BUNSEKI KAGAKU Abstracts

The real-time detection of an increase in the atmospheric aerosol number concentration due to Asian dust and outdoor facility construction was studied with a stochastic method, called FUMI theory (function of mutual information). It is difficult to find this event in its early stage by means of instrumental analysis, since the instrumental output originating from the event is so small that it can almost be hidden under, or rather overlapped with, the omnipresent instrumental noise. Difficulty comes from the fact that the background and objective signal are both subject to random fluctuations. If an observed value exceeds a detection limit, the hypothesis that the observed one originates from a natural cause other than the Asian dust or outdoor facility construction would be denied. The following methods are elaborated to make the early detection of the event more practical with satisfactory precision: continuous shift of a time domain used for the detection-limit estimation; removal of spike noise and output judged as a signal in our method from the domain; classification of a signal in the scale of the detection limit.

Certified reference materials of pure oxygen were produced by National Metrology Institute of Japan mainly for the metrological traceability source of JCSS oxygen in nitrogen standard gases. The property value of the certified reference material is the amount of substance of oxygen which was determined by the subtraction method described in ISO/IEC 6142:2001. The expected impurity components in the certified reference material were CO, CO₂, CH₄, N₂O, H₂O, Ar and N₂. CO, CO₂, CH₄ and N₂O in the certified reference material were determined by FT-IR with a long-path gas cell. Ar and N₂ were determined by GC-TCD with an oxygen absorber, and H₂O was determined by a capacitance hygrometer. The stability of the amount of substance of impurities was monitored. The impurities except for CO₂ were not detected and were regarded as being stable. The amount of substance of CO₂ seemed to increase. The uncertainty for long-term stability of the property value was determined from the expected increase of the CO₂ amount of substance on the expiration date. The typical certified value and its expanded uncertainty (k = 2) are 0.9999993 mol mol⁻¹ and 0.9 μmol mol⁻¹, respectively. The dominant uncertainty for the certified value was the uncertainty for the impurity analysis and long-term stability. The stability was also monitored after the certification. The increase in the CO₂ amount of substance is smaller than the uncertainty for the long-term stability, and drift of the amount of substance of oxygen is smaller than the expanded uncertainty of the certified value.

Reactive chemical species with high kinetic energy can be confined when plasma is formed in solutions. The kinetic energy reaches up to above several thousand Kelvin. We can expect that the characteristic plasma in solutions will provide novel chemical reaction fields where chemical products that do not formed under ambient conditions can be obtained due to collisions between the chemically active species with high kinetic energy in the plasma and surrounding solute, and solvent molecules in a condensed phase. Here, we report on the development of a microscopic optical discharge cell that enables us to monitor the spatial distributions and temperatures of chemical species in the microscopic and heterogeneous reaction field. The microscopic optical discharge cell will contribute to the measurements, analyses and control of the novel plasma-in-solution chemical reaction fields that are going to be applied in environmental detoxification, material processing, and medical surgery.

To examine the increase of the polycyclic aromatic hydrocarbons (PAHs) concentrations and natural recovery for the sediment of the Yoro tidal flat, caused by a fire in a neighboring refinery on March 11, 2011, we measured the concentration of eight PAHs containing from three to five rings in the sediment collected between April 2011 and May 2012. After one month from the fire, the PAH concentrations of the sediment samples ranged from 1.4 to 19 μg kg-dry⁻¹ in shallow sediment (0 – 5 mm) and from 2.0 to 31 μg kg-dry⁻¹ in deep regions (10 – 15 cm). The concentrations were about 2 – 5 times as high as those before the outbreak of the fire, and were dominated by phenanthrene, fluoranthene, and pyrene, which were derived from the combustion of propane and butane. The PAH concentrations of the sediment gradually decreased with a lapse of time, and then returned to the same levels as before the fire over about 10 months. This reduction of the PAHs in the sediment is largely attributed to the benthos living in the Yoro tidal flat through their biological activities, such as bioturbation and metabolic activities.

Many spectrophotometric methods by flow-injection analysis (FIA) have been reported, which are based on the reaction of chromium(VI) with diphenylcarbazide. In those methods, organic solvents, such as acetone, ethanol, 1-propanol, are used to dissolve diphenylcarbazide, so that the reagent solution contained organic solvent in high or less concentration. However, it is preferable to reduce the amount of organic solvent flowing into the system, especially in cases using a peristaltic pump. In this study, FIA with the reagent solution containing acetone less than the conventional methods was examined using a compact manifold, which consists of an all-in-one peristaltic pump, injector, thermostat and photometric detector. The absorbance was measured at 540 nm. The reagent conditions and the FIA parameters were examined for optimization; the reagent solution (H₂SO₄ 0.36 mol L⁻¹-diphenylcarbazide 0.5 g L⁻¹-5 v/v% acetone) and carrier (water) were both flowed at a flow rate of 0.425 mL min⁻¹, the reactor was maintained at 40°C, and a 200 μL sample was injected. Under these conditions, the calibration curve was linear from 0.005 to 5 mg L⁻¹ (R²: 0.9998) of chromium(VI) and the relative standard deviation was 3% (n = 5) at the 0.005 mg L⁻¹ level. Good results were obtained in recovery tests using sample solutions from soil leaching and content tests according to the Japanese environmental quality standards for soil pollution.

The demand to measure the concentration of cesium is increasing. This is because such R&D as an adsorbent or a resin for removing radioactive cesium, and a shift of cesium to food is flourishing. The measurement conditions of cesium with atomic absorption spectrometry based on background-correction using Zeeman splitted spectrum has been optimized. In flame atomic absorption method, the addition of potassium nitrate (5000 mg L⁻¹ as potassium) as an ionization inhibitor improved the sensitivity because the ionization of cesium was controlled. The detection limit (3σ) of cesium by this method was 0.04 mg L⁻¹. In electrothermal atomic absorption method, 1000 mg L⁻¹ potassium tungstate as a matrix modifier improved the linearity of the calibration curve and the sensitivity of cesium. The detection limit (3σ) of cesium by this method was 0.18 μg L⁻¹. The proposed method was applied to the determination of cesium in food reference materials. The analytical results were in good agreement with certified values.

In this study, we present the first example of the separation of DNA by capillary electrophoresis (CE) using a new sieving matrix, a mixture of the poly-β-cyclodextrin (poly-β-CD) and poly(ethylene oxide) (PEO). The poly-β-CD and PEO were used as a pseudostationary phase to improve the resolution of DNA fragments. CE separation was performed using a DB-17 coating capillary at an applied voltage of −10 kV (detector at anode side). Ammonium acetate buffer (25 mmol L⁻¹, pH 6.0) was used as a background electrolyte and all sample solutions were prepared by the buffer. The best CE separation was obtained at a concentration of 5 mg mL⁻¹ poly-β-CD and 1 mg mL⁻¹ PEO. Under these conditions, 13 DNA fragments with sizes ranging from 200 bp to 4000 bp were completely resolved within 12 min, and the peak efficiencies ranged from 91000 to 234000 plates m⁻¹. The results presented in this study show the advantage of PEO containing poly-β-CD for DNA separation, including rapidity, high resolving power, and ease of analysis.

We developed a simple and fast determination method of hexamethylenetetramine (HMT) by using liquid chromatography/tandem mass spectrometry to evaluate its concentration in river water. Well-defined peaks of HMT were obtained by using a hydrophilic interaction column. A calibration curve showed good linearity (R² = 0.999). The instrumental detection limit and the instrumental quantification limit were 0.06 μg L⁻¹ and 0.16 μg L⁻¹, respectively. Only filtration was adopted for river-water sample pretreatment; the detection limit of HMT was calculated to be 0.12 μg L⁻¹. The recoveries of HMT added to pure water and river water ranged from 102% to 106% and from 92% to 104%. HMT was detected from 6 of 13 grab samples taken from Tone River system between May 18th and May 20th; the maximum concentration was 150 μg L⁻¹.

Many studies have shown that polyphenols in green tea have antioxidant activity, anti-inflammatory effects, and preventive effects against degenerative diseases, such as cardiovascular diseases and neurodegenerative diseases. We determined nine polyphenols (gallic acid, (−)-gallocatechin, (−)-epigallocatechin, (+)-catechin (C), (−)-epicatechin (EC), (−)-gallocatechin gallate, (−)-epigallocatechin gallate, (−)-catechin gallate (CG), (−)-epicatechin gallate (ECG)), and caffeine in seven commercially available bottled green-tea drinks by semi-micro HPLC. One of the bottled tea drinks contained a small excess of EC, ECG, C, where C and CG represent heat-epimerized from EC and ECG. We determined the polyphenol contents in different green-tea leaves, and then found that the different contents of EC and ECG in the tea leaves can be attributed to different varieties (Zairaishu and Yabukita). Zairaishu contained notably higher EC, ECG, C, and CG.