A new chemiluminescence system for determination of cobalt

The chemiluminescence of the reaction of tartaric acid with hydrogen peroxide in the presence of Co(II) in alkaline buffer media has been examined. The maximum emission wavelength is 460 nm. The kinetic curve of the chemiluminescence system has been modelled with a computer, and the reaction conditions have been optimized. Foreign ions, such as Fe(II), Cr(III) and Mn(II), interfere when present in more than 10-fold ratio to Co(II), but several ions can be tolerated when present in higher ratios to Co(II). The concentration range of linear response is from 3.5 x 10(-9) to 2.0 x 10(-6) g/ml, and the detection limit is 4 x 10(-11) g/ml. The procedure has been satisfactorily applied to determine trace cobalt in human blood serum.     

The second-order scattering study of the Tb(III)-RNA and determination of RNA

The second-order scattering technique (SOS), using a common spectrofluorometer, was first developed as a sensitive instrumental analysis method for determination of the ribonucleic acid (RNA). The results indicate that RNA had a weak SOS peak and the Tb(III) ion can greatly enhance the SOS intensity of RNA with the maximum peak located at 612.0 nm. Mechanism study shows that the peak results from the long-range assembly of Tb(III) ion on the molecular surface of RNA. At the pH 7.50 and with cetyltrimethylammonium bromide (CTMAB) (6.0 x 10(-5)M), the enhanced SOS intensity was in proportion to the concentration of RNA in the range of 2.0 x 10(-8) to 2.0 x 10(-5)g/ml. The detection limit was 1.96 ng/ml. The relative standard deviation (five replicates) was within +/-5% in the linear range. This method has been used satisfactorily for the determination of both synthetic and real samples. In comparison with most other methods for the determination of ribonucleic acids, this method is more sensitive.     

Determination of polyphenols by high-performance liquid chromatography with inhibited chemiluminescence detection.

A chemiluminescence reaction detector was developed for the detection of polyphenols separated by HPLC based on the inhibition of chemiluminescence from the luminol-potassium hexacyanoferrate(III) reaction by polyphenols. The separation was carried out on a RP-C18 column at 37 degrees C by using stepwise gradient elutions. The detection limits are in the range of 6.8 x 10(-7)-2.0 x 10(-9) g/ml for catechol, protocatechuic acid, chlorogenic acid, rutin, resorcinol, hydroquinone and p-tert.butylpyrocatechol. The method is sensitive, selective, fast and simple. It has been successfully applied to the determination of chlorogenic acid and rutin in real tobacco samples.     

Extractive-spectrophotometric determination of trace iron(II) with di-2-pyridylmethanone 2-(5-nitro)pyridylhydrazone

The optimum conditions for the extractive-spectrophotometric determination of trace iron(II) with di-2-pyridylmethanone 2-(5-nitro)pyridylhydrazone have been established. Iron(II) reacts with this reagent at pH 2.0-7.5 to form an uncharged 1:2 (metal-to-ligand) complex, which can be extracted with toluene. Beer's law is obeyed over the range up to 0.84 mug/ml of iron(II) at 505 nm. The molar absorptivity of the extracted species is 5.83 x 10(4) 1.mole(-1).cm(-1). The proposed method is extremely sensitive and reproducible, and has been satisfactorily applied to the determination of total iron in freshwater samples by adding ascorbic acid to reduce iron(III).     

Spectrophotometric determination of flucloxacillin in pharmaceutical preparations using some nitrophenols as a complexing agent

Some nitrophenols are proposed as chromogenic reagents for the spectrophotometric determination of flucloxacillin. The reagent forms a greenish yellow 1:1 complex with flucloxacillin at pH 9.0. This complex is stable for at least 3.0 h after its formation. The greenish yellow charge transfer complex species has an absorption maximum at 446, 435, 442, 473 and 439 nm for p-nitrophenol (I), 2,4-dinitrophenol (II), 3,5-dinitrosalycilic acid (III), picramic acid (IV) and picric acid (V), respectively, with a molar absorptivity between 1.43 x 10(4) and 2.59 x 10(4) l mol(-1) cm(-1). Beer's low is valid over the concentration range 2.0-40 microg ml(-1) of flucloxacillin. The detection and quantitation limits as well as relative standard deviation were also calculated. The reagents have been successfully used for the spectrophotometric determination of flucloxacillin in pure form and in pharmaceutical preparations.     

A new catalytic kinetic spectrophotometric method for determination of iron

The catalytic effect of iron(III) on the oxidation of reduced Rhodamine B with hydrogen peroxide in acetic acid medium has been studied. The reaction is highly accelerated by potassium thiocyanate. A new catalytic kinetic spectrophotometric method for the determination of iron has been developed. Iron(III) can be determined by the fixed time method with a detection limit of 4 x 10(-11) g/ml.     

Preconcentration of trace copper with yeast for river water analysis

A sensitive and selective method has been introduced for the determination of ultra trace amounts of Ru(III) based on its catalytic effects on the oxidation of Brilliant green (BG) by sodium bromate. A flow injection method has been used with spectrophotometric detection. The method is based on measuring the decrease in absorbance of BG at lambda(max)=615 nm. The decrease in absorbance of BG is linear with the concentration range of 0.005-0.500 mug ml(-1) Ru(III). The limit of detection is 0.002 mug ml(-1). The influence of reagent concentration, manifold parameter and potential interference species has been investigated. The method was used for the determination of ruthenium in synthetic samples with satisfactory results.     

Synthesis of 5-(5-nitro-2-pyridylazo)-2,4-diaminotoluene and its application to spectrophotometric determination of microamounts of palladium

A new pyridylazo reagent, 5-(5-nitro-2-pyridylazo)-2,4-diaminotoluene (5-NO(2)-PADAT) has been synthesized, and found to be a good chromogenic reagent for palladium. In sulfuric acid, hydrochloric acid and perchloric acid palladium reacts with 5-NO(2)-PADAT to form a 1:1 chelate, exhibiting an absorption maximum at 592 nm. The apparent molar absorptivity is 1.25 x 10(5) l(-1) mol(-1) cm(-1). Beer's law was obeyed in the range 0-0.9 microg ml(-1) Pd. Relatively large amounts of co-existing elements, including all other noble metals, can be tolerated. The method is simple and rapid, with high sensitivity and good selectivity and was applied to the determination of palladium in some industrial samples with satisfactory results.     

A new and rapid method for the solvent extraction of Ru/III/ with 1,2,3-benzotriazole into 1-pentanol

A new and rapid method has been developed for the quantitative extraction of Ru/III/ with 1,2,3-benzotriazole /1,2,3-BT/ into 1-pentanol. The extraction coefficient value of Ru/III/ between 1-pentanol and an aqueous 5% solution of 1,2,3-BT in 2M sodium acetate-acetic acid buffer showed a maximum value of E=46 at pH 4.5. The effect of various other parameters on the extraction coefficient of Ru/III/ such as solvents, anions, cations, etc. have also been studied. The stoichiometry of metal:reagent determined by the method of substoichiometric extraction and slope ratio method was found to be 13. Decontamination factors for many elements in the substoichiometric extraction of Ru/III/ were also evaluated.     

Analytical application of a new thiazolylazo reagent, 2-(2-benzothiazolylazo)-5-dimethylamino-4-tolylarsonic acid Spectrophotometric determination of palladium

A new thiazolylazo reagent, 2-(2-benzothiazolylazo)-5-dimethylamino-4-tolylarsonic acid, has been synthesized and found to be a good chromogenic reagent for palladium. A 1:1 blue chelate (lambda(max) = 718 nm) is formed in a sulphuric or nitric acid medium. The molar absorptivity is 6.65 x 10(4) l. mole(-1).cm(-1). Beer's law is obeyed in the range 0-1.6 mug/ml Pd. Relatively large amounts of co-existing elements, including noble metals, can be tolerated.     

Solvent extraction of Ru(III) with 2-mercaptobenzimidazole into n-butanol

A new and rapid method has been developed for the quantitative extraction of Ru(III) with 2-mercaptobenzimidazole into n-butanol. The extraction coefficient of Ru(III) between n-butanol and an ethanolic solution of 1% 2-mercaptobenzimidazole showed a maximum value ofE=161 at a pH of 2.0. The effect of various other parameters on the extraction coefficient value of Ru(III) such as solvent effect, anions, cations, etc. have also been studied. The stoichiometry of metal to reagent has also been determined by the method of substoichiometric extraction and by the slope ratio method and was found to be 1∶3. Decontamination factor for various elements in the substoichiometric extraction of Ru(III) were also evaluated.     

Reversed phase HPLC determination of titanium(IV) and iron(III) with sodium 1,2-dihydroxybenzene-3,5-disulfonic acid

A highly sensitive method has been developed for the determination of titanium(IV) and iron(III) by ion-pair reversed phase liquid chromatography using sodium 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron) as a precolumn chelating reagent. The metal - Tiron chelates were separated on a C₁₈ (ODS) column; the mobile phase was a 2:8 (v/v) mixture of acetonitrile and acetate buffer (0.04 mol/L, pH 6.2) containing 2.0 × 10^?3 mol/L Tiron, 0.04 mol/L tetrabutylammonium bromide, and 0.1 mol/L potassium nitrate. The detection limits for titanium(IV) and iron(III) are 0.5 and 2.0 μg/L, respectively. The method has been applied to the simultaneous determination of titanium(IV) and iron(III) in river water samples and has furnished highly precise results.     

Flow-injection chemiluminescence determination of ofloxacin and levofloxacin in pharmaceutical preparations and biological fluids.

A novel, rapid and sensitive analytical method is described for determination of ofloxacin and levofloxacin by enhanced chemiluminescence (CL) with flow-injection sampling. The method is based on the CL reaction of the Ce(IV)-Na2S2O4-ofloxacin/levofloxacin-H2SO2 system. The enhanced CL mechanism was developed and the optimum conditions for CL emission were investigated. The CL intensity was correlated linearly (r = 0.9988) with the concentration of ofloxacin (or levofloxacin) in the range of 1.0 x 10(-8) - 1.0 x 10(-7) g ml(-1) and 1.0 x 10(-7) - 6.0 x 10(-6) g ml(-1). The detection limit (S/N = 3) is 7 x 10(-9) g ml(-1). The relative standard derivation (RSD, n = 11) is 2.0% for ofloxacin at 4 x 10(-7) g ml(-1) and for levofloxacin at 6 x 10(-7) g ml(-1). This method has been successfully applied for the determination of ofloxacin and levofloxacin in pharmaceutical preparations and biological fluids with satisfactory results.     

Flow injection with inhibited chemiluminescence method for the determination of dopamine hydrochloride.

A simple rapid and accurate flow injection inhibitory chemiluminescence method has been developed for the determination of dopamine hydrochloride based on its inhibition of the chemiluminescence from the luminol-potassium hexacyanoferrate(III) system. The linear range of determination is 4.0 x 10(-9) - 4.0 x 10(-7) g ml(-1) for dopamine hydrochloride and the detection limit is 1.14 x 10(-9) g ml(-1). The method has been applied to determine the content of dopamine in pharmaceutical preparation with satisfactory results.     

Studies on 2-(2-thiazolylazo)-5-diethylaminophenol as a precolumn derivatizing reagent in the separation of platinum group metals by high performance liquid chromatography

Five platinum group metals, Pt(II), Ir(IV), Ru(III), Rh(III) and Os(IV) have been separated by high performance liquid chromatography (HPLC) using 2-(2-thiazolylazo)-5-diethylaminophenol (TADAP) as a precolumn derivatizing reagent. The whole analysis was completed on a C(18) column in 23 min at 574 nm, with the mobile phase of methanol-water (69.5:30.5, v:v) containing 4 mmol l(-1) tetrabutylammonium bromide (TBA Br) and 10 mmol l(-1) pH6.0 acetate buffer. The detection limits (S/N=3) of Pt(II), Ir(IV), Ru(III), Rh(III) and Os(IV) were 0.39, 9.74, 1.64, 0.29 and 1.29 ng ml(-1), respectively. This method was rapid, sensitive and simple.     

Nucleic acids analysis with nano-Ag-Tb(III) by a resonance light scattering technique.

The nano-Ag-terbium(III)-mucleic acids system was observed by a resonance light scattering (RLS) technique for the first time, and the quantitative analysis of nucleic acids at nanogram levels was established. Studies showed that the RLS intensity of the nano-Ag-terbium(III) system can be obviously enhanced by nucleic acid, which was characterized by the RLS spectrum and the UV-Vis spectrum. In this system, the nanoparticles were only of a definite size and in a limited particle concentration region. Further research indicated that under the optimum conditions, the enhanced intensity of RLS is in proportion to the concentration of nucleic acids in the ranges of 7.0 x 10(-9) g ml(-1) to 8.0 x 10(-6) g ml(-1) for calf thymus DNA (ctDNA), 2.0 x 10(-8) g ml(-1) to 1.0 x 10(-6) g ml(-1) for fish sperm DNA (fsDNA) and 1.0 x 10(-9) g ml(-1) to 1.0 x 10(-7) g ml(-1) for yeast RNA (yRNA). The detection limits were 1.4 ng ml(-1) for ctDNA, 1.2 ng ml(-1) for fsDNA and 0.85 ng ml(-1) for yRNA, respectively. Synthetic and real samples were determined satisfactorily.     

Catalytic spectrophotometric determination of trace aluminium with indigo carmine

A new catalytic spectrophotometric method is described for the determination of trace amounts of Al(III). The methods based on catalytic action of Al(III) on the oxidation of indigo carmine (IC) by ammonium persulfate in hexamethylene tetramine-hydrochloric acid ((CH2)6N4-HCl) buffer medium (pH 5.4) and in the presence of surfactant-TritonX-100. The effects of some factors on the reaction speed were investigated. Aluminium concentration is linear for 0-1.2x10(-7) g/ml in this method. The detection limit of the proposed method is 1.96x10(-8) g/ml. Most of the foreign ions except for Cu(II), Fe(III) do not interfere with the determination, and the interference of Cu(II) and Fe(III) in this method can be removed by extraction with sodium diethyldithiocarbamate-carbon tetrachloride (DDTC-CCl4). This system is a quasi-zero-order reaction for Al(III), but it is a quasi-first-order reaction for IC. The apparent rate constant is 2.62x10(-5) s-1 and the apparent activation energy is 6.60 kJ/mol in the system. The proposed method was applied to the determination of trace aluminium(III) in real samples with satisfactory results.     

Kinetic spectrophotometric analysis of pantoprazole in commercial dosage forms.

A kinetic spectrophotometric method has been developed which is based on the oxidation of pantoprazole with Fe(III) in sulfuric acid medium. Fe(III) subsequently reduces to Fe(II), which is coupled with potassium ferricyanide to form Prussian blue. The reaction is followed spectrophotometrically by measuring the increase in absorbance with time (1-8 min) at 725 nm. The initial rate method is adopted for constructing the calibration graph, which is linear in the concentration range of 5-90 microg ml(-1). The regression analysis yields the calibration equation, nu = 3.467 x 10(-6) + 4.356 x 10(-5)C. The limits of detection and quantitation are 1.46 and 4.43 microg ml(-1), respectively. The proposed method was optimized and validated both statistically and through recovery studies. The experimental true bias of all samples is < +/-2.0%. The method has been successfully applied to the determination of pantoprazole in pharmaceutical preparations.     

A new coordination mode of the photometric reagent glyoxalbis(2-hydroxyanil) (H2gbha): bis-bidentate bridging by gbha2- in the redox series [(mu-gbha)[Ru(acac)2]2]n (n = -2, -1, 0, +1, +2), including a radical-bridged diruthenium(III) and a Ru(III)/Ru(IV) intermediate

The bis-bidentate bridging function of gbha2- with N,O-/N,O- coordination was observed for the first time in the complex (mu-gbha)[Ru(III)(acac)2]2 (1). Density functional theory calculations of 1 yield a triplet ground state with a large (deltaE > 6000 cm(-1)) singlet-triplet gap. Intermolecular antiferromagnetic coupling was observed (J approximately -5.3 cm(-1)) for the solid. Complex 1 undergoes two one-electron reduction and two one-electron oxidation steps; the five redox forms [(mu-gbha)[Ru(acac)2]2]n (n = -2, -1, 0, +1, +2) were characterized by UV-vis-NIR spectroelectrochemistry (NIR = near infrared). The paramagnetic intermediates were also investigated by electron paramagnetic resonance (EPR) spectroscopy. The monoanion with a comproportionation constant K(c) of 2.7 x 10(8) does not exhibit an NIR band for a Ru(III)/Ru(II) mixed-valent situation; it is best described as a 1,4-diazabutadiene radical anion containing ligand gbha*3-, which binds two ruthenium(III) centers. A Ru(III)-type EPR spectrum with g1 = 2.27, g2 = 2.21, and g3 = 1.73 is observed as a result of antiferromagnetic coupling between one Ru(III) and the ligand radical. The EPR-active monocation (K(c) = 1.7 x 10(6)) exhibits a broad (deltanu(1/2) = 2600 cm(-1)) intervalence charge-transfer band at 1800 nm, indicating a valence-averaged (Ru3.5)2 formulation (class III) with a tendency toward class II (borderline situation).     

Fluorimetric trace determination of cerium(III) with sodium triphosphate

Sodium triphosphate acts as a specific reagent for enhancing the fluorescence intensity of cerium(III). The purpose of this study was to investigate the spectrofluorimetric determination of trace amounts of Ce(III) in sodium triphosphate solution. The excitation and emission wavelengths are 303.5 nm and 353 nm respectively. Optimum sodium triphosphate concentration is found to be 0.074 g l(-1) at room temperature. The fluorescence varies linearly with the concentration of cerium(III) in the range 0.001-45 mug ml(-1). The detection limit is 9.4 x 10(-4)mug ml(-1). The relative standard deviations for 30 mug ml(-1) and 0.05 mug ml(-1) Ce(III) in 0.074 g l(-1) sodium triphosphate solution are 1.1% and 0.72% respectively. Quenching effects of other lanthanides and some inorganic anions are described. This method is a direct and rapid analytical method for the determination of Ce(III) in rare earth mixtures and cerium concentrates.