Vol. 47, No. 3
March 1998
Hirotsugu Minami, Yukari Ishizu*, Atsuko Shinohara, Momoko Chiba** and Ikuo Atsuya*
*Department of Materials Science, Kitami Institute of Technology, 165, Koen-cho, Kitami-shi, Hokkaido 090-8507
**Department of Epidemiology and Environmental Health, Juntendo University School of Medicine, 2-1-1, Hongo, Bunkyo-ku, Tokyo 113-8421
It has been found that spectral interferences based on the molecular absorbance occurs at 196.0 nm of the selenium absorption line when a selenium sample solution containing 100 µg/ml of palladium in 3 mol/l sulfuric acid as a matrix modifier is measured by graphite furnace AAS equipped with a polarized d.c. Zeeman-effect background-correction system. Spectral interferences were observed when both biological powdered samples or the above-mentioned solution samples were measured. The degree of the spectral interferences depended on the amounts of potassium coexisting in the samples. When the amounts of potassium coexisted at more than ca. 30 µg, the molecular absorbance at 196.0 nm increased tenfold compared with the certified values for the certified reference materials. It was considered that the spectral interferences were caused by the molecular absorption, such as potassium sulfide or potassium chloride, because it was not observed when a sample solution containing potassium nitrate was measured.
Keywords: graphite furnace AAS; spectral interferences; determination of selenium; polarized Zeeman effect background correction.
Tatsushi Wakisaka, Naoki Morita, Tadashi Hirabayashi* and Taketoshi Nakahara**
*Kao Corporation, Materials and Process Research Laboratories, 1334, Minato, Wakayama 640-8580
**Department of Applied Chemistry, College of Engineering, Osaka Prefecture University, 1-1, Gakuencho, Sakai-shi, Osaka 599-8531
A useful and rapid procedure is described for the determination of trace phosphorus, sulfur, chlorine, bromine, and iodine by means of an energy dispersive X-ray fluorescence spectrometer (EDXRF) with monochromatic excitations. Using monochromatic excitations, the detection limits for phosphorus, sulfur, chlorine (Cr-Kα, 5.41 keV), bromine (Mo-Kα, 17.44 keV), and iodine (W-continuum, 40 keV) were found to be 4.6, 1.7 , 0.7, 0.09 and 0.5 µg g-1, respectively. The relative standard deviations in five replicate measurements were 0.9~1.3%. The proposed method was applied to the direct determination of sulfur in the NIST Residual Fuel Oil, and others. The results obtained by the proposed method were in good agreement with the certified values. Bromine in a seawater sample, as well as iodine and bromine in a brine sample were determined by the proposed method. The obtained results were in good agreement with those obtained by ion chromatography.
Keywords: energy dispersive XRF; monochromatic excitation; determination of trace non-metalic elements; seawater; brine.
Norio Manabe, Kingo Furukawa, Tsuyoshi Toyoda* and Sadao Mori**
*Suzuka Research Laboratory, Sumitomo Wiring Systems Co., Ltd., 1820, Nakanoike, Mikkaichi, Suzuka-shi, Mie 513-0803
**Department of Industrial Chemistry, Faculty of Engineering, Mie University, Tsu-shi, Mie 514-8507
The best conditions for rapid baseline stabilization, a stable baseline, and precise measurements of the retention volumes and average molecular weight of polystyrene(PS) were studied. It was assumed that a stable baseline could be obtained by keeping the temperature difference between both sides of a refractive index(RI) detector cell , reference and sample, constant. Under this assumption, the best combination of the temperatures of the column, RI cell, room, and mobile phase were examined. The adjustment of the temperatures of the column, mobile phase and RI cell to room temperature, for example 25°C was the best for the stability of the baseline. This temperature condition made it possible to shorten the time to attain a stable baseline. The time required to stabilize the baseline was 40 minutes, and the baseline fluctuation was 2.2×10-7 RIU/h. The second appropriate condition was keeping the temperatures of the column and RI at 40°C and those of the room and the mobile phase at 25°C. Adjusting the temperatures of the column and RI to room temperature was required if the temperature of the mobile phase was not controlled.
Keywords: size exclusion chromatography; stability of baseline; polystyrene standard sample; temperature of mobile phase; room temperature control.
Kunihiro Watanabe, Naomori Yokoiwa, Masayuki Itagaki and Nobuyuki Koura*
*Department of Industrial Chemistry, Faculty of Science and Technology, Science University of Tokyo, 2641, Yamazaki, Noda-shi, Chiba 278-8510
(Received 1 December 1997, Accepted 10 January 1998)The spectrophotometric determination of the average valence of Ce in Nd-Ce-Cu oxides was performed using o-tolidine. Each sample was dissolved in a HCl solution in the presence of o-tolidine, which was oxidized with Ce(IV) in a 2e step to intensely yellow quinonediimine in a weakly acidic solution. Then, Ce(IV) was reduced to Ce(III). Ce(IV) was determined over the range of 0.3~20 µg based on the absorbance observed at 437 nm on the oxidant of o-tolidine. The optimum conditions for the determination of Ce(IV) in Ce oxides were as follows: total volume, 6ml; o-tolidine concentration, 1.7×10-3%; pH, 1.0 (adjusted with HCl); reaction time, 2min; reaction temperature, 65°C; sample amount taken, 0.2~1.1 mg. On the other hand, the total Ce was determined by inductively coupled plasma atomic-emission spectrometry. The average valence of Ce (nav) could be calculated according to the following equation: nav= {[Ce(IV)]/[Ce]total}+3. The average valence of Pr in the Pr-Ba-Cu-O semiconductor was determined by the same procedure as that proposed for Ce. Cu(III) did not interfere with the determination of Ce(IV) and Pr(IV). The average valence of Ce in a sample was obtained to be 3.23. The results agree well with those obtained by the KMnO4 method. By the proposed method, the lower limit of Ce(IV) determination was 0.3 µg and the amount of consumed sample could be decresed down to 0.2 mg.
Keywords: average valence determination; cerium; praseodymium; o-tolidine.
Kunihiro Watanabe, Kunihiro Ohba, Arkin Iburaim, Masayuki Itagaki and Nobuyuki Koura*
*Department of Industrial Chemistry, Faculty of Science and Technology, Science University of Tokyo, 2641, Yamazaki, Noda-shi, Chiba 278-8510
(Received 16 September 1997, Accepted 9 January 1998)A new preconcentration on-line system for trace copper(II) determination was developed based on the adsorption of copper(II) on the walls of Teflon tubes using flow injection analysis (FIA). Copper(II) was concentrated as hydroxide or colloid on the inner walls of Teflon tubes. The present FIA apparatus had triple channels, and dual injectors were used in a carrier stream. A nitric acid solution (100 µl) was loaded in the sample loop of one injector. The sample solution containing copper(II) was loaded in another injector, where copper(II) was adsorbed. The copper(II) adsorped on a Teflon capillary tube (3 m in length, i.d. 0.5 mm) was eluted on-line with a nitric acid solution, and was then determined with ascorbic acid and o-phenylenediamine by fluorometry. The copper(II) was determined over the range of 0.025 to 200 ppb by the present method. The detection limit for copper(II) was 0.008 ppb. The RSD was 2.3% for 1 ppb Cu(II) (n=7). The treatment of Teflon tubes with a 2 M NaOH solution enhanced the adsorption of copper(II). The optimum conditions of copper(II) determination by the present method were as follows: sample solution, pH 6.0; NaOH concentration, 2 M; adsorption flow rate, 0.4 ml/min; adsorption time, 10 min. The interference in the determination of copper(II) with diverse ions, i.e. V(V) Cr(VI), Fe(III), Hg(II), Mn(II), Cd(II), La(III), Y(III) and Tl(I) could be decreased by adsorption preconcentration without a masking agent. The results of a trace Cu(II) determination in tap water showed good agreement with the values obtained by graphite-furnace AAS.
Keywords: flow injection analysis; adsorption on Teflon; ascorbic acid; o-phenylenediamine; fluorometric determination.
Kyoko Fujimoto, Masao Ito, Makoto Shimura and Keiichi Yoshioka*
*Technical Research Laboratories, Kawasaki Steel Corp., 1, Kawasaki-cho, Chuo-ku, Chiba 260
(Received 17 November 1997, Accepted 6 January 1998)The determination of trace amounts of phosphorus in high-purity silicon has been investigated. A sample was decomposed by a mixed acid vapor of hydrofluoric acid and nitric acid in a pressure bomb. The presence of 0.5 ml of sulfuric acid prevented the loss of phosphorus during the decomposition. Phosphorus in the residue was converted to molybdophosphate and collected on a polycarbonate filter as an ion pair with dodecyltrimethylammonium bromide (DTMAB). The molybdophosphate-DTMAB ion pair was dissolved in 0.2 ml of conc. sulfuric acid, and diluted to 5~10 ml with water. The molybdenum in the solution was determined by isotopic dilution/ICP-MS, which resulted in the determination of phosphorus. The interference with silicon, aluminium, and iron was almost negligible up to a concentration as high as 100~1000 times that of phosphorus; also, a µg g-1 level of arsenic in silicon materials did not interfere with the phosphorus determination. The lower limit of detection was under 0.01 µg g-1 in silicon based on 3σ of blank values.
Keywords: trace amounts of phosphorus in silicon; pressured acid-vapor decomposition; collection as molybdophosphate on an filter; indirect determination of phosphorus; isotopic dilution/ICP-MS.
Makoto Torigai, Tong Ouyang, Kiyoshi Iwashima*, Masahiro Osako and Masaru Tanaka**
*The Institute of Basic Environmental Research, Environmental Control Center Co., Ltd., 323-1, Shimoongata-machi, Hachioji-shi, Tokyo 192-0154
**Department of Waste Management Engineering, National Institute of Public Health, 4-6-1, Shirokane-dai, Minato-ku, Tokyo 108-0071
Municipal-waste incineration fly-ash samples were digested by microwave-digestion procedures with an acid mixture of HClO4-HNO3-HF. Then, selenium in the digested sample solution (in 1 M-HCl, trace-HClO4) was directly determined using graphite-furnace AAS with a Zeeman-effect background correction. Platform atomization was used and peak-area absorbance measurements were utilized. Palladium and nickel were used as modifiers. The palladium modifier stabilized selenium at a higher temperature than did the nickel modifier, resulting in a better sensitivity. An aqueous calibration curve was used and the method of additions was not necessary. The present investigated method was applied to the analysis of a certified reference material (BCR No. 176). The analytical result was in good agreement with the certified value. The present method has been successfully applied to the analysis of actual samples.
Keywords: ZGFAAS; selenium; direct determination; municipal-waste incineration fly-ash; microwave digestion.
Hiroyuki Sakai
Railway Technical Research Institute, Administration Division, 2-8-38, Hikari-cho, Kokubunji-shi, Tokyo 185-8540
(Awarded by Hiroshima University, dated September 22, 1997)Novel sensitive chemiluminescence (CL) systems were developed and it was applied for detection in ion chromatography (IC). It was difficult to combine CL detection with IC because considerable differences exist in the optimum operating condition for each system. A convenient eluent, BaCl2, for both luminol (Lm)/H2O2/KOH-CL and IC was, however found. As a result, it was possible to detect Co(II) selectively with 1.0 pg ml-1 detection limit (DL). Similarly, combination of CL and ion exclusion mode IC was examined to determine weak acid anions like silicate. Millimolar concentrations of HClO4 was effective as eluent and also resulted in their elution of the anions in their unionized molecular acid form. The molecular acids cause CL by acting as a catalyst in the oxidation of Lm by H2O2 and dissolved oxygen. However, there is considerable background CL emission generated by Lm and H2O2 in the absence of any analyte. It was found that this background CL was dramatically reduced by eliminating H2O2, and the weak acids also causes CL even in the absence of H2O2. Lower DL of 0.10 ng ml-1 Si(IV) was obtained under this condition. Moreover, when Lm itself was eliminated from the CL reagent leaving only KOH in the reagent, faint CL emission generated by the neutralization of HNO3 and KOH was obtained. When IC was conducted with a KOH eluent and HNO3 was mixed with the column effluent continuously in a post column reaction mode, the CL was quenched quantitatively by anions eluted from IC. Halide and oxo-anions were detected at ng ml-1 levels with enough separation to give no interference each other. These results appeared that these CL methods were useful to determine inorganic ions, especially anions.
(Received 19 December, 1997)
Keywords: chemiluminescence; luminol; heavy metal ions; weak acid anions: neutralization; halide ions