Fabrizio Volpi

Structure-dependent photocatalytic degradation of polychlorobiphenyls in a TiO2 aqueous system

Abstract Three positional isomers for each polychlorobiphenyl (PCB) homologous group tetra-, penta-, and hexachlorosubsubstituted were irradiated in a TiO 2 (anatase) semiconductor aqueous suspension. Parent PCB disappearance was studied as a function of irradiation time, and a correlation between isomer substitution pattern and the photodegradative behavior was shown. In each group, the slowest disappearance trend was exhibited by the isomer with unsubstituted ortho positions, thereby capable of adapting into a planar structural configuration with minimum (estimated) energy requirement. In general, photodegradation rate increased with increasing degree of ortho chlorosubstitution.

Polychlorinated biphenyl, dibenzodioxin, and dibenzofuran occurrence in the general environment in Italy

Abstract Topsoil and sediment samples from the Italian general environment were assayed for PCBs, PCDDs, and PCDFs. PCB levels appear to range between 6.2 × 102 and 1.6 × 104 ng/kg in open areas and between 1.2 × 102 and 6.8 × 102 ng/kg in cave samples. PCDD plus PCDF levels, as TCDD equivalents (TE units), are between 1.0 × 10−1 and 4.3 ngTE/kg in open areas, and between 5.7 × 10−2 and 1.2 × 10−1 ngTE/kg in cave samples. The less chlorinated PCB homologs seem to reach higher relative levels in cave sediments than in the topsoil of open areas, this probably due to a lower dissipation rate. PCDD plus PCDF levels (TE units) versus cumulative PCB levels provide highly significant linear regression in logarithmic coordinates.

Levels of 4-chloro-2-methylphenoxyacetic acid (MCPA) in the urine of northern Italy occupationally exposed agricultural workers

MCPA residues were assayed in 18 urine samples collected from northern Italy herbicide spraymen. Urine was collected within less than or equal to 24 hr from workshift start and kept at -20 degrees C until analysis. Twenty-five-milliliter urine specimens were ether-extracted at pH 1 and then the free MCPA was turned into its methyl ester. Detection and quantitation were carried out by high-resolution gas chromatography coupled with low-resolution mass spectrometry (hrGC-lrMS) run in the multiple ion detection (MID) mode. Specimen mass chromatograms were referred to MCPA methyl ester external standards. Detection thresholds were 25 and 10 ppb when S/N ratios of approximately 10 and 2.5, respectively, were adopted for the quantitation ion mass. Mean recovery was better than 80% over the full concentration range tested (10-1000 ppb). Urine analysis yielded the following results: eight outcomes fell in the 10-50 ppb range, five outcomes in the 50-150 ppb range, and five in the 150-500 ppb range.

Influence of relative response factor in the determination of organic microcontaminants with isotopically labeled standards

The use of isotopically labeled internal standards in the analysis of organic microcontaminants entails the determination of relative response factors (RRFs) of the unlabeled with respect to the labeled compounds. RRFs were measured daily during 28 replicate polychlorobiphenyl (PCB) analyses on two different sets of samples. Daily RRFs allowed more precise results to be attained than those provided by mean RRFs, the latter being the mean of all the daily RRFs obtained during the same series of analyses. Analytical applications to food matrices are presented, including the PCB contamination profile of an olive oil and that found in a matrix of Italian national mean diet. Based on the latter sample, also the polycyclic aromatic hydrocarbon (PAH) daily intake of Italians is assessed. Seven PAHs are determined.