Determination of inorganic arsenic and organic arsenic compounds in marine organisms by hydride generation/cold trap/gas chromatography— mass spectrometry

The behavior of arsenite, methylarsonic acid, dimethylarsinic acid, trimethylarsine oxide, dimethyl-R-arsine oxides, and trimethyl-R-arsonium compounds (R = carboxymethyl, 2-carboxyethyl, 2-hydroxyethyl) toward sodium borohydride and hot aqueous sodium hydroxide was investigated. The arsines obtained by sodium borohydride reduction of the undigested and digested solutions were collected in a liquid-nitrogen cooled trap, separated with a gas chromatograph, and detected with a mass spectrometer in the selected-ion-monitoring mode. The investigated arsenic compounds were stable in hot 2 mol dm^?3 sodium hydroxide except arsenobetaine [trimethyl(carboxymethyl)arsonium zwitterion] that was converted to trimethylarsine oxide, and dimethyl(ribosyl)arsine oxides that were decomposed to dimethylarsinic acid. Hydride generation before and after digestion of extracts from marine organisms allowed inorganic arsenic, methylated arsenic, arsenobetaine, and ribosyl arsenic compounds to be identified and quantified. This method was applied to extracts from shellfish, fish, crustaceans, and seaweeds.     

Spectrophotometric study and analytical application of rare-earth Tiron complexes-II Determination of europium

The absorption spectra of europium-Tiron complexes in aqueous solution have been measured from 340 to 600 nm. The absorbance at 390 and 420 nm follows Beer's law up to 0.8 mg ml (pH 6.2-6.6). Other rare earths except for cerium(III) did not interfere. The interference of cerium could be removed by addition of ascorbic acid. The combining ratio of Tiron to europium has been found to be 1:1.     

Microscopic evidence of antiferromagnetic long range ordering in the organic free radical, 1,3-bisdiphenylene-2-phenyl allyl (BDPA) benzene complex

ESR study of an organic free radical, BDPA-benzene complex, presents microscopic evidence of the antiferromagnetic long range order with a Néel temperature of 1.698 K, which is in good agreement with the transition temperature indicated by a heat capacity measurement.     

Magnetic anisotropy of Sm2Fe14B single crystal

Magnetization measurements have been made on a Sm₂Fe₁₄B single crystal in magnetic fields up to 140 kOe. The easy direction of the magnetization lies along [100] in the tetragonal structure P4₂/mnm. Magnetic anisotropy energies at 290K along [110] and [001] have been estimated to be 5.8×10⁶ and 1.1×10⁸ erg/cm³, respectively, both becoming much larger at lower temperature. No evidence of the spin canting of Nd₂Fe₁₄B type is observed even at 4.2K.     

Implementing solenoid microcoils for wide-line solid-state NMR

Solid-state nuclear magnetic resonance (NMR) probeheads using solenoid microcoils with an inner diameter of 300-400 microm are developed for the study of mass-limited solid samples. Some attention is paid to the mechanical ruggedness of the probes allowing sample changing. The performance, in terms of sensitivity and RF-characteristics, of these probeheads is studied for (1)H, (31)P, and (27)Al in different model compounds in view of the feasibility of specific applications. The results show that the sensitivity is high enough to detect approximately 10(14) spins/sqrt Hz with a signal-to-noise ratio of 1 in a single scan. A specific advantage of microcoils for solid-state NMR applications is that they can generate extremely high RF-fields if implemented in appropriate circuits. Using RF-powers in the hundreds of Watts range, RF-fields well in excess of 1MHz can be made. This allows the excitation of spectra of nuclei whose resonance lines are dispersed of several megahertz. This is particularly useful for quadrupolar nuclei experiencing large quadrupolar interactions as is demonstrated for (27)Al in single crystal and powdered minerals.