copper were 15.7 and 6.3 µg g−1, respectively. Multiple linear regression models between the laser-induced breakdown spectroscopy intensity and the mass fraction of lead and copper were constructed. Good agreement was observed between the actual concentrations and predicted values obtained by the models. These results demonstrate that the laser-induced breakdown spectroscopy coupled with multiple linear regression is suitable for the determination of heavy metals in Chinese traditional medicine. [ABSTRACT FROM PUBLISHER]

The direct determination of analytes in aqueous solution using laser-induced breakdown spectroscopy (LIBS) has several difficulties, including low spectral signal, poor stability, and rapid quenching of the plasma. In this study, chelate resin and anion exchange resin were used to adsorb the chromium ions Cr(III) and Cr(VI) from the liquid onto a solid substrate, thus avoiding the drawbacks of liquid analysis with LIBS. Cr(III) and Cr(VI) were separated by selective adsorption on these two distinct resins. The following analytical parameters were optimized: flow rate of sample solution for preconcentration on the resins, laser pulse energy, and integral delay time of the ICCD detector. Calibration curves displayed excellent linearity, with correlation coefficients of 0.994 for Cr(III) and 0.993 for Cr(VI). The analytical limits of detection (LODs) were 0.088 mg L−1 for Cr(III) and 0.27 mg L−1 for Cr(VI), and were lower than those in most previous studies. The relative uncertainty of Cr(III) in single and mixed solutions ranged from 2.50% to 4.25% and 4.75% to 14.0%, respectively, and that of Cr(VI) ranged from 2.88% to 7.67% and 11.5% to 13.9%, respectively. Recovery from natural spring water was 92.50–99.86% for Cr(III) and 97.70–98.75% for Cr(VI). Recovery from sewage wastewater using this method was 99.80% for Cr(III) and 107.6% for Cr(VI). These results show that this method can be successfully applied to the determination and separation of chromium ions in aqueous solution. [ABSTRACT FROM AUTHOR]

Ferrous iron (Fe(II)) is essential to organisms, but ferric iron (Fe(III)) is toxic. Monitoring Fe(II) and Fe(III) in solution can improve our understanding of Fe biogeochemistry and toxicity. However, it is difficult to rapidly determine Fe in different valence states in solution using traditional methods. A novel method, laser-induced breakdown spectroscopy coupled with chelating resin selective enrichment by adjusting the solution pH, for determining Fe(II) and Fe(III) in solution is presented here. The sample solution flow rate and solution pHs were optimized to obtain a better enrichment effect. The calibration curve for Fe(II) and Fe(III) were established and the limits of detection were 0.120 mg L−1 and 0.142 mg L−1, respectively. Single valence state Fe in an Fe(II) and Fe(III) mixed solution was separated based on the enrichment abilities of Fe(II) and Fe(III) at different pH values of the chelating resin, and the separation relative error ranges were 0.25%–1.12% and 3.05%–7.24%, respectively. The recoveries of Fe(II) and Fe(III) in real spring water were 100.62% and 99.11%, respectively. The results indicated that the method of LIBS coupled with chelating resin selective enrichment can rapidly and accurately quantify Fe in different valence states in aqueous solution. [ABSTRACT FROM AUTHOR]

The trace mercury in an aqueous solution was determined by laser-induced breakdown spectroscopy (LIBS) with the assistance of a solution cathode glow discharge (SCGD) system. The aqueous solution was converted to the gas phase using a high voltage DC discharge, and then the generated mercury vapor was cooled by a gas–liquid separator to improve the concentration of the mercury. Finally, a 1064 nm wavelength Nd:YAG laser was used to produce the plasma. In the present experiment, the characteristic spectral line of Hg i 253.65 nm was selected for the analysis, under the optimal conditions of LIBS, to investigate the influences of the acid anion, the discharge current, the sample flow rate and the carrier gas flow rate. The temporal behavior of the electron temperature and electron number density were also investigated; the results show that the electron temperature decreases from about 10 900 K to 8800 K with a delay time from 200 ns to 6 μs and that the electron number density is in the orders of 1017 and 1018 cm−3, and decreases with delay time. The analytical performance of this method was evaluated under optimized conditions, and a calibration curve of Hg was plotted based on the different concentrations measurement results, and the detection limit (LOD) of Hg was calculated to be 0.36 mg L−1. By this experimental configuration, the detection limit and sensitivity of Hg are improved to some extent. This method provides an alternative analytical method for the measurement of trace mercury in water. [ABSTRACT FROM AUTHOR]