Discrete Nebulization for Sample Introduction of High Salt Solutions in Flame Atomic Absorption Spectrometry

The detection of copper in high salt solutions using flame atomic absorption spectrometry with discrete nebulization of microliter volumes compared to conventional continuous nebulization for sample introduction was investigated. Using continuous nebulization, a decrease in absorbance signal and uptake rate with increasing salt concentration, a detection limit of 0.02 μg/mL for copper, and precision deteriorating with increasing salt concentration in the 1–3% range was found. Discrete nebulization showed similar trends with decreasing absorbance signal with increasing salt concentration, but had the advantage that the microliter volumes used prevented clogging of the burner. At low microliter volumes and high salt concentrations, the precision deteriorated to around 10% and detection limit to 0.3 pg/mL. The technique was rapid, simple and did not produce memory effects.     

A Synthetic Supramolecular Receptor for the Hydrosulfide Anion

Hydrogen sulfide (H₂S) has emerged as a crucial biomolecule in physiology and cellular signaling. Key challenges associated with developing new chemical tools for understanding the biological roles of H₂S include developing platforms that enable reversible binding of this important biomolecule. The first synthetic small molecule receptor for the hydrosulfide anion, HS^?, using only reversible, hydrogen‐bonding interactions in a series of bis(ethynylaniline) derivatives, is reported. Binding constants of up to 90 300±8700 m ^?1 were obtained in MeCN. The fundamental science of reversible sulfide binding, in this case featuring a key CH???S hydrogen bond, will expand the possibility for discovery of sulfide protein targets and molecular recognition agents.     

The thermodynamics of the A–B transition in superfluid He as a probe of the A-phase gap node geometry

We have used a magnetic field gradient to stabilise the phase boundary between the A- and B-phases of superfluid ³He inside a quasiparticle black body radiator down to 146 μK. The radiator technique enables us to measure very accurately the density of quasiparticle excitations and therefore the temperature of the B-phase inside the radiator. As we ramp the field through the transition we can observe the cooling (warming) effect when the volume of A-phase is increased (decreased). From these measurements we deduce the temperature dependence of the latent heat, which provides the lowest temperature verification yet of the existence of nodes in the A-phase order parameter.     

Vibrational Raman effect for molecules in ground states with nonzero spin

The effect of spin degeneracy, on the Raman selection rules is investigated. The vibroelectronic processes among the degenerate components of the electronic ground state can give asymmetric contributions to the Raman tensor elements. However, the conservation of spin in a Raman scattering process prevents some of these vibroelectronic transitions. The resulting tensor element species are compared with those obtained for singlet ground states.     

Rapid method for the preparation of a robust optical pH sensor

A simple and rapid method for the preparation of a fluorescence-based optical pH sensor is described. The sensor is based on excitation ratiometric detection of a methacryloyl-modified analog of the well-known fluorescent pH indicator dye, 8-hydroxy-1,3,6-pyrene trisulfonic acid (HPTS). The modified dye, 6-methacryloyl-8-hydroxy-1,3-pyrene disulfonic acid (MA-HPDS), is similar in structure and function to HPTS. However, unlike HPTS, the presence of the methacrylate moiety allows MA-HPDS to participate as a comonomer in a free radical polymerization reaction. Covalent immobilization by this method is simple, as the preparation of the modified dye is accomplished in a single reaction step and its subsequent reaction with a comonomer results in simultaneous immobilization and purification. Sensors were prepared by copolymerization of the MA-HPDS with poly(ethylene glycol) diacrylate. Minimal leaching of the immobilized dye was observed from the HPDS-PEG matrix. The copolymer of HPDS and PEG-DA is fully autoclavable. The sensor is useful over the pH range of 6-9, with excellent reproducibility. Ionic strength effects on the apparent pKa of the immobilized dye are small and predictable.