COMPARISON OF LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY INTERFACES FOR THE ANALYSIS OF POLYCYCLIC AROMATIC-COMPOUNDS

Three liquid chromatography/mass spectrometry interfaces were evaluate d for their suitability for the analysis of complex mixtures of polycy clic aromatic compounds (PACs). Preliminary qualitative experiments, w hich used a carbon black extract as test material, confirmed that the moving belt interface is mechanically awkward, is limited with respect to the mobile phase composition which it can tolerate, and is not eff icient in detecting the more volatile compounds, For these reasons it was not examined further, although it performed well for larger PACs a nd provided electron ionization (EI) mass spectra, The particle beam ( PB) interface also provides Fl spectra, but detection limits are poor (low nanogram range) and calibration curves are nonlinear, Only seven of the 16 PACs targeted for quantification in a complex coal tar refer ence material could be detected because of the difficulty the PB inter face has with the analysis of com; pounds with very high or very low v olatility, The heated pneumatic nebulizer (HPN) interface, which uses atmospheric pressure chemical ionization, produces both molecular ions (M(.+)) and protonated molecules (MH(+)) of PACs, Detection limits we re in the low picogram range, and calibration curves were linear, Usin g the HPN interface, 17 target PACs in the coal tar reference material could be detected and quantified within satisfactory agreement with c ertified values when perdeuterated internal standards were employed.