A generic approach for the determination of residues of alkylating agents in active pharmaceutical ingredients by in situ derivatization-headspace-gas chromatography-mass spectrometry.

A simple, reliable and fast procedure for the simultaneous determination of residues of some common alkylating agents (AAs), such as mesylates, besylates, tosylates and sulfates, employed in drug synthesis, has been developed by in situ derivatization-headspace-gas chromatography-mass spectrometry. Pentafluorothiophenol is used as a derivatizing agent in different water/dimethyl sulfoxide ratios. Compared to former analytical procedures, this approach returns improvements in analysis time, selectivity, analyte stability and method sensitivity (LOD=0.11 microgg(-1) for methyl tosylate). The method exhibits low matrix dependence, excellent accuracy, precision (R.S.D.=2.8-10% range at 1 microgg(-1)) and robustness through the use of deuterated internal standards. Knowledge of the synthetic route allows a targeted approach to the determination of specific AAs since the procedure does not distinguish between acid species. The procedure was successfully applied to different pharmaceutical matrixes, and is particularly suitable for routine analysis with high sample throughput.

Determination of perfluorocarboxylic acids in aqueous matrices by ion-pair solid-phase microextraction-in-port derivatization-gas chromatography-negative ion chemical ionization mass spectrometry.

A rapid, selective and simple analytical procedure using tetrabutylammonium as ion pair in conjunction with solid-phase microextraction followed by in-port derivatization-GC-negative ion chemical ionization mass spectrometry was developed. The procedure allows an accurate determination of perfluoroalkylcarboxylic acids in aqueous samples at ng L(-1) levels (i.e. method detection limit 20 ng L(-1) forperfluorodecanoic acid) improving previous GC methods in terms of analysis time and sensitivity. Ammonia as reagent gas in the negative ion chemical ionization mass spectrometry increased the sensitivity at least 3-fold compared to methane for perfluorocarboxylic acid butyl esters. The developed procedure was successfully applied to effluents from wastewater treatment plants (i.e. 0.05-8.2 microg L(-1)) and harbor seawaters.

Fast solid-phase extraction-gas chromatography-mass spectrometry procedure for oil fingerprinting. Application to the Prestige oil spill.

A rapid and simple fractionation procedure using solid-phase extraction (SPE) cartridges was developed for an accurate determination of aliphatic and polycyclic aromatic hydrocarbons in petroleum residues and further application in chemical fingerprinting of oil spills by gas chromatography-mass spectrometry (GC-MS). Among the adsorbents evaluated, SiO2/C3-CN exhibited the best selectivity, providing, by elution with n-hexane (4 ml) and n-hexane-CH2Cl2 (1:1) (5 ml), two well-resolved aliphatic and aromatic hydrocarbon fractions, with recoveries of 97 +/- 7.2 and 99.7 +/- 13.9%, respectively. The SPE fractionation procedure was compared with the conventional silica-alumina adsorption chromatography showing similar results but practical advantages in terms of reproducibility, analysis time, solvent reduction and cost. Moreover, is particularly suitable for routine analysis with a high sample throughput. The developed methodology was tested in the characterization of fuel-oil samples collected along the Spanish north-west coast, after the Prestige oil spill accident.

Determination of linear alkylbenzensulfonates in aqueous matrices by ion-pair solid-phase microextraction-in-port derivatization-gas chromatography-mass spectrometry.

Trace determination (low ng/ml) of linear alkylbenzensulfonates (LASs) in water was achieved by solid-phase microextraction (SPME) of ion-pairs formed with tetrabutylammonium. This ion-pairing reagent served two purposes. First, it allowed the extraction of LAS with the polydimethylsiloxane fiber by counterion association and second, the derivatization of the formed LAS ion pairs in the GC injection port at 300 degrees C to form the corresponding sulfonated butyl esters. The methodology developed allows the isomer specific determination of LAS at low detection limits (0.16-0.8 ng/ml), depending on the alkyl chain lengths of LASs with RSDs of 10-12%. Furthermore, the developed methodology was applied to urban wastewater and sea water and compared with a solid-phase extraction (SPE) method (e.g. C18 and strong anion-exchange sorbent) to obtain concordant values for urban wastewater. Moreover, the developed SPME methodology overcame the procedural blank and matrix-dependent recoveries found in the SPE methodologies at low LAS concentrations.

Accurate determination of 2,4,6-trichloroanisole in wines at low parts per trillion by solid-phase microextraction followed by GC-ECD.

A headspace solid-phase microextraction (HS-SPME) procedure at 30 degrees C with a 100 microm PDMS fiber of a saturated NaCl solution stirred at 1100 rpm combined to GC-ECD for the 2,4,6-trichloroanisol (TCA) determination in wines has been developed. Due to the matrix complexity and ethanol absorption into the fiber, the internal standard selection was crucial to obtain unbiased results. Thus, matrix effects were observed when analyzing different types of Spanish wines (white, early, and vintage red wines) spiked with TCA at low concentration levels (i.e., <40 ng L(-)(1)). In contrast, the use of 2,4,6-tribromoanisole (TBA) as internal standard overcame these matrix effects, whereas the use of 2,4,6-trichlorophenyl ethyl ether led to inconsistent results. The developed HS-SPME-GC-ECD methodology reaches a limit of quantitation for TCA in wine within 2.9-18 ng L(-)(1), with a relative standard deviation of 2.5-13.4%, depending on the TCA concentration level and wine characteristics. This analytical method is comparable to the existing methodologies based on HS-SPME followed by GC-MS in terms of accuracy, precision, length of determination, and length of quantification; however, analysis cost is reduced.