2,3-Diphenylquinolizinium bromide as a fluorescent derivatization reagent for amines

2,3-Diphenylquinolizinium bromide (2,3-DPQ) is proposed as a fluorogenic reagent for amino compounds. A spectrofluorimetric method based on its use is described which allows the determination of μg ml^?1 to ng ml^?1 levels of primary and secondary amines, including aromatic and cyclic compounds. The precision of the method was 4–8% (relative standard deviation) (n=10). The influence of several external factors on the derivatization reaction was studied using piperidine as a model compound. The analytical reaction can be effected at room temperature, which avoids the degradation of labile sample amines, e.g., catecholamines, and simplifies the experimental procedure. The presence of an excess of a basic catalyst (triethylamine) was critical for the reaction to develop satisfactorily. Fluorescence due to the reaction product was detected 5 min after the start of the analytical reaction.     

Ultraviolet spectrophotometric determination of primary and secondary aliphatic amines by formation of dithiocarbamates

Primary and secondary aliphatic amines (ca. 0.2–6 μg ml^?1) determined at 250 and 280 nm, respectively, after in situ derivatization to dithiocarbamates in a carbon disulphide/ aqueous sodium hydroxide two-phase system. Alcohols, aromatic and tertiary amines do not interfere.     

Flow-injection spectrophotometric determination of arylamines and sulphonamides by diazotization and coupling in a micellar medium

In a sodium dodecyl sulphate (SDS) micellar solution, the rate of coupling of a diazonium ion with N-(1- naphthyl)ethylenediamine (NED) increases greatly, the protonation of the resulting azo dyes takes place at higher pH values and the dyes are more soluble. These favourable features were applied to the development of a simple flow-injection spectrophotometric procedure for the determination of diazotizable substances of pharmaceutical interest. Limits of detection in the range 0.2–0.5 μg ml^?1 (signal-to-noise ratio=3), with relative standard deviation of 0.7–3% (n=3) for 5 μg ml^?1 standards, were obtained.     

Determination of aniline in vegetable oils by diazotization and coupling in a microemulsion medium

A microemulsion containing sodium dodecyl sulphate and n-pentanol in a mass ratio of 1 : 4, water and a vegetable oil was investigated using pseudo-tenary phase diagrams. The medium can co-solve important amounts of vegetable oils and aqueous solutions over a wide range of ionic strengths. A procedure for the determination of 1.4–140 μg ml^?1 of aniline in vegetable oils using ionic diazotization and coupling reactions was developed. The absorbance was measured in an optically clear microemulsion containing 4% or 20% of oil. The procedure is much simpler and rapid than the official chromatographic methods and gives almost the same limits of detection (ca. 05 μg ml^?1) using no more than 1 ml of sample. The repeatability for 30 μg ml^?1 aniline was 2%. Acid-base titrations in the microemulsion medium permitted the evaluation of the protonation constant of the dye.     

Selective Kinetic Spectrophotometric Determination of Nitrite in Food and Water

Abstract

A highly selective and sensitive method for the kinetic spectrophothometric determination of sub-microgram amounts of nitrite has been development based on its reaction with Nile blue 2B in acidic medium. The reaction is monitored spectrophotometrically at 595 nm at a fixed time of 4.5 min. The change in absorbance at 595 nm is related to the concentration of nitrite in the range 0.005 - 1.100 μg.ml^?1 The detection limit is 0.001 μg.ml^?1. The relation standard deviation is 1% for 0.020 μg.ml^?1 of nitrite for ten replicate measurements. Most common anions and cations do not interfere. The procedure was applied to the determination of trace amounts of nitrite in sausage and water.     

Reverse-FIA with spectrophotometric detection method for determination of vitamin C

Simple reverse flow injection analysis (rFIA) manifold with spectrophotometric detection was developed for an indirect determination of ascorbic acid. Parameters such as stability, accuracy and precision were established for the method and evaluated statistically to assess the applications of the method. Ascorbic acid in this procedure accelerates dediazoniation reaction of formed diazonium ions; hence its quantity can be determined by monitoring the derivatization product from coupling unreacted diazonium ion with phenol to give an azo dye (coupling reaction). The rFIA design was based on the injection of sodium nitrite into an acidic p-aminoacetophenon carrier stream in which diazonium ion was formed. This ion was inhibited by ascorbic acid stream before coupling with the phenol-Na₂CO₃ stream. Under optimum conditions, ascorbic acid acts in accordance with the Beer??s law at two concentration ranges 0.4?C6.5 ??g ml^?1 (R = 0.9995) and 7.0?C20.0 ??g ml^?1 (R = 0.9949), with detection limits of 0.25 ??g ml^?1. The developed method was applied to the determination of vitamin C in pharmaceutical formulations which produced satisfactory results compared with the standard methods reported in the British Pharmacopoeia.     

Quantitative Study of the Interaction between ATP and Aromatic Amines in Aqueous Solution

The interaction between adenosine-5??-triphosphate (ATP) and some aromatic amines (L), namely 1,2-phenylenediamine, 2-(2,4-diaminophenoxy)ethanol, 4-N-(2-hydroxyethyl)2,4-diaminoanisole, 4,5-diamino-1-N-(2-hydroxyethyl)pyrazole and 1,3-bis(2,4-diaminophenoxy) propane, was studied at T=298.15 K and I=0.06 mol?L^?1 in NaCl aqueous solution. For all of the investigated systems, the formation of [(ATP)(L)H _i ]^(i?4) species (i=1 to n+2; n=maximum protonation degree of the amine) with high yields (60?C80?%) were found. The ionic strength and temperature dependences of the complex formation constants were studied using semiempirical equations. The sequestering ability of the aromatic amines toward ATP was defined by calculating the pL₅₀ parameter (the total ligand concentration, as ?log₁₀ C _L, able to bind 50?% of ATP). The dependence of pL₅₀ on pH, ionic strength and temperature is reported. Moreover, it was found that the overall formation constants are reasonably linearly dependent on the number of protons in the complex species. Comparison with the stability of the species of analogous systems, such as ATP?Caliphatic amines and pyrophosphate?Caliphatic amines, is reported. For all these systems a fairly linear dependence was found of the formation constants on the basicity of the amines.     

Determination of nitrite by simple diazotization method

A simple and rapid spectrophotometric method for the determination of nitrite is described. This is based upon simple diazotization reactions involving p-nitroaniline (PNA) and sulfanilamide (SA) with ethyl acetoacetate (EAA) as the coupling agent. The absorbance was measured at 507 and 356 nm, respectively. The method is optimized for acidity, amount of reagents required, amount of sodium hydroxide and the tolerance amount of other ions. The range of linearity for PNA-EAA couple was 0.05-6.0 μg ml⁻¹ of nitrite with molar absorptivity of 1.59×10⁴ l mol⁻¹ cm⁻¹; while that for SA-EAA couple was found to be 0.2-3.0 μg ml⁻¹ and 1.22×10⁴ l mol⁻¹ cm⁻¹, respectively. The method has been applied to various water and soil samples.     

Spectrophotometric determination of osmium with phthalimide dithiosemicarbazone by means of complex formation and catalytic reactions

Phthalimide dithiosemicarbazone forms a 1:1 complex with osmium at pH 3.3–4.5 (?₄₅₀ = 1.3 · 10⁴ l mol^?1 cm^?1 ) which is applied to the photometric determination of osmium; Beer's law is obeyed for the range 1–12 μg Os ml^?1. The oxidation of the reagent with cerium(IV) is catalyzed by osmium(VIII), and this reaction allows a more sensitive procedure for the determination of osmium; the calibration curve is linear over the range 0.05–0.4 μg Os ml^?1. The interferences in both procedures are described.     

Gas-chromatographic determination of aliphatic amines in natural surface water and wastewater

A procedure was developed for the gas-chromatographic determination of aliphatic amines C₇–C₂₀ with prederivatization by N-methyl-bis(trifluoroacetamide), in the concentration range of natural surface water, to 10^?4-1 mg/L, and wastewater, to 10^?3-1 mg/L. The conditions were optimized for the extraction preconcentration of aliphatic amines with toluene from natural surface water and wastewater. The detection limit for aliphatic amines at a signal-to-noise ratio of 3: 1 was 50 ng/L.     

Spectrophotometric determination of nitrite in polluted waters using 3-nitroaniline

Nitrite reacts with 3-nitroaniline in the presence of hydrochloric acid to form a diazonium cation, which is subsequently coupled with N-(1-naphtyl)ethylenediammonium chloride to form a stable purple azo dye. The method is suitable for the determination of 0.01–0.80 μg ml^?1 nitrite. The reactions are very fast and require no control of temperature. The observed molar absorptivity and Sandell's sensitivity of the azo dye are 4.9 × 10⁴ l mol^?1 cm^?1 and 9.4 × 10^?4 μg cm^?2, respectively. The method is free from most interferences. The method has been applied successfully to polluted river water.     

A new analytical reaction for the determination of perrhenate

Perrhenate is quantitatively extracted into methyl isobutyl ketone from aqueous solutions containing copper(II), azide and an excess of 2,2'-bipyridine. Measurement of the extracted copper either by spectrophotometry or by atomic absorption spectrometry, allows the determination of perrhenate in the ranges 16–40 μg ml^?1 or 3–16 μg ml^?1 in the final dilution, respectively. The procedure is highly selective, being applicable in the presence of a large concentration of molybdate and a considerable number of foreign ions. The extracted species corresponds to the formula CuN₃(bipy)₂ ReO₄.     

Spectrofluorometric determination of zinc with 1,5-bis(2,3-dihydroxyphenylmethylene) thiocarbohydrazone

1,5-Bis(2,3-dihydroxyphenylmethylene)thiocarbohydrazone was synthesized; its ionization constants are reported. A procedure is described for the spectrofluorimetric determination of 5–540 ng ml^?1 zinc in 60/40 (v/v) ethanol/water medium, acetate-buffered to apparent pH 6.5 (λ_ex=400 nm, λ_em=508 nm). Interferences were evaluated and the procedure was applied with good results to the determination of zinc in potable waters (0.3–3 μg ml^?1) and lubricating oils.     

A convenient method for the synthesis of N-hydroxyureas

Treatment of amines with 1-(4-nitrophenol)-N-(O-benzylhydroxy)carbamate yields the O-benzyl protected N-hydroxyureas. Hydrogenation of the O-benzyl protected N-hydroxyureas over 5% Pd/BaSO₄ cleanly gives the N-hydroxyureas in good yield. In addition to primary and secondary aliphatic and aromatic amines, this method converts amino sugars to the corresponding N-hydroxyureas without extensive protecting group chemistry.     

Fluorescent Complexes of Nucleic Acids/8-Hydroxyquinoline/Lanthanum(III) and the Fluorometry of Nucleic Acids

Abstract

The ternary fluorescent complexes of nucleic acids/8-hydroxyquinoline/ lanthanum (III) were studied. Nucleic acids in the study involve natured and thermally denatured calf thymus DNA, fish sperm DNA and yeast RNA. In the range of pH 8.0–8.4 (controlled by NH₃-NH₄Cl buffer) ternary fluorescent complexes are formed which emit at 485.0 nm for calf thymus DNA and at 480.0 nm for yeast RNA (when excited at 267.0 nm) and emits at 483.0 nm for fish sperm DNA when excited at 265.0 nm. Based on the fluorescence reactions sensitive fluorometric methods for nucleic acids were proposed. Using optimal conditions, the calibration curves were linear in the range of 0.4–3.6 μg˙ml^?1 for calf thymus DNA, 0.4–4.0 μg-ml^?1 for fish sperm DNA and 0.4–4.0 μg˙ml^?1 for yeast RNA, respectively. The limits of determination (3σ) were 0.076 μg˙ml^?1 for calf thymus DNA, 0.068 μg˙ml^?1 for fish sperm DNA and 0.329 μg˙ml^?1 for yeast RNA, respectively. Five synthetic samples were determined with satisfaction.

     

Determination of mixtures of ampicillin and cloxacillin in pharmaceuticals by second-derivative spectrophotometry

Mixtures of ampicillin-Na and cloxacillin-Na are assayed by peak-to-baseline and zero-crossing second-derivative spectrophotometry. The procedure does not require any separation step. Calibration plots are linear (r = 0.9999) up to 30 μg ml^?1 of ampicillin-Na at 216 nm and up to 40 μg ml^?1 ampicillin-Na or cloxacillin-Na at 228 nm or 248.8 nm, respectively, in the presence of one another. Detection limits at the p = 0.05 level of significance, range from 0.15 pg ml^?1 to 0.33 μg ml^?1. The method was successfully applied to commercial injections and capsules containing these penicillins.     

Determination of vanadium and titanium in steel by inductively coupled plasma atomic emission spectrometry with modified use of a tungsten boat furnace atomizer for atomic absorption spectrometry

For electrothermal sample introduction, a commercially available tungsten boat atomizer for atomic absorption spectrometry (AAS) was transferred to a vaporizer for inductively coupled plasma atomic emission spectrometry (ICP-AES). The modification retained as much of the original design of the atomizer as possible, so that the apparatus could be switched easily between conventional tungsten boat furnace (TBF)-AAS and TBF-ICP-AES. By using this system, a procedure for the determination of vanadium and titanium in steel was investigated. The detection limits (S/N=3) of vanadium and titanium were 3.9 and 1.5 ng ml^?1, respectively. The relative standard deviations for five replicate determinations were ca. 3% for both elements. The calibration graphs were linear up to 100 μg ml^?1 vanadium(V) and 10 μg ml^?1 titanium(IV). Results of analyses of some low-alloy steel samples are given.     

Extraction-spectrophotometric determination of tungsten with thiocyanate and some amidines

The procedure is based on reduction of W(VI) to W(V) by tin(II) chloride in 6 M hydrochloric acid, and extraction of the resultant thiocyanate complexes with a benzene solution of amidine. The complex coagulates and is dissolved in the benzene by addition of 1-pentanol. The maximum molar absorptivities of the complexes with 8 amidines in benzene/1-pentanol (9:1, v/v) are in the range 12 100–18 400 mol^?1 cm^?1. The simplest compound, N,N-diphenylbenzamidine gives the best sensitivity; the linear range covers 5–90 μg W in 10 ml of final solution; the detection limit is 2 ng W ml^?1. The method is applied to alloy steels.     

Facile synthesis of 2-carboxanilido-3-arylquinazolin-4-ones from N1-(2-carboxyphenyl)-N2-(aryl)oxalamides

A simple and efficient approach for the synthesis of novel 2-carboxanilido-3-arylquinazolin-4-ones via the one-pot condensation of readily available N¹-(2-carboxyphenyl)-N²-(aryl)oxalamides with various aromatic amines is described. Notably, this methodology allows us to synthesize 3-aryl-quinazolin-4-ones using aromatic amines with various substituents, both electron-donating and electron-withdrawing, which ensures structural diversity of the products and an atomic-economic process.     

Studies on the configuration of nitrogenous stereogenic centres in adducts of rhodium(II) tetraacylates with chiral amines: the application of 1H and 13C NMR spectroscopy

The ¹H and ¹³C NMR spectra of enantiomerically pure amines (S)-N,N-dimethyl-1-phenylethylamine, (S)-N-methyl-1-phenylethylamine, (S)-N-ethyl-1-phenylethylamine and (S)-N-ethyl-N-methyl-1-phenylethylamine in the presence of a twofold molar excess of dirhodium(II) tetratrifluoroacetate and dirhodium(II) Mosher’s acid derivatives [(4S) and (4R)] were measured in CDCl₃ as a solvent. The amines having various substituents at the nitrogen atom (H, CH₃ and CH₂CH₃) formed in such conditions as an equilibrium mixture of C_SN_R and C_SN_S 1:1 adducts. The signals of both diastereoisomers were observed in NMR spectra at either room temperature (303 K) or moderately decreased temperatures (263–273 K). The rates of mutual diastereoisomer conversion were estimated by selective inversion recovery experiments and varied from less than 0.1 to ca. 10 s^?1, depending on the ligand and temperature. Analysis of ¹³C NMR data and NOE experimental data resulted in the unambiguous determination of the configuration at the nitrogen atom with respect to the carbon stereogenic centre.Modelling of adduct structures and calculations of molecular energy and NMR parameters (GIAO) using Density Functional Theory (DFT) were performed in order to support the experimental findings. The calculations were carried out using 3-21G//B3LYP (structure optimizing) and 311G(2d,p)/LanL2DZ//B3LYP theory levels (molecular energy and NMR shielding).