| The research project described herein consists of three main parts. In the first part, a method was developed for achieving increased confidence in the selective determination of polychlorinated biphenyls (PCBs) using GC-MS/MS. The optimized method required three injections, with homolog classes sequentially monitored as: 1-4-7-10, 2-5-8, and 3-6-9, respectively. The method was demonstrated for extracts of small samples (∼750-1000 mg) from a variety of freshwater biota. Application of the method resulted in more accurate quantitation, correcting an average 5.3% relative error (false positive bias) and a total error of 31% in observed concentration. In the second part, a new method for fast, selective, and sensitive analysis of organometallics associated with soil, sand, and humic substances was studied using Triphenyl arsine (TPA) as a representative organometallic compound. The method is based the Chromatoprobe(TM), with detection by the pulsed flame photometric detector (PFPD). The Chromatoprobe(TM)-GC-PFPD combination was found to provide a number of novel features that have the potential to enhance the analysis of organometallics compounds in complex matrices, among them extraction-free analysis, higher sensitivity (with detection limits for As in the ppb range), and minimization of interferences (e.g., carbon-, phosphorus-, or sulfur-containing compounds). In the third part, three new methods for the characterization of natural organic matter (NOM) in soils using tetramethylammonium hydroxide (TMAH) methylation-pyrolysis with GC-MS detection were developed and evaluated. First, an off-line methylation pyrolysis method was devised in which soil or a humic acid standard was mixed with TMAH, heated in a sealed Pyrex or quartz tube, and extracted with various organic solvents. Next, an on-line methylation pyrolysis method was studied in which the sample and TMAH were mixed and allowed to react on-line inside a micro glass vial that was introduced directly into the GC injector port using the Chromatoprobe(TM). Finally, a custom pyrolysis furnace (1200°C) coupled to a conventional Purge and Trap Concentrator was designed, fabricated, and tested for the on-line (direct) pyrolysis of samples. Comparison of the three approaches indicates that the offline methylation pyrolysis method is the most effective for NOM characterization. |
