Vol. 55 No. 4
April, 2006
Hideyuki Yoshida1, Hitoshi Nohta1 and Masatoshi Yamaguchi1
1 Faculty of Pharmaceutical Sciences, Fukuoka University, 8-19-1, Nanakuma, Johnan-ku, Fukuoka-shi, Fukuoka 814-0180(Received 1 January 2006, Accepted 7 February 2006)
A highly selective and sensitive method with a novel concept is introduced for the assay of biological substances. This method is based on an intramolecular excimer-forming fluorescence derivatization with a pyrene reagent, followed by reversed-phase liquid chromatography. Polyamines, polyphenols, and polycarboxylic acids, having two or more reactive functional groups in a molecule, were converted to the corresponding polypyrene-labeled derivatives by a reaction with an appropriate pyrene reagent. These derivatives afforded intramolecular excimer fluorescence (440~520 nm), which can clearly be discriminated from the monomer (normal) fluorescence (360~420 nm) emitted from pyrene reagents and monopyrene-labeled derivatives of monofunctional compounds coexisting in the samples. By intramolecular excimer fluorescence detection, highly selective and sensitive determinations of polyamines including histamine and basic amino acids, polyphenols, and polycarboxylic acids including acidic amino acids could be achieved. Furthermore, the methods were successfully applied to the determination of various biological and environmental substances in real samples, which required only a small amount of samples and a simple pretreatment.
Keywords : excimer fluorescence; fluorescence derivatization; liquid chromatography; spectrofluorometry; pyrene.
Saori Hirata1 and Keiji Gamoh1
1 Faculty of Education, Kochi University, 2-5-1, Akebono-cho, Kochi-shi, Kochi 780-8520(Received 3 October 2005, Accepted 16 December 2005)
In chromatographic analysis, a suitable derivatization of the functional groups has sometimes been used to enhance the sensitivity and selectivity for detection. Transforming low-molecular organic acids to the corresponding 2-nitrophenylhydrazide derivatives has been more extensively used as a suitable derivatization method for liquid chromatography/mass spectrometric (LC/MS) detection. In the present study, LC/MS detection with electro spray ionization (ESI) was successfully applied to the analysis of middle-chain fatty acids (MFA): pentanoic, hexanoic, heptanoic, octanoic, nonanoic and decanoic acid, as their 2-nitrophenylhydrazide derivatives (2-NPHs). At the point of derivatization, microwave irradiation was successfully used to prepare 2-NPH derivatives. Of a range of analytical conditions that were examined, the optimum results were obtained by using reversed-phase liquid chromatography and a mixture of acetonitrile/ammonium formate. The effects of the chromatographic and ionization parameters, ionization mode and cone voltage on the sensitivity of 2-NPHs of MFA were examined. The negative-ion spectra of 2-NPHs of MFA showed molecular-related ions, [M-H]-, whose ions were the most abundant. Linear plots of the peak area versus the concentration were obtained for MS detection over the range 0.05~10 µM for most 2-NPHs of MFA. The limits of detection of 5.5~10.5 nM (signal-to-noise ratio 3) were attained in a selected-ion monitoring (SIM) mode. These results showed that 2-NPHs of MFA contribute to the enhancement of LC/MS detection, and the 2-NPH derivatization using microwaves has a potential to simplify the conventional analytical method for MFA.
Keywords : middle-chain fatty acid; 2-nitrophenylhydrazide(2-NPH) derivatization; microwave irradiation; LC/MS; electro spray ionization.
(Received 19 December 2005, Accepted 14 February 2006)
The laser ablation (LA) method brings purposeful effect for quantitative analysis. A new LA system has been developed for inductively coupled plasma mass spectrometry (ICP-MS). This system consists of a high-frequency Q-switched laser and 2 scanning mirrors for moving the ablation spot in an adequate area without any vacant space. The influence of elemental fractionation (non-stoichiometric generation of vapor species) can be removed by repetitive radiation of this pattern on the same area. Particles generated with 0.6 W of average laser power in the developed LA system gave intensity and stability nearly equal to that of a 500 µg/ml solution steel sample in solution ICP-MS. The analytical performance of the developed LA-ICP-MS was compared with that of a solution ICP-MS using NIST steel SRMs. The developed system is no less than the usual solution ICP-MS in accuracy and precision. The correlation coefficients between the contents and the intensity ratios to Fe were over 0.99 in most elements. The relative standard deviation (RSD) obtained by LA-ICP-MS revealed that this system could analyze iron samples with good precision. The results of an ultra trace-level analysis of high-purity iron showed that the developed LA-ICP-MS was able to analyze ppm levels of concentration with a 20~30 ppb level of standard deviation. The detection limits were 10 ppb levels in most elements.
Keywords : laser ablation; repetitive radiation; ICP-mass spectrometry; fractionation.
Kazuki Kageshima1, Takaya Takei2 and Yoshinori Sugitani2
1 Laboratory, Utena Co., Ltd., 575-3, Kitano-machi, Hachiohji-shi, Tokyo 192-0906(Received 19 December 2005, Accepted 17 February 2006)
The stability of an emulsion could be monitored by high-frequency spectroscopy. The results for an o/w-type emulsion showed that the frequency shifts with the passage of time were affected by the speed of stirring and/or by the temperature of storage. The amount of the frequency shifts was in good agreement with the average particle size observed by an optical microscope. This means that high-frequency spectroscopy can detect the progress of a creaming effect due to separation of the emulsion. A similar series of experiments was conducted for an w/o-type emulsion and a commercial product of emulsion, leading to similar observation results. These results show that high-frequency spectroscopy is effective for a rapid evaluation of the stability of w/o- and o/w-type emulsions as well as a multi-ingredient emulsion.
Keywords : emulsion; high-frequency spectroscopy; separation; creaming; stability.
Kyoko Fujimoto1 and Atsushi Chino2
1 Steel Research Laboratory, JFE Steel Corporation, 1, Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba 260-0835(Received 24 November 2005, Accepted 27 January 2006)
Trace amounts of mercury, lead, and cadmium at a level of ng g-1 in steel were determined by ICP-MS after cation-exchange chromatographic separation. The sample was decomposed with nitric acid, and the analytes were separated from the iron matrix in 1 M hydrofluoric acid solution, using the cation-exchange resin packed in a mini-column. The elements adsorbed on the resin were eluted by 8 M hydrochloric acid solution and determined by ICP-MS simultaneously. The lower limits of detection based on 3σ of blank values were 2 ng g-1 for mercury, 9 ng g-1 for lead, and 0.5 ng g-1 for cadmium.
Keywords : cation exchange chromatographic separation; trace mercury, lead and cadmium in steel; simultaneous analysis by ICP-MS.
Kunihiro Watanabe1, Takashi Osawa1, Junichi Iwata1 and Masayuki Itagaki1
1 Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641, Yamazaki, Noda-shi, Chiba 278-8510(Received 17 November 2005, Accepted 7 February 2006)
The flow-injection analysis of arsenic in steels using a Teflon (PTFE) filter tube concentration method was investigated. Arsenic coprecipitated with beryllium hydroxide at pH 10, which was collected with a filter tube for 5 min. The precipitate was eluted with 1 M nitric acid at 0.6 ml/min, and the eluate was reacted with ammonium molybdate; the molybdoarsenate complex was reduced with ascorbic acid. The obtained molybdenum blue complex was determined by spectrophotometry at 840 nm. In the presence of phosphorus, which shows the same behavior as arsenic, the absorbance A2 was proportional to the sum of the concentration of arsenate and phosphate. The absorbance A1, which was obtained by reducing the arsenate to arsenite with thiosulfate, corresponded to the concentration of phosphate alone. Then, the arsenate concentration was given as A2-A1. The calibration curve for arsenic was linear over the range of 0 to 100 ppb. The limits of detection and determination for arsenic were 0.7 and 2 ppb, respectively. The relative standard deviation for 20 ppb As was 1.3% (n=8). The iron as a matrix did not interfere with the determination of As up to a million-fold to arsenic amount. The determination results for arsenic in available steel certified reference materials, which did not include phosphorus, showed good agreements with the certified values.
Keywords : flow injection analysis; filter tube concentration; arsenic; steel; molybdenum blue.
(Received 21 July 2005, Accepted 4 January 2006)
A convenient method was proposed for the spectrophotometric determination of total nitrogen in sewage and river-water samples. Each water sample was taken into glass bottles with screw caps and then heated at 120°C for 30 min after the addition of potassium peroxodisulfate, by which nitrogen-containing compounds were quantitatively oxidized into nitrate. The determination of the resulting nitrate was performed by measuring the absorbance at 540 nm after a diazotization coupling reaction of N-naphthylethylenediamine and sulfanylamide in the presence of nitrite generated from the reduction of nitrate with vanadium chloride. The proposed method could be applied to the determination of total nitrogen in sewage and river-water samples. Analytical data obtained by the proposed method were highly correlated to those determined by the UV method (JIS method). The sensitivity of the proposed method is superior to those of spectrophotometric methods reported so far.
Keywords : total nitrogen; vanadium chloride; spectrophotometry; diazotization; nitrate.
Sahori Takeda1, Zyun Siroma2 and Kazuaki Yasuda2
1 National Institute of Advanced Industrial Science and Technology (AIST), Bio-based Polymers Group, Research Institute for Innovation in Sustainable Chemistry, 1-8-31, Midorigaoka, Ikeda-shi, Osaka 563-8577(Received 26 December 2005, Accepted 25 January 2006)
The application of capillary electrophoresis/mass spectrometry was investigated concerning the separation and identification of ionic components generated by degradation of the polymer electrolyte membrane for fuel cells. A model degraded sample was prepared by Fenton oxidation of a Nafion® membrane. Model and control samples were dissolved in a water/2-propanol (1/1) mixed solution, and used for an investigation. In the mass detection for the anionic components, an unknown compound was observed at m/z 297. The migration behavior of the component in capillary electrophoresis suggested that the component is highly acidic. The structure of the compound was estimated by an analysis of its migration behavior and its mass spectrum. The component was probably generated by a side-chain cleavage of Nafion®.
Keywords : capillary electrophoresis; mass spectrometry; fuel cell membrane; degradation; ionic component.
Yuko Kitamaki
National Institute of Advanced Industrial Science and Technology, National Metrology Institute of Japan, Organic Analytical Division, Tsukuba Central 3-10, 1-1-1, Umezono, Tsukuba-shi, Ibaraki 305-8563
(Award by the Gifu University dated March 25, 2005)
An analytical method that utilized a specific interaction was studied for the improvement of analytes detection sensitively and selectively. First, inorganic nitrogen species (nitrate, nitrite and ammonium ions) were simultaneously determined by microcolumn ion chromatography. Nitrate and nitrite were retained on the anion-exchange column, and monitored directly by a UV detector. On the other hand, ammonium ion was not retained, and the effluent from the UV detector was merged with the post-column reaction reagent, followed by detection with a fluorescence detector. The latter fluorescence detection was based on the post-column reaction of ammonium ion with o-phthalaldehyde and it was effective for the determination of ammonium ion sensitively. In this study, the eluent and the post-column mixing reagent solution were supplied by using a single micropump in order to obtain a stable baseline. Second, iodate was determined sensitively by using cyclodextrin (CD) as an inclusion host. It is known that iodate react with iodide to produce triiodide under acidic condition. In the addition of CD, the sensitivity of iodate was increased significantly. It was proposed that the triiodide was formed largely since the equilibrium of the reaction was toward the formation of the CD-triiodide inclusion complexes. The same phenomenon was occurred in the determination of bromate. The use of this kind of specific interaction in HPLC is effective to improve the sensitivity and selectivity, which can not be achieved only with instrumental analysis.
(Received December 6, 2005)
Keywords : HPLC; specific; sensitivity; selectivity; postcolumn mixing; mircopump.
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