J.M. Bayona

Systematic characterisation of long-chain aliphatic esters of wool wax by gas chromatography–electron impact ionisation mass spectrometry

A detailed structural characterisation of the aliphatic high-molecular-mass esters extracted from raw wool based on high-temperature gas chromatography-electron impact ionisation mass spectrometry is described. The raw wool esters extracted are in the range of C37 to C54 (i.e., molecular mass 550-788). The selected ion chromatogram exhibited four isomers for the esters with an odd number of carbon atoms (i:a, i:n, a:n and n:n) and five for those with an even number of carbon atoms (i:i, a:a, i:n, a:n and n:n). Isomeric structural elucidation is discussed with respect to the long-chain fatty acid and long-chain fatty alcohol structures, on the basis of chromatographic retention behaviour and mass spectral information.

Comprehensive evaluation of the extraction variables affecting the determination and stability of native butyl- and phenyl-tin compounds from sediment

The effect of several extraction variables such as acid concentration and strength (e.g. for HCland HOAc), the presence of complexing agents (e.g. tropolone, sodium diethyldithiocarbamate) in the extracting mixture, solvent polarity (e.g. hexane, toluene) and sonication time for native butyl- and phenyl-tin compounds from sediment was evaluated. A toluene-HOAc mixture (10:4) yields the highest extraction efficiency for all the analytes and minimizes the degradation of trialkyl- and triaryl-tins during the extraction under sonication. In addition, losses of underivatized monobutyltin and monophenyltin were minimized in several steps of the analytical procedure. The analytical procedure developed was validated against existing CRMs for butyltin determination.

Effects of complexing agents and acid modifiers on the supercritical fluid extraction of native phenyl‐ and butyl‐tins from sediment

The effects of: (1) the modifier type (methanol and formic, acetic and propionic acids), (2) complexing agents (diethylammonium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate) either with or without acidic modifiers, (3) the extraction temperature (50–80 °C) and pressure (30–50 MPa), (4) the extraction procedure (static–dynamic or dynamic), and (5) the volume of static modifier, on the extraction efficiency of native butyl- and phenyl-tin compounds from sediment, were evaluated comprehensively. The highest extraction efficiency for butyl- and phenyl-tin compounds was obtained at 30 MPa and 50 °C by using CO2 modified with acetic acid (200 μl in the cell). Supercritical fluid extraction (SFE) extracts were hexylated and determined by GC–FPD using a 610 nm bandpass filter without any clean-up step. In summary, the developed analytical procedure is robust (no restrictor clogging; free from FPD interferences), it is low-cost (no complexing agents needed), it has a high sample throughput (<3 h), it is independent of the matrix for the determination of butyltin compounds in sediment, and it provides the highest precision among the SFE procedures reported for organotin determination.

Determination of novel aromatic amines in environmental samples by gas chromatography/mass spectrometry.

A number of compounds belonging to five chemical classes of aromatic amines were identified by electron impact mass spectrometry, both in the vapor phase and in suspended particulate matter collected in an area subjected to heavy traffic. This paper presents the mass spectra of new aromatic amines, proposed mechanisms for formation of the major ions obtained by electron impact, concentrations of each class in 13 environmental samples, and the distribution of the individual compounds of the major chemical classes (greater than 80% by weight).