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Investigation on the compositions of unsymmetrical dimethylhydrazine treatment with different oxidants using solid-phase micro-extraction-gas chromatography-mass spectrometer.

ABSTRACT: The majority of unsymmetrical dimethylhydrazine (UDMH) treatments produce lots of toxic by-products, among which N-Nitrosodimethylamine (NDMA) is a strong carcinogen. The compositions of the by-products are important for evaluating the treatment efficiency and understanding the UDMH degradation mechanism to achieve UDMH mineralization. The intermediate and end products of UDMH treatment with different oxidants were investigated by using a simple and fast method, solid-phase micro-extraction (SPME) in combination with gas chromatography-mass spectrometry (GC-MS). The effects of several parameters (coating fibre, salt addition, pH, sampling time and desorption time) were studied to optimize analyte recovery. The best response can be attained by the 65 µm PDMS/DVB fibre at pH 7 during 10 min after desorption of 1 min in the GC inlet. The intermediate and final oxidative products of UDMH wastewater treatment with different oxidants (O₃, Mn²⁺/O₃, Fe²⁺/H₂O₂) were investigated. The results showed that the UDMH treatment with O₃ could lead to high yields of NDMA. Metal catalytic ozonation could largely minimize the formation of NDMA. No NDMA was observed in the final decontaminated samples after treatment with Fe²⁺/H₂O₂. The NDMA formation and degradation mechanism were discussed based on the intermediates. This study is expected to provide useful information for controlling NDMA formation during UDMH wastewater treatment.

SUBMITTER: Huang D

PROVIDER: S-EPMC6549943 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Simultaneous Quantification of Opioids in Blood and Urine by Gas Chromatography-Mass Spectrometer with Modified Dispersive Solid-Phase Extraction Technique.

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| S-EPMC5047463 | biostudies-literature

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| S-EPMC9077832 | biostudies-literature

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| S-EPMC7023010 | biostudies-literature

Carboxylated Multiwalled Carbon Nanotubes as Dispersive Solid-Phase Extraction Sorbent to Determine Eighteen Polychlorinated Biphenyls in Vegetable Samples by Gas Chromatography-Mass Spectrometry.

Project description:A simple, rapid, and reliable method based on dispersive solid-phase extraction (d-SPE) and gas chromatography-mass spectrometry (GC-MS) was developed for quantitating polychlorinated biphenyls (PCBs) in vegetable samples. Parameters affecting both the extraction yields and cleanup efficiency, including the type and volume of extraction solvent, extraction time, type and volume of cleanup sorbent, and cleanup time, were optimized. Matrix effects were evaluated, and matrix-matched calibration was recommended. Under the optimized conditions, carboxylated multiwalled carbon nanotubes (MWCNTs-COOH), which exhibit excellent adsorption capabilities due to large surface area and unique structure, were employed as d-SPE sorbent to remove interfering substances, rather than the analytes, from vegetable samples. Satisfactory linear relationship was observed for all PCBs across a concentration range of 5-500??g/kg with correlation coefficients no less than 0.9993. Four representative vegetables (cucumber, tomato, lettuce, and cabbage) were selected as matrices for method validation. Each matrix was spiked at concentrations of 5, 10, and 100??g/kg to evaluate recoveries, which ranged from 84.5% to 116.5% with relative standard deviations (n=6) between 0.6% and 17.6%. The limits of detection and the limits of quantification ranged from 0.3 to 1.4??g/kg and 0.8 to 4.5??g/kg, respectively. Twelve real vegetable samples were analyzed using the proposed method. Three of the target PCBs were detected in one lettuce sample with the total concentration of 17.9??g/kg.

| S-EPMC6720675 | biostudies-literature

Binary Eluent Based Vortex-Assisted Matrix Solid-Phase Dispersion for the Extraction and Determination of Multicomponent from Musk by Gas Chromatography-Mass Spectrometry.

Project description:A green, flexible, and effective strategy was proposed to quantify four target compounds (muscone, ethyl palmitate, ethyl oleate, and ethylparaben) from musk by binary eluent based vortex-assisted matrix solid-phase dispersion (MSPD) extraction coupled with GC/MS. Single-factor tests and orthogonal design were employed to optimize the MSPD parameters. In addition, the binary eluent system, methanol, and ethyl acetate 3 : 7 (v/v) were used to extract the target analytes. Finally, C 18 was applied as the easily available dispersant and the sample powder was ground for 2 min. Thereafter, the mixture was rapidly extracted with the binary eluents under whirling for 3 min. Eventually, the analysis of the samples was completed within 12 min by GC/MS. All correlation coefficients (r) of four targets were more than 0.9991. The recoveries of all target compounds ranged from 92.8% to 101% while their RSDs were less than 6.94%. There was no significant matrix interference for the analysis. Thus, the combination of vortex-assisted MSPD with GC/MS was considered as a novel, rapid, and environmentally friendly quantitative approach for musk samples.

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