Electrokinetic sample injection for high‐sensitivity CZE (part 2): Improving the quantitative repeatability and application of electrokinetic supercharging‐CZE to the detection of atmospheric electrolytes

Electrokinetic supercharging (EKS) is defined as a technique that combines electrokinetic sample injection with transient ITP. Quantitative repeatability of EKS‐CZE and the other CE methods using electrokinetic sample injection process is usually inferior in comparison with the CE methods using hydrodynamic or hydrostatic injection. This is due to some effects, such as the temperature change and the convection of the sample solution in the reservoir, as well as the change of the distance between an electrode and a capillary end (D_ec). In particular, we have found that the D_ec change might most seriously affect the repeatability, especially when the electrode is a thin Pt wire that could be unintentionally bent during sampling. By using a Teflon spacer to fix D_ec to 1.1 mm, the RSD of peak area (n=5) was decreased from 20 to 3.4% in EKS‐CZE for several metal cations. This D_ec dependence of the sample amount injected was supported by computer simulation using CFD‐ACE+ software. The improved repeatability (down to 5.1% at n=5, averaged RSD for Co²⁺, Li⁺, Ni²⁺, Zn²⁺ and Pb²⁺) was also experimentally attained by increasing the D_ec to ca. 20 mm, which was also effective to obtain high sensitivity. Since the temperature and the convection effects on the repeatability are comparatively small in a proper laboratory environment, these effects were estimated from the EKS‐CZE experiments using conditions such as warming and agitating the sample solution during EKS process. Finally, EKS‐CZE was applied to the detection of ions from atmospheric electrolytes in high‐purity water exposed to ambient air for 2 h. The microgram per liter levels of anions (chloride, sulfate, nitrate, formate, acetate and lactate) and cations (ammonium, calcium, sodium and magnesium) could be detected using conventional UV detector.     

Concise and stereoselective synthesis of 2,5- and 2,4-disubstituted thiazole amino acid subunits for synthesizing thiazole-containing peptides

A concise, highly stereoselective synthesis of 2,4- and 2,5-disubstituted thiazole amino acids was developed. These are important building blocks for various biologically active thiazole-containing natural peptides and their regioisomeric analogues. The fundamental reactions are diastereoselective addition of (4- or 5-bromothiazol-2-yl)lithium to N-tert-butanesulfinyl imine with subsequent Pd-catalyzed phenoxycarbonylation.     

Photoelectron spectral intensities of some first transition series elements in metal cyanides containing inequivalent atoms

Photoelectron spectral intensities of some first transition series elements were studied for metal cyanides containing inequivalent atoms. The spectra of low-spin ions coordinated via carbon to the cyanide ion, and of high-spin ions coordinated through nitrogen were separately obtained from manganese, iron, and cobalt cyanides. Metal 2p spectra obtained as sums of the appropriate spectra of low- and high-spin ions were nearly coincident with the spectra of the compounds containing inequivalent atoms. These results show that the intensity of the 2p electron for each atom must include the main peak and perhaps multiplet splitting effects, shake-up effects, and the inelastic scattering tail, and verify the non-interaction nature of the inequivalent atoms in these compounds.     

Increase in aminobutyrate aminotransferase and cholineacetyltransferase in cerebrum of aged rats

We previously reported an increase in aminobutyrate aminotransferase (GABA-T) activity in the cerebrum of Alzheimer patients. In the present study, we investigated whether such findings are common in the usual aging process as well. We examined the activity of various enzymes, which were examined in the previous study, in the cerebrum of Wistar-Kyoto rats and spontaneously hypertensive rats. In the two strains, we compared the enzyme activities between the two groups of animals, 5 weeks and 13 weeks of age. In both strains, the older animals had significantly higher activities of GABA-T and choline acetyltransferase (ChAc-T). In spite of other enzymatic changes coexisting, the above two enzymes were suggested by discriminant function analysis to be playing a major role in the multiple enzymatic changes in the cerebrum of the animals.     

Determination of the oxidation states of bismuth and copper in superconductor Bi-Ca-Sr-Cu-O by oxidation-reduction titration

Summary The oxidation state of the superconductor Bi-Ca-Sr-Cu-O was determined by two procedures. One was ferrous-chromate titration after dissolution of the sample in manganous nitrate solution. The other was the titration after dissolution in ferrous ion solution. The former procedure gives the concentration of a state like pentavalent bismuth and the latter gives the sum of concentrations of a state like pentavalent bismuth and a state like trivalent copper or peroxide. The result of the titration shows that the superconductor oxide has the state like pentavalent bismuth but not like that of trivalent copper. This is a striking contrast to YBa₂Cu₃O_7–y having a high concentration of the latter state. Although the result was compared with X-ray photoelectron spectra, a clear relationship between them was not obtained.

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Bestimmung der Oxidationsstufen von Bismut und Kupfer im Supraleiter Bi-Ca-Sr-Cu-O durch Redoxtitration

     

Ion chromatography for determination of nitrite and nitrate in seawater using monolithic ODS columns

A fast and highly sensitive ion chromatographic method using monolithic ODS columns was developed for the determination of nitrite (NO2-) and nitrate (NO3-) in seawater. Two monolithic ODS columns (50 mm x 4.6 mm i.d. + 100 mm x 4.6 mm i.d.) connected in series were coated and equilibrated with 5 mM cetyltrimethylammonium chloride (CTAC) aqueous solution. The column efficiency with 0.5 M NaCl as the mobile phase did not decrease in spite of the increase in flow rate of the mobile phase. Thus, good chromatograms were obtained within 3 minutes for NO2- and NO3 in artificial seawater without interferences by coexisting ions. The detection limit (S/N = 3) with UV detection at 225 nm was 0.8 and 1.6 microg/L for NO2- and NO3-, respectively. The characteristics of the monolithic CTA(+)-coated ODS columns were discussed. The present method was successfully applied to the fast and sensitive determination of NO2- and NO3- in real seawater samples.     

Effect of backing metals in the X-ray fluorescence spectral analysis of metal films and its application

Summary The enhancement effect of the backing metal on the x-ray intensity of an element in a film has been studied. This effect is dependent on the wave length of the x-ray absorption edge of the element in the film. In the case of nickel film, the infinite thickness at which this effect is lost is about 20, and the infinite thickness is independent on the kind of backing metals. It has also been recognized that this enhancement effect is convenient for increasing the x-ray intensity of small amounts of an element. The application of this effect has been demonstrated for the determination of small amounts of nickel and cobalt, which were concentrated in an organic precipitate.

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Zusammenfassung Die verstärkende Wirkung des Grundmetalls auf die Röntgenstrahlenintensität eines Elementes in einem Überzugsfilm wurde untersucht. Diese Wirkung ist abhängig von der Wellenlänge der Röntgenabsorptions-kante des Elementes im Überzug. Im Falle eines Nickelüberzugs beträgt die Dicke, bei der diese Wirkung aufhört, etwa 20. Diese Dicke ist unabhängig von der Art des Grundmetalls. Die Erscheinung kann zur Erhöhung der Röntgenfluorescenzintensität kleiner Mengen eines Elementes benutzt werden. Als Anwendungsbeispiel wird die Bestimmung kleiner Mengen Nickel und Kobalt beschrieben, die in einem organischen Niederschlag konzentriert wurden.