A validated approach for analysis of heterocyclic aromatic compounds in sediment samples.

The scientific literature is replete with analytical methods for the analysis of homocyclic aromatic compounds especially polycyclic aromatic hydrocarbons and their alkylated analogs. However, there is a paucity of methods for the analysis of nitrogen-, sulfur- and oxygen-containing polycyclic aromatic compounds (PACs). The lack of commercially available analytical standards, the presence of many structural derivatives and isomers and lack of certified reference materials all contribute to the inherent challenges in measuring these compounds. Gas chromatography coupled with a tandem mass spectrometer was used to develop two multiple reaction monitoring methods to detect and quantify fifty-three non-halogenated and halogenated hetero-polycyclic aromatic compounds (HPACs). Because of their greater polarity, strongly non-polar solvents typically employed to extract homocyclic PACs from sediment samples did not yield acceptable recoveries of our target analytes. By adding ethyl acetate to dichloromethane (50:50), recoveries of our target analytes using accelerated solvent extraction increased markedly. The performance characteristics of the validated method including accuracy [> than 67% for 46 (out of 53) analytes], inter- and intra-day precision [<30% for all analytes, (expressed as relative standard deviation)], limits of detection (0.1 to 2.3 ng/g) and quantitation (1.5 to 7.6 ng/g) imply that the method is fit for its intended purpose. A sediment sample from a known contaminated site in Canada was analyzed for both homo- and hetero-PACs. Measured concentrations of Σ27HPAC (7.3 µg/g, dry weight) were significantly smaller (p<0.05) than Σ16PAHs (80.9 µg/g, dry weight) and Σ30Alkylated-PAHs (14.2 µg/g, dry weight). These results suggest that the developed method is an effective and efficient approach for the targeted analysis of HPACs and their halogenated derivatives in sediment samples.

Dipicolylamine-Based Fluorescent Probes and Their Potential for the Quantification of Fe3+ in Aqueous Solutions.

We have synthesized two ligand systems, N(SO2)(R1)dpa (L1) and N(SO2)(R2)dpa (L2), where R1 = biphenyl and R2 = azobenzene, which are sulfonamide derivatives of the NNN-donor chelating dipicolylamine. Both L1 and L2 can be used as sensors for detecting Fe3+ and are highly sensitive and selective over a wide range of common cations. Time-dependent density functional theory (TDDFT) calculations confirmed that the key excitations of L2 and the [Fe(L2)(H2O)3]3+ model complex involve -R2-unit-based π and π* charge transfer. L2 demonstrates a relatively high photostability, a fluorescence turn-on mechanism, and a detection limit of 0.018 µM with 1.00 µM L2 concentration, whereas L1 has a detection limit of 0.67 µM. Thus, both ligands have the potential to be used as fluorosensors for the detection of Fe3+ in aqueous solutions.