Gas chromatographic--mass spectrometric determination of phenylacetic acid in human blood.

Phenyl acetic acid, a metabolite of 2-phenyl ethylamine, acts as a neuromodulator in the nigrostriatal dopaminergic pathway stimulating the release of dopamine. The evaluation of phenyl acetic acid concentration in the biological fluid reflects phenyl ethylamine levels thus allowing the assessment of the modulatory role of this endogenous substance. Changes in biological fluids levels of 2-phenylethylamine and/or in its metabolite have been reported in affective disorders, such as depression and schizophrenia. Recently, the occurrence of the "attention deficit hyperactivity syndrome" has been frequently reported in childhood population and involvement of dopaminergic dysfunction in this disease has been suspected. A fast, reliable and reproducible method for the determination of phenyl acetic acid in human blood, is therefore needed in order to have a screening tool for monitoring both healthy childhood population and suspected "attention deficit hyperactivity syndrome" patients. The gas chromatographic-mass spectrometric method here described makes use of a deuterated internal standard in order to overcome problems related to the lack of reproducibility often encountered when a derivatization step is performed.

"Cold" solid-phase microextraction method for the determination of volatile halocarbons present in the atmosphere at ultra-trace levels.

Anthropogenic volatile halocarbons are compounds of great enviromnental concern because of their involvement in global change phenomena. They are present in the atmosphere at concentration levels in the order of parts per trillion by volume. The chosen analytical method for their determination is capillary gas chromatography coupled to mass spectrometry, preceded by an enrichment step on suitable adsorbent resins. The method here presented makes use of the solid-phase microextraction as a pre-analytical technique, using sub-ambient temperature in order to enhance the retention capability of the fiber coating. The proposed method was evaluated in terms of extraction efficiency, linearity, reproducibility, andlimits of detection. Results obtained showed that trace atmospheric halocarbons are detectable even when enriching very small air sample volumes. A good chromatographic resolution is obtained as a consequence of the extremely low injection volume. Finally a standard GC-MS instrumentation equipped with a simple split-splitless injector was employed, thus avoiding the use of expensive dedicated apparatus. The method was also applied to the analysis of actual samples collected both in remote, and in semi-remote sites.

New liquid chromatography/electron ionization mass spectrometry methods in water analysis.

A method to extract and analyze organic compounds from water is presented. A solid phase micro-trap (micro-SPE) directly connected to the micro-analytical column is used. Sensibility and specificity needed for trace analysis are guaranteed by mass spectrometric electron ionization (EI) detection. A new micro-HPLC/EI-MS interface called Capillary-EI (Cap-EI) is described. The ultimate evolution of this interface is also presented: in this extremely simplified interface the analytes are nebulized, vaporized and ionized in the small volume of the ion source. This interface, called Direct-EI, exploits nano- and micro-HPLC columns with a mobile phase flow rates ranging from 0.3 to 1.5 microL/min. Contemporary use of micro SPE, Cap-EI or Direct-EI gives us a powerful technique to identify and quantify organic pollutants at part per billion level (ppb).