Molar Ratio Method Research Articles

Complexation of ethyl 2-aryl(alkyl)sulfonylamino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylates with nonferrous metal ions

Complexation of sulfonyl derivatives of the Gewald thiophenes (SGT) with Cu(II), Co(II), Ni(II), Zn(II), and Cd(II) ions in ammonia solutions was studied. The molar ratio method, the Job’s method of continuous variation, and coductometric titration revealed ratios [M(II)]: [SGT] = 1: 2. The composition of preparatively isolated complexes was confirmed by IR spectroscopy and elemental analysis data. Solubility product constants for precipitates of the complexes and complexation equilibrium constants were calculated. Solubility product constants for M(II) complexes was shown to be dependent on the nature of sulfonyl substituent in SGT series.

A critical evaluation of proxy methods used to estimate the acidity of atmospheric particles

Abstract. Given significant challenges with available measurements of aerosol acidity, proxy methods are frequently used to estimate the acidity of atmospheric particles. In this study, four of the most common aerosol acidity proxies are evaluated and compared: (1) the ion balance method, (2) the molar ratio method, (3) thermodynamic equilibrium models, and (4) the phase partitioning of ammonia. All methods are evaluated against predictions of thermodynamic models and against direct observations of aerosol–gas equilibrium partitioning acquired in Mexico City during the Megacity Initiative: Local and Global Research Objectives (MILAGRO) study. The ion balance and molar ratio methods assume that any deficit in inorganic cations relative to anions is due to the presence of H+ and that a higher H+ loading and lower cation / anion ratio both correspond to increasingly acidic particles (i.e., lower pH). Based on the MILAGRO measurements, no correlation is observed between H+ levels inferred with the ion balance and aerosol pH predicted by the thermodynamic models and NH3–NH4+ partitioning. Similarly, no relationship is observed between the cation / anion molar ratio and predicted aerosol pH. Using only measured aerosol chemical composition as inputs without any constraint for the gas phase, the E-AIM (Extended Aerosol Inorganics Model) and ISORROPIA-II thermodynamic equilibrium models tend to predict aerosol pH levels that are inconsistent with the observed NH3–NH4+ partitioning. The modeled pH values from both E-AIM and ISORROPIA-II run with gas + aerosol inputs agreed well with the aerosol pH predicted by the phase partitioning of ammonia. It appears that (1) thermodynamic models constrained by gas + aerosol measurements and (2) the phase partitioning of ammonia provide the best available predictions of aerosol pH. Furthermore, neither the ion balance nor the molar ratio can be used as surrogates for aerosol pH, and previously published studies with conclusions based on such acidity proxies may need to be reevaluated. Given the significance of acidity for chemical processes in the atmosphere, the implications of this study are important and far reaching.

SPECTROPHOTOMETRIC DETERMINATION OF ATORVASTATINE CALCIUM

Atorvastatin Calcium reduces the level of cholesterol and lipoproteins in blood plasma, inhibits cholesterol synthesis in liver, increasing the number of low-density lipoproteins. It also reduces cholesterol in patients with homozygous familial hypercholesterolemia, which is usually resistant to lipid-lowering therapy. In today's world physical and chemical methods of analysis,including absorption spectrophotometry in the visible spectrum, which is characterized by ease of performance, availability, accuracy and selectivity,playsleadership role in quality assurance of medicines,The aim of research was the development of highly sensitive, simple and valid spectrophotometric methods of atorvastatin calcium tablets determination based on reaction with bromocresol purple (BCP). To achieve this goal the following objectives have been set:determine the optimal conditions for the photometric response of atorvastatin calcium BCP and calculate analytical performance sensitivity reactions;install coefficients stoichiometric ratio "atorvastatin- BCP";develop techniques for the quantitative determination of atorvastatin calcium tablets;conduct the validation of the developed techniques.When choosing solvent solubility of atorvastatin calcium and BCP, and maximum optical density obtained solutionwere taken into account. Experimentally, it was found that atorvastatin calcium interacts with BCP in acetone medium to form a colored product with a maximum at 399 nm in absorbance. The value of molar absorbance coefficient is 3.8*103, which indicates high sensitivity of reactions.To check the accuracy of the proposed methods,they were validated by key characteristics, namely, linearity, precision, accuracy and robustness.The results processed by least squares methods show linearity over the entire range of its application.Precision was determined at the level of convergence.Accuracy was established by additives method.Evaluation of robustness was conducted by identifying factors that affect the value of the optical density - namely, the number of added reagents.Conclusions:1. It has been established that atorvastatin calcium interacts with BCP at room temperature in acetone medium. The investigated reaction is high: the molar absorption coefficient is3.8*103.2. It has been found that atorvastatin calcium and BCP react in the ratio 1: 1, by the molar ratiomethod and by the continuous changes.3 The method of spectrophotometric assay of atorvastatin calcium tablets from different manufacturers has been developed.4 The developed method has been proved in the following validation characteristics as linearity, precision, accuracy and robustness.

Complexes of Pd(II) and Zn(II) chlorides with anthracene-containing α-amino oxime derived from the naturally occurring monoterpenoid (+)-3-carene

The complex Pd(HL)Cl2 (I) was obtained (HL is the anthracene-containing chiral α-amino oxime derived from the natural monoterpenoid (+)-3-carene). Single crystals of its solvate [Pd(HL)Cl2] · 0.33EtOH (II) were grown. According to X-ray diffraction data (CIF file CCDC no. 1008947), the crystals are built from mononuclear molecules of complex I and uncoordinated EtOH molecules. The coordination environment of the Pd atom in complex I (PdCl2N2) makes up a distorted square (trapezoid). The compound HL acts as a chelating bidentate ligand. The [Pd(HL)Cl2] and EtOH molecules are united into chains through weak hydrogen bonds. The photoluminescence (PL) of HL and the system ZnCl2-HL in acetonitrile was studied. The emission spectra show three bands at 394, 415, and 440 nm. The photoluminescence of the system ZnCl2-HL in solution is more intense than that of HL. A study of the system ZnCl2-HL by the molar ratio method in conjunction with emission spectroscopy suggests the formation of the complex Zn(HL)Cl2 in acetonitrile.

Rapid, synergistic extractive spectrophotometric determination of copper(II) by using sensitive chromogenic reagent N″,N″′-bis[(E)-(4-fluorophenyl) methylidene]thiocarbonohydrazide

A rapid and simple spectrophotometric method was developed for the determination of copper(II) by using newly synthesized chromogenic reagent, N″,N″′-bis[(E)-(4-fluorophenyl)methylidene]thiocarbonohydrazide [bis(4-fluoroPM)TCH]. The reagent is highly sensitive and it forms yellow colored ternary complex with copper(II) in presence pyridine having composition 1:1:2 (M:L:Py) in the acidic pH range. Absorption of colored complex in amyl acetate is measured with reagent as a blank at λmax 375nm. The synergistic effect is observed due to pyridine forming adduct with reagent in the organic phase. Beer’s law was obeyed in the concentration range from 2.0 to 14μgmL−1 for copper(II)–[bis(4-fluoroPM)TCH]–Py complex. Molar absorptivity and Sandell’s sensitivity values for Cu(II)–bis(4-fluoroPM)TCH]–Py complex are 0.42545×105 and 0.0014μg/cm2, respectively. The selectivity of the developed method was checked in the presence of various foreign ions. The developed method showed relative standard deviation (R.S.D.) of 0.13% for n=10. The composition of Cu(II)–[bis(4-fluoroPM)TCH]–Py complex was determined by known methods such as Job’s method of continuous variation, mole ratio method and slope ratio method. It is found that the ternary complex is stable for more than 24h. Various factors influencing on the degree of complexation, such as, effect of pH, reagent concentration, synergent concentration, solvent etc. were studied. The accuracy and reliability of method was verified by AAS. This method is found to be simple, rapid and reproducible.

Investigation of Iron Complex Formation of Anti-Hypertensive Drug: Methyldopa

The drug administered for any disease may play an unwanted function in biological system. They may have multiple counter effects, one of which is their interaction to bioactive metals. Iron is most common bio essential metal and is reported to interact with antihypertensive drug methyldopa. In the present study, above said complex is analyzed by UV-Visible spectrophotometry. Formation constant of the complex is calculated by using mole ratio method and single point statistical method which is in the range of 1010, values are also calculated which are independent of pH like formation constant. Absorbance maxima were found to be dependent on pH. At lower pH complex shows two broad bands centered at 430 nm and 730 nm. With the rise in pH later peak shifts toward lower wavelength, so 615 nm is selected for further studies. Molar extinction coefficient of the complex is explored by serial dilution method. At all wavelengths it increases with increase in pH. Mole ratio and slope ratio methods are used for exploring stoichiometry. Metal to ligand combining ratio in the complex is 1:2 at pH 4.0 and pH 4.5 while 1:3 at pH 5.0 and pH 5.5.

Solvent Extraction and Spectrophotometric Determination of Ce (IV) by Using 2-Hydroxy-3-Methoxy Benzaldehyde Oxime as an Analytical Reagent

2-Hydroxy-3-methoxy benzaldehyde oxime (2H3MBO) as a photometric reagent for the extractive spectrophotometric determination of cerium (IV) (Ce(IV)) is presented in this paper. The reagent 2H3MBO gave instantaneous and light pink colour with Ce(IV) in the pH range of 3.2–4.4. The system obeys Beer's law in the concentration range of 1.0–50.0 μg/mL at 440 nm. The limit of detection (LOD) is calculated by using standard deviations of a blank solution at confidence limit 95.0%, which is found to be 0.336μg/mL. The stoichiometry of the complex is established as 2:1 (M:L) by Job's method of continuous variation and confirmed by a mole ratio method. The standard deviation and the coefficient of variance are presented. The results of the prescribed procedure applied for the determination of the micro amounts of Ce(IV) in various synthetic samples.

New Analytical Technique for Determination of Trace Amount of Co (II) by Using a UV-Visible Spectrophotometric Method with Photometric Reagent

The compound 3-nitrosalicylaldehyde thiosemicarbazone (3-NSTS) is proposed as a new photometric reagent for the extractive spectrophotometric determination of Co (II). It reacts with Co (II) and form a stable colored complex in the pH range 5.5 to 6.5. This was well extracted in n-butanol. The absorption spectrum of Co (II): (3-NSTS) complex in n-butanol shows maximum absorbance at 460 nm. The system obeyed Beer's law up to 2–6 μg cm−3. The molar extinction coefficient was found to be 8.846 × 103 L mol−1cm−1 and the sensitivity of the method as defined by Sandell's sensitivity was 6.688 × 10−3 μg cm−2. The Composition of the extracted species was determined by Job's continuous variation method, mole ratio method and slope ratio method and it was found to be 1:2. The proposed reagent is satisfactorily applied for the determination of trace amount of Co (II) from synthetic and commercial samples.

Extraction and Spectrophotometric Determination of Mn(II) with N, N’’-bis (Ohydroxy-acetophenone) Ethylene Diimine Derivative as an Analytical Reagent

The spectrophotometric method is coupled with solvent extraction technique and used for the determination of Mn(II) using N, N’’-bis (O-hydroxy-acetophenone) ethylene diimine (HAPED) as an analytical reagent. This reagent is synthesised in the laboratory and characterised by NMR, IR, mass and elemental analysis for its purity. The reagent forms a light yellow -colored stable complex with manganese metal, which can be quantitatively extracted into chloroform at pH 5.2. This Mn (II)-HAPED complex in chloroform exhibit intense absorption peak at 370nm. Beer's law is obeyed in the range of 1–10 ppm of manganese solution giving linear and reproducible graph. The stoichiometric ratio of complex studied by Job's continuous variation method, mole ratio and slope ratio method. The molar absorptivity and Sandell's sensitivity are also calculated. The molar absorptivity is 1,730.77 L/mol/cm and Sandell sensitivity is 0.0318 μg/cm2. The proposed method is rapid, sensitive, reproducible, accurate and has been satisfactory applied for determination and separation of Mn(II) in commercial mixtures, pharmaceutical samples and alloys.

Spectro-Potentiality and Thermodynamic Studies on Schiff Base Hydrazone Derivatives Complexes with Some Transition Elements

A new hydration Schiff base consisting of 7-chloro-4-(o-hydroxy benzilidenehydrazo) quinoline, with metal complexes of some divalent metal ions, Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) complexes were studies. Spectrophotometrically obeyed Beer's law up to certain values, 6.6×103, 8.0×103dm3mol-1cm-1, respectively, indicating that the ligand HL could be used to detect Co(II) and Ni(II) in such concentrations, the study was performed also for Fe (III)-complexes. Conductance and thermodynamically used molar ratio method to determine the stoichiometry of the complexes obtained confirmed the formation of 1:1 and 1:2, M:L complexes. The standard thermodynamic parameters viz. ΔG, ΔH and ΔS, for the proton-legend and the stepwise metal-ligand complexes eluated were analyzed in terms of the electrostatic (eel) and non-electrostatic (crates, c) components. ΔHc was found to be linearly correlated with the acceptor number of the metal ion (ANM), and ΔH el was linearly correlated with the ionic radii of the metal ion. The calculated values for ΔG°, ΔH° and ΔS° concluded that the complexion process processed spontaneously.

Synthesis, Characterization and Stability Study of V(IV), Zr(IV), Rh(III), Pd(II), Cd(II) and Hg(II) Complexes with Pyrazol Derivative

In this work lactone (1) was prepared from the reaction of p-nitro phenyl hydrazine with ethylacetoacetate, which upon treatment with benzoyl chloride afforded the lactame (2). The reaction of (2) with 2-amino phenol produced a new Schiff base (L) in good yield. Complexes of V(IV), Zr(IV), Rh(III), Pd(II), Cd(II) and Hg(II) with the new Schiff base (L) have been prepared. The compounds (1, 2) were characterized by FT-IR and UV spectroscopy, as well as characterizing ligand (L) by the same techniques with elemental analysis (C.H.N) and (1H-NMR). The prepared complexes were identified and their structural geometries were suggested by using elemental analysis (C.H.N), flame atomic absorption technique, FT-IR and UV-Vis spectroscopy, in addition to magnetic susceptibility and conductivity measurements. Metal to ligand [M:L] ratio was obtained for all complexes in ethanol using molar ratio method, which gave comparable results with those obtained for the solid complexes. As well as the apparent stability constant of the complexes have been studied with the time and their color were stable for more than 4 hrs., furthermore the molar absorptivity have been calculated.

Synthesis, Characterization and Stability Study of V(IV), Zr(IV), Rh(III), Pd(II), Cd(II) and Hg(II) Complexes with Pyrazol Derivative

In this work lactone (1) was prepared from the reaction of p-nitro phenyl hydrazine with ethylacetoacetate, which upon treatment with benzoyl chloride afforded the lactame (2). The reaction of (2) with 2-amino phenol produced a new Schiff base (L) in good yield. Complexes of V(IV), Zr(IV), Rh(III), Pd(II), Cd(II) and Hg(II) with the new Schiff base (L) have been prepared. The compounds (1, 2) were characterized by FT-IR and UV spectroscopy, as well as characterizing ligand (L) by the same techniques with elemental analysis (C.H.N) and (1H-NMR). The prepared complexes were identified and their structural geometries were suggested by using elemental analysis (C.H.N), flame atomic absorption technique, FT-IR and UV-Vis spectroscopy, in addition to magnetic susceptibility and conductivity measurements. Metal to ligand [M:L] ratio was obtained for all complexes in ethanol using molar ratio method, which gave comparable results with those obtained for the solid complexes. As well as the apparent stability constant of the complexes have been studied with the time and their color were stable for more than 4 hrs., furthermore the molar absorptivity have been calculated.

Tailoring, physicochemical characterization, antibacterial and DNA binding mode studies of Cu(II) Schiff bases amino acid bioactive agents incorporating 5-bromo-2-hydroxybenzaldehyde

Five novel Cu(II) complexes derived from the condensation between 5-bromosalicylaldehyde (bs) and α-amino acids (L-alanine, l-phenylalanine, L-aspartic acid, L-histidine and L-arginine) were synthesized and characterized by their elemental analyses, thermogravimetric analysis, IR, mass and electronic spectra, conductance and magnetic measurements. Moreover, the stoichiometry and the stability constants of the prepared complexes have been determined spectrophotometrically using continuous variation and molar ratio methods. The obtained results indicated that the Schiff bases of the amino acids: L-alanine, L-phenylalanine, L-histidine and L-arginine behave as tridentate ligands. The ligands are coordinating with the Cu(II) via azomethine nitrogen, deprotonated carboxylate oxygen and phenolic oxygen. However, in the case of L-aspartic, the ligand acts as tetradentate due to the coordination of the second carboxylate group. Based on the studies of magnetic moments and electronic spectra, a square planar geometry has been proposed for all Cu(II) complexes except bromsalicylaldehydine aspartate complex which has a distorted tetrahedral structure. The representative Schiff bases and their Cu(II) complexes were tested in vitro for their antibacterial activity against two Gram-positive bacteria (Micrococcus luteus and Bacillus cereus) and one Gram-negative bacteria (Pseudomonas aeruginosa). All the complexes showed activity against the organisms more than the free Schiff base ligands and the activity increases with the increase in concentration of test solution containing the new complexes. Moreover, the interaction of the prepared Schiff base amino acid Cu(II) complexes with calf thymus DNA has been investigated by absorption spectra, viscosity and gel electrophoresis measurement and the mode of CT-DNA binding to the complexes has been explored. The investigated complexes exhibit cooperative binding and presumably intercalate into DNA and follow the trend: bsarc>bshc>bsalc>bsphalc>bsasc.

The interaction of Alizarin Red with Tryptophan by Voltammetry

The interaction of Alizarin Red (AR) with Tryptophan (Trp) was investigated by first order derivative linear sweep voltammetry. In pH5.2 NaAc-HAc buffer solution, AR had a well-defined voltammetric reductive peak at -0.392V(vs.SCE).After Trp addition, the peak current of AR decreased apparently with no change of the peak potential and no appearance of new peaks. The study about the effect of scan rate on peak current showed that a new electro-inactive complex was formed as a result of interaction of AR with Trp, which decreased the peak current. Based on the formation of AR-Trp complex, the conditions of interaction and the electrochemical detection were carefully investigated and the binding ratio was obtained by mole ratio method. Finally the character of the electrode process was discussed by the effect of scan rates on AR-Trp interaction system.

Synthesis, Spectral Study and Theoretical Treatment of Some Transition Metal Complexes of 5-(4-Nitro Phenyl)-4-Amino-3-Mercapto Propenyl-1,2,4-Triazole Ligand

In the present work, we synthesized a series of metal complexes of Co(II), Ni(II), Cu(II), Zn(II) and Au(III) from newly synthesized ligand 5-(4-Nitro Phenyl)-4-Amino-3-Mercapto Propenyl-1,2,4-Triazole (L) in alcoholic medium. These compounds were characterized by several techniques using FT-IR, UV-Visible spectrophotometer, thermal gravimetric TG analyses, magnetic susceptibility, Flame Atomic Absorption technique, elemental analysis and conductivity measurements. From the spectral studies, an octahedral monomer structure was proposed for all complexes except Cu(II) complex has dinuclear structure. The nature of the complexes formed in ethanolic solution has been studied following the molar ratio method and the result recorded 1:1 molar ratio for all complexes. Semi-empirical methods (ZINDO/1, ZINDO/S and PM3) were carried out to evaluate the heat of formation ∆H˚f, binding energy ∆Eb, and dipole moment for all complexes expect Au(III) complex that used AMBER method, also the vibration frequencies and electronic transitions were calculated for prepared ligand to make comparison with experimental results. Electrostatic potential, HOMO and LUMO energies for ligand were calculated to determine the reactive sites of new ligand.

SYNTHESIS AND SPECTRAL STUDIES OF METAL COMPLEXES WITH 3,4,6,7-O,O,O,O-TETRAKIS-(CARBOXY(CHLORO)METHYL)-L-ASCORBIC ACID (H4L)

The reaction of L-ascorbic acid with the dichloroacetic acid in the presence of potassium hydroxide gave new product 3,4,6,7-O,O,O,O-tetrakis(carboxy(chloro)methyl)-L-ascorbic acid (H 4 L), which was isolated and characterized by 1 H, 13 C-NMR, elemental analysis (CHN), thermogravimetric analysis (TGA), UV-visible and Fourier Transform infrared (FTIR) methods. The complexes of the ligand (H 4 L) with metal ions, M +2 = (Cu, Co, Ni, Cd and Hg) were synthesized and characterized by FTIR, UV-Visible, molar conductance, atomic absorption, magnetic susceptibility, thermogravimetric analysis (TGA) and molar ratio methods. The analysis showed the evidence of binding of the metal ions with (H 4 L) through the bidendate carboxylato group manner resulting in six-coordinated metal ion. The TLC for (H 4 L) and complexes showed one spot for each indicating the purity of these compounds.

Novel flow injection analysis methods for the determination of total iron in blood serum and water

This work describes rapid, sensitive and highly precise methods for the determination of total iron in blood serum and water samples, using batch, nFIA and rFIA techniques. The proposed methods are based on the selective oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) by iron(III). The absorbance of the resultant green solution of radical cation (ABTS·+) was monitored spectrophotometrically at λmax=415nm. The reaction is stoichiometric with a ratio of 1:1 (Fe(III):ABTS) as determined by Job׳s and molar ratio methods. The proposed methods allow for the determination of Fe(III) in the ranges 0–4.5mgL−1 (LOD 25.5µgL−1, %RSD 0.97%, n=7); 0 to 4.5mgL−1 (LOD 370µgL−1, %RSD 1.28%, n=7) and 0 to 2.7mgL−1 (81.6µgL−1, %RSD 0.76%, n=6) for batch, nFIA and rFIA techniques, respectively. The proposed methods show high selectivity to Fe(III), as indicated by the high tolerance limits for common interfering ions. The nFIA method was applied in total iron assay in camel blood serum, whereas batch and rFIA methods were successful in the determination of total iron in municipal pipeline water and spiked groundwater. Statistical analysis indicated insignificant differences in accuracy and precision between the results obtained by the developed methods and ICP-AES or phenanthroline methods.

New metal complexes of N3 tridentate ligand: Synthesis, spectral studies and biological activity

New tridentate ligand 3-amino-4-{1,5-dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethylimino]-2phenyl-2,3-dihydro-1H-pyrazol-4-ylazo}-phenol L was synthesized from the reaction of 1,5-dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethylimino]-2-phenyl-2,3-dihydro-1H-pyrazol-4-ylamine and 3.4-amino phenol. A complexes of these ligand [Ni(II)(L)(H2O)2 Cl]Cl, [pt(IV)(L)Cl3]Cl and [M(II)(L)Cl]Cl (M=Pd (II), Zn (II), Cd (II) and Hg (II) were synthesized. The complexes were characterized by spectroscopic methods and magnetic moment measurements, elemental analysis, metal content, Chloride containing and conductance. These studies revealed octahedral geometries for the Ni (II), pt (IV) complexes, square planar for Pd (II) complex and tetrahedral for the Zn (II), Cd(II) and Hg (II) complexes. The study of complexes formation via molar ratio and job method in DMF solution has been investigated and results were consistent to those found in the solid complexes with a ratio of (M:L) as (1:1). The thermodynamic parameters, such as ΔE*, ΔH*, ΔS* ΔG* and K are calculated from the TGA curve using Coats–Redfern method. Hyper Chem-8 program has been used to predict structural geometries of compounds in gas phase. The synthesized ligand and its metal complexes were screened for their biological activity against bacterial species, two Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonasaeruginosa).

SYNTHESES AND CHARACTERIZATION OF COPPER (II) AND PALLADIUM (II) COMPLEXES WITH 2-(ARYLMETHYLENEACETYL)BENZIMIDAZOLE

Metal complexes formed through the reaction of 2-(Arylmethyleneacetyl) benzimidazole (L1-L4) with copper (II) and palladium (II) ions were prepared and characterized by elemental analysis, conductance measurements, infrared spectra, electronic absorption spectra, X-ray diffraction and thermal analyses. The 2-(Arylmethyleneacetyl)benzimidazole (L1-L4) coordinate as neutral bidentate ligands. The final product in all the cases of TG thermogram of the complexes was found to be metal oxides. Complexes of copper (II) and palladium (II) with 2-(Arylmethyleneacetyl)benzimidazole in solution were studied by spectrophotometric methods and the formation constants and stioichiometries of the complexes were calculated to be 1:2 (M : L) as calculated by continuous variations and the mole ratio methods. The stability sequence is in agreement with the Irving-Williams rule

Spectrofluorometric Method for Determination of Al3+ with 3-Hydroxy-2-Naphthalenecarboxylic Acid and its Application to Milk Samples

On the basis of affinity of Al3+ ions toward functional groups of 3-hydroxy-2-naphthalenecarboxylic acid (3H2NA), a high stable complex between Al3+ and 3H2NA in 5 % methanol/water solution was established. The mole ratio method showed that a stable complex by taking part of acetate and 3H2NA with the stoichiometric ratio of 1:1:1 and stability constant of 8.6 × 106 is formed. Under the optimum conditions for the complex formation, a rapid spectrofluorometric determination of trace amounts of Al3+ (λ ex = 366 nm, λ em = 460 nm) was proposed. The optimum conditions involve 3H2NA concentration of 1.0 × 10−5 M, buffering pH of 4.5 (acetic/acetate system), and ionic strength of 0.01 M. The fluorescence intensity exhibited a good linearity against the Al3+ concentration in the range 5.0 × 10−8–5.0 × 10−6 M with the detection limit of 1.3 × 10−8 M. No considerable interference was observed due to the presence of coexisting anions and cations. The method was applied successfully to the determination of trace amounts of Al3+ in milk. Validation of the measurements was confirmed using graphite furnace atomic absorption spectrophotometry.