A novel method for measuring the concentration of chloroform based on kinetic parameters at atmosphere

Negative Atmospheric Pressure Chemical Ionization of Chlorinated Hydrocarbons Studied by Ion Mobility Spectrometry (IMS) and IMS-MS Techniques

Negative polarity atmospheric pressure chemical ionization of selected chlorinated hydrocarbons (tetrachloromethane CCl₄ and hexachloroethane C₂Cl₆, dichloromethane CH₂Cl₂, trichloromethane CHCl₃, 1,1,1,2-tetrachloroethane 1,1,1,2-C₂H₂Cl₄, 1,1,2,2-tetrachloroethane 1,1,2,2,-C₂H₂Cl₄ 1,1,2-trichloroethane 1,1,2-C₂H₃Cl₃, and 1,1,2-trichloroethane 1,1,2-C₂HCl₃) was studied using ion mobility spectrometry (IMS) and IMS combined with time-of-flight mass spectrometer (IMS-TOF MS) techniques, in the dry air and at two different drift gas temperatures (323 and 373 K). The ionization was performed using the O₂^-CO₂(H₂O)_0,1 reactant ions (RIs), and the dominant ionization reaction was the dissociative electron transfer. The ionization resulted in the appearance of Cl^- ions for all substances and [O₂H..Cl]^- ions, which were absent in the case of perchlorinated substances. The quantum-chemical calculations at the density functional theory level of theory using the ωB97X-D/aug-cc-pVTZ method were performed to calculate the thermochemical data (heats of formations, electron affinities, reaction enthalpies) for RIs, neutral substances, neutral fragments, and the anionic fragments. The calculations supported the experimental observations regarding the endothermicity of the Cl^- channel for all substances and the exothermicity of the [O₂H..Cl]^- channel for the tetrachloro- and trichloroethanes.

Compact photoacoustic spectrophone for simultaneously monitoring the concentrations of dichloromethane and trichloromethane with a single acoustic resonator

Chlorinated hydrocarbons are frequently used as reagents and organic solvents in different industrial processes. Real-time detection of chlorinated hydrocarbons, as toxic air pollutants and carcinogenic species, is an important requirement for various environmental and industrial applications. In this study, a compact photoacoustic (PA) spectrophone based on a single acoustic resonator for simultaneous detection of trichloromethane (CHCl₃) and dichloromethane (CH₂Cl₂) is first reported by employing a low-cost distributed feedback (DFB) laser emitting at 1684 nm. In consideration of the significant overlapping of absorption spectral from trichloromethane and dichloromethane, the multi-linear regression method was used to calculate the concentrations of CHCl₃ and CH₂Cl₂ with special characterization of the absorption profile. The current modulation amplitude and detection phase in the developed PA spectrophone was optimized for high sensitivity of individual components. The measurement interference of CHCl₃ and CH₂Cl₂ on each other was investigated for accurate detection, respectively. For field measurements, all optical elements were integrated into a 40 cm × 40 cm × 20 cm chassis. This paper provides an experimental verification which strongly recommends this sensor as a compact photoacoustic field sensor system for chlorinated hydrocarbon detection in different applications.