Noriko Ohno

Simultaneous spectrophotometric determination of iron and copper in serum with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)aniline by flow-injection analysis

Abstract A method for the simultaneous spectrophotometric determination of iron and copper by flow-injection analysis was developed using 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)aniline. The flow system utilizes a double-beam spectrophotometric detector with two flow cells. The reagent forms water-soluble chelates with Cu(II) and Fe(II) in an acetate-buffered medium at pH 4.5. The molar absorptivities of the complexes are 65 000 l mol−1 cm−1 at 578 nm for Cu(II) and 87 000 l mol−1 cm−1 at 558 nm for Fe(II). In one reaction coil Fe(II) is oxidized to Fe(II) by KIO4, so the Fe(II) chelate is not formed and only the coloured complexes with Cu(II) are monitored in the first flow cell. In a second reaction coil, the solution merges with sodium ascorbate solution to reduce Cu(II) and Fe(III) to Cu(I) and Fe(II). Thus only the Fe(II) complex is measured in the second flow cell. Cu(II) and Fe(II) in the range 50–200 μg l−1 are determined at 558 nm. The sample throughput is 30 h−1 with a precision of 1.2%

Routine assay of creatinine in newborn baby urine by spectrophotometric flow-injection analysis

Abstract Creatinine was determined spectrophotometrically by flow-injection analysis with use of the Jaffe reaction. The detection limit was 3 μg ml−1 and the relative standard deviation (n = 10) was 0.6% for 50 μg ml−1 of creatinine. The sample throughput was 102 h−1. Creatinine in newborn baby urine can be assayed sensitively and rapidly.

Formation of ternary ion associates using diprotic acid dyes and its application to determination of cationic surfactants

A sensitive and selective method is described for the determination of cationic surfactants, such as benzethonium, benzalkonium, cetylpyridinium and trimethylstearylammonium, based on the formation and extraction of ternary ion associates with an acid dye (bromophenol blue or bromochlorophenol blue) and quinidine. Quinidine reacts with divalent anionic dyestuffs to form a bulky 1∶1 complex anion, which is extractable into 1,2-dichloroethane as ternary ion associates with cationic surfactants in nearly neutral media. The ternary ion associate gives a blue product. Linearity of the calibration curve is improved and the extractability of the cationic surfactants is enhanced in the presence of quinidine. In addition, many other amines do not interfere with the determination. The blue ion associates can be used for the selective and sensitive spectrophotometric determination of cationic surfactants.

Spectrofluorimetric determination of berberine in oriental pharmaceutical preparations by flow-injection analysis coupled with liquid-liquid extraction

Abstract A sensitive and rapid determination of berberine was carried out by flow-injection analysis. Berberine was successfully extracted in the presence of sodium perchlorate. The calibration graph was linear over the range 4 × 10 −9 -1 × 10 −6 mol dm −3 . The sample throughput was 42 h −1 .

Simultaneous two- and three-component determinations in multicomponent mixtures by extraction-spectrophotometry and thermochromism of ion-association complexes.

A selective method of determination of amines and quaternary ammonium salts by solvent extraction and thermochromism of ion-association complexes has been established. The method is based on the formation of ion-association species with tetrabromophenolphthalein ethyl ester and the thermochromism effect in the organic phase at low temperature. The absorbance of the red amine charge-transfer complexes decreases quantitatively (DeltaA) with increase in temperature (DeltaT), and Delta A Delta T is characteristic of a particular species. This characteristic has been applied for the sensitive and selective determination of amines. The absorbance of the blue quaternary ammonium ion-association complexes does not vary with temperature, however, and the quaternary ammonium compounds can be determined without interference by amines because of the disappearance of the red species at 60 degrees . Methylephedrine, diphenhydramine, ephedrine (amines), benzethonium and/or berberine (quaternary ammonium compounds) in two- and three-component mixtures can be determined by using the thermochromism effect. The method is highly selective, sensitive and reproducible.

Double-membrane phase separator for liquid-liquid extraction in flow-injection analysis

Abstract A double-membrane phase separator for liquid-liquid extraction in flow-injection analysis was designed and its usefulness was examined in order to achieve smooth, long-term and efficient phase separation with good reproducibility. The construction and performance of the flow-injection system using the phase separator were illustrated by the extraction of berberine-perchlorate ion associates.

Spectrophotometric determination of iron in boiler and well waters by flow injection analysis using 2-nitroso-5-(N-propyl-N-sulphopropylamino)phenol

2-Nitroso-5-(N-propyl-N-sulphopropylamino)phenol (nitroso-PSAP) forms a water-soluble chelate with iron. The molar absorptivity of the complex is 4.3 × 104 l mol-1 cm-1 at 753 nm. Iron (4–100 µg l–1) is easily and selectively determined in a flow injection system because divalent transition metals (Ni, Co, Cu, Zn and Cd) at the 500 µg l–1 level do not interfere. The method has an average recovery error of ±1% and the sampling rate is 25 samples h–1. A simple procedure for the determination of iron in boiler and well waters is described.

Improved determination of methamphetamine, ephedrine and methylephedrine in urine by extraction-thermospectrometry

A selective spectrophotometric method has been developed for the determination of stimulant drugs in urine. The method is based on colour development and thermochromism of ion-association compounds in the organic phase caused by mixing a 1,2-dichloroethane solution of the stimulant drug and a 1,2-dichloroethane solution of tetrabromophenolphthalein ethyl ester (TBPE.H). Methamphetamine, ephedrine and methyl-ephedrine bases extracted in a highly alkaline medium with 1,2-dichloroethane react with TBPE.H in 1,2-dichloroethane solution to form red ion-association complexes. The complexes show characteristic and stoicheiometric thermochromism with variation in temperature. Both the colour reaction and thermochromism in the organic phase were applied to the simultaneous and sensitive determination of two stimulant drugs in urine. The determination limits were about 0.16 µg ml–1.

Flow injection analysis of cationic disinfectants in pharmaceuticals using ion associates formed between sulphonephthalein dyes and quinidine

Cationic disinfectants were reacted with bromochlorophenol blue and quinidine in 1,2-dichloroethane to form a blue ternary ion associate. The extraction system was introduced into a two-line flow manifold. The sampling rate was 30 h−1 and the calibration graphs were linear up to 5×10−5 mol/l for benzethonium and berberine.

Batchwise and flow-injection methods for thermo-spectrophotometric determination of acetylcholine and choline with tetrabromophenolphthalein ethyl ester

Abstract A selective spectrophotometric method was established for the determination of acetylcholine (Ach) and choline (Ch) by liquid—liquid and thermochromism of ion association complexes. This method is based on the formation of ion association compounds with tetrabromophenolphthalein ethyl ester (TBPE · H) and thermocromism of ion associates in the organic phase, where selectivity can be improved. The absorbance of blue Ach and/or Ch ion association complexes does not vary with temperature changes, but that of the red amine complexes disappears when the temperature of the absorbance measurements is kept at 45°C. A two-line manifold was constructed for the flow-injection method. The sample is injected into the buffered stream adjusted to pH 11 and mixed with the extracting TBPE · H dichloroethane solution. The organic phase separated with a polytetrafluoroethylene porous membrane passes through a temperature-controlled micro flow cell (45°C) and the absorbance of the organic phase is measured. The sample throughputs were 36 h −1 for both Ach and Ch. The calibration graphs were linear in the range 6.25 × 10 −5 –7.5 × 10 −6 mol dm −3 for Ach and 1.25 × 10 −6 –1.5 × 10 −5 mol dm −3 for Ch. The relative standard deviation was 1.2% for 5 × 10 −6 mol dm −3 Ach ( n = 5_ and 1.2% for 1 × 10 −5 mol dm −3 Ch ( n = 8).