Shukuro Igarashi

Homogeneous liquid-liquid extraction by pH dependent phase separation with a fluorocarbon ionic surfactant and its application to the preconcentration of porphyrin compounds

Aqueous perfluorooctanoate (PFOA−) solution of water-miscible organic solvent (SOLV), such as dioxane and acetone, was separated into two immiscible phases reversibly by charge neutralization of PFOA− ion with proton (H+) (pKa value of HPFOA was 1.01, atI = 0.1, 20 °C). The transparent heavier phase, in which HPFOA was concentrated quantitatively, consisted of three components in the molar ratio of HPFOA∶SOLV∶H2O = 1∶4.0∶6.6 for acetone system, and 1∶0.47∶1.9 for dioxane system, respectively. This separation provides a new homogeneous liquid-liquid extraction method, which can be successfully applied to the ultra-high preconcentration of water-soluble porphyrin compounds: 104-fold concentration was achieved within 20 min.

Homogeneous liquid-liquid extraction method for spectrofluorimetric determination of chlorophyll a.

A new homogeneous liquid-liquid extraction using a fluorocarbon ionic surfactant, Zonyl FSA (FSA), having a diethylthioether group as a spacer between the perfluoroalkyl group and carboxyl group has been developed. In this FSA method, the phase separation phenomena were observed at mild pH (below pH 6). Moreover, by using this extraction method as a preconcentration, a highly sensitive spectrofluorometric determination of chlorophyll a was established. The results for the standard chlorophyll a were as follows. The concentration factor (V(w)/V(o)) was 200 (water phase, V(w), 20 cm(3), water-immiscible phase, V(o), 100 mul), the distribution ratio, log D, was 4.85, the extraction percentage, E, was 99.7%, and the procedure time was approximately 30 min. The calibration curve was linear in the concentration range 2 x 10(-11)-3 x 10(-7) mol dm(-3) and the detection limit (S/N=3) was 1 x 10(-11) mol dm(-3). The relative standard deviation was 0.72% for 10(-8) mol dm(-3) (five determinations).

Homogeneous liquid–liquid extraction followed by X-ray fluorescence spectrometry of a microdroplet on filter-paper for the simultaneous determination of small amounts of metals

Homogeneous liquid–liquid extraction with perfluorooctanate ion (PFOA–) was utilized for the preconcentration of certain types of metal chelates, such as diethyldithiocarbamate, 1,10-phenanthroline and desferrioxamine B. Under the experimental conditions {i.e., [PFOA−]T = 6.0 × 10−3 mol l−1, [acetone]T = 2.0 vol%, [HCl]T=0.72 mol l−1, room temperature}, the maximum concentration factor was 500-fold. A method was then developed to determine those metal chelates deposited in a microdroplet on filter-paper using X-ray fluorescence spectrometry. As a result, when three types of chelating agent were used together in the process, 15 metal ions [Ti(IV), Zr(IV), V(V), Nb(V), Ta(V), W(VI), Fe(II), Co(II), Ni(II), Pd(II), Cu(II), Au(III), Hg(II), Bi(III) and Se(IV)] were simultaneously determined. The recovery of each metal was ca. 83–100%, except for W(VI) which was 60.2%. The calibration curves for each metal ion were linear over the range from 5.0 × 10−7 to 1.0 × 10−5 mol l−1. The detection limits were at the 10−8 mol l−1 level and the relative standard deviations were below 5%.

Room temperature phosphorescence of palladium(II) — coproporphyrin III complex in a precipitated nonionic surfactant micelle phase: determination of traces of palladium(II)

The palladium(II)—coproporphyrin III complex was distributed and concentrated in the surfactant phase precipitated from a homogeneous micellar solution of Triton X-100 by heating for 20 to 30 min at a temperature above its cloud point. This concentrated complex had strong phosphorescence at room temperature. Based on these findings, the room temperature phosphorimetric determination of 10−9 M levels of Pd(II) was developed. The detection limit (signal-to-noise ratio = 3) was 2 × 10−9M (2.7 ng Pd2+/15 ml), and the relative standard deviation was 2.1% for 1 × 10−6M (1.6 μg Pd2+/15 ml) (6 determinations).

Highly sensitive spectrophotometric determination of nitrite ion using 5,10,15,20-tetrakis(4-aminophenyl)porphine for application to natural waters

Abstract A water-soluble porphyrin having the aminophenyl group, 5,10,15,20-tetrakis(4-aminophenyl)porphine, reacts with nitrite ion, and produces a large spectral change (Δe = 3.0 × 105 l mol−1 cm−1, 434 nm). There are few interfering substances and it is easy to establish the reaction conditions because the spectral change mechanism is based only on diazotization. A highly sensitive spectrophotometric determination of nitrite was developed on this basis. The calibration graph was linear in the range 0 to 4.0 × 10−7 mol l−1 (0–18 ng ml−1). The detection limit { S N = 3} was 4.0 /sx 10−9 mol l−1 (0.18 ng ml−1), and the relative standard deviation was 1.0% (at 2.0 × 10−7 mol l−1 nitrite, 10 determinations). This method has been applied to the determination of nitrite in rain, tap and spring water without any pretreatment.

Flow injection spectrophotometric determination of ng ml−1 levels of cobalt(II) using the photochemical decomposition of a cadmium(II)-water-soluble porphyrin complex

Abstract Cadmium(II)-5,10,15,20-tetrakis(4-sulfophenyl)porphine complex (CdL) (Soret band: maximum wavelength ( λ max ) = 432 nm , molar absorptivity ( ϵ ) = 4.8 × 10 5 l mol −1 cm −1 ) was found to be uniquely decomposed by irradiation with blue light around 432 nm. However, the cobalt complex of the same ligand ( λ max = 432 nm , ϵ = 2.8 × 10 5 l mol −1 cm −1 ) was stable to visible light. A highly sensitive flow injection system for cobalt(II) ions was developed by the use of these photochemical properties which allows an elimination of the absorbance blank of the reagent CdL in the spectrophotometric detection of Co(II) following the exchange reaction: CdL + Co 2+ → Co ( III ) L + Cd 2+ . The calibration graph for cobalt(II) was linear in the range 1 × 10 −7 –1 × 10 −6 mol l −1 . The apparent molar absorptivity of the cobalt complex obtained from the calibration slope was 1.2 × 10 4 l mol −1 cm −1 . The relative standard deviation was 0.6% (10 determinations) for 6.8 × 10 −7 mol l −1 cobalt. The detection limit ( S N = 3 ) was 3.45 × 10 −8 mol l −1 (2 ng ml −1 ).

Homogeneous liquid–liquid extraction method for the selective spectrofluorimetric determination of trace amounts of tryptophan

Twenty-one amino acids were derivatized with fluorescamine (FLA) under basic conditions (pH 9) and the extraction of the amino acid-FLA derivatives was investigated using a homogeneous liquid-liquid extraction with perfluorooctanoic acid (HPFOA) based on phase separation under strongly acidic conditions. Under the optimum concentration conditions for the reagents ([PFOA]T = 3 x 10(-3) mol dm-3, [acetone]T = 3 vol.%, [HCl]T = 1.8 mol dm-3), the concentration factor was approximately 1000-fold (i.e., 30 microliters of the sedimented liquid phase was produced from 33 ml of the homogeneous aqueous solution). The percentage extraction (E) was determined for the 21 amino acid-FLA derivatives; the value for the tryptophan (Trp)-FLA derivative was 80.9%, whereas the other derivatives were not almost extracted (E < 0.4%). The Trp-FLA derivative was selective for the extraction using the homogeneous liquid-liquid extraction method with HPFOA. After the sedimented liquid phase containing Trp-FLA has been placed on a polytetrafluoroethylene filter-paper, the fluorescence intensity was determined using a spectrofluorimeter with filter-paper as the solid-sample holder. The calibration graph of Trp was linear over the range 1.0 x 10(-8)-1.5 x 10(-6) mol dm-3. The relative standard deviation for the central value of the calibration graph was 4.5% (five determinations) and the detection limit (S/N = 3) was 8.9 x 10(-9) mol dm-3. When the proposed method was applied to the highly sensitive spectrofluorimetric determination of Trp in animalin-L syrup, the results were satisfactory.

UV-detection capillary electrophoresis for benzo[a]pyrene and pyrene following a two-step concentration system using homogeneous liquid–liquid extraction and a sweeping method

10(-9) mol l-1 levels of polycyclic aromatic hydrocarbons (PAHs) suspected for certain noxious materials can be determined and separated by UV-detection capillary electrophoresis following a two-step concentration system. When the conditions of the homogeneous liquid-liquid extraction were [THF]T = 5 vol%, [HCl]T = 0.66 mol l-1, and [PFOA]T = 2 x 10(-3) mol l-1 (i.e., the volume of sample solution; 50 ml-->sedimented phase; 30 microliters), the extraction percentages of benzo[a]pyrene (Bap) and pyrene (Py) at 10(-6) mol l-1 were 102 and 97.5%, respectively. Also, when the total concentration factor(volume ratio), which includes that of the sweeping method, was 8335-fold, the determination range of Bap was 6.4 x 10(-9)-8.0 x 10(-7) mol l-1 and for Py, 8.0 x 10(-9)-7.0 x 10(-7) mol l-1. The detection limits (3 sigma) of Bap and Py were 1.6 x 10(-9) and 4.8 x 10(-9) mol l-1, respectively.

Highly Sensitive Spectrophotometric and Spectrofluorometric Determinations of Albumin with 5,10,15,20-Tetrakis(4-sulfophenyl)porphine

Abstract The 5,10,15,20-tetrakis(4-sulfophenyl) porphine (TPPS) has a highly sensitive absorption spectrum {Soret band: molar absorptivity (e) = 5.0x105 M−1 cm−1 at 434 nm} and a red intense fluorescence. Moreover, it was determined that TPPS reacted rapidly with albumin at room temperature. The absorbance and the fluorescence intensity of TPPS were remarkably and quantitatively decreased by this reaction. Based on these facts, new spectrophotometric and spectrofluorometric determinations of serum albumin were developed. Each calibration curve was linear in the determination range of 0.1 ~ 9.0 μg/ml by spectrofluorometric determination and in the range of 0.2 ~ 6.0 μg/ml by spectrophotometric determination. The fluorometric detection limit was 0.05 μg/ml and the spectrophotometric one was 0.1 μg/ml. Further, the relative standard deviation (5 determinations) for 5 μg/ml albumin was 2.1 % (spectrofluorimetry) and 2.6% (spectrophotometry), respectively. When these methods were applied to the determination o...

Spectrofluorimetric determination of traces of zinc with the cadmium—α,β,γ,δ-tetrakis(4-sulphophenyl) - porphine complex

Abstract A highly sensitive spectrofluorimetric method for the determination of zinc was established by using the metal ion substitution reaction of the cadmium—α,β,γ,δ-tetrakis(4-sulphophenyl)porphine (H 2 P 4− ) complex with zinc ion. The zinc complex, ZnP 4− , was quantitatively formed within 3 min at room temperature in the pH range 10–11. The relative fluorescence intensity ratio, F (ZnP 4− )/ F (CdP 4− ), was 37.0 at λ(em) = 604 nm [λ(ex) = 422 nm]. The calibration graph was linear over the concentration range 5–100 ng Zn 2+ ml −1 in sample solution. The detection limit (signal-to-noise ratio = 3) was 0.15 ng Zn 2+ ml −1 and the relative standard deviation was 1.39% for 16.6 ng Zn 2+ ml −1 (ten determinations). Results are given for the application of the method to the determination of Zn 2+ in tap water.