In-tube silylation in combination with thermal desorption gas chromatography-mass spectrometry for the determination of hydroxy polycyclic aromatic hydrocarbons in water

For the determination of hydroxy polycyclic aromatic hydrocarbons (OH-PAHs), a simple and sensitive method based on the silylation of OH-PAHs using N,O-bis(trimethylsilyl)trifluoro acetamide (BSTFA) in combination with thermal desorption gas chromatography-mass spectrometry (TD-GC-MS) is described. This method was performed by way of direct silylation in a TD unit (in-tube silylation) coupled to a GC inlet. Both a good detection limit (4.1-1200 pg L⁻¹, S/N = 3) and higher precision (relative standard deviation < 4% on average) were achieved for 21 OH-PAHs studied using the full scan mode (m/z = 40-550). These good results were due to the highly efficient derivatization of the OH-PAHs, which was attributed to not only the moisture-free environment and programmable heating in the TD tube for the in-tube silylation, but also to the constant vapor generation of BSTFA using a capillary introduction method. Although recoveries of 21 OH-PAHs from the spiked 3% NaCl solution ranged between 9 and 304%, those of 11 OH-PAHs fell between 70 and 130% (R.S.D. < 11%). Thus, the present method was applied to a seawater sample collected from an industrial port, and nine OH-PAHs including 1- and 2-OH-fluorenone and 1,8- and 2,6-OH-anthraquinone were determined at concentrations of 0.49-5.8 ng L⁻¹. Along with these OH-PAHs, significant amounts of several long chain fatty acids (C₁₂, C₁₆, C₁₈, C₂₀ and C₂₂) and bisphenol A were also identified in the seawater sample using reference data in a library of mass spectra (match factor: >80%).