Forced degradation studies of medroxyprogesterone acetate injectable suspensions (150 mg/ml) with implementation of HPLC, mass spectrometry, and QSAR techniques.

Medroxyprogesterone acetate (MPA) injectable products are a key commodity for reproductive health and are available in the global market from a variety of manufacturing sources. Depending on the climatic zone conditions of the destination country for product use, MPA injectables are at risk of exposure to adverse transport and storage conditions. Analytical methods are available that quantify impurity levels in MPA and MPA injectable products, but minimal information is publicly available on the source of impurity and degradation product generation or the safety risk of these compounds. Forced degradation studies were conducted on MPA and MPA injectables to gain a better understanding of potential sources of impurities and degradation products. Furthermore, QSAR analysis was conducted to assess the toxicity risk of known impurities. More impurities were generated under acidic, basic, light, and oxidative forced degradation conditions relative to thermal degradation, however thermal exposure is the most likely adverse condition to be experienced by these products. Even if impurities are present in MPA injectables, QSAR analysis found that known impurities for MPA are apparently no more of a safety risk than MPA.

Investigating the relative stabilities and electronic properties of small zinc oxide clusters.

We report a combined experimental and theoretical study investigating small zinc oxide clusters. A laser vaporization source and a time-of-flight (TOF) mass spectrometer are employed to produce and identify anionic clusters in the Zn(n)O(m) (n = 1-6, m = 1-7) size regime. The adiabatic detachment energy (ADE) and vertical detachment energy (VDE) of Zn(3)O(3)(-) and Zn(3)O(4)(-) clusters are determined via anion photoelectron spectroscopy. We have utilized density functional theory (DFT) calculations to explore the possible geometries of neutral and anionic Zn(3)O(m) (m = 3-5) clusters, while the theoretical ADE and VDE values are compared with experimental results. The experimentally observed relative abundances among the Zn(3)O(m)(-) (m = 3-5) clusters are investigated through calculations of the detachment energies, dissociation energies, and HOMO-LUMO gaps. We find that the Zn(3)O(3) cluster maintains enhanced stability compared to their oxygen-rich counterparts. Furthermore, by coupling the experimentally obtained photoelectron angular distributions of Zn(3)O(3)(-) and Zn(3)O(4)(-) with electronic structure calculations, the nature of the highest occupied molecular orbitals is discussed, with the goal of aiding the isolation (ligand-capped)/deposition of these building blocks.

Exploring similarities in reactivity of superatom species: a combined theoretical and experimental investigation.

The replacement of group 10-based materials by superatoms has gained great attention due to studies presenting similarities in electronic character and reactive nature between pairs. The current study extends the concept to systems of larger and varied composition as the pairs PdO(+) and ZrO(2)(+) as well as NiO(+) and TiO(2)(+) are interacted with C(2)H(4) and CO through DFT calculations and guided-ion-beam mass spectrometry. It is determined that the pairs readily oxidize C(2)H(4) while oxygen transfer is limited towards CO. Interestingly, within the reaction profiles for oxidation of C(2)H(4) by PdO(+) and NiO(+), a spin crossover is observed which greatly increases the exothermicity of the process. This investigation presents a major step in identifying replacements for expensive group 10 metals in catalytic materials.

Cooperative effects in the oxidation of CO by palladium oxide cations.

Cooperative reactivity plays an important role in the oxidation of CO to CO(2) by palladium oxide cations and offers insight into factors which influence catalysis. Comprehensive studies including guided-ion-beam mass spectrometry and theoretical investigations reveal the reaction products and profiles of PdO(2)(+) and PdO(3)(+) with CO through oxygen radical centers and dioxygen complexes bound to the Pd atom. O radical centers are more reactive than the dioxygen complexes, and experimental evidence of both direct and cooperative CO oxidation with the adsorption of two CO molecules are observed. The binding of multiple electron withdrawing CO molecules is found to increase the barrier heights for reactivity due to decreased binding of the secondary CO molecule, however, reactivity is enhanced by the increase in kinetic energy available to hurdle the barrier. We examine the effect of oxygen sites, cooperative ligands, and spin including two-state reactivity.