Jaakko Laakia

University of Helsinki, Helsinki, Province of Southern Finland, Finland

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Publications (7)16.69 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: This study presents an atmospheric pressure ionization high resolution ion mobility spectrometer (IMS) equipped with a multi-ion source platform, which together with the design of the drift tube chamber allows the use of various atmospheric pressure ionization (API) methods, namely electrospray ionization (ESI), corona discharge atmospheric pressure chemical ionization (CD-APCI), atmospheric pressure photo ionization (APPI), and radioactive atmospheric pressure chemical ionization (R-APCI). The instrument thus allows one to study samples using the same drift tube with different ionization techniques either in positive or in negative ion mode. The instrument has a high resolving power, around 100, and a reproducible reduced mobility value of ∼1.48cm2/Vs (relative standard deviation below 1%) for 2,6- di-tert-butylpyridine (2,6-DtBP) was obtained with all of the ionization methods. The shape of the ion pulse as a function of gate opening time and how this affect the resolving power is discussed based on the observed differences between calculated and measured resolving power.
    International Journal of Mass Spectrometry 12/2010; 298(1-3):24-29. · 2.14 Impact Factor
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    ABSTRACT: This study demonstrates how positive ion atmospheric pressure photoionization-ion mobility spectrometry-mass spectrometry (APPI-IMS-MS) can be used to produce different ionic forms of an analyte and how these can be separated. When hexane:toluene (9:1) is used as a solvent, 2,6-di-tert-butylpyridine (2,6-DtBPyr) and 2,6-di-tert-4-methylpyridine (2,6-DtB-4-MPyr) efficiently produce radical cations [M](+*) and protonated [M + H](+) molecules, whereas, when the sample solvent is hexane, protonated molecules are mainly formed. Interestingly, radical cations drift slower in the drift tube than the protonated molecules. It was observed that an oxygen adduct ion, [M + O(2)](+*), which was clearly seen in the mass spectra for hexane:toluene (9:1) solutions, shares the same mobility with radical cations, [M](+*). Therefore, the observed mobility order is most likely explained by oxygen adduct formation, i.e., the radical cation forming a heavier adduct. For pyridine and 2-tert-butylpyridine, only protonated molecules could be efficiently formed in the conditions used. For 1- and 2-naphthol it was observed that in hexane the protonated molecule typically had a higher intensity than the radical cation, whereas in hexane:toluene (9:1) the radical cation [M](+*) typically had a higher intensity than the protonated molecule [M + H](+). Interestingly, the latter drifts slower than the radical cation [M](+*), which is the opposite of the drift pattern seen for 2,6-DtBPyr and 2,6-DtB-4-MPyr.
    Journal of the American Society for Mass Spectrometry 09/2010; 21(9):1565-72. · 3.59 Impact Factor
  • Boreal Environment Research 01/2010; 15:513-532. · 1.75 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: Negative corona discharge atmospheric pressure chemical ionization (APCI) was used to investigate phenols with varying numbers of tert-butyl groups using ion mobility spectrometry-mass spectrometry (IMS-MS). The main characteristic ion observed for all the phenolic compounds was the deprotonated molecule [M-H](-). 2-tert-Butylphenol showed one main mobility peak in the mass-selected mobility spectrum of the [M-H](-) ion measured under nitrogen atmosphere. When air was used as a nebulizer gas an oxygen addition ion was seen in the mass spectrum and, interestingly, this new species [M-H+O](-) had a shorter drift time than the lighter [M-H](-) ion. Other phenolic compounds primarily produced two IMS peaks in the mass-selected mobility spectra measured using the [M-H](-) ion. It was also observed that two isomeric compounds, 2,4-di-tert-butylphenol and 2,6-di-tert-butylphenol, could be separated with IMS. In addition, mobilities of various characteristic ions of 2,4,6-trinitrotoluene were measured, since this compound was previously used as a mobility standard. The possibility of using phenolic compounds as mobility standards is also discussed.
    Rapid Communications in Mass Spectrometry 09/2009; 23(19):3069-76. · 2.51 Impact Factor
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    ABSTRACT: Ionized acetates were used as model compounds to describe gas-phase behavior of oxygen containing compounds with respect to their formation of dimers in ion mobility spectrometry (IMS). The ions were created using corona discharge at atmospheric pressure and separated in a drift tube before analysis of the ions by mass spectrometry. At the ambient operational temperature and pressure used in our instrument, all acetates studied formed dimers. Using a homolog series of n-alkyl-acetates, we found that the collision cross section of a dimer was smaller than that of a monomer with the same reduced mass. Our experiments also showed that the reduced mobility of acetate dimers with different functional groups increased in the order n-alkyl <or= branched chain alkyl <or= cyclo alkyl < aromat. For mixed n-alkyl dimers we found that the reduced mobility of acetate dimers having the same number of carbons, for example a dimer of acetyl acetate and hexyl acetate has the same reduced mobility as a dimer composed of two butyl acetates. The fundamental behavior of acetate monomers and dimers described in this paper will assist in a better understanding of the influence of dimer formation in ion mobility spectrometry.
    Journal of the American Society for Mass Spectrometry 09/2008; 19(9):1361-6. · 3.59 Impact Factor
  • European Journal of Pharmaceutical Sciences - EUR J PHARM SCI. 01/2008; 34(1).
  • [show abstract] [hide abstract]
    ABSTRACT: The results from a 1-year measurement period concerning the diurnal PM2.5 and PM10 organic carbon (OC) and black carbon (BC) concentrations are presented for a traffic-influenced site in the Helsinki metropolitan area. The measurements were based on aerosol sampling using a virtual impactor and the subsequent thermal–optical analysis to distinguish between OC and BC. Backup filters were used to estimate and correct for the positive sampling artefact. Daily-average concentrations in PM2.5 varied between 1.0 and 8.5 μg C m−3 for OC, and between 0.3 and 5.7 μg C m−3 for BC. Annual-average concentrations of OC and BC were 3.0 and 1.2 μg C m−3, respectively, in PM2.5, and 4.2 and 1.3 μg C m−3 in PM10. On an annual level, particulate organic matter (POM=1.6×OC) accounted for 50±14% and 36±8% (average±1σ) of the total PM2.5 and PM10, respectively, whereas BC stayed lower at 14±8% and 7±4%. Typically more than 90% of BC resided in the PM2.5 size fraction. The contribution of coarse particles (>2.5 μm) to the overall OC varied between the 0% and 67% (median 27%). The effect of meteorological conditions on the variability of OC and BC concentrations was examined, and the contribution of secondary organic aerosol to the total fine organic aerosol was estimated.
    Atmospheric Environment 01/2002; · 3.11 Impact Factor

Publication Stats

42 Citations
32 Downloads
402 Views
16.69 Total Impact Points

Institutions

  • 2008–2010
    • University of Helsinki
      • • Department of Chemistry
      • • Laboratory of Analytical Chemistry
      Helsinki, Province of Southern Finland, Finland
    • University of Copenhagen
      • Department of Chemistry
      Copenhagen, Capital Region, Denmark
  • 2002
    • Research Institute of the Finnish Economy, Finland, Helsinki
      Helsinki, Southern Finland Province, Finland