Di-2-pyridyl ketone 2-furoylhydrazone as a reagent for the fluorimetric determination of low concentrations of aluminium

The synthesis and properties of di-2-pyridyl ketone 2-furoylhydrazone as an analytical reagent are described. A rapid procedure for the fluorimetric determination of aluminium at the 10-100 ng ml level, at pH 6.1-6.5 (lambda(exc) 395 nm, lambda(em) 465 nm) has been established. Interferences have been evaluated, and the procedure has been applied satisfactorily to determination of aluminium in sea-water.     

Spectrofluorometric determination of hesperidin by manual and flow-injection methods

A reliable and highly sensitive method for the determination of hesperidin is described. It involves the formation of a highly fluorescent complex between hesperidin and aluminium (III) in a micellar medium. There is a linear relationship between fluorescence intensity (λ_em = 496 nm, λ_ex = 391 nm) and hesperidin concentration over the range 5 × 10^–7– 2 × 10^–5 mol L^–1. The detection limit is 79 μg L^–1. The method can easily be adapted to a flow system using a three-channel manifold, the peak height being proportional to the hesperidin concentration over the range 1 × 10^–6– 1 × 10^–4 mol L^–1. Manual and flow-injection procedures have been successfully applied to the determination of hesperidin in orange peel and orange juice.     

Kinetic fluorometric methods for the determination of phosphates at the nanogram level using a lead(II)-catalyzed pyridoxal 2-pyridylhydrazone-hydrogen peroxide reaction

Fluorometric methods for the determination of phosphate (1.5 × 10^?6–3.1 × 10^?6M), diphosphate (7.0 × 10^?7–2.0 × 10^?6M), and triphosphate (2.0 × 10^?7–2.7 × 10^?6M) are described. The analytical procedure is based on the inhibition of polyphosphate ions on the oxidation of pyridoxal 2-pyridylhydrazone (PPH) by hydrogen peroxide, catalyzed by low concentrations of lead(II) ions. The reactions are followed by means of the rate of appearance of the fluorescence (λ_ex = 355 nm, λ_em = 425 nm). The effect of the variables is studied. The kinetic parameters of the reactions are reported and rate equations are suggested. The results are interpreted according to the discernment of the chemistry of complex formations.     

Spectrofluorimetric determination of 1-(3-chlorophenyl)-4-methyl-7,8-dimethoxy-5H-2,3-benzodiazepine

A sensitive fluorimetric method for the determination of 1-(3-chlorophenyl)-4-methyl-7,8-dimethoxy-5H-2,3-benzodiazepine (5 × 10^?8?6 × 10^?4) g ml^?1) is described. The method is based on acid hydrolysis and aldol condensation in alkaline solution to give a compound which shows intense fluorescence at 440 nm.     

Spectroscopic characterization of 2-naphthylcarbene

The 308 nm excimer laser flash photolysis of 2-naphthyldiazomethane produces triplet 2-naphthylcarbene (λ_max = 362 nm) which decays with the observed pseudo-first-order rate constants (k_exptl) of 5.54 ± 0.03 × 10⁶; 3.33 ± 0.4 × 10⁶; 1.64±0.02 × 10⁷; and 3.05±0.4 × 10⁶ s^-1 in n-pentane, 2,2,4-trimethylpentane (2,2,4-TMP), benzene and Freon 113 respectively. In hydrocarbon solvents the observed decay of triplet 2-naphthylcarbene is correlated with the pseudo-first-order growth of the 2-naphthylmethyl radical (λ_max = 378 nm). Direct kinetic measurements of the reaction of triplet 2-naphthylcarbene in 2,2,4-TMP with cyclohexane, styrene, methanol and carbon tetrachloride yielded bimolecular quenching rate constants of 1.48 ± 0.04 × 10⁶;4.33 ± 0.1 × 10⁷;7.25 ± 0.5 × 10⁶; and 3.35 ± 0.07 × 10⁶M^-1S^-1. It is also found that 2-naphthylcarbene reacts with acetonitrile (k_q = 5.28 ± 0.1 × 10⁵ M^-1 s^-1) to form a nitrile ylide intermediate with a λ_max = 372 nm. These results are interpreted in terms of a rapid singlet-triplet 2-naphthylcarbene equilibrium.     

Spectrofluorometric determination of hesperidin by manual and flow-injection methods

A reliable and highly sensitive method for the determination of hesperidin is described. It involves the formation of a highly fluorescent complex between hesperidin and aluminium (III) in a micellar medium. There is a linear relationship between fluorescence intensity (λ_em = 496 nm, λ_ex = 391 nm) and hesperidin concentration over the range 5 × 10^–7– 2 × 10^–5 mol L^–1. The detection limit is 79 μg L^–1. The method can easily be adapted to a flow system using a three-channel manifold, the peak height being proportional to the hesperidin concentration over the range 1 × 10^–6– 1 × 10^–4 mol L^–1. Manual and flow-injection procedures have been successfully applied to the determination of hesperidin in orange peel and orange juice. Received: 21 October 1998 / Revised: 16 December 1998 / Accepted: 25 December 1998     

Covalent binding and fluorimetric determination of dialdehydes using aminated silica nanoparticles and ethylenediamine fluorescein

The possibility of formation of a ternary (sandwich) compound of a dialdehyde (malondialdehyde, glutaraldehyde, or glyoxal) with ethylenediamine fluorescein thiocarbamyl (EDF) and silica nanoparticles noncovalently modified with polyethyleneimine (SiO₂/PEI) with the subsequent fluorimetric determination of the dialdehyde was demonstrated. The mixed Schiff base SiO₂/PEI–dialdehyde–EDF (sandwich) is formed in an acetic acid solution on heating in a water bath. The sandwich and the excess of SiO₂/PEI were separated from the unreacted fluorophore by centrifugation; the precipitate was washed and resuspended in water, and the fluorescence of solution was measured (λ_ex = 470 nm, λ_em = 520 nm). The duration of an analytical cycle was no longer than a half-hour. The limit of detection of dialdehydes in pure water is 1 × 10^–5 M, and the analytical concentration range is 2 × 10^–5–3 × 10^–4 M (for malondialdehyde). The repeatability RSDs in this concentration range were 3–5% (n = 3). The comparable concentrations of sulfamethoxazole, sulfadiazine, pyracetam, and chloramphenicol and 1 × 10^–5 M of ceftriaxone, ceftazidime, metamizole (analgin), isoniazid, and amikacin caused no interference with the determination of 3 × 10^–4 M malondialdehyde; protein noticeably interfered. The determination of glyoxal and glutaraldehyde in disinfectants was carried out.     

Analytical applications of 4-(4′-methyl-2′-thiazolylazo)-2-methyl-resorcinol: Spectrophotometric determination of vanadium

4-(4′-Methyl-2′-thiazolylazo)-2-methyl-resorcinol reacts with vanadium (V) to produce a bluish-violet 1:1 complex (λ_max = 560 nm, ? = 2.50 × 10⁴M^?1 · cm^?1, 50% methanol-water medium), which allows the spectrophotometric determination of 0.1 to 1.4 ppm of vanadium. The method has been applied to the determination of vanadium in several low-alloy steels.     

Fluorimetric Determination of Thiamine with Cobalt(II)

Abstract

A rapid fluorimetric method is reported for the determination of thiamine based upon its interaction with Co(II) ion in the presence of base and a nonionic Triton X-100 micellar medium. The effect of different experimental variables upon the fluorescence intensity were assessed. The detection limit for thiamine is 5.0 × 10^?8M (λ_ex =375nm, λ_em =433nm). The method was successfully applied for determination of thiamine in variety of samples with good accuracy being achieved.     

Spectrofluorimetric Flow Injection Determination of Glycerol & Ethylene Glycol with Alizarin Navy Blue

ABSTRACT

A simple and accurate procedure for indirect spectrofluorimetric determination of glycerol and ethylene glycol in aqueous media was developed. Alizarin Navy Blue can be oxidized by potassium periodate to produce a fluorescent compound, that can be detected fluorimetrically (λ_ex = 370 nm, λ_em = 516 nm) by a flow through method. Glycerol and ethylene glycol react with periodate decreasing its concentration and thus the forming the basis for an indirect determination of these compounds. The influence of acid concentration, reagent concentration and manifold variables were studied. For glycerol and ethylene glycol linear calibration curves were obtained in the ranges of 4.8 × 10^-7 – 8.7 × 10^-5 M and 6.4 × 10^-7 – 8.7 × 10^-5 M, respectively. The limit of detection (defined as the concentration that gives a signal three times the standard deviation of the background signal) for glycerol and ethylene glycol was 3.2 × 10^-7 M and 4.3 × 10^-7 M, respectively. The proposed method was applied for determination of glycerol and ethylene glycol in synthetic and real samples. The results obtained were satisfactory.     

A Selective Fluorimetric Method for the Determination of Some β-Lactamic AntibioticsSupported by Natural Science Foundations of China and Shandong province

Abstract

Based on the reaction between acetylacetone-formaldehyde and β-lactamic antibiotics at pH=4.0, in which product can emit strong fluorescence, a selective simple fluorimetric method is described for the determination of both α-aminocephalosporins (namely cepharadine and cefalexin) and 6-aminopenicillanic acid (6-APA) in pure form and in pharmaceutical form. Other β-lactamic antibiotics free from α-amino group do not interfere with the assay. The linear ranges are 1.0×10^?4-8.0×10^?2 mg/ml, 2.0×10^?4-3.0×10^?2 mg/ml and 3.0×10^?4-2.0×10^?2mg/ml for cepharadine, cefalexin and 6-APA, respectively. Their detection limits (S/N=3) are 3.0×10^?5mg/ml, 4.0×10^?5mg/ml and 6.0×10^?5mg/ml.     

Electrocatalytic determination of hydroquinone with Mn+ modified gold-5-amino-2-mercaptobenzimidazole self-assembled monolayer electrodes

Application of immobilized metal cations on the topside of gold-5-amino-2-mercaptobenzimidazole self-assembled monolayer (Au-5A2MBI-Mⁿ⁺ SAM, Mⁿ⁺:Cu²⁺ or Ag⁺) for electrocatalytic determination of hydroquinone (H₂Q) is described by voltammetric method. Several parameters were investigated to evaluate the performance of the sensors. Calibration curves for H₂Q concentrations were linear from 1.0 × 10^-5 to 4.0 × 10^-4 M (r = 0.998) for Au-5A2MBI, from 1.0 × 10^-5 to 6.0 × 10^-4 M (r = 0.998) for Au-5A2MBI-Cu²⁺, and from 2.0 × 10^-6 to 2.0 × 10^-5 M (r = 0.996) and 1.0 × 10^-4 to 1.0 × 10^-3 M (r = 0.991) for Au-5A2MBI-Ag⁺ SAM modified electrode. The respective detection limits were found as 6.5 × 10^-6, 4.6 × 10^-6 and 1.8 × 10^-7 M. Both Cu²⁺ and Ag⁺ ions were found to have a good electrocatalytic effect on the oxidation of H₂Q; however, Ag⁺ was a more effective catalyst and showed better sensitivity and lower detection limit than all other tested electrodes. Au-5A2MBI-Ag⁺ SAM electrode was used as a suitable sensor for determination of H₂Q in a radiolysis developing agent as real sample. The results obtained by using proposed sensor and that obtained by an ASTM reference method were in good agreement at the 95% confidence level.     

Extraction of PCDD/PCDF from soil with supercritical CO2: Optimization by a three-level factorial design approach

A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements (Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe) in water samples. Firstly, differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) is used for the direct simultaneous determination of Cd, Pb, Cu, Sb and Bi in 0.1 M HCl solution (pH = 1) containing 2 M NaCl. Then, differential pulse cathodic stripping voltammetry (DPCSV) is used for the determination of Se in the same solution. Zn is subsequently determined by DPASV after raising the pH of the same solution to pH 4. Next, the pH of the medium is raised to pH 8.5 by adding NH₃/NH₄Cl buffer solution for the determination of Mn by DPASV. Ni and Co are determined in the same solution by differential pulse adsorptive stripping voltammetry (DPAdSV) after adding DMG (1 × 10^–4 M). Finally, 1 × 10^–5 M 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is added to the solution for the determination of Fe by DPAdSV. The optimal conditions are described. Relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels. The lower detection limits for the investigated elements range from 1.11 × 10^–10 to 1.05 × 10^–9 M, depending on the element determined. The proposed analysis scheme was applied for the determination of these eleven elements in some ground water samples.     

Fluorometric Determination of Traces Of Mg(II) Using 1, 5-Dihydroxyanthracuinone as Reagent

Abstract

The florescent characteristics of the complex formed by 1, 5-dihydroxyanthraquinone with Mg(II) in aqueous ethanol (λ_ex 490 nm,λ_em=600 nm; pH_ap=9.1-9.6; 10% H₂O; reagent concentration=4×10^?5M) are described. The stoichiometry and the stability constant (1:1 and log K=4.90) are determined. A new fluorometric method for the determination of 10-100 ppb Mg(II) is proposed.     

Triphenyltetrazolium chloride as a new analytical reagent for molybdenum(VI): Application to plant analysis

Solvent extraction of molybdenum(VI) ion associate with triphenyltetrazolium chloride (TTC) has been studied. TTC was proposed as reagent for the spectrophotometric determination of micro amounts of molybdenum(VI) at λ_max 250 nm. The optimum conditions for extraction of molybdenum(VI) as an ionassociation complex with TTC has been determined. Beer’s law is obeyed in the range of 0.5–10 μg/mL molybdenum(VI). The molar absorptivity of the ion-pair is 1 × 10⁶ L/mol cm. The sensitivity of the method is 9.6 × 10⁻⁵ μg/cm². The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase are: distribution constant K _D = 32.64, extraction constant K _ex = 2.19 × 10¹⁰ association constant β = 6.71 × 10⁸. The interferences of different cations, anions on molybdenum(VI) determination were also investigated. A sensitive and selective method for the determination of microquantities of molybdenum(VI) has been developed. The determination was carried out without preliminary separation of molybdenum. A novel procedure of molybdenum(VI) extraction and spectrophotometric determination in different plant samples was examined.     

Extraction and spectrophotometric determination of trace amounts of tin(II) with diphenylglyoxal bis(2-hydroxybenzoylhydrazone)

Diphenylglyoxal bis(2-hydroxybenzoylhydrazone) has been used as a sensitive reagent for the spectrophotometric determination of tin. This reagent forms an orange-yellow complex with stannous ion at pH 3.5–7.0 (λ_max = 455 nm, ? = 2.25 × 10⁴ liter mol^?1/cm^?1 while no reaction is observed with quadrivalent tin. The colored complex extracted into isobutyl methyl ketone has been used for the spectrophotometric determination of trace amounts of tin(II). The molar absorption in the organic solvent is 3.54 × 10⁴ liter mol^?1 cm^?1 and the compound shows its maximum absorbance at 455 nm. The interferences of foreign ions have been determined.     

Spectrofluorimetric Determination of Reduced Glutathione Using Organic Nanoparticle Probes

Introduction Reduced glutathione (GSH) is a very important tripeptide.1 GSH widely exists in living tissues. In ani-mal organization, the concentration of free glutathione is in the range 0.5—10.0 mmol/L. Usually over 99% of glutathione is present in the reduced form in all organ-isms.2 Intermediates of GSH biosynthesis such as cys-teine, g-glutamyl-cysteine (g-Glu-Cys) or cysteinyl-gly- cine (Cys-Gly) also occur in the cell but at much lower concentrations.3 GSH plays an important bio…     

Analytical applications of 3-(2′-thiazolylazo)-2,6-diaminopyridine: Spectrophotometric determination of palladium

3-(2′-Thiazolylazo)-2,6-diaminopyridine reacts with palladium(II) in strongly perchloric acid media, to produce a blue 1:1 complex (λ_max = 665 nm, ? = 1.37 × 10⁴ liters · mol^?1 · cm^?1), which allows the spectrophotometric determination of 0.6 to 4.5 ppm of palladium. The method is applied to the determination of palladium in small samples of hydrogenation catalysts.     

Differential kinetic thermal lens determination of aniline and 4-nitroaniline

Thermal lens spectrometry was used for the differential kinetic determination of aniline (over the concentration range of 8 × 10⁻⁴–3.2 × 10⁻³ M) and 4-nitroaniline (2 × 10⁻⁴–1.6 × 10⁻³ M) present in combination in a single sample based on the oxidation reaction with periodate ions in an acidic medium (this determination is not possible with the spectrophotometric monitoring of the rate of reaction). The thermal lens procedure (λ_e = 488.0 nm; 80 mW) was characterized by good performance characteristics in the determination of aniline (c _min = 3 × 10⁻⁴ M; c _d = 8 × 10⁻⁴ M) and 4-nitroaniline (c _min = 7 × 10⁻⁵ M; c _d = 2 × 10⁻⁴ M), simplicity, and rapidity.     

Extraction and spectrophotometric determination of zinc in coal fly ash and pond sediments with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of zinc with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid. The reagent forms a stable, blue 1:2 zinc/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the zinc(II) complex is 1.26 × 10⁵ l mol^?1 cm^?1 at 610 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper and nickel can be masked with dimethylglyoxime and aluminium and iron with a mixture of sodium fluoride and triethanolamine. The method is applied to the determination of zinc in coal fly ash and pond sediments with good precision and accuracy.