title: Use of radiation sources with mercury isotopes for real-time highly sensitive and selective benzene determination in air and natural gas by differential absorption spectrometry with the direct Zeeman effect.
abstract: A new analytical portable system is proposed for the direct determination of benzene vapor in the ambient air and natural gas, using differential absorption spectrometry with the direct Zeeman effect and innovative radiation sources: capillary mercury lamps with different isotopic compositions ((196)Hg, (198)Hg, (202)Hg, (204)Hg, and natural isotopic mixture). Resonance emission of mercury at a wavelength of 254 nm is used as probing radiation. The differential cross section of benzene absorption in dependence on wavelength is determined by scanning of magnetic field. It is found that the sensitivity of benzene detection is enhanced three times using lamp with the mercury isotope (204)Hg in comparison with lamp, filled with the natural isotopic mixture. It is experimentally demonstrated that, when benzene content is measured at the Occupational Exposure Limit (3.2 mg/m(3) for benzene) level, the interference from SO2, NO2, O3, H2S and toluene can be neglected if concentration of these gases does not exceed corresponding Occupational Exposure Limits. To exclude the mercury effect, filters that absorb mercury and let benzene pass in the gas duct are proposed. Basing on the results of our study, a portable spectrometer is designed with a multipath cell of 960 cm total path length and detection limit 0.5 mg/m(3) at 1 s averaging and 0.1 mg/m(3) at 30 s averaging. The applications of the designed spectrometer to measuring the benzene concentration in the atmospheric air from a moving vehicle and in natural gas are exemplified.
authors: Institute of Technical Physics, Riga Technical University, P.Valdena 3, Riga LV 1050, Latvia. Electronic address: gitar@latnet.lv.
authors: Gita
authors: G
authors: Revalde
authors: St. Petersburg State University, Universitetskaya nab., 7/9, St. Petersburg 199034, Russia.
authors: Sergey
authors: S
authors: Sholupov
authors: St. Petersburg State University, Universitetskaya nab., 7/9, St. Petersburg 199034, Russia.
authors: Alexander
authors: A
authors: Ganeev
authors: St. Petersburg State University, Universitetskaya nab., 7/9, St. Petersburg 199034, Russia.
authors: Sergey
authors: S
authors: Pogarev
authors: St. Petersburg State University, Universitetskaya nab., 7/9, St. Petersburg 199034, Russia.
authors: Vladimir
authors: V
authors: Ryzhov
authors: Institute of Atomic Physics and Spectroscopy, University of Latvia, Skunu 4, Riga, Latvia.
authors: Atis
authors: A
authors: Skudra
mesh_terms: D065638:Absorption, Radiation; D000393:Air Pollutants / Q000032:analysis*; D001554:Benzene / Q000032:analysis*; D004784:Environmental Monitoring / Q000295:instrumentation*; D004867:Equipment Design; D057230:Limit of Detection; D008629:Mercury Isotopes / Q000032:analysis; D059206:Natural Gas / Q000032:analysis*; D013054:Spectrophotometry, Atomic / Q000295:instrumentation*
chemical_list: D000393:Air Pollutants; D008629:Mercury Isotopes; D059206:Natural Gas; D001554:Benzene
keywords: Ambient air analysis; Benzene determination; Isotope light sources; Mercury determination; Natural gas analysis; Zeeman-effect spectrometry