Cryogenic ion vibrational predissociation (CIVP) spectroscopy of a gas-phase molecular torsion balance to probe London dispersion forces in large molecules.

We present the design of the newly constructed cryogenic Fourier-transform ion cyclotron resonance (FT-ICR) ion trap for infrared ion spectroscopy. Trapped ions are collisionally cooled by the pulsed introduction of buffer gas into the cell. Using different buffer gases and cell temperatures, we record action spectra of weakly bound neutral gas-analyte complexes with an IR laser source. We show for the first time that ion-He complexes can be observed in an ICR cell at temperatures around 4 K. We compare the experimental vibrational spectra of Ag(PPh) obtained by tagging with different neutral gases: He, Ne, Ar, H, and N to computed vibrational spectra. Furthermore, the conditions necessary for the formation of neutral tags within an ICR ion trap are studied.

Blood and breast milk samples from inhabitants living in dwellings treated with DDT in indoor residual spraying show high DDT levels. This is of concern since mothers transfer lipid-soluble contaminants such as DDT via breastfeeding to their children. We focused on DDT use in South Africa and used a pharmacokinetic model to identify the dominant DDT uptake routes (food vs. inhalation), to estimate DDT levels in human lipid tissue over the full lifetime of an individual, and to determine the amount of DDT transferred to children during pregnancy and breastfeeding. In particular, the effects of breastfeeding duration, parity, and the mother's age on the DDT concentrations of mother and infant were estimated. The model results suggest that primiparous mothers have greater DDT concentrations than multiparous mothers which lead to higher DDT exposure for their first-born children. Furthermore, DDT in the body mainly originates from diet (92-95%). Our modeled DDT levels reproduce the levels found in South African biomonitoring data within a factor of five or less.

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