A liquid chromatography/tandem mass spectrometric approach for the determination of gangliosides GD3 and GM3 in bovine milk and infant formulae

A liquid chromatographic/tandem mass spectrometric method using pneumatically assisted electrospray ionisation (LC/ESI-MS/MS) was developed for the determination of gangliosides GD3 and GM3 in milk and infant formulae. The gangliosides were extracted in a chloroform/methanol/water environment and cleaned up by solid-phase extraction (SPE) on an end-capped C8 sorbent. The gangliosides were detected in negative ion mode after separation on a reversed-phase (RP) C5 analytical column. From the different ganglioside molecular species, product ions at m/z 290 corresponding to an N-acetylneuraminic acid fragment were produced in the collision cell and used in selected reaction monitoring. A standard addition technique was applied for quantification. The relative repeatability standard deviations were less than 5% for GD3 (level 10 mg/L) and 14% for GM3 (level 0.1-0.2 mg/L).     

Tackling matrix effects during development of a liquid chromatographic-electrospray ionisation tandem mass spectrometric analysis of nine basic pharmaceuticals in aqueous environmental samples

When developing an LC-MS/MS-method matrix effects are a major issue. The effect of co-eluting compounds arising from the matrix can result in signal enhancement or suppression. During method development much attention should be paid to diminish matrix effects as much as possible. The present work evaluates matrix effects from aqueous environmental samples in the simultaneous analysis of a group of nine specific pharmaceuticals with LC-ESI/MS/MS: flubendazole, propiconazole, pipamperone, cinnarizine, ketoconazole, miconazole, rabeprazole, itraconazole and domperidone. Solutions to diminish signal suppression were examined: optimisation of the sample preparation, decrease of the flow rate, and the use of appropriate internal standards. Several SPE-stationary phases were tested in view of retention of the analytes: Oasis HLB, C8, Phenyl, Strata X-polymer RP sorbent and Strata X-polymeric SCX/RP sorbent. Oasis HLB showed the best retention for all analytes. The Oasis HLB SPE-method was optimised, but analyses showed high matrix suppression. Therefore, a second SPE-method, on a phenyl stationary phase (the second best option), was also optimised. A comparison of the matrix effect was made between the two procedures: the phenyl-method was less subject to matrix effects, however, the average matrix effect (ME%) of 46% indicated that matrix effects where still present. Several optimisation options for the phenyl-method were evaluated: addition of a ferric nitrate solution before extraction, application of an alkaline wash step, and use of a second SPE-cartridge, either a NH2-column or a florisil column. A more efficient sample clean-up was achieved by applying the extract after extraction on the phenyl column and after dilution with chloroform, onto a NH2-column (average ME%: 53%). In addition, applying a post-column split (1:5), further reduced matrix effects (average ME%: 65%). Labelled internal standards are the best way to tackle matrix effects, but no such internal standards were commercially available for the analytes of interest. The thorough search and application of four internal standards (structural analogues) was beneficial and compensates the matrix effect partially (average ME%: 83%). In an attempt to reduce the analysis time Speedisk phenyl columns were applied. Under these conditions matrix effects decreased even more while recoveries were between 91 and 109%. Different kinds of surface water samples were analyzed, and different matrix effects were observed. For this reason, standard addition will be used to perform quantitative analysis.     

A highly selective bicyclic fluoroionophore for the detection of lithium ions

The macrobicyclic molecule, 21-(9-anthrylmethyl)-4,17,13,16-tetraoxa-1,10,21-triazabicyclo [8.8.5]tricosane-19,23-dione, I, was designed, synthesized and characterized as a fluoroionophore for the selective, optical detection of lithium ions. Compound I is based on a bridged diazacrown structure, which provides a semirigid binding framework. Binding takes place by electrostatic interactions between the oxygen atoms of the crown and the cation and is transduced to fluorescence emission from an attached anthracene fluorophore. In a 75:25 dichloromethane/tetrahydrofuran solvent mixture, I acts as an intramolecular electron transfer "off-on" fluorescence switch, exhibiting a greater than 190-fold enhancement in fluorescence emission intensity in the presence of lithium ions. The relative selectivity of I for lithium ions over sodium, potassium and ammonium ions was found to be log K(Li+,Na+) approximately -3.36, log K(Li+,K+) approximately -1.77 and log K(Li+,NH4+) approximately -2.78.     

Nitroxide bound beta-cyclodextrin: is there an inclusion complex?

236CDTIPNO, a derivative of the persistent free radical TIPNO (1,1-dimethylethyl 2-methyl-1-phenylpropyl nitroxide) covalently bound to a permethylated-beta-cyclodextrin, was prepared. Self-association of 236CDTIPNO in water was proved by solvent- and competition-dependent EPR spectroscopy experiments with 2,6-di-O-Me-beta-cyclodextrin (DIMEB) and permethylated-beta-cyclodextrin (TRIMEB) as external hosts competing for accommodation of the TIPNO moiety. Temperature-dependent EPR spectra were simulated with a novel two-dimensional (field-temperature) EPR simulation program that afforded a full determination of the thermodynamic parameters characterizing the rate constants of the self-inclusion reaction derived from Arrhenius and Eyring models. This method allows separating the line broadening effects due to relaxation from a chemical exchange, even if only the fast exchange regime is accessible experimentally. The activation parameters for the forward and backward steps were consistent with an equilibrium between a nonassociated form and a weakly associated form, with activation free enthalpies for each reaction of around 34 kJ.mol(-)(1).     

A diverse suite of spiroacetals, including a novel branched representative, is released by female Bactrocera tryoni (Queensland fruit fly)

A remarkably diverse suite of spiroacetals including a novel member of the rare, branched chain class has been identified in the glandular secretions of Bactrocera tryoni, the most destructive horticultural pest in Australia.     

A new class of silica cross-linked micellar core-shell nanoparticles

Micellar nanoparticles made of surfactants and polymers have attracted wide attention in the materials and biomedical community for controlled drug delivery, molecular imaging, and sensing; however, their long-term stability remains a topic of intense study. Here we report a new class of robust, ultrafine silica core-shell nanoparticles formed from silica cross-linked, individual block copolymer micelles. Compared with pure polymeric micelles, the main advantage of the new core-shell nanoparticles is that they have significantly improved stability and do not break down during dilution. We also studied the drug loading and release properties of the silica cross-linked micellar particles, and we found that the new core-shell nanoparticles have a slower release rate which allows the entrapped molecules to be slowly released over a much longer period of time under the same experimental conditions. A range of functional groups can be easily incorporated through co-condensation with the silica matrix. The potential to deliver hydrophobic agents into cancer cells has been demonstrated. Because of their unique structures and properties, these novel core-shell nanoparticles could potentially provide a new nanomedicine platform for imaging, detection, and treatment, as well as novel colloidal particles and building blocks for mutlifunctional materials.     

Synthesis and spectroscopic properties of a hexapyrenylbenzene derivative

In this paper, we present a synthetic approach to the first hexapyrenylbenzene starting from 4,5,9,10-tetrahydropyrene. Absorption and fluorescence spectroscopic measurements show strong and red-shifted fluorescence both from locally excited pyrene states and from the excitonic manifold of the aggregate. [structure: see text]     

Two- and three-dimensional mapping of the iron distribution in the apoplastic fluid of plant leaf tissue by means of magnetic resonance imaging

A three-dimensional nuclear magnetic resonance imaging (MRI) technique for non-invasive mapping of iron in the apoplastic fluid of plant compartments was developed. The new technique was applied to a leaf of red stem dogwood (Cornus stolonifera). The results are compared with MRI measurements of iron distributions in two dimensions and with total reflection X-ray fluorescence results.     

Parity-violating electron scattering from 4He and the strange electric form factor of the nucleon

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 4He at an average scattering angle = 5.7 degrees and a four-momentum transfer Q2 = 0.091 GeV2 . From these data, for the first time, the strange electric form factor of the nucleon G(E)s can be isolated. The measured asymmetry of A(PV) = (6.72 +/- 0.84(stat) +/- 0.21(syst) x 10(-6) yields a value of G(E)s = -0.038 +/- 0.042(stat) +/- 0.010(syst), consistent with zero.