Abstract: Flow injection analysis coupled with membrane introduction mass spectrometry (FIA-MIMS) with on-line derivatization is shown to allow fast, accurate, nearly interference-free, and sensitive (low µg/L) quantitation of phenolic compounds in water. On-line FIA derivatization of the phenolic compounds is performed by acetic anhydride acetylation in a K2CO3-buffered alkaline medium. The phenol acetates so formed efficiently permeate a silicone membrane and are directly transferred to the mass spectrometer, in which they are analyzed with selectivity and high sensitivity via selected ion monitoring. FIA-MIMS analysis was performed for aqueous solutions of phenol, 2-methylphenol, 4-chlorophenol, 4-chloro-3-methylphenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol, and detection limits in the 0.5-20 µg/L (ppb) range were observed for an analytical frequency of six samples/h. FIA-MIMS for phenolic compound analysis is considerably less time-consuming and labor intensive than most chromatographic methods based on liquid-liquid extraction and pre-concentration procedures and is therefore applicable for on-line and in-situ monitoring of phenols in wastewaters and in the environment. FIA-MMS employing acetic anhydride derivatization is also virtually free of interferences since it combines chemical, membrane, and enhanced MS selectivity; hence quantitation of phenolic compounds can be performed in the presence of congeners.

Abstract: This work describes the first fully direct coupling of solid-phase microextraction (SPME) with mass spectrometry. An inlet system using a septum as the only interface between the ambient and the high-vacuum mass spectrometer was constructed to allow the introduction of the SPME needle directly into the ionization region of a mass spectrometer. The PDMS-coated fiber was then placed and exposed exactly between the two ionization filaments. Uniform heating of the fiber, efficient thermal desorption, and electron ionization of the analytes were achieved. Using this new analytical technique, here termed fiber introduction mass spectrometry (FIMS), we have been able to detect and quantitate several volatile (VOC) and semivolatile (SVOC) organic chemicals (carbon tetrachloride, benzene, toluene, xylenes, γ-terpinene, diisoamyl ether, chlorobenzene, and many PAHs) and two herbicides (Sylvex and its methyl ether) from aqueous solutions at low-ppb to ppt levels using either SPME headspace or solution extraction. FIMS shows high sensitivity (ng/L), good reproducibility, and accuracy, providing therefore a simple and effective approach to rapid analysis of VOC and SVOC in various matrixes.

Abstract: The solubilization of ethanol and the aromatic hydrocarbons benzene, toluene and the isomeric ethylbenzene and xylenes (BTEX) in water in contact with commercial samples of ethanol-containing Brazilian gasoline was monitored on-line by membrane introduction mass spectrometry (MIMS) and BTEX and ethanol concentrations in water after prolonged contact were measured by flow injection analysis (FIA) coupled with MIMS (FIA-MIMS). The cosolvent effect of ethanol, which is known to increase BTEX solubility in water, was also found to speed up BTEX solubilization as compared with ethanol-free gasoline. The ethanol cosolvent effect was also compared with that of methyl tert-butyl ether (MTBE). Chemometric multivariate analysis applied to FIA-MIMS mass spectra of the ethanol-BTEX aqueous solutions formed after prolonged contact with gasoline samples showed that identical samples cluster closely whereas small variances in BTEX composition occurring among and within the three different types of ethanol-containing Brazilian gasoline are easily detected as they cause great dispersion in the chemometric plots.