Mechanistic characterization of iron-catalyzed oxidation of polysorbate 80: The role of ferrous iron, hydrogen peroxide, and superoxide.

We investigated the role of individual radical species during Fe-catalyzed oxidation of PS80. Solutions containing 1 gL PS80 (0.1 % w/v) in 10 mM acetate buffer (pH 6) were exposed to various amounts of either Fe(II) or Fe(III), hydrogen peroxide (HO), and various enzymes or antioxidants.

Near UV Light Photo-Degradation of Lactate and Related α-Hydroxycarboxylates in the Presence of Fe(III): Formation of Carbon Dioxide Radical Anion.

In recent studies we have reported on the near-UV light-induced degradation of iron complexes of various pharmaceutical excipients, such as Fe(III)-citrate and Fe(III)-amino acid complexes. Mechanistic studies revealed a common photo-degradation pattern, i.e.

Near-UV and Visible Light Degradation of Iron (III)-Containing Citrate Buffer: Formation of Carbon Dioxide Radical Anion via Fragmentation of a Sterically Hindered Alkoxyl Radical.

Citrate is a commonly used buffer in pharmaceutical formulations which forms complexes with adventitious metals such as Fe. Fe-citrate complexes can act as potent photosensitizers under near-UV and visible light exposure, and recent studies reported evidence for the photo-production of a powerful reductant, carbon dioxide radical anion (CO), from Fe-citrate complexes (Subelzu, N.; Schöneich, N.

Ion-molecule interactions enable unexpected phase transitions in organic-inorganic aerosol.

Atmospheric aerosol particles are commonly complex, aqueous organic-inorganic mixtures, and accurately predicting the properties of these particles is essential for air quality and climate projections. The prevailing assumption is that aqueous organic-inorganic aerosols exist predominately with liquid properties and that the hygroscopic inorganic fraction lowers aerosol viscosity relative to the organic fraction alone. Here, in contrast to those assumptions, we demonstrate that increasing inorganic fraction can increase aerosol viscosity (relative to predictions) and enable a humidity-dependent gel phase transition through cooperative ion-molecule interactions that give rise to long-range networks of atmospherically relevant low-mass oxygenated organic molecules (180 to 310 Da) and divalent inorganic ions.

Dual-Balance Electrodynamic Trap as a Microanalytical Tool for Identifying Gel Transitions and Viscous Properties of Levitated Aerosol Particles.

The formation of gelatinous networks within an aerosol particle significantly alters the physicochemical properties of the aerosol material. Existing techniques for studying gel transitions rely on bulk rheometry, which is limited by contact with the sample, or microrheological techniques such as holographic optical tweezers, which rely on expensive equipment and high-powered lasers that can degrade light-absorbing aerosol. Here, we present a new technique to probe the microrheological characteristics of aerosol particles and explore gel formation under atmospheric conditions in a contactless environment without the need for high-power light sources.