ABSTRACT
·OH plays a crucial role in many fields, having aroused wide public concern in the world. Atmospheric Pressure Plasma Jet, which can be achieved by portable device due to working without the vacuum environment, has the advantages of high concentration of reactive species, high electron temperature and low gas temperature. It has become an important research topic in the field of gas discharge with a strong prospect. Especially, how to induce plasma jet to produce ·OH has become a new hotpot in the field of low-temperature plasma. It has been reported that mass ·OH can be induced successfully when water vapor is added to the working gas, but it will be unstable when the concentrate of water reaches a certain degree. Thus, a device of argon plasma jet with a Ring-to-Ring Electrode Configuration has been designed to interact with water in the surrounding air to generate ·OH under atmospheric pressure. In order to increase the production of ·OH, ultrasonic atomizing device is introduced to promote water concentration around the plasma plume. The generating rule of OH(A2J) induced by water has been extensively studied under different voltages and flow rate. ·OH output induced by the plasma has been tested by emission spectrometry, and at the meanwhile, Ar atomic spectral lines at 810.41 and 811.48 nm are also recorded in order to calculate the electron temperature in argon plasma plume. The results show that the water surrounding the plasma plume can be induced to produce ·OH, and OH(A2 ∑+) output increases with the electrode voltage rising from 20 to 28 kV. When the flow rate increases from 100 to 200 L x h(-1), the OH(A2∑+) output increases, but from 200 to 600 L x h(-1), it decreases. The production rules of OH(A2∑+) is the same as that of electron temperature. Therefore, the presumption is proved that ·OH output mainly affected by electron temperature.
ABSTRACT
A device based on electrolyte cathode atmospheric glow discharge atomic emission spectroscopy (ELCAD-AES) has been developed to determine the metal ion Pb in water. The emission intensity of Ph was significantly enhanced with the increase concentration of Pb, and the emission intensity has a linear relationship with concentration while the concentration of Pb in the range of 10-80 mg x L(-1). The effects of discharge current and easily ionizable elements on the emission spectral of Pb were investigated, and the emission intensity reached greatest when the discharge current increased to 70 mA, and the easily ionizable elements generated weak effect on the emission spectral of Pb. The effect of acidification regent on emission spectral of Pb was discussed. It was found that it perform best when acidified with HNO3, and reducing the pH can improve the emission intensity of Pb effectively. The emission intensity of Pb at different region was detected near cathode region, thus obtained the best detection position. Under the optimized experimental parameters, the detection limit of Ph was 0.7 mg x L(-1) and relative standard deviation was 1.7%. The recovery of samples was 95%-106%, result and shows that this method has better accuracy. These results provide an available method for further research of detection trace heavy mental elements in water using ELCAD-AES.
ABSTRACT
Toxic metal elements in waters and wastewaters contaminate the environment and greatly threaten the health of human beings, therefore developing a rapid monitor for metal residues in aqueous solutions is urgently required. In the present work, a new homemade apparatus of electrolyte cathode atmospheric glow discharge emission spectroscopy was developed and described. It can detect and discriminate many kinds of trace mental elements by atomic emission spectrum from atmospheric pressure liquid cathode glow discharge. In order to estimate the analytical performance of the present atmospheric pressure electrolyte cathode glow discharge emission spectroscopy system, the detection limit values for Na, Li, Cu, Pb and Mn were obtained based on 3sigma of the background signal, and the current limits of detection were 0.008, 0.005, 1.1, 2.06 and 1.95 mg L(-1), respectively. It demonstrates that the atmospheric pressure electrolyte cathode glow discharge emission spectroscopy has a promising application in real time measurements of metal residues in aqueous solutions.
Subject(s)
Electrolytes , Metals/analysis , Water Pollutants, Chemical/analysis , Atmospheric Pressure , Electrodes , Heavy Metal Poisoning , Ions , Limit of Detection , Poisoning , Spectrum Analysis , WaterABSTRACT
In the present work, a simply designed and easy made micrometer plasma jet device operating under atmospheric pressure was characterized. The microplasma jet operates in many kinds of working gas at atmospheric pressure, such as Ar, He, N2 etc, and is powered by a direct current power source. It can generate high current density glow discharge. In order to identify various excited species generated by the direct current microplasma jet device, the optical emission spectra of the jet with argon or nitrogen as working gas were studied. Based on the optical emission spectroscopy analysis of argon microplasma jet, the electron excitation temperature was determined to be about 3 000 K by the intensity ratio of two spectral lines. It is much lower than the electron excitation temperature of atmospheric pressure plasma torch, and hints that the atmospheric pressure direct current microplasma jet is cold compared with the atmospheric pressure plasma torch. The emission spectra of the N2 second positive band system were used to determine the vibrational temperature of the atmospheric pressure direct current microplasma jet. The experimental result shows that the molecular vibrational temperature of N2 is about 2 500 K. The electron density of the microplasma jet is about 10(13) cm(-3), which can be estimated from the electrical parameters of the discharge in the microplasma jet. A simple example of application of the microplasma jet is given. General print paper surface was modified with the microplasma jet and afterwards a droplet test was carried out. It was shown that the microplasma jet is more efficient in changing the hydrophilicity of general print paper.
ABSTRACT
Microhollow cathode discharge or microdischarge is an efficient method to generate plasma in a high pressure gas. In the present work, the emission spectra were observed in an atmospheric pressure argon direct current microdischarge apparatus, using a stainless steel capillary as the cathode, and a stainless steel mesh as the anode. It was shown that all of the seventeen argon spectral lines arose from electronically excited argon atom 4p-4s transition in the wavelength range of 690-860 nm. The dependences of emission intensity on the discharge current, gas pressure and argon flow rate were investigated. The experimental results show that the emission intensity increased with discharge current from 1 to 6 mA and argon flow rate from 100 to 700 mL x min(-1). The dependence of emission intensity on gas pressure exhibited different characteristics, i.e., spectral signal increased with the gas pressure, but reached the intensity maximum at 13.3 kPa, and decreased afterwards. The argon atom spectral lines 763.51 and 772.42 nm were chosen to measure the electron excitation temperature by the intensity ratio of two spectral lines. The electron excitation temperature was determined to be in the range of 2000 to 2800 K in the atmospheric pressure argon microdischarge. The changes in electron excitation temperature with discharge current, gas pressure and argon flow rate were explored, indicating that the electron excited temperature increased with the discharge current, but decreased when gas flow rate or argon pressure increased.
ABSTRACT
Ion mobility spectrometry (IMS) is a very fast, highly sensitive, and inexpensive technique, it permits efficient monitoring of volatile organic compounds like alcohols. In this article, positive ion mobility spectra for six alcohol organic compounds have been systematically studied for the first time using a high-resolution IMS apparatus equipped with a discharge ionization source. Utilizing protonated water cluster ions (H2O)n H+ as the reactant ions and clean air as the drift gas, alcohol organic compounds, ethanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol and 2-octanol, all exhibit product ion characteristic peaks in their respective ion mobility spectrometry, that is a result of proton transfer reactions between the alcohols and reaction ions (H2O)n H+. The mixture of these alcohols, including two isomers, has been detected, and the results showed that they could be distinguished effectively in the ion mobility spectrum. The reduced mobility values have been determined, which are in very well agreement with the traditional 63Ni-IMS experimental values. The exponential dilution method was used to calibrate the alcohol concentrations, and a detection limit available for the alcohols is in order of magnitude of a few ng/L.
