ABSTRACT
Abstract Ion mobility spectrometry ( IMS) based explosives detectors is wieldy deployed at the check points of airport, etc, so the development of new ionization method to replace the radioactive 63 Ni ion source in IMS is highly demanded. In this study, a novel negative corona discharge was developed for ion mobility spectrometer for rapid detection of trace explosives, which was running in the unidirectional mode to efficiently remove nitrogen oxides and ozone produced from the discharge process. The diameter of target electrode was 3 mm, the distance between the needle and the target electrode was 2 mm, the discharge voltage was 2400 V and the flow rate of drift gas was 1200 mL/min. Under the optimized conditions, the dominant reactant ions was O-2(H2O)n and could be used to directly detect the common explosives, such as trinitrotoluene (TNT), ammonium nitrate (AN), nitroglycerin (NG), pentaerythritol tetranitrate (PETN) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The limit of detection of TNT was 200 pg/μL. These results indicated that negative corona discharge ionization source, with the advantanges of the high sensibility, simple structure and no radioactivity, could be used as a potential and promising ionization source for ion mobility spectrometry to detect explosives.
ABSTRACT
A miniaturized atomic emission spectrometer composed of a corona discharge source and a handheld charge-coupled device detector was constructed for the sensitive determination of trace mercury, with photochemical vapor generation for sample introduction. By using formic acid, mercury vapor was generated under the irradiation of UV light, and then the vapor was introduced into the corona discharge area with the carrier gas flow of argon. The optical signals were captured and analyzed by the charge-coupled device detector at 253. 7 nm. Under the optimized conditions including 4% formic acid, discharge voltage of 90 V, and carrier gas flow rate of 200 mL/min, the stable detection signals were obtained ( RSD=2. 5%). The calibration curves were plotted with the concentration of mercury ranging from 0. 5 to 1000 ng/mL, with a correlation coefficient >0. 99 and the limit of detection of 0. 03 ng/mL. Two certified reference materials were analyzed, and a t-test demonstrated that the determined results by the proposed method had no significant difference with the certified values at the confidence level of 95%. Water samples collected from both Funan River in Chengdu and the Lotus Pond on campus of Sichuan University were analyzed as well, with the recoveries of standard addition between 93 . 8% and 103%. The miniaturized instrumentation demonstrated several advantages including easy construction, low power consumption, high sensitivity, and portability for field analysis.
ABSTRACT
Many air anion generators have been developed which can be divided into two ty pes including the one of ultrasonic water atomization and the one of corona disc harge.Being in a priority position of market,the latter has solid,simple structu re and is convenient to operate,which can generate high-consistency air anion.