The complete destruction of separate mixtures of 1.1 mM 4-chlorophenol (aqueous) and 0.61 mM pentachlorophenol (aqueous slurry) take place in the presence of 0.5 g of iron particles in 10 mL of 0.32 mM ethylenediaminetetraacetic acid (EDTA) under ambient air under room temperature conditions. Under this reaction condition, the time required to reach complete disappearance to the detection limit of GC-FID for each compound was 4 h for 4-chlorophenol and 70 h for pentachlorophenol. Electrospray ionization mass spectral (ESI-MS) analysis of the 4-chlorophenol reaction mixture after its complete disappearance indicated non-chlorinated, primarily low molecular weight products; however, Clfrom 4-chlorophenol was not detected due to adsorption onto the iron or its corrosion products. Radical trap and control experiments suggest that the mechanism for destruction initiates with dioxygen activation, leading to the formation of reactive oxygen species (ROS) and ultimately ring opening of the phenolic compounds. This is the first example of an abiotic system capable of the complete destruction of an organic pollutant under room temperature and pressure conditions through dioxygen activation chemistry.

The acid dissociation and ferric stability constants for complexation by the flavonoids 3-hydroxyflavone (flavonol), 5,7-dihydroxyflavone (chrysin), and 3',4'-dihydroxyflavone in 50:50 (v/v) ethanol/water are determined by pH potentiometric and spectrophotometric titrations and the linear least-squares curve-fitting program Hyperquad. Over the entire range of pH and reagent concentrations spanning the titration experiments, the stoichiometry for iron-flavonoid complex formation was 1:1 for all three flavonoids examined. The three flavonoids were chosen for their hydroxy substitution pattern, with each possessing one of the three most commonly suggested sites for metal binding by the flavonoids. On the basis of the calculated stability constants, the intraflavonoid-binding site competition is illustrated as a function of pH via speciation curves. The curves indicate that the binding site comprised of the 3',4'-hydroxy substitutions, the catecholic site, is most influential for ferric complexation at the physiological pH of 7.4. The possibility for antioxidant activity by flavonoid chelation of ferric iron in the presence of other competitive physiological complexing agents is demonstrated through additional speciation calculations.

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Solid-phase micro extraction (SPME) and on-fiber derivatization followed by Gas Chromatography coupled with Flame Ionization Detection (GC-FID) or Selected Ion Monitoring Mass Spectrometry (GC-SIMMS) allows for simple yet sensitive quantification for the hexamethyldisilazane derivative of the beta-agonist clenbuterol. Using an 85- micro m polyacrylate fiber, the analysis method is optimized with respect to extraction time, derivatization time and temperature, and solution pH. In addition, the use of a rapid temperature ramping injection port allows for optimization of fiber desorption conditions. Under optimal conditions, the limits of detection for the hexamethyldisilazane derivative of clenbuterol are 1.1 ppb by FID and 0.20 ppb by SIMMS.

The common metal chelation agents, DTPA and EDTA are often used as models for physiological low-molecular weight iron complexes in biochemical studies, or for common biochemical protocols. In the biochemical literature there are apparent conflicts as to whether EDTA and DTPA are pro-oxidant or antioxidant additives. This apparent conflict is puzzling since in chemical systems FeIIEDTA and FeIIDTPA are well known Fenton reaction reagents. In this investigation we examined the voltammetric characteristics of the iron complexes of EDTA, DTPA, and citrate and the effect of the ligand:metal ratio (L:M) on the electrocatalytic (EC') waves that result from reduction of H2O2 by this complex. At a ratio of 1:1, the cyclic voltammetric waves of the complexes indicate the presence of a reversible species corresponding to the Fe(II/III)L couple, along with a second irreversible reduction peak. The second irreversible voltammetric peak decreases at higher L:M ratios for EDTA and citrate. The 1:1 iron complexes of EDTA, DTPA, and citrate clearly induce the catalytic reduction of H2O2. In the presence of a greater than 100 fold excess of H2O2 relative to iron, higher L:M ratios greatly reduced the catalytic EC' wave compared to the 1:1 ratios. At H2O2:Fe ratios less than 50, the L:M ratio has very little effect of the EC' current. These observations may explain the apparent discrepancies in the biochemical literature. Addition of EDTA or DTPA may enhance oxidative processes if the L:M is low (less than unity), whereas rates of on-going oxidative processes may decrease if that ratio, along with the relative amount of H2O2, are both high (excess ligand). The impact of this study is of particular importance given the widespread use of these ligands in biochemical studies.

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