Stationary phase-based two-dimensional chromatography combining both covalent and noncovalent interactions on a single HPLC column

A new type of 2-D separation material was synthesized and studied. The material is suitable for 2-D chromatography utilizing both covalent and noncovalent interactions. The first dimension is boronate affinity chromatography, and the second dimension is RP chromatography (or vice versa). The polymeric media were prepared using p-vinylphenylboronic acid as the functional monomer. This monomer was selected due to the presence of the boronic acid group for the cis-diol/boronate interaction in boronate chromatography. Two crosslinkers were evaluated, namely ethylene glycol dimethacrylate and divinylbenzene. The crosslinker content was varied to maximize the polymer strength and the RP performance of the packed column. Several parameters were evaluated to define the optimum for polymer strength and column performance including crosslinker, porogen, initiator, and column-packing parameters. The polymer-based HPLC columns were successful in separating phenol, catechol, dimethylphthalate, and hydroquinone under RP conditions, and thus can be used as an RP HPLC column. The columns were also successful in separating catechol and adenosine under boronate chromatography conditions, and thus can be used as a boronate affinity column. Moreover, the two types of chromatography can be performed consecutively on the same column during one complete chromatographic run, making it a 2-D chromatography. Under these 2-D conditions, the catechol was separated from a mixture of phenol, catechol, dimethylphthalate, and hydroquinone; the adenosine ribonucleoside was separated from a mixture of adenosine ribonucleoside, adenosine deoxyribonucleoside, and uridine deoxyribonucleoside. This type of single-column 2-D HPLC eliminates the requirement of a complex and expensive multidimensional HPLC instrument and provides increased peak capacity for separation.     

Nonlinear Optical Properties of Benzylic Amide [2] Catenanes: A Novel Versatile Photonic Material

Abstract

Benzylic amide catenanes are a class of synthetically-accessible interlocked molecular rings which can rotate one through the other depending on the nature of the local environment. The rings contain four phenyl units each and interlocking also affords their packing in novel, highly interacting ways that may lead to unexpected properties thus opening up the possibility of developing new materials. Third harmonic generation in benzylic amide catenane solutions was measured at a wavelength of γ = 1064 nm, with the fundamental and the harmonic wavelengths in the region of transparency of the material. The thoroughly non resonant value of the hyperpolarisability γ(-3ω; ω, ω, ω) was found to be (6.5 ± 0.7) × 10^?35 esu with a negligible imaginary part, in agreement with the value of (6.8 ± 0.9) × 10^?35 esu calculated from a bond-additivity model of hyperpolarisability. The static second order hyperpolarisability predicted by a Molecular Orbital model was about a factor four less than the experimental value. Second hyperpolarizability values of several solvents were also measured at the fundamental wavelength of γ = 1064 nm.     

Isolation of an [SNS]Pd(II) pincer with a water ladder and its Suzuki coupling activity in water

A water-compatible Pd(ii) pincer with a hybrid [SNS]-donor set, [L(1)PdCl]Cl.2H(2)O [L(1) = bis-(2-(i-butylsulfanyl)-ethyl)-amine] has been isolated and crystallographically characterized; its solid lattice at 223 K contains a ladder-like water polymer of tetramers and extensive H-bonding exists among the cation, anion and water cluster, and this water-soluble complex is active in Suzuki-Miyaura coupling of phenylboronic acid and selected aryl bromides in water at 75 degrees C.     

Cobalt-catalyzed hydrogen desorption from the LiNH2-LiBH4 system

A doping of 5 wt% CoCl2 considerably decreases the dehydrogenation temperature of a mixture of LiNH2 and LiBH4. More that 8 wt% of hydrogen can be released at ca. 155 degrees C. X-Ray absorption near edge structure (XANES) spectroscopy indicated the formation of metallic Co after ball milling CoCl2 with LiNH2 and LiBH4. Extended X-ray absorption fine structure (EXAFS) spectroscopy measurements revealed that Co particles have poor crystallinity and are finely dispersed in the sample, which could lead to a high catalytic efficiency.     

Stepwise assembly of linearly-aligned Ru-M-Ru (M = Pd, Pt) heterotrimetallic complexes with sigma-4-ethynylpyridine spacer

Two heterotrinuclear oligomeric complexes [trans-RuCl(C[triple bond, length as m-dash]Cpy-4)(dppm)(2)](2)[MCl(2)] (M = Pd ; M = Pt ) are prepared from the metalloligand trans-[RuCl(C[triple bond, length as m-dash]Cpy-4)(dppm)(2)] (dppm = Ph(2)PCH(2)PPh(2), ). The resultant linear alignment of the metals [Ru-M-Ru] is imposed by a combinative use of trans-directed spacers and planar metals with trans-juxtaposed donor sites. Ligand exchange of with [Pd(CH(3)CN)(4)][PF(6)](2) gives trans-[Ru(CH(3)CN)(C[triple bond, length as m-dash]Cpy-4)(dppm)(2)][PF(6)] (). All complexes are characterized by single-crystal X-ray crystallography and solution spectroscopy. Acid-base titration on suggested protonation of the pendant pyridyl. Complexes and also undergo protonation at the C[triple bond, length as m-dash]C moiety under acid conditions. The inter-conversion of alkynyl and vinylidene functionality is described. The dual acid and base characters of makes it a potential metalloligand towards basic and acidic fragments in multinuclear heterometallic assemblies.     

Capillary electrophoresis with inductively coupled plasma-mass spectrometric and electrospray time of flight mass spectrometric detection for the determination of arsenic species in fish samples

CE was coupled to inductively coupled plasma MS (ICP-MS) and ESI-MS to identify and quantify the arsenic species arsenobetaine (AsB), arsenite (As(III)), arsenate (As(V)), and dimethylarsinic acid (DMA). A GC-flame ionization detector (FID)-based German standard method and ICP-MS were used for validation of the data obtained for arsenobetaine and total arsenic, respectively. LODs obtained with the CE-ESI-TOF-MS method were 1.0x10(-7) M for AsB, 5.0x10(-7) M for DMA, and 1.0x10(-6) M for As(III) and As(V). For the CE-ICP-MS method, LODs were 8.5x10(-8) M for AsB, 9.5x10(-8) M for DMA, 9.3x10(-8) M for As(III), and 6.2x10(-8) M for As(V). While CE-ICP-MS provided high sensitivity and better reproducibility for quantitative measurements, CE-ESI-MS with a TOF mass analyzer proved to be valuable for species identification. With this setup, fish samples were prepared and analyzed and the obtained data were successfully validated with the independent methods.