Determination of carbon dioxide evolution rates using a novel noninstrumental microrespirometer

A novel noninstrumental microrespirometer was developed to determine carbon dioxide evolution rates of solid or liquid samples at microL/h levels accurately and rapidly. The respirometer is based on the simple principle of acid-base titration at a steady-state of carbon dioxide absorption/evolution. The structure and operation of the microrespirometer are simple and the cost is modest in comparison to instrumental methods. The microrespirometer is suitable for laboratory studies and field routine examinations of food, agricultural, and environmental samples.     

Effect of lithium alkoxide and hydroxide on polymerization initiated with alkyllithium

The effects of lithium tert-butoxide on rates of initiation, propagation, and polymerization of butyllithium-initiated polymerization of butadiene and styrene were examined. Toluene and cyclohexane were used as solvent and the experiments covered BuLi/-t-BuOLi ratios from 1:0 to 1:6. Both polymerization and propagation rates declined in the presence of alkoxide. The initiation rate in cyclohexane increased to a maximum at BuLi/t-BuOLi ratio of 1:0.5 and then decreased. A mechanism of rapid dissociation of butyllithium oligomer by alkoxide and multiple complexation of butyllithium with excess alkoxide is proposed. Lithium alkoxide also reduced the copolymerization rate but did not affect the copolymerization characteristies. Water reacted with organolithium compound rapidly to form hydroxide. It was found that the hydroxide reacted very slowly with more organolithium compound in hydrocarbon solution to form oxide. Their effects on polymerization were investigated.     

Determination of some precious metals by neutron activation analysis

A neutron activation procedure for the determination of Ru, Pd, Os, Ir, Pt and Au in a single irradiation in silicate rocks, meteorites and sulfide ores has been developed. An alkali fusion was used to dissolve and mix 100 to 200 mg powder samples with appropriate carriers. The individual metals were separated and brought to a state of high radiochemical purity by distillation, ion exchange and solvent extraction techniques. Precious metal activities were counted by both γ and β-methods. The procedure was evaluated by replicate analyses of the granite and diabase rock standards, G-1 and W-1 and a Cu−Ni sulfide matte which had previously been analysed by emission spectrographic and spectrophotometric methods. The results were compared with previously published data. A major discrepancy was found only for Ir in W-1.     

Low surface energy polymers and surface-active block polymers. III. Adamantyl-containing polymers

Two adamantyl-containing oxazoline monomers. 2-(1-adamantyl)-2-oxazoline, A , and 2-(1-adamantylmethyl)-2-oxazoline, B , were synthesized, and polymerized in 1,2-dichlorobenzene to give polymers PA and PB respectively. Both polymers are highly crystalline and showed very high T_m's (269°C for PA and 320°C for PB ) and little solubility in common organic solvents. Annealed PA showed a critical surface tension of 23.6 dyne/cm. PB was not soluble in the many organic solvents tested at room temperature. Due to its high T_m and insolubility, contact angle measurements on PB were impossible. Diblock copolymers based on different weight ratios of A and 2-ethyl-2-oxazoline, E , showed relatively narrow molecular weight distribution (MWD) when methyl p-nitrobenzenesulfonate, I , was used as initiator. After annealing, diblock polymers with B/I = 7, 10, or 12 showed T_m's (200–281°C); after quenching the same samples showed T_c's (160–171°C), which were lower than that of pure PB , 215°C. The quenched diblocks showed single T_g's (63–82°C) which implies that these short blocks are compatible. Diblock polymer with B/I = 5 and E/I = 20 was amorphous and displayed inverse emulsifying ability in styrene + water emulsion polymerization. BEB type triblock polymers prepared using ethylene glycol dinosylate as initiator had broader MWD and higher T_m's compared to their diblock counterparts with the same B/E wt% and B/I ratios. These triblock polymers were not completely soluble in styrene and/or water and therefore could not be used as emulsifying agents.     

Chiral supercritical fluid chromatography/tandem mass spectrometry for the simultaneous determination of pindolol and propranolol in metabolic stability samples

A chiral packed-column supercritical fluid chromatographic (pSFC) system coupled to tandem mass spectrometer (MS/MS) for the rapid measurements of (R,S)-propranolol and (+/-)-pindolol in metabolic stability samples was developed. The effects of the eluent flow rates and compositions, as well as of the nebulizer temperature, on the chromatographic performance and the ionization efficiency of the analytes in positive ion mode under pSFC conditions were studied. The ionization mechanism of the analytes in the CO2/methanol atmospheric pressure chemical ionization (APCI) environments with or without the use of an additive was studied. The chiral pSFC-APCI-MS/MS approach requiring approximately 2 min per sample was applied for the simultaneous determination of two pairs of racemic drugs in in vitro samples at low nanogram per milliliter concentrations.     

Dibromomethane as one-carbon source in organic synthesis: total synthesis of (±)- and (−)-methylenolactocin

A general method was developed to construct monocyclic α-methylene-γ-butyrolactone moiety. The key step is to introduce the α-methylene group by the ozonolysis of mono-substituted alkenes followed by reacting with a preheated mixture of CH₂Br₂-Et₂NH. Application of this key step in the total synthesis of the (±)- and (−)-methylenolactocin was described.     

High pressure liquid chromatography of standard and amniotic fluid phospholipids

A method for the HPLC separation of phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylcholine (PC), and sphingomyelin (SPH) was achieved using five in-series columns packed with LiChrosorb, Partisil, and μ-Porasil adsorbents, a solvent mixture of chloroform/methanol/ammonium hydroxide (50 : 36 : 6.7, by volume), and a Pye LCM2 Moving Wire (FID) detector. The same phospholipid mixture was also separated using four μ-Porasil columns with the same eluent and detector. The latter conditions were found to be suitable for the analysis of phospholipids obtained after centrifuging, extraction, and precipitation of surface-active lipid components of patient amniotic fluid collected at amniocentesis section. The lecithin/sphingomyelin (L/S) ratios, determined by the HPLC method, correlated well with those determined by the TLC technique in four normal pregnancies, whereas results of shake tests did not correlate too well with L/S ratios determined by the above two chromatographic methods. Besides the lecithin/sphingomyelin ratio, the present method was able to supply additional information: the concentrations of phosphatidylglycerol and phosphatidylinositol, for prediction of fetal lung maturity, and the palmitic acid content of amniotic fluid phosphatidylcholine.     

Spectroscopic correlations between supermolecules and molecules. Anatomy of the ion-modulated electronic properties of the nitrogen donor in monoazacrown-derived intrinsic fluoroionophores

The synthesis, absorption and emission spectra, fluorescence quantum yields, and fluorescence lifetimes of three compound series of trans-4,4'-disubstituted aminostilbenes (1-3) are reported. The chromo-/fluoroionophoric behavior of the monoaza-15-crown-5- (A15C5) and monoaza-18-crown-6 (A18C6)-derived species (1A(5)()-3A(5)() and 1A(6)()-3A(6)()) in acetonitrile and dichloromethane are also investigated. Great similarities in electronic spectroscopic properties (chemical shifts, wavelength, intensity, and lifetime) between the metal ion-complexed supermolecules and the corresponding chloro-substituted molecules have been observed: namely, 1A(5)()/Ca(2+)-3A(5)()/Ca(2+) approximately 1A(6)()/Ba(2+)-3A(6)()/Ba(2+) approximately 1C-3C in acetonitrile and 1A(5)()/Na(+)-2A(5)()/Na(+) approximately 1A(6)()/K(+)-2A(6)()/K(+) approximately 1C-2C in dichloromethane. Such spectroscopic correlations allow us to define the metal ion-modulated electronic character of the azacrown nitrogen atom in the ground and excited states and, in turn, to gain insights into the observed fluoroionophoric behavior of these probes in terms of the size and direction of fluorescence shifts and intensity variations.     

A new technique for labeling of Lipiodol with 188Re in the treatment of hepatic tumor

A new method for the synthesis of ¹⁸⁸Re-Lipiodol without using a chelating agent and to evaluate the stability and biodistribution of the new agent in rats with hepatic tumors was attempted. Eighteen male Sprague -Dawley rats with liver tumors were sacrificed at 1, 24, and 48 hours (six rats at each time) after injection of approximately 7.4 MBq (0.2 mCi) of ¹⁸⁸Re Lipiodol via the hepatic artery. Samples of tumor, liver and other organs were collected and tissue concentration (%ID/g) of the markers were calculated. Our data showed a high level of radioactivity in the hepatic tumors at every time of the study. The ratios of tumor to normal liver tissue concentration (T/N ratio) were 7.62 at 1 hour, 8.03 at 24 hours, and 7.70 at 48 hours. Except for the liver, kidneys and lungs, concentrations in other organs were low. The new method for labeling Lipiodol with ¹⁸⁸Re is simple and has potential for the treatment of hepatic tumors This revised version was published online in July 2006 with corrections to the Cover Date.     

Measurement of small angle based on a (1 0 0) silicon wafer and heterodyne interferometer

In this paper, a new optical material application and a heterodyne interferometer are proposed for measuring small angles. In the proposed interferometer, the optical material is a (1 0 0) silicon wafer applied to compose a new architecture of small angle sensor. The small angle measurement used the phase difference which is dependent on the incident angle at the silicon wafer surface to deduce the angular variation. The proposed architecture is simple and uses the common path method to compare test and reference signals; thus, small angles can be easily and accurately measured by estimating the phase difference. The experimental results demonstrate the feasibility of this method. The angular resolution and sensitivity levels superior to 7 × 10^?5° (1.3 × 10^?6 rad) and 150 (deg/deg), respectively, were attainable in a dynamic range of 0.45°.