M.H. Bollaín

Evaluation of two solid-phase extraction procedures for the preconcentration of chlorophenols in drinking water

Two off-line concentration procedures for the determination of sixteen chlorophenols in drinking water were developed. One involves acetylation of the samples and their subsequent preconcentration over graphitized carbon black cartridges. In the other, chlorophenols are derivatized following preconcentration over cross-linked styrene-divinylbenzene. The two proposed procedures are compared in terms of chlorophenol recoveries, throughput and breakthrough volume of the cartridges. The acetylated derivatives of chlorophenols are determined highly selectively at the concentration levels established by international legislation using gas chromatography in combination with microwave induced plasma atomic emission spectroscopy.

Speciation of organotin compounds in marine biomaterials after basic leaching in a non-focused microwave extractor equipped with pressurized vessels

A rapid method for the speciation of butyl- and triphenyltin compounds in marine biotissues is described. A non-focused microwave extractor, operating at a power of 950 W and equipped with 12 pressurized vessels, was used to achieve fast sample leaching with tetramethylammonium hydroxide. The pH of the liquid extract was adjusted to 5. Organotins were ethylated with sodium tetraethylborate, extracted in isooctane and determined by means of a microwave-induced plasma atomic emission detector coupled to a gas chromatograph. The stability of butyl and phenyl compounds, exposed to the microwave energy, was studied as a function of the vessel temperature. The possibility of simultaneous carried-out extractions and the use of microwave to perform the ethylation and extraction of organotin compounds was also studied. The full procedure was validated with certified material NIES-11 and with real samples, by comparison with a classic leaching method using tetramethylammonium hydroxide without microwave.

Characterization and differentiation of monovarietal grape pomace distillate from native varieties of Galicia.

Monovarietal grape pomace distillates (orujo) of six native varieties of Vitis vinifera L. from Galicia (Albarino, Treixadura, Godello, Loureira, Dona Branca, and Torrontes) have been thoroughly analyzed considering esters, alcohols, major aldehydes, monoterpenes, sesquiterpenes, norisoprenoids, and diterpenes. Albarino and Loureira distillates showed similar profiles of terpenic compounds, with the Loureira products having higher contents of monoterpenols. Native Torrontes distillate from Galicia is principally characterized by marked levels of some sesquiterpenes such as cadinene isomers and epizonarene. On the other hand, Treixadura, Godello, and Dona Branca grape pomace distillates seem not to have any marked terpenic content, and their single separation is difficult. PCA data treatments showed a good separation among the terpenic-rich varieties. Also, the p-menthen-9-al isomers, typical flavors in honey citrus and dill herb (derived from 8-hydroxylinalool), are reported for the first time in grape pomace distillate.

Analysis of structural isomers of polychlorinated phenols in water by liquid-nitrogen-trapping gas chromatography-Fourier transform infrared spectroscopy

A procedure is described for the identification and determination of structural isomers of polychlorinated phenols in drinking water. First, their acetylation and concentration on graphitized carbon cartridges are carried out. Detection is accomplished by gas chromatography (GC) coupled with Fourier transform infrared spectroscopy (FTIR) using a direct deposition (DD) interface. In this way it is possible to accurately identify and differentiate variably substituted isomers of chlorophenols, which is very difficult or even impossible to do by means of the widespread gas chromatography-mass spectrometry (GC-MS) instrumentation. Chlorophenols occurring in water samples have been identified according to their IR spectra and additionally the identification was confirmed by means of the MS-MS spectra obtained with a GC-MS-MS tandem instrument.

Quantification of two chromatographic unresolved dichlorophenols using gas chromatography-direct deposition-fourier transform infrared spectrometry and multivariate calibration

Abstract A method for the quantification of two chromatographically unresolved dichlorophenol isomers in water is described. Acetylation and concentration on graphitized carbon cartridges are carried out as a preliminary step. Detection is made by gas chromatography (GC) coupled to Fourier transform infrared spectroscopy (FTIR), using a direct deposition interface (DD). Infrared spectra in the maximum of the unresolved peak of 2,5- and 2,4-dichlorophenol for a series of standards with different amounts of these two compounds are used, to elaborate a multivariate calibration model (PLS-1 algorithm). By the method described, concentrations of dichlorophenol isomers in water at ng/ml level can be determined.