Polyaniline-polyvinyl alcohol (PAPVA) colloids consisting of polyaniline (PA) and polyvinyl alcohol (PVA) were prepared. This colloid is electrochemically active and can adsorb various anions. The adsorption occurs electrochemically or chemically. The selectivity sequence of the PAPVA colloid toward monovalent anions was SCN^->ClO₄^- >BF₄^->Br^->Cl^-_??_CF₃COO^-_??_C₆H₅SO₃^-. Adsorption ability of the PAPVA colloid toward each anion was enhanced when large anions such as C₆H₅SO₃^-, were doped into the colloid.

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It was found that the extraction percent (E%) values of U(VI), Th, Zr and Fe(III) from 0.1mol dm^-3 (M) HNO₃ solution by 0.1M TOPO in cyclohexane solution are 98, 78, 85 and 85%, respectively. Among these elements, only U(VI) and Th were found to be stripped from their organic phase by 0.1M sodium citrate solution. Cerium, copper and cadmium were not extracted by trioctylphosphine oxide (TOPO) under similar conditions. Based on these equilibrium results, a liquid emulsion membrane (LEM) was prepared from TOPO/Span 80/sodium citrate and the factors affecting its stability were studied. Permeation of U(VI) into this membrane was kinetically studied in detail. Its forward permeation rate was found to be mainly dependent on TOPO concentration and slightly dependent on U(VI) and HNO₃ concentration of the external phase. Permeation results showed that it is possible to recover 98% of U(VI) and 82% of Th from 0.1M HNO₃ solution containing Ce, Zr, Fe(III), Cd, and Cu by the membrane. The recovered U(VI) and Th were contaminated with less than 2% of Fe(III).

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An iminodiacetic acid-type chitosan chelating resin selectively adsorbed germanium(IV) from aqueous solutions over the range of strongly acidic to weakly basic media. The adsorption capacity of the chitosan resin for germanium(IV) was about 1mmol g^-1 in acidic media. The selective separation of germanium(IV) from tellurium(VI) and boron was achieved with a column method using the chitosan resin. The breakthrough points of germanium(IV) in the chitosan resin columns were about 70 bed volumes over the range of strongly acidic to weakly basic media. The germanium(IV) adsorbed on the column was almost quantitatively recovered by elution with aqueous sodium hydroxide. On the other hand, it was difficult to separate germanium(IV) from tellurium(VI) using a column of the polyamine-type chitosan chelating resin.

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In order to change the ion-exchange selectivity of anion exchange resin, especially to make the ion-exchange of divalent anions more difficult, the surface of gel-type anion exchange resin was modified by the adsorption of an anionic polyelectrolyte: polycondensation product of sodium naphthalene sulfonate and formaldehyde. After the adsorption of the polymer, ion exchange capacity decreased and the rate of ion exchange reaction became slow, though ion exchange equilibrium constants between two anions did not change. Especially, the ion exchange rate of divalent anions was slower than that of the monovalent anions. Because an anionic polyelectrolyte layer was formed on the resin particle, the ion exchange of anions with anion exchange site was retarded by a sieving effect due to the layer. The divalent anions became difficult to ion exchange compared with the monovalent anions due to the existence of the layer which was charged opposite to the charge of the ion exchange groups. Using the modified anion exchange resin, separation of nitrate ions from sulfate ions was attempted.

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The total reflection x-ray fluorescence (TXRF) method is a powerful tool for the surface analysis of flat materials, such as Si wafers. The probing depth of TXRF is an important factor in a quantitative TXRF analysis. This is the first time that the probing depth under total-reflection conditions was experimentally evaluated by analyzing the takeoff-angle dependence of x-ray fluorescence. Our experimental results, measuring different incident angles, fit the theoretical curves. Finally, the relationship between the probing depth and the incident angle was obtained. We found the takeoff-angle dependent measurement of x-ray fluorescence to be a powerful means for determining the probing depth in the TXRF method.

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The solvent extraction of aluminum(III), gallium(III) and indium(III) with phenylacetic acid using 1-octanol and benzene as solvent was performed at 25°C and at 0.1mol dm^-3 constant ionic strength in the aqueous phase (NaClO₄). The respective extraction constants of every extracted species in the present extraction systems were found to be larger than in the previous decanoic acid systems for these metal ions. The extraction of indium(III) phenylacetates was found to be distinct from that of aluminum(III) and gallium(III) in both systems using 1-octanol and benzene. Phenylacetic acid was found to be superior to decanoic acid as an extracting agent for these metal ions.

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A rapid and sensitive spectrophotometric method for the determination of sodium linear-dodecylbenzenesulfonate (DBS) with 1-pentyl-4-(4-aminonaphthylazo)-pyridinium bromide (PANP) in the presence of sodium dodecyl sulfate (SDS) is proposed. The method is based on the formation of the ion associate of DBS with PANP, and does not require any solvent-extraction procedure. PANP was found to react selectively with DBS to form an ion associate, which caused a new light-absorption near to 416nm. The apparent molar absorptivity of the DBS-ion associate with PANP was found to be 4.6×10⁴ dm³ mol^-1 cm^-1 at 416nm. A calibration graph was linear over the ranges from 0.1 to 2.0×10^-6mol dm^-3 DBS. The relative standard deviation (n=10) for 1.2×10^-6mol dm^-3 DBS was 2.0%. The proposed method can be applied preferably to the determination of DBS in river-water samples.

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A simple spectrophotometric method is proposed for the direct determination of PHO₃^2- and P₂O₇^4- ions. In acidic solutions containing 50%(v/v) CH₃COCH₃, the Mo(VI)-Mo(V) reagent reacts directly with PHO₃^2- and p₂O₇^4- ions to form the respective heteropoly blues. The amounts of mixed-valence blue species thus formed depended linearly on the PHO₃^2-and P₂O₇^4- concentrations in the ranges 1×10^-5-1×10^-3M and 2×10^-5-2×10^-4M, respectively. Interferences from foreign ions are also discussed.

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The solvation structures of the nickel(II) ion in six nitriles have been determined using X-ray absorption fine structure spectroscopy. The coordination number and the Ni-N bond length are 6 and 206.9±0.6pm in acetonitrile, 5.9±0.2 and 206.9±0.6pm in propionitrile, 6.0±0.2 and 206.8±0.6pm in butyronitrile, 6.0±0.2 and 206.8±0.6pm in isobutylonitrile, 6.0±0.2 and 206.8±0.6pm in valeronitrile, and 6.0±0.2 and 206.5±0.7pm in benzonitrile, respectively. The structure parameters around the nickel(II) ion in all the nitriles are not affected by the bulkiness of the nitrile molecules. On the basis of the obtained structure parameters, we have discussed the structural characteristics around the nickel(II) ion with nitrogen and oxygen donor solvents and the reaction mechanisms for nitrile exchange on the nickel(II) ion.

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Based on a vapor-liquid equiribrium of ammonia, a simplified and rapid technique was developed for the determination of the total inorganic and ammoniacal nitrogens in aqueous solution. Ammonium ion was converted into gaseous ammonia by adding a sodium hydroxide solution to a sample solution. The generated ammonia was directly introduced into a quartz cell in order to measure the molecular absorption. As for the determination of the total inorganic nitrogen, the sample solution was pretreated with titanium(III) chloride solution in order to reduce nitrate and nitrite ions to ammonium ion. The ammonia was then evolved and determined in the same manner as mentioned above. The detection limit (3S/N) of 0.01μg cm^-3 for both ammonia and the total inorganic nitrogen was obtained. The calibrationgraph was linear up to 0.8μgN cm^-3 for each nitrogen species. The relative standard deviations for five replicate measurements were 3.9, 4.5 and 4.7% for 0.40μg cm^-3 of nitrogen present in the form of ammonium, nitrate and nitrite ions, respectively. The analytical results for some environmental and industrial water samples are presented.

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The simultaneous determination of chloride and bromide ions in environmental water by X-ray fluorescence spectrometry after precipitation as silver halides in the presence of ammonium nitrate was developed. Calibration curves for chloride and bromide ions were linear from 0.2 to 7.5mg/l(10-375μg/50ml) and from 0.0025 to 1.0mg/l(0.125-50μg/50ml), respectively. The relative standard deviations were less than 3% for both ions. To clarify the effect of bromide ion in environmental water on trihalomethane (THM) formation during a water treatment with chlorine, the concentrations of the chloride and bromide ions in rain- and river-water samples were measured by the present method.

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An inductively coupled oxygen plasma (O₂ICP) using a 40.68MHz generator with a maximum radio-frequency (RF) power of 4kW was evaluated as an ion source for mass spectrometry (MS). Although the intermediate and central Ar flows are completely replaced with O₂, a certain amount of Ar should be added to the outer gas for a stable plasma discharge. The proposed O₂ ICP discharge is more stable than N₂ ICP, because of the lower dissociation energy of O₂. The sampling depth, RF power and carrier flow rate of O₂ for maximum analyte signals were found to be 7mm above the work coil, 2.4kW and 1.41min^-1, respectively. Under the optimized conditions, O⁺ is strongly observed in the mass spectra. The sensitivity of the proposed O₂ ICP is inferior to those of Ar and N₂ ICP_s, and decreases with increasing the mass number of the analyte. Although the average kinetic energy of the analyte ions in the O₂ ICP is almost equivalent to that of the Ar ICP, its distribution is wider. A wide energy distribution seems to lead to a higher ratio of doubly charged ions to singly charged ions. The ratio of monoxide ions to singly charged ions is much higher than those in Ar and N₂ ICP_s.

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A highly sensitive and convenient analytical method for the direct determination of selenium in biological samples by GF-AAS with a solid sampling technique using a graphite miniature cup was established by using a Pd solution containing 3 mol/l sulfuric acid or a Pd solution containing 0.1 mol/l nitric acid as a matrix modifier in order to prevent the volatilization of selenium. The determination of μg/g levels of selenium in biological samples was performed using calibration curves prepared by a selenium standard solution containing 100μg/ml of Pd in 3mol/l sulfuric acid as the matrix modifier. On the other hand, the pre-ashing concentration technique, which was previously developed by us, was applied to the determination of 10ng/g levels of selenium in biological samples. The analytes in biological samples were concentrated by decomposing the sample matrix with a conventional electrothermal muffle furnace at 600°C for 30min. At the pre-ashing stage, a Pd solution containing 0.1mol/l nitric acid was added, because the addition of the Pd solution containing sulfuric acid caused charring and coagulation of the samples. The concentration factor for selenium in biological samples was 10 to 40. The analytical results of several NIST biological certified reference materials obtained by the proposed method were in good agreement with the certified values. The detection limit of GF-AAS was 0.13ng of selenium; therefore, 3.3ng/g levels of selenium in biological samples is detectable by the proposed method.

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This paper describes the development of potentiometric detection systems with increased sensitivity for flow injection analysis (FIA). The detection systems are based on homogeneous crystalline membranes which are sensitive to chloride, bromide and iodide anions and copper, cadmium and lead cations. Two types of potentiometric detection systems have been established: one has two tubular electrodes sensitive to the same species placed sequentially, in which one of the electrodes works alternatively as a reference electrode (sequential detector system); the other type comprises a tubular potentiometric detector with two membranes and a conventional reference electrode (double membrane detector system). In the latter, totalling the potentials of each membrane is performed externally using an electronic summing device. The behavior of the two detection systems was evaluated in a low-dispersion FIA manifold. Their characteristics were similar to those of single membrane tubular electrodes, except for the calibration slope, for which a value approximately double was obtained.

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This work reports on the development, optimization and application of an FIA manifold to the sequential determination of calcium and magnesium cations in haemodialysis solutions. A tubular electrode sensitive to calcium and an atomic absorption spectrophotometer to measure magnesium were used as a detection processed. The system included a dialysis unit to enable sample dilution, since they presented high levels of the species to be determined. The system performance was optimized to obtain the maximum slope of calibration lines to Ca²⁺ and Mg²⁺ by means of the Taguchi Parameters Design (TPD). An L₉(3⁴) saturated orthogonal array led to the following optimized conditions: flow rate, 3.0ml/min; sample volume injected, 20μl; reactor length, 100cm; ionic strength, 3M. Under these conditions, the analytical procedure was robust and lead to reproducible results which were insensitive to variations in the glucose concentration. The developed system presents a high sampling rate (80 samples/h). The results obtained by the FIA system were compared with those given by the process of visual titration (10 samples/h) used as a reference method; it was found that both methods were in good agreement.

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A microwave-assisted digestion system enabling simultaneous treatment of thirty-six samples with oxidizing acidic media in double-closed vessels was devised. Aluminum was subsequently separated from the digested solution through solid phase extraction by prior reacting with 8-quinolinol and adsorbing onto the simple XAD-4 resin column. In the separated fraction, Al, being in a state free from matrix interferences, can be directly determined with electrothermal atomic absorption spectrometry (ETAAS) simply by an external calibration standard. With meticulous control of analytical blank introduced in the sample pretreatment steps, a good performance of analytical accuracy and limit of detection can be achieved. The proposed method, featuring freedom from potential interference in ETAAS and relatively fast sample throughput, can conveniently serve as a reference and/or an alternative method for the direct ETAAS method commonly used for routine clinical purposes.

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A flow-injection conductimetric system procedure is proposed for the determination of paraoxon. The method is based on the inhibition of immobilized acetylcholinesterase in controlled porous glass beads (CPG) with acetylcholine as substrate. The enzymatic reaction is inhibited by a diethyl-p-nitrophenylphosphate (paraoxon) solution. A 1, 1′-trimethylene-bis(4-formylpyridinium bromide)dioxime solution was used to reactivate the enzyme. The correlation between the peak height, for a given acetylcholine concentration, is linear from 1.0×10^-7 to 5.0×10^-5mol l^-1 of paraoxon; therefore, the quantitative limit of detection was about 1.0×10^-7mol l^-1 of paraoxon. For semi-quantitative purposes, the limit can be considered to be about 1.0×10^-8mol l^-1. The relative estimated standard deviation obtained using a 1.0×10^-3mol l^-1 acetylcholine solution and a 5.0×10^-6mol l^-1 paraoxon solution was 2.2% (n=8).

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Flow-through type magnesium ion-selective optodes based on a neutral ionophore and a lipophilic cationic dye have been developed. The optodes were prepared by coating pellicular octadecylsilica beads with a lipophilic organic liquid containing magnesium ionophores, a lipophilic cationic dye and a lipophilic anionic additive, and packing the beads into a flow-through optical cell. Two neutral magnesium ionophores (K22B5 and K22B1B5) and two novel lipophilic cationic dyes (KDC-1 and KDC-2) were synthesized and tested for preparing the optodes. Among the developed optodes, an optode based on the ionophore K22B1B5 and a cationic dye (KDC-2) produced the best magnesium ion optode with a relatively high Mg²⁺ sensitivity and selectivity. This optode showed a fast and reproducible response to magnesium ion, even in a high concentration of background ions.

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Potentiometric behaviors of bilayer lipid membranes (BLMs) incorporated with such ionophores as valinomycin, crown ethers and acyclic polyethers were described for various alkali and alkaline earth metal ions. The ionophores were directly incorporated into planar BLMs formed by the folding method. Among seven kinds of ionophores examined, only the valinomycin- and ETH 4120-based BLMs generated potentiometric Nernstian responses. However, simultaneous incorporation of anionic sites, such as sodium tetrakis[3, 5-bis(trifluoromethyl)phenyl]borate (NaTFPB) or potassium tetrakis(4-chlorophenyl)borate (KTpClPB), was found generally effective for inducing potentiometric Nernstian responses of the ionophore-based BLMs. The added anionic sites were also found to decrease the membrane resistance, leading to improvement of probability of potential measurements, and to lower the detection limits by maintaining Nernstian slopes, thereby providing a basis for quantitative BLM sensors. By comparing the potentiometric responses of ionophore-incorporated BLMs with and without added anionic sites, the role and significance of the anionic sites in potentiometric response of BLMs based on ionophores was discussed.

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A new sensor for determining the colchicine concentration in aqueous solution is described which uses a bifurcated optical fiber and a micrometer-sized flow cell. The sensing membrane, which contains 2-(4-diphenylyl)-6-phenylbenzoxazole (PBBO), can form a nonfluorescent complex with colchicine and quench the membrane fluorescence. The usable determination range covers from 2×10^-4 to 2×10^-6mol l^-1 colchicine. Satisfactory reproducibility, reversibility and a relatively short response time have been realized. Alkali and alkaline earth metal salts as well as various pharmaceutical species have little or no effect on the sensor response. The sensor can be used for determining the colchicine concentration in pharmaceutical tablets with results that are in satisfactory agreement with those obtained by the pharmacopoeial method.

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A new spectroelectroanalytical method for the simultaneous determination of iron and copper is presented in terms of the spectroelectrochemical properties of complexes of iron and copper with 2, 2′-bipyridine. By using long optical pathlength thin-layer cells, the differences in the absorbance after complete potential-controlled redox reactions of the two complexes (ΔA) were proportional to the investigated concentration over ranges from 2×10^-7M to 5×10^-5M for iron and from 4×10^-7M to 1×10^-4M for copper, respectively. The proposed method offers a higher selectivity than conventional spectrophotometry. In addition, a preconcentration proceudre for copper was taken in 0.2M NH₃•H₂O-NH₄Cl for 1min; the deposited copper was then dissolved into a solution containing 2, 2′-bipyridine as a chromogenic reagent; ΔA, recorded as before, was used as the analytical signal to determine trace copper. The apparent molar absorptivity obtained was ca. 6times that without electrodeposition. Iron and copper in aluminum alloys and pig serum were satisfactorily determined by the proposed methods.

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New polymeric electrodes responding to tiamulin hydrogen fumarate were constructed by incorporating tiamulin tetraphenylborate and tiamulin phosphotungstate ion-pair complexes into PVC membranes, with the latter giving the best linear and Nernstian response. The electrodes exhibited a linear response over the concentration range 10^-2-10^-6 mol l^-1. The pH did not affect the response of the electrodes within the range 2-8. Direct potentiometry was used to assay tiamulin hydrogen fumarate in pharmaceutical formulations and in the bulk form. The results were compared with those obtained with non-aqueous titration for the antibiotic in the bulk form and with HPLC for commercial formulations.

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Chromium(III) and Chromium(VI) have been speciated by capillary electrophoresis(CE) with on-column UV-Vis detection at 254nm and a negative potential. Chromium(III) has been converted to an anionic complex using ethylenediaminetetraacetate (EDTA) to be detected simultaneously with Cr(VI) by CE. A cationic surfactant, cetyltrimethylammonium bromide (CTAB), was added to a buffer solution of 10mM phosphate in order to reverse the electroosmotic flow (EOF) in the capillary. This results in a short analysis time and better peak shapes. The effect of the buffer pH over the range of 6 to 11 on the separation of each species has been observed. Nitrate and chromate have been nicely separated at a higher pH. Linear calibrations for chromate and a chromic EDTA complex were established over the concentration range of 50-200pg/nl with detection limits of 1.5pg/nl and 5pg/nl, respectively, using a 10mM phosphate buffer and a 0.5mM CTAB solution.

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A sensitive and selective method for the determination of guanosine 3′, 5′-cyclic monophosphate in human urine is described. The method uses high-performance liquid chromatography with fluorescence detection. Guanosine 3′, 5′-cyclic monophosphate and other guanine nucleotides in human urine, after a clean-up with an anion exchanger cartridge (TOYOPAK DEAE S), gave fluorescence products by a reaction with 3, 4-dimethoxyphenylglyoxal in a neutral medium. The formed derivatives were separated using reversed-phase high-performance liquid chromatography. The limit in the detection (S/N=3) of guanosine 3′, 5′-cyclic monophosphate is 4.4pmol on the column.

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A method for the sequential analysis of reducing sugars has been developed based on repetition of the following procedures: 1) derivatization of a reducing oligosaccharide with 8-amino-2-naphthalenesulfonic acid (ANS) to produce a Schiff base, 2) reduction of the base with sodium cyanoborohydride, 3) methoxycarbonylation of the secondary amino group, 4) cleavage of the glycoside bond next to the reducing end, through intramolecular acid hydrolysis by the action of a sulfonic acid group of the ANS derivative, 5) identification of the liberated reducing end by high-performance liquid chromatography (HPLC), and finally 6) recovery of the resultant oligosaccharide fragment from the cleavage reaction mixture. A satisfactory yield in the cleavage reaction and a quantitative recovery of the oligosaccharide fragments were obtained when the cleavage reaction of the ANS derivative was carried out at 140°C for 30min in dioxane-dimethyl sulfoxide (7:3). The method was successfully applied to the sequential analysis of some reducing di-and trisaccharides.

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A highly selective organic phosphates analyzer was developed based on a column-switching technique using a titania (TiO₂) precolumn and an anion-exchange analytical column. In the preliminary examination, it was proved that the titania column strongly retains the organic phosphates under acidic conditions while it shows no retention in alkaline eluents. Based on these findings, the organic phosphates were selectively trapped on the titania precolumn in an acidic eluent, transferred to an anion-exchange column by a basic eluent and detected by coloration after a postcolumn phosphomolybdic acid reaction. When 25.0μM each of phospho-amino acids solution was determined (injection volume, 100μl), the relative standard deviations were 2.3-2.8% (n=5). The detection limits (S/N=3) of the phospho-amino acids were ca. 2.0μM as the injected concentration. The present analyzer was successfully applied to the analysis of the phosphorylation products of a heptapeptide (kemptide).

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