Construction Of A Novel Solution Cathode Glow Discharge Spectroscopy And Its Application To Multi-Element Analysis

Heavy metal pollution in water caused by industrial sewage discharge is usually the source of heavy metal pollution in soil,crops and organisms.Meanwhile,heavy metal pollution in water has the characteristics of high mobility,easy migration and transformation,large polluted area and wide contamination.For a long time,water heavy metal pollution has been the focus of the national regulation.Water quality monitoring as a"beacon"of management work,which promotes water quality monitoring market rapid development,the growing demand for water quality monitoring equipment.Market analysis as the benefit of continuous fermentation,water quality monitoring market will be the first environmental monitoring equipment market segment.Therefore,with the deterioration of water pollution,it is urgent to establish a fast,sensitive,portable and high-flux metal ions analyzer to realize the real-time online analysis of heavy metal elements in field water.In this paper,on the basis of the portable metal ions analyzer based on solution cathode glow discharge atomic emission spectrometry（SCGD-AES）,which has been preliminaries set up,starting from the structure design of SCGD device,it is improved and optimized in different ways,so as to improve the stability and sensitivity of the instrument in the actual detection application.This paper mainly expounds the following research contents and results:（1）Modification of portable high-flux solution cathode glow discharge atomic emission spectrometry device:Replaced traditional quartz capillary with high temperature resistant alumina capillary to provide a steady and sustainable condition for the discharge of microplasma and reduce the frequency of replacing capillary.With the addition of the nested double quartz tube semi-closed system,the atmospheric N₂ background radiation could be greatly reduced or even eliminated,which not only creates a stable discharge space for microplasma,but also enhances the spectral signal-to-back ratio.When the discharge voltage,electrolyte velocity and electrode spacing were 1060 V,2.1 m L·min^-1 and 3.0 mm,respectively,the limits of detection of Zn,Cd,Ni,Ag,Cu and Pb in SCGD-AES system could be ameliorated to6,5,14,0.8,3,16μg·L^-1.（2）Multi-element simultaneous sensitization of solution cathode glow discharge atomic emission spectrometry by using portable semiconductor anode refrigeration:A portable semiconductor anode refrigeration-solution cathode glow discharge atomic emission spectrometry analysis system（SAR-SCGD-AES）was established to alleviate the red-heat effect of electrode and improve the stability of microplasma.On this basis,the increase of discharge voltage promoted the excitation of Zn,Cd,Ni,Cu,Cr and Pb elements,and realized the sensitization of multielement synchronous analysis of SCGD-AES.The limits of detection of these elements were ameliorated2-8 times,reaching 5,4,11,6,80,12μg·L^-1,respectively.The detection results of metal elements in reference material of stream sediment（GBW07312）,sewage from galvanization plant and seawater samples by this method were highly consistent with the reference values or the detection results of the inductively coupled plasma-optical emission spectroscopy（ICP-AES）.Furthermore,the addition of formic acid in electrolyte effectively improved the sensitivity of elements on the basis of semiconductor anode refrigeration,and the net intensities of the emission lines corresponding to these metal elements could be advanced by 150-750%.（3）On-line determination of Chromium in sewage by cathode glow discharge atomic emission spectrometry in hydrogen-helium atmosphere:A method for the determination of chromium content in samples by cathode glow discharge atomic emission spectrometry operated in hydrogen-helium mixed atmosphere was established.Hollow titanium tubes were used as miniaturized SCGD-AES metal anode instead of tungsten rod to introduce the discharge gas.It was verified that the excitation conditions of SCGD-AES could be improved by hydrogen-helium mixed atmosphere（H₂ content of 3%）.The experimental parameters such as gas flow rate,electrolyte type and flow rate,discharge voltage and spacing were optimized.The results showed that the limit of detection of chromium was improved from 650μg·L^-1（discharging in air）to 106μg·L^-1 with great repeatability(RSD=1.3%,10 mg·L^-1).The determination results of chromium in brown rice flour reference material（GBW（E）100619）and actual industrial sewage by this method consistent with those obtained by ICP-AES and the recoveries was 92.4-104.0%.