Rapid Determination of Sub-ppm Heavy Metals in the Solution State via Portable X-ray Fluorescence Spectrometry Based on Homogeneous Liquid-Liquid Extraction in a Ternary Component System.

The rapid determination of sub-ppm heavy metals in the solution state was examined via portable X-ray fluorescence spectrometry (XRF) based on homogeneous liquid-liquid extraction (HoLLE) in the water-ethanol-dimethyl phthalate ternary component system. The percentage of cadmium extracted into the sedimented liquid phase was 91.3%. After phase separation, the volume ratio (Va/Vs) of the aqueous phase (Va) and the sedimented liquid phase (Vs) was 121 (29.0 → 0.240 mL). Based on an analysis of the sedimented liquid phase in the solution state via the portable XRF, the presence of cadmium was determined over a concentration range of 0.100 - 4.00 mg L-1.

ß-Cyclodextrin as a Metal-anionic Porphyrin Complexation Accelerator in Aqueous Media.

The rate of the complexation reaction between anionic porphyrins and 11 metal ions was found to be accelerated by the presence of ß-cyclodextrin (ß-CD) in aqueous media at room temperature without the need for additional heating or sonication. The porphyrin complexation reaction with metal ions under aqueous conditions can be difficult due to the strong hydration energy between the metal ions and water. In this study, the specific role of ß-CD as an accelerator was determined and found to enhance the typically slow reaction of the porphyrin with metal ions. A significant acceleration effect was exhibited when the model anionic porphyrin, 5,10,15,20-tetraphenyl-21H,23H-porphine-tetrasulfonic acid, and Pb(II) ions were combined in the presence of ß-CD. Other than for Hg ion, the addition of ß-CD decreased the metalation reaction time from 30 to 2 min. The order in the degree of acceleration was Pb >> Zn, Cd > Cu > Fe, Pd > Sn >> Ag, Co, Mn. Using Pb(II) as the model ion, it was determined that the complexation rate constant was enhanced by a factor of 2.4, while the dissociation rate constant was diminished by a factor of 135 in the presence of added ß-CD relative to that in its absence. Overall, the complex was much more stable (formation equilibrium constant 324-fold greater in the ß-CD medium. The formation of a ternary complex (cf. bicapped complex; (ß-CD)2-porphyrin-metal ion) was demonstrated through the use of nuclear magnetic-resonance spectroscopy and mass spectrometry. This acceleration effect is expected to be applicable systems in which porphyrin ligands are employed for determining of metal ions in chemical analysis and separation science.

Flow injection spectrophotometric analysis of human salivary α-amylase activity using an enzyme degradation of starch-iodine complexes in flow channel and its application to human stress testing.

Flow injection spectrophotometric analysis (FIA) of human salivary α-amylase was developed using an enzyme degradation reaction of starch-iodine complexes. In this proposed method, the salivary α-amylase, known as a human stress indicator, is directly and rapidly determined without any pretreatment. In this study, the optimum starch-iodine complexes (i.e., optimum molecular weight and amylase-amylopectin compounding ratio) were selected, and their rapid degradation in the flow channel was investigated to determine salivary amylase in the FIA system. The determination range of α-amylase was obtained from 0.25 to 5.0 kilo Novo unit per milliliter (KNU/mL), and these concentrations were equivalent to the real concentration of amylase in human saliva. The quantitative values obtained by this method were found to be highly reproducible with 1.6% (n=25) of the relative standard deviation for 1.0 KNU/mL. The detection limit (3σ) was 60 NU/mL. In addition, the method requires small volume of a sample (20 µL), and 30 samples was sequentially measured within one hour. Real human saliva collected before and after exercise was utilized to demonstrate the feasibility of human stress test and analytical performance of this approach.

Quenching-Chemiluminescence Determination of Trace Amounts of l-Tyrosine Contained in Dietary Supplement by Chemiluminescence Reaction of an Iron-Phthalocyanine Complex.

The chemiluminescence (CL) signal immediately appeared when a hydrogen peroxide solution was injected into an iron-phthalocyanine tetrasulfonic acid (Fe-PTS) aqueous solution. Moreover, the CL intensity of Fe-PTS decreased by adding l-tyrosine. Based on these results, the determination of trace amounts of l-tyrosine was developed using the quenching-chemiluminescence. The calibration curve of l-tyrosine was obtained in the concentration range of 2.0 × 10(-7) M to 2.0 × 10(-5) M. Moreover, the relative standard deviation (RSD) was 1.63 % (n = 5) for 2.0 × 10(-6) M l-tyrosine, and its detection limits (3σ) were 1.81 × 10(-7) M. The spike and recovery experiments for l-tyrosine were performed using a soft drink. Furthermore, the determination of l-tyrosine was applied to supplements containing various kinds of amino acids. Each satisfactory relative recovery was obtained at 98 to 102%.

Flow injection analysis combined with a hydrothermal flow reactor: application to kinetic determination of trace amounts of iridium using a water-soluble porphyrin.

A new type of flow injection analysis (FIA) system combined with an extremely high temperature reactor, namely hydrothermal flow injection analysis (HT-FIA), has been successfully constructed for the first time. Fundamental characteristics of HT-FIA system, such as limit temperature, pressure, and flow rate, were examined as an analytical tool. To demonstrate the potential of HT-FIA, the catalytic activity of Ir(IV) for the degradation of a water-soluble porphyrin, 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid (TPPS), was applied for the determination of trace amounts of Ir(IV). Although the indicator reaction is very slow at room temperature, HT-FIA system enables to accelerate the reaction. A linear calibration curve was acquired at 10(-8)M level of Ir(IV) and the interferences of platinum group metal ions were examined. The detection limit of Ir(IV) was 5.8 × 10(-9)M and a fairly high-throughput analysis, of which more than 30 samples can be analyzed within 80 min, was achieved.

"Turn-on" fluorescent polymeric microparticle sensors for the determination of ammonia and amines in the vapor state.

Cross-linked acrylic ester microparticles (EG50OH) with absorbed fluorescent probe molecules, such as fluorescein and acridine orange were successfully fabricated and employed as "turn-on" fluorescent sensors for the detection and determination of ammonia and organic amine vapor concentrations. Using EG50OH microparticles that had fluorescein (fluorescein fluorescent microparticle, FL-FMP sensor) incorporated as the fluorescent probe molecule (with lambda(ex) = 450 nm; lambda(em) = 528 nm), the detection limit achieved for ammonia vapor was 0.73 ppm, the response being linearly dependent on concentration over the range of 1.0-250 ppm gaseous ammonia. The FL-FMP responded to organic amines with the relative signal response following the order: triethylamine > tert-butylamine > diethylamine > n-propylamine > ammonia. A limit of detection of 0.048 ppm triethylamine vapor was achieved using this FL-FMP sensor. The sensor response is based on the acid-base properties of the fluorescent probe molecules. The fluorescent probes immobilized in/on the EG50OH are in a microenvironment such that they are in their neutral or protonated states and only exhibit weak fluorescence. Upon exposure to ammonia or amine vapor, the fluorescent species are deprotonated and exhibit much greater fluorescence emission ("turned-on" due to exposure to these basic analytes). The ease of fabrication and aforementioned properties of these fluorescent microparticle sensors are such that they should be amenable for use in a variety of situations requiring the detection or monitoring of ammonia and amines in the vapor state.

Time measurement-visual analysis of L-cysteine using the autocatalytic sodium sulfite/hydrogen peroxide reaction system and its application to length detection-flow analysis.

Trace amounts of L-cysteine can function as a trigger, i.e., reaction initiator, in the autocatalytic sodium sulfite/hydrogen peroxide reaction system. Rapidly changing of pH after induction time is visually confirmed by color changing of bromothymol blue in this autocatalytic reaction. Based on this finding, microg L(-1) levels of L-cysteine were measured over time using the autocatalytic reaction system. The determination range using the above method was 5.0 x 10(-8)-2.5 x 10(-6)M, the detection limit (3 sigma) was 1.8 x 10(-8)M (1.94 microg L(-1)), and the relative standard deviation was 2.41% at an l-cysteine concentration of 5 x 10(-7)M (n=5). This method was also applied to length detection-flow injection analysis. The determination range for the flow injection analysis was 2.0 x 10(-7)-1.0 x 10(-5)M. The detection limit (3 sigma) was 1.4 x 10(-7)M (17.0 microg L(-1)), and the relative standard deviation was 0.91% at an initial L-cysteine concentration of 10(-6)M (n=5).

Characteristic redox potential-time curve in the iron(II)/nitric acid autocatalytic reaction and its application to a time measurement-determination of folic acid.

A characteristic redox potential-time curve of the iron(II)/nitric acid autocatalytic reaction was applied to a time measurement-determination for sub-microM levels of folic acid. The determination range was 7.5 x 10(-7) - 1.5 x 10(-5) M, the detection limit (3 sigma) was 5.9 x 10(-7) M, and the relative standard deviation was 3.6% (n = 5).

Adsorption behaviors of high-valence metal ions on desferrioxamine B immobilization nylon 6,6 chelate fiber under highly acidic conditions.

Adsorption behaviors of the high-valence metal ions Zr(IV), Hf(IV), Ti(IV), V(V), Nb(V), Ta(V), and Mo(IV) on desferrioxamine B (DFB) immobilization nylon 6,6 chelate fiber was investigated under highly acidic conditions. Though the complexes of DFB and the high-valence metal ions were extracted without selectivity by solvent extraction, the only zirconium ions showed higher adsorption percentages than that of other high-valence metal ions on the DFB immobilization nylon 6,6 chelate fiber. Adsorption properties were caused that limited the freedom of DFB by chemical immobilization. Especially, hafnium ions and zirconium ions, which have similar chemical properties, showed different adsorption behavior in highly acidic aqueous solutions. Zirconium ions were quantitatively adsorbed up to 13.5 micromol/g.

Time measurement-visual analysis of nickel(II) using autocatalytic reaction with sodium sulfite/hydrogen peroxide system and its application to the length detection-flow analysis.

Trace amounts of nickel(II) can function as a trigger (= reaction initiator) in an autocatalytic reaction with the sodium sulfite/hydrogen peroxide system. Based on this finding, sub-microg L(-1) levels of nickel(II) were determined by a time measurement using the autocatalytic reaction. The detection range using the above method was 10(-9)-10(-5) M, the detection limit (3sigma) was 8.1x10(-10) M (0.047 microg L(-1)), and the relative standard deviation was 2.66% at nickel(II) concentration of 10(-7) M (n = 7). This method was applied to length detection-flow injection analysis. The detection range for the flow injection analysis was 2x10(-9)-2x10(-3) M. The detection limit (3sigma) was 1.4x10(-9) M (0.082 microg L(-1)), and the relative standard deviation was 1.86 at initial nickel(II) concentration of 10(-6) M (n = 7).

Powerful preconcentration method for capillary electrophoresis and its application to analysis of ultratrace amounts of polycyclic aromatic hydrocarbons.

For environmental analyses, a high-performance and powerful preconcentration system exceeding 1 x 10(7)-fold was developed that was composed of a blue cotton method (solid extraction method)/homogeneous liquid-liquid extraction method/on-line concentration method for capillary electrophoresis (CE). This system was named the "triplex concentration system" and it was achieved by finding a new phase-separation phenomenon (homogeneous liquid-liquid extraction) from a water-miscible organic solvent. Parts per trillion levels of polycyclic aromatic hydrocarbons (PAHs) were used as model analytical targets in this study. With the proposed method, 20-L levels of environmental water could be preconcentrated up to 1 x 10(7)-fold within a maximum of 1 h. The parts per trillion levels of PAHs were easily determined even using UV/CE, which has a serious sensitivity problem, and the detection limit of benzo[a]pyrene was 3.60 ppt. This system was also used as a practical monitoring method for the Miyata River (in Japan).

Chemiluminescence of iron-chlorophyllin.

The iron-chlorophyllin complex was found to be chemiluminescent (CL) in an acetonitrile (22%)/water mixed solvent. In the presence of hydrogen peroxide, when iron-chlorophyllin was added to the mixed solvent, a sharp CL signal immediately appeared. Also, analysis of the absorption spectra revealed decomposition of iron-chlorophyllin (based on decrease in absorbance at 396 nm), hence iron-chlorophyllin is the CL substance. Moreover, the CL intensity decreased in the presence of potassium thiocyanate (KSCN), indicating that the axial coordinative position of iron-chlorophyllin acts as a point of catalytic activation. In addition, when fluorophores were present with iron-chlorophyllin CL, their CL intensity values were similar to or greater than that of the well-known trichlorophenylperoxalate ester (TCPO) CL. Thus, during the decomposition reaction of iron-chlorophyllin, the latter transfers its energy to the coexisting fluorophores. Moreover, since the decomposed compound in this CL reaction had a fluorescence, it was found that the iron-chlorophyllin also functions as an energy donor. Therefore, the iron-chlorophyllin complex acts not only as a CL substance, but also as a catalyst and energy donor in the reaction.

Determination of ultratrace amounts of ruthenium(III) by the delayed autocatalytic reaction using citric acid.

A method for determination of ultratrace amounts (ppq levels) of ruthenium(III) was developed using a copper(II)-phthalocyanine-3,4',4",4"'-tetrasulfonic sodium salt (Cu-PTS) as an indicator in a potassium bromate autocatalytic reaction system. A satisfactory calibration curve of ruthenium(III) ion was obtained by the time measurement in the concentration range of 1 x 10(-13) M to 5 x 10(-12) M with the relative standard deviation (RSD) of 2.8% (n=5). The determination limits (3sigma) were 3.30 x 10(-14) M (3.34 ppq).

Determination of small amounts of L-ascorbic acid using the chemiluminescence of an iron-chlorophyllin complex.

Chemiluminescence (CL) was immediately observed after an iron-chlorophyllin aqueous solution was added to an acetonitrile/water mixed solution containing hydrogen peroxide. Quenching of the iron-chlorophyllin complex CL was caused by adding L-ascorbic acid. Based on these facts, a determination method involving small amounts of L-ascorbic acid was developed. As a result, this CL system is able to determine L-ascorbic acid over a wide concentration range of 4.0 x 10(-12) to 4.0 x 10(-4) mol L(-1). Also, coexisting substances, such as sugar and vitamins, did not interfere with the determination. Moreover, the participation to the CL was not observed when using other reducing agents, such as hydroxylamine hydrochloride. As an application for practical use, L-ascorbic acid in soft-drink powder was determined. The experimental value was almost the same as the calculated one (5.30 x 10(-5) mol L(-1)).

Adsorption and desorption properties of trans-resveratrol on cellulose cotton.

The adsorption and desorption properties of trans-Resveratrol (Res) on the cellulose cotton were investigated under various conditions, such as the pH, alcohol percentage, temperature and equilibrium times. Moreover, the acidic-dissociation constants were determined to be pKa1 = 8.01, pKa2 = 9.86 and pKa3 = 10.5 by a curve-fitting method. Also, it was found that the adsorption depended on the temperature and salting effect. On the other hand, the desorptions from cellulose were examined using several kinds of water-miscible organic solvents (methanol, ethanol, acetone and THF).

Preconcentration technique for nonylphenol using cellulose cotton with homogenous liquid-liquid extraction for liquid chromatographic analysis.

A powerful preconcentration method for nonylphenol (NP) has been developed for liquid-chromatography by combining the use of cellulose cotton (solid-phase extraction) with homogeneous liquid-liquid extraction. A 100 ml of sample solution was preconcentrated using cotton, and the eluate obtained (acetonitrile; 5 ml) was further preconcentrated to 50 microl within 10 min using a homogeneous liquid-liquid extraction method (volume ratio, 2,000-fold; 100 ml--> 50 microl). The sample concentration increases from preconcentration was 1,599-fold, and NP was extracted into the sedimented phase at 80%. The proposed method was applied to high performance liquid chromatography with fluorescence detection (FL/HPLC); the lowest determination limit obtained was 1.0 x 10(-9) mol l(-1).

Determination of lower sub ppt levels of environmental analytes using high-powered concentration system and high-performance liquid chromatography with fluorescence detection.

The proposed method was successful in the determination and separation of lower sub ppt levels of polycyclic aromatic hydrocarbons (PAHs). In this study, a new phase separation phenomenon (i.e., homogeneous liquid-liquid extraction) was developed that rapidly and simply separated an immiscible liquid phase from water-miscible organic solvents. One liter of sample solution was preconcentrated by a solid phase extraction method, then the obtained eluate (5 mL) was further preconcentrated to just 20 microL by this homogeneous liquid-liquid extraction. The 20 [micro sign]L sedimented phase was directly injected into the high-performance liquid chromatography with fluorescence detection (FL-HPLC). The entire preconcentration factor was 50,000-fold. Six kinds of PAHs were determined in the range of 3.0 x 10(-18) approximately 4.5 x 10(-11) mol L(-1). These chemicals were also satisfactorily separated.

Simultaneous determination of iron(II) and iron(III) by micellar electrokinetic chromatography using an off-line selective complexing reaction.

A simultaneous determination with UV detection/capillary electrophoresis for Fe(II) and Fe(III) was achieved using a sulfonated bathophenantholine and desfferioxamine B. When the electrophoretic buffer was 60 mmol l(-1) SDS, 10 mmol l(-1) acetic acid (pH 4.0) and 10 mmol l(-1) ascorbic acid and at -10 kV, the iron(II) and iron(III) could not only be completely separated, but also be sensitively determined.

Determination of ppb levels of tryptophan derivatives by capillary electrophoresis with homogeneous liquid-liquid extraction and sweeping method.

Tryptophan (Trp) derivatives were selectively separated from 24 kinds of amino acid mixture solutions. Capillary electrophoresis (CE) with UV detection using the described pretreatment system was able to separate and determine 4 kinds of Trp derivatives: 5-hydroxy L-tryptophan, 5-methyl L-tryptophan, 1-methyl L-tryptophan and L-tryptophan. The pretreatment system used a combination of a homogeneous liquid-liquid extraction and a sweeping method, the two are different kinds of powerful preconcentration/separation methods. Trp derivatives were thus separated by two different separation systems. First, these derivatives were selectively extracted at 57-100% by a homogeneous liquid-liquid extraction; secondly, they were respectively separated by micellar electrokinetic chromatography (MEKC) with a sweeping effect. The detection limits following complete separation of the Trp derivatives were 10(-8) mol l(-1) levels, respectively. The proposed method provided a more than 10-fold the improvement in sensitivity compared with fluorescence labeling/fluorophotometric analysis; the proposed method was also applied to the component analysis of nutritious medicine.

Homogeneous liquid-liquid extraction and micellar electrokinetic chromatography using sweeping effect concentration system for determination of trace amounts of several polycyclic aromatic hydrocarbons.

A powerful capillary electrophoresis (CE) method, with preconcentration in excess of 100,000-fold, has been developed by using a specific characteristic of perfluoro surfactants. Highly sensitive determination and separation of polycyclic aromatic hydrocarbons (PAH) were achieved by following a combination of two kinds of efficient preconcentration method using perfluoro surfactants. The two preconcentration methods combined were homogeneous liquid-liquid extraction for off-line concentration and a sweeping method as on-line concentration. Five PAH (1,2,3,4-dibenzanthracene, 1,2,5,6-dibenzanthracene, benzo( a)pyrene, benzo( e)pyrene, and pyrene) were investigated, and were completely separated. When the concentration-factor (volume ratio) was 8335-fold, the determination limits were in the range 10(-10) to 10(-9) mol L(-1). The maximum concentration-factor (volume ratio) obtained was 125,000-fold. Addition and recovery experiments were performed for three kinds of natural water (rain water, river water, and spring water).