Lelio Zoccolillo

Analysis of organophosphorus pesticides by gas chromatography–mass spectrometry with negative chemical ionization: a study on the ionization conditions

Abstract The present paper is aimed to study the optimal ionization conditions of 19 organophosphorous pesticides to be analyzed by gas chromatography (GC) with mass spectrometric (MS) detection in negative chemical ionization (NCI). Isobutane, methane, ammonia in methane, and pure ammonia were used as ionizing gases. The effect of the source temperature on the mass spectrum was evaluated for each pesticide considered in this study and for each ionizing gas. The influence of the electron energy, of the emission intensity and of the gas pressure was also studied for ammonia and ammonia in methane. The MS profiles have shown that NCI fragmentation induced by methane, isobutane and ammonia, generally leads to fragmentation by electron capture. Furthermore, significant differences in the mass spectra of several pesticides were recorded by changing the ionizing gas. Finally, the use of pure ammonia leads to a marked reduction of the background noise, with a parallel improvement of the overall sensitivity of the method, with values of the limit of detection (LOD) lower ( −1 ) than those obtained by methane or isobutane.

Halocarbons in Antarctic Surface Waters

Abstract Surface water samples taken during the 1988–89, 1989–90 and 1990–91 Italian expeditions were analyzed for the presence of carbon tetrachloride, trichloroethylene and tetrachloroethylene. The sample analysis was carried out by solvent extraction and capillary GC-ECD-MS determination. The above-mentioned halocarbons were at ng/l level in all water samples investigated.

Halocarbons in Aqueous matrices from the Rennick Glacier and the Ross Sea (Antarctica)

Aqueous matrices from Antarctica were analysed for three volatile chlorinated hydrocarbons (VCHCs): tetrachloromethane (CCl4), trichloroethylene (C2HCl3) and tetrachloroethylene (C2Cl4). The matrices analysed were snow from Rennick Nèvè and Rennick Glacier sampled during the Italian Expeditions of 1995/96 and 1996/97, respectively, and seawater, pack ice, sea-microlayer, subsuperficial water and freshwater, collected during the Italian Expedition of 1997/98. Extractions from the aqueous matrices were carried out in Antarctica (the laboratories of the Italian Base, Terra Nova Bay). Because of the critical space–time conditions in these laboratories, an extraction procedure was developed, suitable for large volumes of water (10 L), in order to combine the extraction of other classes of organic compounds (polychlorinated biphenyls, polycyclic aromatic hydrocarbons and chlorinated pesticides) with those of our direct interest. The VCHC organic extracts were analysed in Italy by GC-ECD and GC-MS. The analyses confirmed the presence of the three halocarbons in Antarctica in quantities ranging from units to some dozens of nanograms per kilogram. The results were evaluated with respect to the local distribution of these compounds and their diffusion on a global scale.

Halocarbons in Antarctic Surface Waters and Snow

Abstract Surface and pit snow samples, collected from Terranova Bay area in Antarctica during the Italian expeditions of 1991–92 and 1992–93, were analysed, for halocarbons, namely tetrachloromethane, trichloroethylene and tetrachloroethylene. The results obtained (including those related with lake and ice water samples previously reported) were evaluated with respect to the worldwide distribution of these compounds and their diffusion to a global scale. Important innovations concerning sensitivity and reproducibility of the analytical method, are also reported.

Evaluation of polycyclic aromatic hydrocarbons in gasoline by HPLC and GC-MS

SummaryIn this paper the evaluation of polycyclic aromatic hydrocarbons (PAHs) in gasoline is described. A procedure involving a double extraction of samples with N-methylpirrolidone-water-phosphoric acid and with cyclohexane has been used followed by HPLC-DAD and GC-MS. The results obtained show that all gasoline samples contain PAHs with two to six rings and no substantial difference was noticed between leaded and unleaded gasoline. The benzo(a)-pyrene content ranged between 1.0–2.0 mg L−1, a comparatively high concentration for a dangerous compound.

Simultaneous Determination of Benzene and Total Aromatic Fraction of Gasoline by HPLC-DAD

SummaryA new method is described for the simultaneous determination of benzene and the total aromatic fraction in gasoline by HPLC coupled with a diode array detector (DAD). The detection wavelength of 205 nm was selected on the basis of the UV spectra of benzene, its homologues and interfering compounds, obtained by diode array detector. The use of this wavelength plays an important role in minimizing positive interference from trace compounds, which have a strong absorbance at 254 nm, the typical wavelength at which aromatics are detected.To develop the method a standard solution of seven aromatics compounds was used (benzene, toluene, ortho-, meta- and para-xylenes, ethyl-benzene and 1,3,5-trimethyl-benzene), each at 5% v/v in hexane to simulate the behavior of a gasoline with 35% v/v of total aromatics.The sensitivity of this method to benzene is in the range of 2×10−3% v/v. This method was also applied to a gasoline with a known percentage of benzene and total aromatics and proved quite accurate.

Carbon-coated glass beads as a gas chromatographic support material

Abstract A new gas chromatographic support material obtained by coating glass beads with a thin layer of carbon is described. The layer is obtained by the pyrolysis of methylene chloride in a closed vessel at 550°. The operating conditions for this material are described; the working characteristics are superior to those of untreated glass beads. Separations of polar and non-polar compounds with various stationary phases are reported.

On-line analysis of volatile chlorinated hydrocarbons in air by gas chromatography–mass spectrometry: Improvements in preconcentration and injection steps

An analytical system composed of a cryofocusing trap injector device coupled to a gas chromatograph with mass spectrometric detection (CTI-GC-MS) specific for the on-line analysis in air of volatile chlorinated hydrocarbons (VCHCs) (dichloromethane; chloroform; 1,1,1-trichloroethane; tetrachloromethane; 1,1,2-trichloroethylene; tetrachloroethylene) was developed. The cryofocusing trap injector was the result of appropriate low cost modifications to an original purge-and-trap device to make it suitable for direct air analysis even in the case of only slightly contaminated air samples, such as those from remote zones. The CTI device can rapidly and easily be rearranged into the purge-and-trap allowing water and air analysis with the same apparatus. Air samples, collected in stainless steel canisters, were introduced directly into the CTI-GC-MS system to realize cryo-concentration (at -120 degrees C), thermal desorption (at 200 degrees C) and for the subsequent analysis of volatiles. The operating phases and conditions were customised and optimized. Recovery efficiency was optimized in terms of moisture removal, cold trap temperature and sampling mass flow. The injection of entrapped volatiles was realized through a direct transfer with high chromatographic reliability (capillary column-capillary column). These improvements allowed obtaining limits of detection (LODs) at least one order of magnitude lower than current LODs for the investigated substances. The method was successfully employed on real samples: air from urban and rural areas and air from remote zones such as Antarctica.

Determination of polycyclic aromatic hydrocarbons in natural waters by thin-layer chromatography and high-performance liquid chromatography

Abstract A procedure is reported for the determination in natural waters of the six polycyclic aromatic hydrocarbons (PAHs) listed by WHO as indicators of pollution. The method consists in continuous liquid—liquid extraction, separation of the PAH fraction by thin-layer chromatography and reversed-phase high-performance liquid chromatography with a spectrofluorimetric detector. The method has been applied to unfiltered samples of river and sea waters with PAH levels below 0.1 ng/l.

Routine determination of polycyclic aromatic hydrocarbons in carbon black by chromatographic techniques

A method is proposed for the determination of polycyclic aromatic hydrocarbons (PAHs) in carbon blacks. The PAHs are extracted from the carbon black with benzene in a Soxhlet apparatus, purified by silica gel thin-layer chromatography, weighed and analysed by gas and/or high-performance liquid chromatography. The total PAH and benzo[a]pyrene (BaP) concentrations in different types of carbon blacks and in different batches of the same carbon black were determined. It is shown that the distribution of the PAH fraction in different types of carbon blacks is almost the same but there are considerable differences in the total amount of the PAH fraction and the BaP concentration.