The adsorption and desorption of humic and fulvic acids on a non-ionic macroreticular resin, Amberlite XAD-2, were studied from the view point of the concentration of aquatic humic substances. Microgram or milligram quantities of humic and fulvic acids were collected on a small column of pulverized XAD-2 (16 mm in diam.×5 mm height) and then desorbed with 10 cm3 of 0.1 mol dm-3 sodium hydroxide solution containing 200 mg of sodium dodecyl sulfate (SDS). The resulting humic solution contained appreciable amounts of SDS (ca. 100 mg), which were removed by introducing the solution onto another XAD-2 column (7 mm in diam.×60 mm height, unpulverized resin). The SDS was completely retained on the resin because of the strong affinity, even in an alkaline solution, whereas nearly all humic substances were passed through the column. The validity of the proposed separation method was evaluated by using synthetic sample solutions.
Aggregates of sodium dodecyl sulfate (SDS) formed on alumina particles were employed as enrichment vehicles of hydrophobic metal-chelates from water samples. To a 50 cm3 suspension of 1.5 g of purified alumina was added 100 mg of SDS; the mixture was then acidified to pH 2, where the anionic surfactant was strongly adsorbed on positively charged alumina surfaces to form admicelles. Nanogram quantities of heavy metals (Co, Ni, Cu, Cd and Pb) in water were com-plexed with APDC at pH 2 - 6 and quantitatively incorporated in the admicelles. A nearly complete desorption was achieved for those metals (except for Co) in 4 mol dm-3 nitric acid with the aid of ultrasonic irradiation. A multielement determination was performed by ICP-MS. The reliability of the proposed method was evaluated by analyzing a certified reference seawater sample.
Secondary equilibrium chromatography has proved a useful tool for determining the polyether complexation constants. Both a cation-exchange and anion-exchange method can be used for this purpose. In the present paper, the applicability and versatility of the latter method, based on the surface complexation of polyethers with ammonium ions anchored on the stationary phase surface, are discussed, and compared with those of the former established method. The precision of the chromatographically determined complexation constants depends on the range of measured retention factors, suggesting that the surface charge density of the stationary phase can be optimized according to the retention ability of polyethers. The anion-exchange method is more versatile than the cation-exchange method from this viewpoint; i.e. the surface density of active groups (thus the retention range) can simply be controlled by preequilibrating the stationary phase with an aqueous solution of appropriate pH.
A practical method for the characterization of the retention behavior in supercritical fluid chromatography (SFC) was pro-posed, based on the retention index. Taking easier comparison with gas chromatography (GC) into consideration, a set of six test compounds were chosen: napthalene, 1-pentadecanol, 2-pentadecanone, n-pentadecanonitrile, isoquinoline and cyclododecane. Dimethylsilicone and carbon dioxide were selected as the standard stationary phase and the standard mobile phase, respectively. Thus, the differences in retention indexes for the test compounds between the SFC conditions in question and the standard SFC conditions, i.e., the ΔI values, were used for the expression of the retention characteris-tics, similarly to use of the McReynolds constants in GC. The difference or similarity of retention behavior could be evaluated by the angle between two vectors having six elements, which corresponded to two SFC conditions. This method could detect the small difference in the retention behavior on a slightly polar stationary phase: 50% methyl, 50% phenylsilicone between GC and SFC. This difference was attributed to the different behavior of cyclic compounds from that of non-cyclic compounds.
In order to reveal the effect of temperature on (i) the dissociation equilibrium of tritiated water (HTO water) and (ii) the reactivity of each anion-exchange resin, the OT-for-OH exchange reaction between each anion-exchange resin and HTO water was studied within the range of 20°C to 80°C in the equilibrium state. In addition, the apparent dissociation constant (pK′) for each resin was estimated by the method of pH-titration. From the observation of the OT-for-OH exchange reaction between each of the following anion-exchange resins and HTO water, the next three items have been found: (1) in the case of acryl-type anion-exchange resin, the effect of temperature on OT-for-OH exchange reaction is larger than that on the reaction in the case of styrene-type one; (2) the radioactivity incorporated into weakly basic anion-exchange resin (OH--form) by the isotope exchange reaction is smaller than that into strongly basic one; (3) in the case of the weak-ly basic anion-exchange resin, the amount of radioactivity incorporated into Cl--form resin by the hydrolysis is larger than the amount of radioactivity incorporated into OH--form resin by the isotope exchange reaction.
It was found that a FIA system with an immobilized enzyme reaction column could be utilized for the determinations of hydrogen peroxide in some water samples, such as rain water and tap water. A column was packed with chitosan beads immobilizing horseradish peroxidase. Under the recommended conditions, it took 5 min for each assay, and the detection limit, which was defined as a signal-to-noise ratio of 3, was 3.0 ng dm-3 of hydrogen peroxide. The relative standard deviation at 1.0 mg dm-3 of hydrogen peroxide was 1.5% (n=20). There was no interference from some coexisting sub-stances having a low oxidation-reduction ability or not; therefore, a standard addition method could be applied to rain water and tap water samples. From such results, it has become clear that the proposed FIA system can be applied to the determination of hydrogen peroxide in water samples, and that the system is suitable for routine analysis in environmental observations.
Water molecules in polyether-polyol have been analyzed by high-frequency spectroscopy. It has been inferred that there exist two types of H2O in polyether-polyol. The first type are those which coordinate directly to the OH group at the end of the polyol chain. The frequency of the maximum absorption peak of these water molecules do not shift with increasing content of H2O in the high-frequency spectra; these may be referred to as non-freezable water. The second type are those which bond to the EO chain in the polyol. Excess water molecules which exist near or in the neighborhood of these H2O should also be included in the second type one. The second type may be referred to as freezable water. These show a frequency shift which reflects the degree of restraint of H2O in the polyol.
The newer electrochemiluminescence (ECL) immunoassay system was established by using both an antibody coated on paramagnetic micro-beads (Capt-MB) as a carrier of the immunoassay and an antibody labeled with ruthenium(II) tris-bipyridine-NHS (Ru-Ab). The ECL excitations were designed to be generated upon the surface of the working electrode which collected the reacted Capt-MB by magnetic force. As a model of the immunoassay, the reaction between alpha-fetoprotein (AFP) and anti-AFP antibodies was used in accordance with the so-called sandwich method, where the sandwich conformation of AFP-(Ru-Ab) was made on the surface of the Capt-MB. The ECL immunoassay system revealed the following results: a) the ECL signal intensity was obtained in proportion to the AFP concentration of each specimen; b) the dynamic range of this ECL immunoassay system was extended to 10000 times of magnitude in the 2-step assay; and c) the detection sensitivity reached to the level of 5 pg/ml in the AFP concentration after 15 min in the 1-step immunoassay.
A new derivatizing reagent, dansylaminomethylmaleic acid (DAM), was synthesized and utilized for the reversible fluorescence labeling of amino groups. The reagent DAM was dehydrated in the presence of (trimethylsilyl)ethoxyacetylene, a dehydrating agent, and the resulting anhydride reacted with amino groups, and could then be liberated under mild acidic conditions. With this reagent, benzylamine was derivatized as a model amino compound. The resultant fluorescent derivative, N-benzyl-2-dansylaminomethylmaleamic acid (BDAM), could be detected at 520 nm with fluorescence excitation at 340 nm. The fluorescence detection limit of BDAM (100 fmol, S/N=3) was smaller than that of intact benzylamine (200 pmol, S/N=10, absorbance at 254 nm). Under mild acidic conditions of pH 5.0, 82% of benzylamine was regenerated from BDAM within a day. With this reagent, insulin was successfully derivatized and 56% of insulin was regenerated.
To analyze serum proteins adsorbed to a hemodialysis membrane, immunostaining with colloidal gold and thermal-lens microscopy were employed. A total of 14 types of hemodialysis membranes were tested. The cross sections of the membranes were stained with fluorescent antibodies. Observations of these specimens using a laser microscope revealed that serum proteins, such as albumin and immuno globulins, tended to adsorb into the inner wall of these membranes. The degree of adsorption of serum proteins varied according to various conditions, such as what materials the membranes were made of or what proteins were adsorbed. For a better quantitative analysis of these proteins, the membranes were stained with immunogold and were observed by a thermal lens microscope. Colloidal gold coated with various anti-human serum proteins was used for the staining, and the quantity of colloidal gold was measured with a thermal-lens microscope. The quantity of colloidal gold, coated with anti-human sera antibody, gradiently decreased from the inner to the outer wall of the membrane. Probably, proteins with larger molecules were adsorbed to the inner parts, and those with smaller molecules were adsorbed to the outer parts of the membrane wall. High-resolution thermal-lens microscopy makes possible the sensitive detection of localized proteins adsorbed to a membrane without extracting it. Thus, the analysis of adsorbed proteins should serve to determine the adaptability of medical appliances to the human body and should also be helpful to a retrospective analysis of substances like drugs which are conjugated to the serum proteins.
Lead-selective solvent polymeric membrane electrodes based on selected thiacrown ethers, poly(vinyl chloride) (PVC), the plasticizer bis(2-ethylhexyl)phthalate [“dioctyl phthalate” (DOP)], and potassium tetrakis(p-chlorophenyl)borate (KTpCPB) (50mol%, relative to the ionophore) as anionic sites are described. The potential measurements were done in the presence of acetate buffer (pH 4.00) and for successively diluted stock solutions of 10-2 M Pb(NO3)2. Potential-pH profiles of membranes based on selected thiacrown ethers demonstrated lack of H+ interference within a wide pH range. The effect of the sample solution composition as well as the inner reference solution on the selectivity and detection range were demonstrated.
The gas chromatographic detection and quantitative determination of various chlorophenolics, resin acids and fatty acids have been carried out in the chlorination and caustic extraction stage effluents generated in the laboratory by bleaching eucalyptus pulp. A number of chlorinated derivatives of phenols, catechols, guaiacols, syringaldehydes, resin acids as well as non-chlorinated saturated, unsaturated fatty and resin acids have been detected. The concentrations of various compounds detected have also been compared with the reported 96LC50 values.
In the presence of perchloric acid, rare-earth elements of europium, terbium and yttrium at large concentrations have well-shaped absorption spectra in the ultraviolet region even without the addition of a chromogenic reagent. However, it is difficult to determine each of them individually, because they have serious overlapping peaks. In this study, a chemometric method, Kalman filter, was used to resolve the overlapped spectra and to determine the individual components. In contrast to conventional implementation of the Kalman filter, an absorption-coefficient matrix derived from a set of mixtures of known composition by multiple linear regression (MLR) was found to yield better results in this work. For a set of synthetic mixtures of europium, terbium and yttrium, their molar absorptivities were determined to be 1945, 3756 and 1446, respectively. The proposed method was also applied to the determination of europium, terbium and yttrium in a sample of phosphor powder product; a satisfactory result was obtained.