Novel membrane inlet mass spectrometric methods for analysis of organic compounds in aqueous and solid samples: Dissertation

Marja Ojala

Research output: ThesisDissertationCollection of Articles

Abstract

Different volatile organic compounds (VOCs) are widely used in industry and due to accidents and fuel emissions the compounds can be discharged into the environment, causing contamination of soil and groundwater. Because of their toxicity the analysis of VOCs is very important. The traditional analytical methods for VOCs, such as static and dynamic headspace gas chromatography-mass spectrometry, are time consuming and difficult to apply in on-line analysis or even on-site analysis. For this reason, a purge-and-membrane mass spectrometric (PAM) method was developed for analysis of VOCs in solid samples. Two versions of PAM-devices are introduced in this study. The characteristics of the method, such as linear dynamic ranges (at least five orders of magnitude), detection limits and repeatability, are presented. The detection limits varied between 5 and 150 µg/kg depending on compounds and soil type, and the repeatability was good when an internal standard was used (RSD < 14%). The effects of soil parameters such as humidity and the content of organics on desorption were studied. Both soil type and moisture content had an effect on peak areas. In addition, moisture content had an inversely proportional effect on desorption times in the case of garden soil. Furthermore, the effects of PAM-parameters such as the preheating time and temperature are presented in detail. Even a preheating time of only ten minutes was suitable for analysis. The use of different purge gases was studied. In addition, an application of the analysis of VOCs in pharmaceuticals is presented. Some preliminary tests for water analysis with PAM were carried out. The results obtained with the PAM-method for soil samples were compared with those of static headspace gas chromatography. Both spiked and authentic soil samples were used in analysis and two different laboratories took part in the testing. The agreement between testing methods and laboratories was good. The results show that the new PAM-MS method is very promising for the determination of volatile organic compounds in solid samples. Other advantages of the method are short analysis times (only a few minutes per sample), the non-requirement for pretreatment of samples, and for environmental and health risk reasons the fact that solvents are not used. A membrane inlet mass spectrometry (MIMS) method was developed for testing volatile organic sulphur compounds, terpenes and phenolic compounds in water samples. Different conventional chromatographic methods were used to compare results. Detection limits obtained were at the low ppb level. Analysis times are short, only a few minutes, and no pretreatment of the samples is needed. Phenolic compounds were analysed both directly from water and after acetylation in aqueous phase. The detection limits obtained after acetylation increased from 5-fold for di- and trichlorophenols to 100 fold for 4-nitrophenol. The MIMS-method combined with the Solver program made it possible to calculate the amounts of monoterpenes and sesquiterpenes in water samples. It is worthy of notice that MIMS-Solver was the only reliable method (of four) to measure low concentrations of sulphur compounds in water samples.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • University of Helsinki
Supervisors/Advisors
  • Kotiaho, Tapio, Supervisor, External person
Award date11 Jan 2002
Place of PublicationEspoo
Publisher
Print ISBNs951-38-5963-0
Electronic ISBNs951-38-5964-9
Publication statusPublished - 2001
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • volatile organic compounds
  • membrane inlet mass spectrometry
  • determination
  • soil analysis
  • aqueous systems
  • pharmaceuticals
  • chromatography
  • samples
  • pretreatment, phenols

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