BUNSEKI KAGAKU Abstracts

The on-capillary dissociation reaction properties of the Zn(II) complex with 1,5-bis(2-hydroxy-5-sulfophenyl)-3-cyanoformazan ([Zn-HSCF]) have been studied using the Capillary Electrophoretic Reactor (CER). The solvolytic dissociation reaction rate constant (k_d) of [Zn-HSCF] under the optimal conditions for CE separation at pH 8.80 was determined to be 4.3×10⁻⁵ (half-life period was 4.5 hours) with ligand substitution mode CER. Thus, it is clear that [Zn-HSCF] is extremely inert at pH 8.80 in a kinetic sense. On the other hand, [Zn-HSCF] was not detected at pH 5.10 in the CE system. The k_d value at pH 5.10 was determined to be 3.7×1 by a batch-wise method with a ligand substitution technique using EDTA as a substitution ligand. The half-life period was calculated to be only 3 minutes, suggesting that almost all [Zn-HSCF] dissociates on the time scale of CE separation at pH 5.10. From an estimation of the free ligand concentration profiles in the capillary during CE separation processes, it was shown that CE separation gives an almost thermodynamically unsuitable environment for [Zn-HSCF] at both pH 8.80 and 5.10. Thus, it is concluded that the detection selectivity of metal complexes in the pre-capillary derivatization CE depends on the kinetic stability, i.e. the dissociation reaction inertness of the metal complexes, though their thermodynamic stability is necessary only for the pre-capillary derivatization step.

We investigated the separation of the regioisomers (reverse isomers) of 1,2-diacyl-rac-glycerols by reversed-phase HPLC on columns containing endcapped and non-endcapped ODS phases. The reverse isomers of 1,2-diacylglycerols, having various pairs of acyl groups including saturated and unsaturated chains, were chromatographed as 3,5-dinitrophenylurethanes (DNPU) using acetonitorile as the mobile phase. Baseline separations were achieved for the reverse isomers of very different pairs of acyl groups, such as caprylate/palmitate and stearate/arachidonate, on both endcapped and non-endcapped ODS columns, which retained longer less-polar isomers with a lower degree of unsaturation or shorter chain at the sn-1(3) position. The latter columns, however, markedly shortened the elution times of the derivatives compared to the former columns. Most commercially available ODS columns are fully endcapped so as to decrease any undesirable influence of residual silanol. The present study, however, demonstrates that non-endcapped ODS phases are more suitable for reverse isomer separation than fully endcapped ones.

Laser-induced fluorescence detection using diode lasers as excitation light sources has been applied to the highly sensitive analysis of polyaromatic hydrocarbons, amino acids, DNA, and proteins. Diode lasers emitting at the near-infrared to red region were employed for direct and indirect fluorescence detections. In addition, to enhance the sensitivity in capillary electrophoresis, Hadamard transform capillary electrophoresis has been developed. The method includes multiple injection, followed by an inverse Hadamard transformation. Optically gated injection, electrokinetic injection using a microchip, and electrokinetic injection using a laser-fabricated capillary have been developed for achieving multiple sample injection. These methods have permitted multiple sample injection in capillary electrophoresis. The results obtained by Hadamard transform capillary electrophoresis showed a significant improvement in the S/N.

In this paper, we introduce a new method to measure the amount of water of crystallization in D-glucose powder using terahertz (THz) wave spectroscopy. We measured five crystalline D-glucose samples: one anhydrous, one monohydrate, and three in various states of partial dehydration, whose water content was measured independently by using Karl Fischer's method. By analyzing the THz absorption spectra, particularly the absorption peaks at 60.3, 65.6, and 80.5 c, which are strongly correlated with the hydration ratio, we could obtain a highly reliable analytical curve, with a correlation coefficient of 0.9509 and a standard error of prediction of 0.714. This study suggests the possibility of measuring the water of crystallization nondestructively, without using an organic solvent.

The decomposition ratio of various organic compounds in chemical oxygen demand measurements using potassium permanganate (COD_Mn) was studied as a function of the decomposition time. We focused on the relationship between decomposition behaviors of organic compound including simple compounds as a partial structure and those of these simple organic compounds. The decomposition ratio of phenols by the COD_Mn method was comparatively high for a short decomposition time. The phenol moiety in Triton X-100 and tyrosine was decomposed as well as phenol. The decomposition behaviors of non-ionic surfactants were successfully explained based on those of simple organic compounds. As mentioned above, the relationship between the decomposition ratio of simple organic compounds and that of organic compounds including these simple organic compounds as a partial structure was revealed.

A ligand-exchange liquid chromatography/mass spectrometric (LC/MS) analysis of mono- and oligo-saccharides has been developed. The successful separation and detection of a mixture of seven monosaccharides, four disaccharides and two trisaccharides was performed using an improved ligand-exchange column, which was a semi-rigid styrene-divinylbenzene copolymer-based Pb-type cation-exchange resin (ULTRON PS-80P/5S), and electrospray ionization mass spectrometry (ESI-MS). Water was used as a mobile phase to separate the above-mentioned saccharides within 12 min. The ESI interface was used in a negative-ion mode for LC/MS, which produced reasonable signals from their negative ions ([M−H]⁻). The effect of aqueous ammonia, which was used as an additive to the eluent, was also examined. An increase of the detection sensitivities of the saccharides was observed when aqueous ammonia was used as the additive at a concentration of 2％ (v/v). The effects of the separation and ionization parameters, column temperature and cone voltage on the sensitivity and linearity were examined. Linear plots of the peak area versus the concentration were obtained for MS detection over the range of 5〜1000 μM (r²＝0.951〜0.999) for each saccharide. The detection limits of the target saccharides, calculated at S/N＝3, ranged from 0.25 to 2.00 pmol. The reproducibility of the retention times and the peak areas were 0.66〜1.2％ and 0.96〜2.86％, respectively. Then, those results were compared with the results by using a Ca-type ligand-exchange column, which confirmed the usefulness of the Pb-type ligand-exchange LC/MS analysis of mono- and oligo-saccharides.

A dummy cathode brings about the sputtering of non-conductive ceramics, like SrTiO₃ in a helium glow discharge ion source. This study addresses that phenomenon. A dummy cathode with an outer diameter of 20 mm and an aperture diameter of 5 mm was prepared from a Ta sheet using electrical-discharge machining. A Ta plate with a 10 mm aperture diameter was used as an anode plate. The optimal electric discharge parameter was obtained at a He flow rate of 10 mL/min and a discharge voltage of 2 kV. The discharge current was about 2 mA. The ion intensities of Ti, Sr, and Ta reached 10⁻¹⁰ A level in peak-area integrated intensity at a mass resolution of 4000. The ion intensity the ratios to Ta, Ti : Ta and Sr : Ta, were both 0.26 : 1. Under these conditions, five data sets were acquired a after pre-discharge for 60 min, which proved that a stable glow discharge continued for 170 min or longer. The relative sensitivity factors of O and Sr to Ti, RSF_O,Ti, and RSF_Sr,Ti, were obtained using the measurement of a SrTiO₃ single crystal; they were, respectively, 0.179 and 2.099.

A novel spectrophotometric method was established for the determination of quinine and its related drugs based on ternary complex formation among o-sulfophenylfluorone, copper(II) and quinine. In the determination of quinine, Beer's low is obeyed in the range of 0.2〜3.2 μg c. The effective molar absorptivity at 590 nm and the relative standard deviation were 2.0×10⁵ dm³ mol⁻¹ cm⁻¹ and 2.0％ (n＝6), respectively. The method was successfully applied to assays of quinine and its related drugs in pharmaceutical preparations. In addition, it was suggested that the ternary complex showed thermochromism.

An electron probe microanalyzer (EPMA) was applied to suspended particulate matter (SPM), hourly collected by a β-ray attenuation method SPM automatic sampler with a polytetrafluoroethylene (PTFE) tape filter, at a monitoring station in Nakahara, Kawasaki, Kanagawa, at 17 : 00 on April 13th and at 7 : 00 on April 19th, 2006. From the results, it was inferred that inorganic secondary particles were partly collected on April 13th, since N and S were detected and Asian dust was collected on April 19th, because the detected chemical elements were very similar to those of Asian dust collected in China in the past. Also, it was found that particles on a carbon-coated PTFE filter could be directly observed and analyzed by EPMA.

Boron determination in a silicon carbide (SiC) sample was carried out by a dissolution technique with an alkaline solution. Using the proposed method, a 0.50 g sample of silicon carbide powder was placed in a platinum dish and fused with 3.0 g of sodium carbonate. After the cake was dissolved in water, boron was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). Through this method, it was possible to determine with high precision the amount of boron in the SiC sample.

Trace metals in natural water are sensitive indicators of geochemical processes and reactions, environmental pollutions, and bioactivities, though these elements are present in extremely low concentrations. Determination of trace metals in natural water is still a challenge for analysts, even using the most advanced available analytical instrument such as ICP-MS. In order to overcome this difficulty, a chelating resin-packed minicolumn was developed to preconcentrate trace metals in natural water. The minicolumn was constructed by packing a slurry of Chelex 100 resin into the space of the outlet of a syringe filter (DISMIC-25HP, ADVANTEC), which was then capped with another syringe filter (Millex-LH, Nihon Millipore Kogyo). Furthermore, a procedure for the preconcentration of trace metals in natural water using the present minicolumn was established by carefully optimizing each operating parameter. As a result, a concentration factor of 20-fold was achieved for trace metals using only 50 mL of a natural water sample, where the recovery values for most of the trace metals were more than 80％ with a standard deviation less than 5％. The effectiveness of the present analytical method was assessed by determining trace metals in seawater certified reference materials (NASS-5, CASS-3, and CASS-4). Furthermore, determination of trace metals in seawater, river water, and mineral water samples was carried out to assess the environmental pollution of trace metals in natural water and the mineral nutriment in mineral water, respectively.

In relation to metallomics research, the multielement determination and chemical speciation of major-to-ultratrace elements in biological samples were investigated by ICP-AES and ICP-MS with the aid of HPLC. First, the determination of multielements in human blood serum donated from healthy volunteers and disease patients was carried out. As a result, it has been suggested that a multielement analysis of serum may be available for the medical diagnosis of specific diseases. Next, the chemical speciation of mercury and the assay of ALP in salmon egg cell cytoplasm were performed using CHAPS-coated ODS and the SEC columns. The existence of some protein-binding mercury and cysteine-binding mercury in salmon egg cell cytoplasm was confirmed. The analytical results indicate that Hg in salmon egg cell cytoplasm binds with proteins containing selenocysteine and/or cysteine residues. In an ALP assay study, the existence of hydrophilic ALP and hydrophobic conjugated proteins of ALP in salmon egg cell cytoplasm was found. Finally, a phosphatidylcholine-coated ODS column was newly developed and applied to a speciation analysis of arsenic compounds in human blood serum. As a result, it was found that arsenite dosed in the vein of a leukemia patient for therapeutic treatment was converted mainly to monomethylarsonic acid and dimethylarsinic acid.