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81.
Electroosmotic volume flow was directly observed in a simple instrument consisting of 1 cm long a home-made support, packed between two polyethylene frits in the polypropylene tube. Equations relating electroosmotic flow (EOF) velocity and pH for two functional groups on the surface of the solid materials were developed. With these equations, we can estimate the dissociation constants of two different kinds of functional groups on modified silica gel materials simultaneously. The dissociation constants of silanol groups, benzene sulfonic acid groups, and alkyl quaternary ammonium groups on the modified and unmodified silica gel supports were estimated. The estimated pK values of the silanol groups on the silica gel and modified silica gel surfaces are between 4.0 and 4.3. The estimated pK values of the benzene sulfonic acid groups and alkyl quaternary ammonium groups on the surface of the modified silica gel are 2.6 and 8.6, respectively. 相似文献
82.
Takamitsu Otake Masahiko Numata Akiko Takatsu 《International journal of environmental analytical chemistry》2016,96(14):1378-1388
Human serum certified reference material (CRM), NMIJ CRM 7407-a, for the analysis of polychlorinated biphenyls (PCBs) was developed by the National Metrology Institute of Japan. A pool of commercially available human serum was used as a raw material of the CRM. This sample is in the form of a liquid comprising approximately 4 g stored in a cryogenic polypropylene vial. Homogeneity assessment was performed, and the material was homogeneous enough for PCB 118, PCB 138, PCB 153, and PCB 194: the relative uncertainties due to inhomogeneity were 2.5–10.5%. The results obtained from the stability assessment indicated that the target PCBs were stable: the relative uncertainties due to instability were 0–14.7%. The certification was carried out using two different types of GC columns for each target PCB to avoid interferences on GC separation; the certified values of the target PCBs (PCB 118, PCB 138, PCB 153, and PCB 194) were 9.7–129.8 ng/kg. This is the first frozen human serum CRM in which PCBs were determined by isotope dilution mass spectrometry. 相似文献
83.
Inagaki K Kuroiwa T Narukawa T Yarita T Takatsu A Okamoto K Chiba K 《Analytical and bioanalytical chemistry》2008,391(6):2047-2054
A new cod fish tissue certified reference material, NMIJ CRM 7402-a, for methylmercury analysis was certified by the National
Metrological Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Cod fish
was collected from the sea close to Japan. The cod muscle was powdered by freeze-pulverization and was placed into 600 glass
bottles (10 g each), which were sterilized with γ-ray irradiation. The certification was carried out using species-specific
isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID–GC–ICPMS), where 202Hg-enriched methylmercury (MeHg) was used as the spike compound. In order to avoid any possible analytical biases caused by
nonquantitative extraction, degradation and/or formation of MeHg in sample preparations, two different extraction methods
(KOH/methanol and HCl/methanol extractions) were performed, and one of these extraction methods utilized two different derivatization
methods (ethylation and phenylation). A double ID method was adopted to minimize the uncertainty arising from the analyses.
In order to ensure not only the reliability of the analytical results but also traceability to SI units, the standard solution
of MeHg used for the reverse-ID was prepared from high-purity MeHg chloride and was carefully assayed as follows: the total
mercury was determined by ID–ICPMS following aqua regia digestion, and the ratio of Hg as MeHg to the total Hg content was
estimated by GC–ICPMS. The certified value given for MeHg is 0.58 ± 0.02 mg kg−1 as Hg.
Figure NMIJ CRM 7402-a: cod fish tissue for MeHg analysis 相似文献
84.
Purity certified reference materials (CRMs) are playing a key role in metrological traceability, because they form the basis
for many traceability chains in chemistry. Recently, the National Metrology Institute of Japan (NMIJ) has developed two purity
CRMs for creatinine (NMIJ CRM 6005-a) and urea (NMIJ CRM 6006-a), because the concentrations of these two compounds are frequently
measured in clinical laboratories for monitoring the renal functions. In the certification of purity CRMs, it is essential
that the materials have been thoroughly characterized for purity, and the purity should preferably be determined directly
by a primary method of measurements. In the development of these two CRMs, we used the purified materials as candidates. The
certified values were assigned based on the results of two different methods; acidimetric titration and nitrogen determination
by the Kjeldahl method. Since both methods cannot distinguish some impurities from the target compounds, major impurities
in the candidate materials were also identified, quantified, and subtracted. These CRMs can provide a traceability link between
routine clinical methods and SI units.
Presented at BERM-11, October 2007, Tsukuba, Japan. 相似文献
85.
We report here an algorithm for calculating a hologram to be employed in a high-access speed microscope for observing sensory-driven synaptic activity across all inputs to single living neurons in an intact cerebral cortex. The system is based on holographic multi-beam generation using a two-dimensional phase-only spatial light modulator to excite multiple locations in three dimensions with a single hologram. The hologram was calculated with a three-dimensional weighted iterative Fourier transform method using the Ewald sphere restriction to increase the calculation speed. Our algorithm achieved good uniformity of three dimensionally generated excitation spots; the standard deviation of the spot intensities was reduced by a factor of two compared with a conventional algorithm. 相似文献
86.
87.
Shin-ichiro Fujii Kazumi InagakiAkiko Takatsu Takashi YaritaKoichi Chiba 《Journal of chromatography. A》2009,1216(44):7488-7492
We performed the quantification of phosphorus in deoxynucleotides using capillary electrophoresis (CE) and micro-HPLC (μHPLC) hyphenated with inductively coupled plasma mass spectrometry (ICP-MS). DNA and its component units have conventionally been determined by photometry; however, more selective and sensitive methods are needed for small biological samples. CE and μHPLC offer the advantages of good separation and small consumption of samples, and ICP-MS is a highly sensitive technique for the determination of a chemical element. Therefore, we have developed an interface device for combining CE and μHPLC with ICP-MS for quantifying nucleotides based on phosphorus content. The interface utilizes 4.5 μL/min for nebulizing and effective introduction of the sample into ICP. The samples of nucleotides and free phosphoric acid were well separated in the CE–ICP-MS measurement, and the calibration curves (1–100 μg/mL) of the nucleotides showed a linear (R2 > 0.999) increase in intensity. Similarly, the samples of nucleotides were baseline separated using μHPLC–ICP-MS, and the calibration curves of the nucleotides were linear (R2 > 0.998). The detection limits of these species and phosphorus in nucleotides using CE–ICP-MS and μHPLC–ICP-MS were 0.77–6.5 ng/mL and 4.0–6.5 ng/mL, respectively. These values were about one or two orders lower than those in a previous report. The sample volumes of these experiments were calculated to be about 10 nL and 50 nL per analysis. Therefore, these analytical methods have the potential to be useful for the determination of biological samples, such as DNA and RNA molecules. 相似文献
88.
We experimentally reveal an unconventional anomalous Hall effect (UAHE) in a quasi-two-dimensional triangular-lattice antiferromagnet PdCrO?. Using high quality single crystals of PdCrO?, we found that the Hall resistivity ρ(xy) deviates from the conventional behavior below T*?20 K, noticeably lower than T(N)=37.5 K, at which Cr3+ (S=3/2) spins order in a 120° structure. In view of the theoretical expectation that the spin chirality cancels out in the simplest 120° spin structure, we discuss required conditions for the emergence of UAHE within Berry-phase mechanisms. 相似文献
89.
90.
Kazuya Takemoto Yoshiki Sakuma Shinichi Hirose Tatsuya Usuki Naoki Yokoyama Toshiyuki Miyazawa Motomu Takatsu Yasuhiko Arakawa 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):185
We present an optical spectroscopy and photon correlation measurement at telecommunication wavelengths performed on single InAs/InP quantum dots. Two main approaches brought high optical quality: an application of a ‘double-cap’ growth method to metalorganic chemical vapor deposition, and fabrication of a small mesa structure using low-damage wet chemical etching. Sharp and discrete exciton transition lines have been observed on the single quantum dots, which widely cover the spectral range of 1.3–1.55 μm. Using a pulsed excitation source and gated single-photon detection modules, we observed a photon antibunching behavior for an isolated exciton emission line, indicating nonclassical light emission near the wavelength of 1.3 μm. 相似文献