High-performance liquid chromatographic assay for pilocarpine in aqueous humor

A high-performance liquid chromatographic assay for pilocarpine has been developed for the determination of pilocarpine in aqueous humor. A structurally similar internal standard is used, and pilocarpine is separated from isopilocarpine under the chromatographic conditions used. A 100-microliter sample is mixed with an aliquot of internal standard at pH 8.3 and extracted with methylene chloride. The extract is evaporated to dryness and the alkaloids are quaternized with p-nitrobenzyl bromide. Following the quaternization, the sample is evaporated to dryness, washed and diluted with a mobile phase--triethylamine mixture and analyzed by high-performance liquid chromatography using a reversed-phase octadecylsilane column with detection at a wavelength of 254 nm. This is a highly sensitive, reproducible and selective assay for measuring pilocarpine at physiological levels in individual aqueous humor samples.     

Photobiological effects of metal ions. Photosensitizing action of uranyl acetate on Escherichia coli K-12

Abstract— The Uranyl acetate sensitized killing of Escherichia coli K-12 by a light source approximating sunlight in both intensity and wavelength distribution is demonstrated to occur at a concentration of 5.0 × 10O^-4M uranyl acetate (pH 7.0). The photosensitized killing was evident after 150 min and almost complete within 320 min. Auxotrophic mutants were isolated from cultures incubated in both light and dark for 160 min at this concentration of uranyl acetate. Binding of UO₂²⁺ to E. coli is shown to occur with 82% of the UO₂²⁺ ions in a 5 × 10^-4M solution (pH 7.0) being bound to the cell wall. In the dark as well as at other pH values the extent of binding was much less. Most of the binding occurred in a time less than 30 min. The observation of rapid binding but delayed photosensitization is attributed to the necessity for penetration of uranyl ions into the cells' interior to effect photosensitization.     

Mass spectra of some syn- and anti-aromatic aldoximes

The mass spectra of eight pairs of geometric isomers of aromatic oximes and four other single aromatic oximes are reported. The loss of H₂O, HO and HCN are major fragmentations from the molecular ion of all the benzaldoximes studies; however, the loss of HCN from the molecular ion did not occur in the oximes of 9-phenanthraldehyde, 1-naphthaldehyde and 2-naphthaldehyde. The halogen substituted benzaldoximes eliminate HCNO and H₂CNO forming an additional fragmentation pathway from the molecular ion. In general, variations were found for each pair of syn- and anti-oximes but no consistent patterns could be found in the spectra for all the syn-isomers versus all of the anti-isomers. The geometric isomerism of four oximes previously reported in the literature have been established for the first time as anti-m-bromobenzaldoxime, syn-9-phenanthraldoxime, syn-1-naphthaldoxime and syn-2-naphthaldoxime. Three new oxime acetates were prepared and their mass spectra are discussed.     

Potential histidine decarboxylase inhibitors. II. 3-(4-Imidazolyl)-2-pyridine and piperidinecarboxylates

The synthesis of methyl 3-(4-imidazolyl)-2-pyridine ( 12 ) and piperidineearboxylates ( 13 ) is described. Hydrolysates of these esters were found to be devoid of inhibitory activity against histidine decarboxylase. 3-Bromoacetyl-2-pieoline ( 2 ) could be converted to 3-(4-imidazolyl)-2-picoline ( 6 ) by two different routes. Treatment of 6 with peroxide and acetic anhydride, followed by transesterification yielded the 2-hydroxymcthyl pyridine ( 9 ). Oxidation of 9 followed by esterification gave the imidazole pyridine acid ester ( 12 ) which after hydrogenation afforded the imidazolylpiperidine ester ( 13 ).     

Aspects of chloride interference in zinc determination by atomic-absorption spectroscopy with electrothermal atomization

During the determination of zinc in a polluted stream by atomic-absorption with electrothermal atomization, chloride was found to exercise a large negative interference (40%) when a carbon-filament atomizer was used, but not when a graphite-furnace atomizer was used. The effect on the filament method was confirmed and shown to be due to the formation of zinc chloride, and further complicated by interaction of this with iron. This interference could be overcome by the use of aqueous ammonia solution or silver nitrate added as matrix modifier. The absence of interference in the graphite-furnace method is attributed to the liberation of hydrogen and removal of chloride as hydrogen chloride. It is further suggested that these observations offer a basis for the exploration of apparently contradictory reports in the literature.     

Synthesis, isolation, and characterization of trisodium tricarbonyliridate (3-), Na3[Ir(CO)3]. Initial studies on its derivative chemistry and structural characterizations of trans-[Ir(CO)3(EPh3)2](-), E = Ge, Sn, and trans-[Co(CO)3(SnPh3)2](-1)

Reduction of Na[Ir(CO)4] by sodium metal in (Me2N)3PO, followed by treatment with liquid ammonia, provided high yields (ca. 90%) of unsolvated Na3[Ir(CO)3], a thermally stable, pyrophoric orange solid. This substance contains iridium in its lowest known formal oxidation state of -3 and has been characterized by IR spectroscopy, elemental analyses, and derivative chemistry, i.e., by its conversion to the triphenylgermyl and triphenylstannyl complexes, trans-[Ir(CO)3(EPh3)2](-), E = Ge, Sn. Single-crystal X-ray structures of the tetraethylammonium salts of these species, as well as [Co(CO)3(SnPh3)2](-), confirm the trigonal bipyramidal nature of the anions, originally predicted on the basis of their IR spectra in the carbonyl stretching frequency region. These structural characterizations provide important additional evidence for the presence of metal tricarbonyl units in Na3[M(CO)3], M = Co, Ir.     

Synthesis, crystal structure, and electronic structure of RbVSe2

RbVSe₂ has been synthesized at 773 K through the reaction of V and Se with a Rb₂Se₃ reactive flux. The compound crystallizes in the orthorhombic space group D_2h²⁴-Fddd with 16 formula units in a cell of dimensions , , and at . The structure possesses infinite one-dimensional chains of edge-sharing VSe₄ tetrahedra separated from the Rb⁺ ions. These chains distort slightly to chains. The V-V distance within these chains is 2.8362(4) Å. First-principles total energy calculations indicate that a non-magnetic configuration for the V³⁺ cations is the most stable.     

Solid-State 67Zn NMR spectroscopic studies and ab initio molecular orbital calculations on a synthetic analogue of carbonic anhydrase

The tris(pyrazolyl)hydroborato zinc complexes [Tp(But,Me)]ZnX (where X = Br, Cl, and OH) have been examined by low-temperature solid-state (67)Zn NMR spectroscopy. The value of the quadrupole coupling constant, Cq, for the zinc increased monotonically with the electronegativity of the bound substituent X, e.g., Br < Cl < OH. Calculations on the methylimidazole complex [(MeImH)(3)Zn(OH)](+) as a model for the active site of carbonic anhydrase indicate that the computed electric field gradient tensor is in good agreement with the experimental and calculated values for [Tp(But,Me)]ZnOH.     

Confocal imaging of porous silicon with a scanning laser macroscope/microscope

High resolution, large area photoluminescence mapping with scanning stage microscopes has proven to be a useful, but slow, quality control technique for compound semiconductor wafers. This paper describes a confocal scanning beam MACROscope-Microscope which can image specimens up to 7.5×7.5 cm in size, in less than 10s, using reflected light, photoluminescence, and optical beam induced current. MACROscope mode provides 5 μm lateral resolution and 300 μm axial resolution. Microscope mode provides 0.25 μm lateral and 0.5 μm axial resolution, with a minimum field of view of 25×25 μm. This instrument can be used to evaluate preparation parameters involved in the manufacture of porous silicon as well as to provide quality control at a macroscopic and microscopic level for the fabrication of porous silicon specimens, wafers, detectors, and similar devices. A brief introduction to confocal microscopy and porous silicon is given. Several confocal and non-confocal photoluminescence and reflected-light images of a porous silicon wafer are shown at macroscopic and microscopic levels. A 3D profile of porous silicon structures reconstructed from confocal slices is also shown.     

Dispersed fluorescence spectroscopy and fluorescence lifetime measurements of excited vibrational levels of CdCH3

Laser-induced excitation and dispersed fluorescence spectra (originating from the 0⁰, 2¹ and 3¹ vibrational levels of the electronic state) of jet-cooled CdCH₃ are presented and assigned. The observation of emission from these levels is a result having important implications for the dynamics of photodissociation of Cd(CH₃)₂. Fluorescence lifetimes for emission from the 0⁰, 2¹ and 3¹ vibrational levels are also presented.