Determination of nickel in water by electrothermal atomic absorption spectrometry with preconcentration on a tungsten foil

A preconcentration method for nickel in waters involving adsorption on tungsten foil, followed by electrothermal atomic absorption spectrometry (ETAAS) with a tungsten tube atomizer is described. The most suitable pH for nickel adsorption was 5 and the optimum immersion time was 2 min. Severe interferences from co-existing elements (Al, Ca, Cu, Fe, K, Mg, Na, Pb and Zn) on the Ni AA signal were observed. Under optimal conditions, the preconcentration of nickel on W foil could eliminate interferences from these elements. The detection limit of nickel by preconcentration-ETAAS was 0.1 ng/ml (3S/N). The method with preconcentration on tungsten foil was applied to the determination of nickel in river water. The recovery of spiked nickel was 93–102%. The tungsten foil preconcentration method is sensitive, simple, and convenient. This adsorption method can be utilized inin situ-sampling of ultra-trace nickel in environmental samples (water). Furthermore, after sampling it is easy to carry and store the W-foil without contamination for long time.     

Di-tert-butylsilylene-directed alpha-selective synthesis of 4-methylumbelliferyl T-antigen

[reaction: see text] We have succeeded in the facile synthesis of 4-methylumbelliferyl T-antigen as a substrate for endo-alpha-N-acetylgalactosaminidase by exploiting the combination of the di-tert-butylsilylene effect and the Mitsunobu reaction.     

Synthesis of cross-linked chitosan possessing N-methyl-d-glucamine moiety (CCTS-NMDG) for adsorption/concentration of boron in water samples and its accurate measurement by ICP-MS and ICP-AES

A chitosan resin derivatized with N-methyl-d-glucamine (CCTS-NMDG) was synthesized by using a cross-linked chitosan (CCTS) as base material. The N-methyl-d-glucamine (NMDG) moiety was attached to the amino group of CCTS through the arm of chloromethyloxirane. The adsorption behavior of 59 elements on the synthesized resin was systematically examined by using the resin packed in a mini-column, passing water samples through it and measuring the adsorbed elements in eluates by ICP-MS. The CCTS-NMDG resin shows high ability in boron sorption with the capacity of 0.61 mmol ml⁻¹ (= 2.1 mmol g⁻¹). The sorption kinetics of this resin was faster than that of the commercially available resins. Other advantages of the synthesized resin are: (1) quantitative collection of boron at neutral pH regions; (2) complete removal of large amounts of matrices; (3) no loss of efficiency over prolonged usage; (4) effective collection of boron in wide range concentration using a mini column containing 1 ml resin; (5) complete elution of boron with 1 mol l⁻¹ nitric acid. The resin was applied to the collection/concentration of boron in water samples. Boron in tap water and river water was found to be in the range of 6-8 μg l⁻¹. The limit of detection (LOD) of boron after pretreatment with CCTS-NMDG resin and measurement by ICP-MS was 0.07 μg l⁻¹ and the limit of quantification (LOQ) was 0.14 μg l⁻¹ when the volume of each sample and eluent was 10 ml.     

Synthesis of 4-aminocycloheptimidazoles

2-Methyl- 1a , 2-phenyl- 1b , and 2-amino-4-(2-methyl-1,3-dioxolan-2-yl)cycloheptimidazole ( 1c ) were treated with hydrazoic acid to give the corresponding 4-aminocycloheptimidazoles, respectively. However, the reaction of 4-(2-methyl-1,3-dioxolan-2-yl)cycloheptimidazole gave complex material. Some approaches to the synthesis of 4-aminonocycloheptimidazole itself are also described.     

Acid-catalyzed reactions of 1- and 3-(α-hydroxybenzyl)indolizines

Treatment of 1-(α-hydroxybenzyl)- and 3-(α-hydroxybenzyl)indolizines with trifluoroacetic acid in dichloromethane gave phenylbis(α-indolizinyl)methanes, bis[α-(indolizinyl)benzyl] ethers and indolizines, depending upon the presence or absence of the substituent at the 2- or 5-position and the reaction conditions used.     

Extraction—spectrophotometric determination of nickel with 4-chloro-2-nitroso-1-naphthol and crystal violet

Six nitrosonaphthol derivatives are evaluated for the determination of nickel(II) after ion-pair formation with zephiramine or crystal violet, 4-chloro-2-nitroso-1-naphthol is the best; its nickel complex forms an extractable pair with crystal violet. The apparent molar absorptivity is 8.2 × 10⁴ l mol^-1 cm^-1 at 611 nm; calibration graphs are linear in the range 0–10^-5 M nickel(II).     

1,4,5-trigermabicyclo[2.1.0]pent-2-en-5-ylium: the isolable bishomocyclopropenylium ion containing a heavier group 14 element

The isolable bishomoaromatic cation containing a heavier Group 14 element, (2,3,5-deloc)-2-phenyl-1,4,5-tris(tri-tert-butylsilyl)-1,4,5-trigermabicyclo[2.1.0]pent-2-en-5-ylium TPFPB- (2+.TPFPB-; TPFPB- = tetrakis(pentafluorophenyl)borate) was synthesized by the reaction of 5-bromo-2-phenyl-1,4,5-tris(tri-tert-butylsilyl)-1,4,5-trigermabicyclo[2.1.0]pent-2-ene (1) with [Et3Si(benzene)]+.TPFPB- in benzene at room temperature. The characteristic bishomoaromatic structure was unambiguously determined by X-ray crystallographic analysis. NMR measurements on 2+.TPFPB- confirmed the nonclassical germyl cation structure in solution and showed strong shielding of homoconjugative carbon atoms. The bishomoaromaticity in 2+ was also investigated by theoretical calculations.     

Nematocidal activity of long alkyl chain amides, amines, and their derivatives on dog roundworm larvae.

The nematocidal activity of amides and amines having a long alkyl chain against the second-stage larva of dog roundworm, Toxocara canis, was examined. Long chain acyl amides with smaller substituents on the nitrogen showed stronger activity and the activity of cyclic amine amides was stronger than that of acyclic ones. In a series of homologous amides, the activity was dependent on the alkyl chain length: it reached a maximum at an optimal chain length and decreased in both shorter and longer homologues. The relationship between the activity and hydrophobicity of the homologues was analysed by the use of the bilinear model. The hydrophobicity of a compound, which gives a maximal activity, was similar for all neutral amides, but amides which have an additional amine group in the molecule had different values. Tertiary amines and their salts having a long alkyl chain also showed nematocidal activities comparable to those of the corresponding amides. The salts killed the larva at concentrations lower than their critical micell concentration, suggesting that they behave as a single molecule for the nematocidal action.     

Ultra-smooth glass channels for bioassay with motor proteins

Optically-flat glass channels were fabricated for the non-fluorescent observation of bio-molecules. Two bioassays of motor proteins were successfully performed, in which nanoscale beads and microtubules were clearly observed by a differential interference contrast (DIC) microscope and a dark-field microscope, respectively. The concentration of hydrofluoric acid (HF) was optimized to obtain an optically flat surface which was evaluated by AFM, SEM and dark-field microscopy. A glass channel was etched using a poly(dimethyl siloxane)(PDMS) microfluidic channel as a mask and sealed with a PDMS-coated coverslip. The channel volume of 2-3 microl realized the drastic reduction of proteins required per assay compared with a conventional flow cell method requiring 20 microl.     

Modified cylindrical cavity-type phase separator for liquid/liquid extraction in flow-injection systems

The dimensions of a cylindrical cavity-type phase separator for liquid/liquid extraction in flow-injection analysis were examined in order to achieve smooth, long-term and efficient phase separations with good reproducibility and high sensitivity. Several kinds of filter (PTFE membrane filters and a phase-separating filter) for the organic phase were also compared. A phase separator with a cylindrical cavity (4.2-mm diameter, 2.3-mm deep) and a conical cavity (5-mm diameter, 1.7-mm deep) was the most desirable. A less expensive phase-separating filter can be used instead of a PTFE membrane filter.