Hydrophobic functional liquids based on trioctylphosphine oxide (TOPO) and carboxylic acids.

Trioctylphosphine oxide (TOPO) is a hydrophobic extracting agent used in a number of commercially important separations of valuable solutes from aqueous streams (with examples ranging from lanthanides, through gallium, to carboxylic acids). TOPO is traditionally used as a solute in kerosene, its extraction efficiency limited by its solubility in the organic diluents. In this work, eighteen hydrogen bond donors (HBDs) were screened for their capacity to liquefy TOPO, employing strategies used to design deep eutectic solvents (DES). The selected HBDs were all useful in separations and were designed to formulate solvent-free, hydrophobic, bi-functional liquid extracting agents. Some TOPO:HBD mixtures yielded hydrophobic liquids that offer potential to be extremely efficient extractants, incorporating high intrinsic concentrations of TOPO. Following this initial screening, two systems: TOPO:malonic acid and TOPO:levulinic acid, were selected for detailed physico-chemical characterisation across their complete compositional ranges. Phase diagrams, thermal stabilities and the mechanism of thermal decomposition are reported, along with densities and insights from 31P NMR spectroscopic studies. The work was concluded with a proof-of-concept demonstration of the use of the TOPO:malonic acid (2 : 1 mol ratio) mixture for the extraction of gallium from acidic chloride feedstock (simulated pre-digestate of zinc leach residue). The loading capacity of the TOPO:malonic acid extractant was three orders of magnitude greater than that of the literature benchmark, encouraging further application-oriented studies.

Frustrated Lewis pairs in ionic liquids and molecular solvents - a neutron scattering and NMR study of encounter complexes.

The presence of the weakly-associated encounter complex in the model frustrated Lewis pair solution (FLP): tris(tert-butyl)phosphine (P(tBu)3) and tris(pentafluorophenyl)borane (BCF) in benzene, was confirmed via PB correlation analysis from neutron scattering data. On average, ca. 5% of dissolved FLP components were in the associated state. NMR spectra of the FLP in benzene gave no evidence of such association, in agreement with earlier reports and the transient nature of the encounter complex. In contrast, the corresponding FLP solution in the ionic liquid, 1-decyl-3-methylimidazolium bistriflamide, [C10mim][NTf2], generated NMR signals that can be attributed to formation of encounter complexes involving over 20% of the dissolved species. The low diffusivity characteristics of ionic liquids is suggested to enhance high populations of encounter complex. The FLP in the ionic liquid solution retained its ability to split hydrogen.

The cost-effectiveness of spinal cord stimulation in the treatment of failed back surgery syndrome.

OBJECTIVES: Healthcare policy makers and payers require cost-effectiveness evidence to inform their treatment funding decisions. Thus, in 2008, the United Kingdom's National Institute of Health and Clinical Excellence analyzed the cost effectiveness of spinal cord stimulation (SCS) compared with conventional medical management (CMM) and with reoperation and recommended approval of SCS in selected patients with failed back surgery syndrome (FBSS). We present previously unavailable details of the National Institute of Health and Clinical Excellence analysis and an analysis of the impact on SCS cost effectiveness of rechargeable implanted pulse generators (IPGs). METHODS: We used a decision analytic model to examine the cost effectiveness of SCS versus CMM and versus reoperation in patients with FBSS. We also modeled the impact of nonrechargeable versus rechargeable IPGs. RESULTS: The incremental cost-effectiveness of SCS compared with CMM was pound5624 per quality-adjusted life year, with 89% probability that SCS is cost effective at a willingness to pay threshold of pound20,000. Compared with reoperation, the incremental cost-effectiveness of SCS was pound6392 per quality-adjusted life year, with 82% probability of cost-effectiveness at the pound20,000 threshold. When the longevity of an IPG is 4 years or less, a rechargeable (and initially more expensive) IPG is more cost-effective than a nonrechargeable IPG. DISCUSSION: In selected patients with FBSS, SCS is cost effective both as an adjunct to CMM and as an alternative to reoperation. Despite their initial increased expense, rechargeable IPGs should be considered when IPG longevity is likely to be short.

Radionuclide impurities in proton-irradiated [18O]H2O for the production of 18F-: activities and distribution in the [18F]FDG synthesis process.

Proton- and neutron-induced activation products in the components of a high-pressure [(18)O]H(2)O target vessel used for the production of (18)F(-) in a medical cyclotron have been identified using high resolution gamma spectrometry. The activities leached from the target vessel into the [(18)O]H(2)O during irradiation, and the distribution of the identified radionuclide impurities in the various cartridges and solutions used in the [(18)F]FDG synthesis process have been measured and are discussed from the perspective of waste disposal. The results indicate that, at the energies and beam currents employed, only a few, relatively short-lived radionuclides are present in the irradiated [(18)O]H(2)O, and that the activities involved (<10 kBq in each case) are well below typical exemption limits. Activities of beta-emitting (3)H in irradiated [(18)O]H(2)O, produced via the (18)O(p,(3)H)(16)O reaction, have also been determined using liquid scintillation spectrometry. Measured activity concentrations, in the range 150-180 kBq g(-1), are consistent with those reported by other workers. Analyses of the synthesised [(18)F]FDG confirm the radiochemical purity of the product, both for (3)H and for gamma-emitting radionuclides in the energy range 25-1650 keV.