DOI: 10.3964/j.issn.1000-0593(2017)02-0588-06

Authors
Fang, L. ; Gu, Y. H. ; Jia, Y. ; Liu, J. G. ; Liu, W. Q. ; Ma, M. J. ; Meng, D. S. ; Wang, Y. Y. ; Zhao, N. J.

Keywords

Laser-induced breakdown spectroscopy; Orthogonal dual-pulse; Spectral enhancement; Signal-to-background ratio; Plasma temperature; Electron density;OPTICAL-EMISSION; ENHANCEMENT

Abstract

In order to improve the detection sensitivity and spectral characteristic of laser-induced breakdown spectroscopy (LIES), re-heating orthogonal dual-pulse configuration is adopted to analyze Fe, Pb, Ca and Mg contained in the sample and soil sample contained different concentrations of heavy mental Cr. Variation relationship between spectral intensity, signal-to-background(SBR) of four characteristic spectral lines Fe I : 404. 581 nm, Pb I : 405. 78 nm, Ca I 422. 67 rim and Mg I : 518. 361 nm and time interval of two laser pulses is discussed, the best time interval of two laser pulses is obtained 1. 0 s. In the condition of single pulse and dual-pulse, the enhancement factor of spectral intensity of four characteristic spectral lines Fe I : 404. 581 nm, Pb I : 405. 78 nm, Ca I : 422. 67 nm and Mg I : 518. 361 nm is respectively 2. 23, 2. 31, 2. 42 and 2. 10; The time evolution characteristic of spectral intensity of characteristic spectral lines Fe I : 404. 581 nm and Ca I : 422. 67 rim is considered, and also the variation relationship between spectral acquisition delay time and SBR of-four characteristic spectral lines, dual-pulse can prolong decay time of spectral intensity and improve the SBR of characteristic spectral lines; time evolution characteristic of plasma temperature and electron density is compared in the condition of single pulse and dual-pulse, maximum elevation of plasma temperature is found to be 730 K, and the maximum increase of electron density is 1. 8 X 10(16) cm(-3). The limits of detection of heavy mental Cr are obtained 38 and 20 mu g center dot g(-1) respectively in condition of single and double pulse, limit of detection of Cr is reduced approximately 2 times by the condition of re-heating orthogonal dual pulse. Results above indicate that reheating orthogonal dual-pulse can improve detection sensibility and spectral characteristic of LIBS technique, which provides an effective method for decreasing the limit of detection of elements.

DOI: 10.3964/j.issn.1000-0593(2017)05-1525-05

Authors
Gu, Y. H. ; Jia, Y. ; Liu, J. G. ; Liu, W. Q. ; Ma, M. J. ; Meng, D. S. ; Yu, Y. ; Zhao, N. J.

Keywords

LIES; Spatial confinement; Enrichment of graphite; Heavy metal in water;INDUCED BREAKDOWN SPECTROSCOPY; CHROMIUM; CHINA

Abstract

According to the need of heavy metal pollution detection in waste water. Pure graphite flake is selected as matrix material, the LIBS method of multiple enrichment of samples combined with spatial confinement is adopted to detect the heavy metals contained in the waste water, and spectral stability and limit of detection of Pb, Cu, Cd and Ni are also analyzed. The experiments uses a wavelength of 1 064 nm Nd : YAG Laser, and a optical spectrometer, which the resolution is less than 0. 1 nm to detect the characteristic spectrum of heavy metal elements content in water. The result shows that this method serves to improve sensitivity and spectral stability of heavy metal in waste water while reducing the limit of detection of heavy metals. The intensity of characteristic spectrum are about 2. 5 times better than it under the condition of non-confinement, the spectral stability has also been improved, RSD is reduced from 11.34% to 8.77% compared with non-confinement condition. The calibration curves of four heavy metal elements have been established, the limits of detection of Pb, Cu, Cd and Ni are lower than 1/6 of discharge standard of national industrial waste water, meeting the demand of heavy metal in industrial waste water online monitoring. This method provides a convincing support for discharge control and online monitoring of warning excessive discharge of heavy metal elements in industrial waste water.

DOI: 10.3964/j.issn.1000-0593(2017)03-0884-05

Authors
Fang, L. ; Gu, Y. H. ; Jia, Y. ; Liu, J. G. ; Liu, W. Q. ; Ma, M. J. ; Meng, D. S. ; Yu, Y. ; Zhao, N. J.

Keywords

Laser-induced breakdown spectroscopy(LIBS); Electrode enrichment; Limit of detection; Heavy metal in water;INDUCED BREAKDOWN SPECTROSCOPY

Abstract

In order to improve the detection sensitivity of laser-induced breakdown spectroscopy (LIES) and lower the limit of the detection of elements, LIBS combined with Aluminum electrode enrichment method is adopted to analyze heavy metals such as Pb, Cdand Ni in the water. The relationship between the characteristic spectral intensity and the key parameters-voltage of electrode method is discussed, the spectral intensity increases first and then decreases with the increase of voltage. The spectral intensity reaches-the maximum value when the enrichment voltage is 1.2 V while the optimal enrichment voltage value is 1.2 V. The stability of characteristic spectral lines of heavy metals is studied, and the relative standard deviation(RSD) of spectral intensity of Pb, Cd and Ni is 5.98%, 4.25 % and 5.27% respectively, the result shows that the spectral line obtained by this method has high stability. A series of samples in the range of 0 similar to 0.13mg.L-1 are prepared and quantitatively analyzed, the limit of detection of Pb, Cd and Ni is obtained 1.2, 3.1 and 1.7 ppb respectively. The above result shows that LTBS combined with aluminum electrode enrichment method can effectively improve the stability of characteristic spectral lines and lower the limit of detection of Pb,Cd and Ni. This research also provides a method to further improve detection sensitivity of LIES and analysis ability of heavy metal in the water.