Summary thesis Hartmut Henneken (English)

Within this thesis, new sampling and analysis strategies for the determination of airborne workplace contaminants have been developed. Special focus has been directed towards the development of air sampling methods that involve diffusive sampling.

In an introductory overview, the current state-of-the-art of sampling and analysis of airborne isocyanates is reviewed. The most important derivatization reagents are introduced, and their application for air analysis with special emphasis on sampling techniques and detection methods is presented.

In a first study, it could be shown that the derivatization reaction with NBDPZ can be used for diffusive sampling of methyl isocyanate (MIC), if reagent-impregnated glass fibre filters were used as collector surface. The method developed was the first one allowing the determination of airborne MIC by means of HPLC-MS/MS and HPLC-FLD. The developed tandem-mass spectrometric method allowed for very sensitive detection down to concentrations of 8×10^-10mol/L, and best performance was obtained at low relative humidity conditions. If long term sampling was carried out at high-humidity conditions, decreased sampling rates were observed.

During further work, it could be shown that the humidity interference was a physical problem, caused by displacement of the hydrophobic NBDPZ reagent away from the glass fibre filter’s surface. A comparison of two different filter materials turned out that the use of less polar SDB filter tapes resulted in higher and reproducible sampling rate values. Furthermore, this study was successfully extended to cover ethyl and phenyl isocyanate as well, being the first time that diffusive sampling was applied for these analytes. In addition, diffusive sampling experiments were performed with 2-MP as derivatizing agent, showing no humidity dependency for both filter types, but difficulties for the determination of phenyl isocyanate.

A validation of the new passive sampler for MIC, EIC and PhIC was executed using NBDPZ-coated SDB filters. The individual sampling rates have been determined for different conditions and concentrations. The measured sampling rates were independent of analyte concentration and relative humidity conditions and were decreasing with increasing size of the analyte molecule. It could further be shown that vapor-phase isocyanic acid could also be determined by diffusive sampling, but owing to background problems, ICA could only be quantified when it was present in concentrations in the high ppb range. For the determinations, ion-trap MS/MS LC methods were used, employing electrospray ionization (for 2-MP) and atmospheric pressure chemical ionization (for NBDPZ). The 2-MP method was used as reference after active sampling using reagent-coated filters. A similar active method was also developed for NBDPZ, however it was only suitable to be used for PhIC sampling.

Ferrocenoyl piperazide was presented as a new pre-column derivatizing agent for the analysis of isocyanates using reversed-phase liquid chromatographic separation, electrochemical oxidation/ionization and mass spectrometry. As only the ferrocene-based derivatives were ionized in the electrochemical cell, MS detection could be performed without interferences from matrix components and background signals, and therefore, very sensitive detection could be achieved considering the used single quadrupole instrument.

The first passive sampling method has been developed for the determination of gas phase peroxyacetic acid (PAA), based on chemisorption of PAA on ADS-impregnated glass fiber filters. The reagent was oxidized by PAA to the corresponding sulfoxide ADSO, and the samples were analyzed by means of LC-UV/vis. The determined sampling rate was constant in the range around 1 ppm, with no interference from humidity being discovered, and the detection limit was ~30 ppb. Thorough investigations were carried out with respect to the selectivity of the method towards hydrogen peroxide observing a minor cross reactivity, which is not crucial for the desired application, but means a certain limitation, as the approximate concentration of airborne hydrogen peroxide should be estimated. The applicability of the new method has been demonstrated by successfully analyzing air samples taken during disinfection of a laboratory area.

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Home News Events Strategic Orientations research groups Publications PhD students Education MESA+ NanoLab Starting entrepreneurs Tech Park Industrial Partners Vacancies Links Sitemap Search	Summary thesis Hartmut Henneken (English) Within this thesis, new sampling and analysis strategies for the determination of airborne workplace contaminants have been developed. Special focus has been directed towards the development of air sampling methods that involve diffusive sampling. In an introductory overview, the current state-of-the-art of sampling and analysis of airborne isocyanates is reviewed. The most important derivatization reagents are introduced, and their application for air analysis with special emphasis on sampling techniques and detection methods is presented. In a first study, it could be shown that the derivatization reaction with NBDPZ can be used for diffusive sampling of methyl isocyanate (MIC), if reagent-impregnated glass fibre filters were used as collector surface. The method developed was the first one allowing the determination of airborne MIC by means of HPLC-MS/MS and HPLC-FLD. The developed tandem-mass spectrometric method allowed for very sensitive detection down to concentrations of 8×10^-10mol/L, and best performance was obtained at low relative humidity conditions. If long term sampling was carried out at high-humidity conditions, decreased sampling rates were observed. During further work, it could be shown that the humidity interference was a physical problem, caused by displacement of the hydrophobic NBDPZ reagent away from the glass fibre filter’s surface. A comparison of two different filter materials turned out that the use of less polar SDB filter tapes resulted in higher and reproducible sampling rate values. Furthermore, this study was successfully extended to cover ethyl and phenyl isocyanate as well, being the first time that diffusive sampling was applied for these analytes. In addition, diffusive sampling experiments were performed with 2-MP as derivatizing agent, showing no humidity dependency for both filter types, but difficulties for the determination of phenyl isocyanate. A validation of the new passive sampler for MIC, EIC and PhIC was executed using NBDPZ-coated SDB filters. The individual sampling rates have been determined for different conditions and concentrations. The measured sampling rates were independent of analyte concentration and relative humidity conditions and were decreasing with increasing size of the analyte molecule. It could further be shown that vapor-phase isocyanic acid could also be determined by diffusive sampling, but owing to background problems, ICA could only be quantified when it was present in concentrations in the high ppb range. For the determinations, ion-trap MS/MS LC methods were used, employing electrospray ionization (for 2-MP) and atmospheric pressure chemical ionization (for NBDPZ). The 2-MP method was used as reference after active sampling using reagent-coated filters. A similar active method was also developed for NBDPZ, however it was only suitable to be used for PhIC sampling. Ferrocenoyl piperazide was presented as a new pre-column derivatizing agent for the analysis of isocyanates using reversed-phase liquid chromatographic separation, electrochemical oxidation/ionization and mass spectrometry. As only the ferrocene-based derivatives were ionized in the electrochemical cell, MS detection could be performed without interferences from matrix components and background signals, and therefore, very sensitive detection could be achieved considering the used single quadrupole instrument. The first passive sampling method has been developed for the determination of gas phase peroxyacetic acid (PAA), based on chemisorption of PAA on ADS-impregnated glass fiber filters. The reagent was oxidized by PAA to the corresponding sulfoxide ADSO, and the samples were analyzed by means of LC-UV/vis. The determined sampling rate was constant in the range around 1 ppm, with no interference from humidity being discovered, and the detection limit was ~30 ppb. Thorough investigations were carried out with respect to the selectivity of the method towards hydrogen peroxide observing a minor cross reactivity, which is not crucial for the desired application, but means a certain limitation, as the approximate concentration of airborne hydrogen peroxide should be estimated. The applicability of the new method has been demonstrated by successfully analyzing air samples taken during disinfection of a laboratory area.