Potentiometric responses of polymeric liquid membranes based on hydrophobic chelating agents to metal ions.

The effect of hydrophobicity of acidic chelating agents as sensing materials on the potentiometric responses of polymeric liquid membranes was investigated. The chelating agents tested were 8-quinolinol (HOx), dithizone (HDz), 1-(2-pyridylazo)-2-naphthol (PAN) and their alkylated analogues, 5-octyloxymethyl-8-quinolinol (HO8Q), di(phexylphenyl)thiocarbazone (C6HDz), 7-pentadecyloxy-1-(2-pyridylazo)-2-naphthol (C15PAN) and a series of N-alkylcarbonyl-N-phenylhydroxylamines (CnPHA, n = 3, 6, 9, 12). The distribution coefficients between membrane solvent and water were determined to evaluate the hydrophobicity of the agents. The potential-pH profiles of the membranes containing hydrophobic chelating agents demonstrated the generation of potentiometric responses, while less hydrophobic agents gave no response. A possible model for the generation of membrane potential is proposed. The charge separation is attained by the permselective uptake of metal cations by the chelating agent anion at membrane/solution interface, where the high hydrophobicity of the agent enables the anionic or deprotonated form of the agents to remain at the membrane/solution interface.

Breast cancer screening by mammography in women aged under 50 years in Japan.

BACKGROUND: The effectiveness of mammographic screening in women aged over 50 years has been confirmed in the United States and Europe, but its effectiveness in women aged from 40 to 49 years remains controversial. The optimum age for effective screening of subjects for breast cancer by mammography in Japan was studied based on the results of mammographic screening. METHOD: The benefit of breast cancer screening in women was examined by stratifying the results of mammographic screening in a Tokushima trial on the basis of age: under 50 years and 50 years or older. The results of conventional screening by physical examination alone, which we performed in a Zentsuji trial, were used as the control. RESULTS: The examinees numbered 13,982 and 18,619 in mammographic screening and screening by physical examination, respectively. Breast cancer was detected in 43 and 22 patients, respectively. The detection rate of breast cancer was 0.31% by mammographic screening, which is about 3 times higher than that (0.12%) by screening using physical examination. Mammographic screening thus showed significantly higher sensitivity (93.5% vs 73.3%, p = 0.015). The proportion of stage I cancer and the absence of nodal involvement were 67.4% and 79.1% by mammographic screening, compared with 31.8% and 59% by physical examination. Our results obtained with mammographic screening were equal to or higher than the results obtained in the United States and Europe. The clinical stage of the breast cancers detected by mammographic screening in the subjects aged under 50 years was stage 0 (DCIS) in one case and stage I in 10 cases, while the group aged 50 years or older showed stage 0 in 11 cases and stage I in 19 cases. There were three cases of false-negative; two false-negative cases were aged under 50 year, while one case was aged 50 years or older. The detection rates of cancer in the group under 50 years and that of 50 years or more were 0.19% and 0.39% by mammograpic screening and 0.09% and 0.15% by the physical examination. The sensitivities in the group under 50 years and that of 50 years or more were 84.6% and 97.0% by mammographic screening and 72.7% and 73.7% by physical examination, showing no significant difference. In the results of mammograms by Wolfe's classification with respect to the age groups, the proportion of DY (dense breast) pattern decreased significantly from 3.5% to 0.2% in women of 50 years or more and from 16.6% to 2.4% in those under 50 years when the values were compared between the period from 1992 to 1995 and the period from 1998 to 1999, respectively (p < 0.0001). CONCLUSION: The above findings suggested the possible effectiveness of mammographic screening not only in women aged 50 years or more but also in those aged under 50 years, in Japan. Therefore, introduction of mammography should be considered at an early date, even for women aged from 40 to 49 years.

Catalytic determination of silver(I) by extractive flow injection analysis.

A new catalytic method for the determination of silver(I) was developed based on a metal exchange reaction between ethylenediaminetetraacetatomercury(II) (Hg(II)-EDTA) in the aqueous phase and bis(diethyldithiocarbamato)copper(II) (Cu(II)-DDTC) in the organic phase. This exchange reaction (Cu(II)-DDTC(org)+Hg(II)-EDTA-->Hg(II)-DDTC(org)+Cu(II)-EDTA, where org denotes the organic phase) was observed to proceed slowly and the Cu(II)-DDTC complex transferred quantitatively to Hg(II)-complex in the organic phase in the equilibrium state. In this system, silver(I) acts as the catalyst and can be determined by measuring the decrease in the absorbance of the Cu(II)-DDTC complex (lambda(max)=435 nm). The reaction was applied to the extractive flow injection analysis of silver(I). The present method allows the determination of silver(I) at 10(-7) mol dm(-3) level with the sampling frequency of 30 h(-1). The relative standard deviation of 0.28% (n=10) was obtained at 4.0x10(-7) mol dm(-3) of silver(I).

Simultaneous determination of bromide and chloride in natural waters by ion-exchange chromatography and direct potentiometry with an ion-selective electrode.

A method has been developed for the sequential determination of bromide and chloride in natural waters by use of ion-exchange chromatography and an ion-selective electrode. Hydrous zirconium oxide has successfully been used as the ion-exchanger.

[Preconcentration of copper (II) and mercury (II) using dithizone and carbon powder followed by neutron activation analysis (author's transl)].

A combined method of dithizone-extraction and carbon powder column adsorption was applied to concentrate trace amounts of copper (II) and mercury (II) in natural water samples before neutron activation analysis. The sample solution was adjusted to pH 1.0 with nitric acid, an aliquot of which as taken in a 500 cm3 separating funnel and then 5.0 cm3 of 0.01% dithizone-benzene and 25 cm3 of n-hexane wee added. The mixture was shaken for 10 min and stood for 30 min. After the aqueous phase was discarded, another aliquot of the sample solution was added. The above procedure was repeated until the treatment of the sample solution (1.00 dm3) was completed. The organic phase was then flown through the column (6mm phi x 50 mmh) containing carbon powder, and the resulting column was dried. The monitor containing 10 micrograms of mercury or copper was also prepared according to the above procedure. The samples and monitors were irradiated together in a pneumatic tube of JRR-3. After cooling, copper and mercury were determined by gamma-spectrometry using 64Cu, 197Hg, respectively. The recovery of trace metal ions obtained by this method was more than 99%, and the present method was found to be applicable to the preconcentration of copper (II) and mercury (II) in natural water samples.

Kinetic studies of ion-exchange of cobalt(II) and nickel(II) on a resin loaded with 5-sulpho-8-quinolinol.

The mechanism of ion-exchange of cobalt(II) and nickel(II) on a resin loaded with 5-sulpho-8-quinolinol has been studied, and the chelate-forming reaction in the resin matrix shown to be rate-determining. The observed rate seems to be related to the rate of water-exchange with the metal ion in the aqueous phase, suggesting that complexation in the resin matrix may proceed according to the Eigen mechanism.

[Bathocuproine disulfonic acid-loaded resin as a preconcentrating agent of trace mercury (author's transl)].

A chelating agent-loaded resin consisting of an anion exchange resin (Dowex 1 X-4) and bathocuproine disulfonic acid (BCS-resin) was prepared. The adsorption behavior of some chalcophile elements as a function of pH by the column method was studied, and mercury was shown to be adsorbed selectively to the BCS-resin at the pH region of 0.5 approximately 1.0, and the BCS-resin was found to be a specific collector for trace mercury in natural water samples before neutron activation analysis. The molar ratio of BCS to mercury(II) in the resin was confirmed to be 1:1 and the resulting chelate was stable at least within a month. The method was applied to the determination of mercury in the Watarase river water sample. The sample solution was adjusted to pH 1.0 with HNO3, filtered and flown through the column (BCS-resin: 4 x 10(-4) mol . g-1 . resin, 7 mm phi x 35 mmH) and the resin was then washed and dried in a desiccator. The monitor containing 10 micrograms of mercury was also prepared according to the above scheme. The samples and the monitor were irradiated together in the pneumatic tube of JRR-3 for 60 min (neutron flux: 2 x 10(13) n . cm-2 . s-1). After cooling for 15 days, gamma-activity of 203Hg was measured. The result was 21 +/- 3 ppt for mercury, indicating that the method was well applicable to the determination of trace mercury in river water samples.

[8-Quinolinol-5-sulfonic acid-loaded resin as a preconcentrating agent in the neutron activation analysis of the chalcophile elements (author's transl)].

A chelating agent-loaded resin consisting of 8-quinolinol-5-sulfonic acid and an anion-exchange resin (HOx-resin) was prepared in order to concentrate trace chalcophile elements in natural water samples selectively before neutron activation analysis. The exchange capacity of the Diaion SA No. 100 for the reagent (1.8 meq . g-1 resin) corresponds approximately to that for chloride ion (1.83 meq . g-1 resin), indicating that 8-quinolinol-5-sulfonic acid is adsorbed quantitatively on the exchange site of the resin through the sulfonate anion in the reagent. The basic conditions for the adsorption of the metal ions on the resin were investigated by employing the column method. The nitrate concentration and the pH of the sample solution affect the adsorption behavior of metal ions. Several solutions containing metal ions with varying pH or varying nitrate concentration were applied to the resin column (35 mm x 7 mm phi) with a flow rate of 2.0 cm3 . min-1. As a result, the optimum conditions for the quantitative adsorption of copper(II), zinc(II), cadmium(II), cobalt(II), nickel(II) and manganese(II) were as follows: NO3- less than 0.01 mol . dm-3 pH greater than 4.6. Furthermore, the feasibility of the above conditions as well as quantitative adsorption of the chalcophile elements was confirmed through the neutron activation analysis of the synthesized metal solutions.

Determination of chlorine in silicate rocks by ion-exchange chromatography and direct potentiometry with an ion-selective electrode.

The method has been developed for determination of chlorine in silicate rocks by ion-exchange chromatography and an ion-selective electrode.

[Preconcentration of trace chalcophile elements by a zincon--loaded resin and its application to neutron activation analysis (author's transl)].

A chelating agent-loaded resin consisting of an anion exchange resin and zincon which has widely been employed as a specific reagent for zinc(II) and copper(II) in spectrophotometry was prepared. The adsorption behavior of some chalcophile elements was studied in detail, with respect to pH, flow rate and exchange capacity. From the results, it was confirmed that the zincon-loaded resin reacts selectively with copper(II), zinc(II), mercury(II) and lead(II) at lower pH region, and the above reaction is stoichiometric as in the case of the reaction of zincon with metal ions in aqueous solution. Furthermore, the zincon-loaded resin was applied to the selective concentration of trace amounts of chalcophile elements in natural water samples prior to neutron activation analysis. Water samples taken from the Watarase River were filtered and the pH of each filtrate was adjusted to ca. 5.5. After preconcentration was made by the column method (zincon-loaded resin: 2 x 10-4 mol/g resin, 1.0 g, 7 mm phi x 35 mm), the resin in the column was washed and dried in a desiccator. The standard material was also prepared according to the above mentioned scheme. The sample and the standard materials packed in polyethylene vials were irradiated for 40 min by a neutron flux of 5 x 10(13 n.cm-2.sec-1 in the JRR-4 of the Japan Atomic Energy Research Institute. After cooling the materials, activity measurements were made. The results were 53 ppb for copper, 0.25 ppb for mercury.