Molar Absorptivity Values Research Articles

Chlorite Ion Interference in the Spectrophotometric Measurement of Chlorine Dioxide

The presence of the Cl2O4− complex, which forms in chlorine dioxide (ClO2) solutions in the presence of chlorite ion, can result in significant error in the spectrophotometric measurement of ClO2. In this article, the significance of the Cl2O4− complex is demonstrated and the formation constant (Keq) and the molar absorptivity of this complex are reported. Based on the Keq and the molar absorptivity values, two methods are proposed to correct for the presence of the complex. By using the equation suggested in this article, the error of the determined ClO2 concentrations is reduced to the level of errors associated with the spectrophotometric measurements.

Determination of Cationic Surfactants in Environmental Samples by Flow Injection Analysis

A new simple flow injection analysis (FIA) procedure for the spectrophotometric determination of cationic surfactants (CSs), i.e. dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB), and cetylpyridinium chloride (CPC), is described. The method is based on absorptivity enhancement of the Bi(III)-I− complex in the presence of CSs. Among the investigated compounds, highest sensitivity is obtained with CPC, so it was selected for detailed study. The apparent value of molar absorptivity of the complex in terms of CPC is (6.00)×103 L mol−1 cm−1 at λmax 505 nm for FIA determination. The detection limit (3σ criterion) of the method for FIA determination is 110 µg L−1. The sample throughput is >140 samples h−1. The effect of analytical and FIA variables in the determination of CPC is described. The composition of the complex is discussed. The method is free from interferences of common ions. The method has been applied to the analysis of surfactant contamination in environmental samples, i.e. pond water, municipal/industrial wastewater, sewage, sediment and soil.

Flow Injection Analysis Spectrophotometric Determination of Palladium

A simple and specific method for flow injection analysis (FIA) spectrophotometric determination of Pd is described. The method is based on color reaction of Pd(II) with organic reagent, i.e., N‐phenylbenzimidoylthiourea (PBITU) over acidity range, 0.2–2.0 M HCl in the 10% (v/v) ethanolic solution. The value of apparent molar absorptivity of the yellow colored complex in the term of Pd is 1.20 × 104 L mol−1 cm−1 at λmax 345 nm. The detection limit (causing more absorbance than 3s) of the method is 80 ng mL−1 of Pd. The optimum working range was 0.25–10.0 µg mL−1 of Pd with slope, intercept, and correlation coefficient of 0.059, 0.006, and +0.99, respectively. The RSD of the method was ±1.1% for six replicate measurements at level of 2.0 µg mL−1 of Pd. The sample throughput of the method is 120 samples hr−1. The composition of the complex is discussed. The method is specific for the determination of Pd as none of the tested ions interfered. The method has been applied for the determination of Pd in the catalytic materials.

On‐Site Determination of Arsenic in Contaminated Water#

ABSTRACT A new spectrophotometric method for the on‐site determination of arsenic in contaminated water samples has been developed. The method is simple, rapid, and selective. It is based on reduction of As(V) to As(III) with ascorbic acid, complexation of As(III) with I− ions in strong HCl medium and extraction of the yellow colored iodo‐complex with N‐octylacetamide into chloroform solution. The optimum acidity range is 4.5–6.0 M HCl/2.5–3.5 M H2SO4. The apparent value (i.e., at two fold enrichment factor) of molar absorptivity in the term of arsenic is (5.00) × 104 L mol−1 cm−1 at λmax, 420 nm. The detection limit (i.e., absorbance causing more absorbance than 3s) of the method is 10 µg L−1 As. The method is free from interference of the ions commonly found to be associated with arsenic in environmental samples. The method has been tested for the field determination of arsenic in contaminated waters (i.e., surface, ground, rice field) of central India. #Accepted for poster presentation in IMA conference to held in Thessaloniki, Greece, 23–27 Sept., 2003.

Spectrophotometric determination of cobalt(II) using some arylazo-bis-acetoximes

A spectrophotometric method has been described for determination of cohalt(II) using p-bromophenylazo-his-acetoxime and o-methoxyphenylazo-bis-acetoxime. The reagents form yellow complexes in the pH range 7.5 to 8.5 and absorb at 376 and 380 nm, respectively. Stability constants and free energy have been calculated. The Beer's law is obeyed in the concentration range 0.2 x 10 - 4 M to 1.4 x 10 - 4 M of cobalt(II). The molar absorptivity and Sandell's sensitivity values are 3947 dm 3 mol - 1 cm - 1 , 14.93 ng cm - 2 and 3079 dm 3 mol - 1 cm - 1 , 19.14 ng cm - 2 , respectively. The interference of various ions has been studied.

Spectrophotometric Determination of Copper(II) Using Diamine-Dioxime Derivative

A simple, rapid and sensitive spectrophotometric method is herewith proposed for the determination of copper (II) by using diamine-dioxime ligand, meso-3,6,6,9-tetramethyl-4, 8-diazaundecane-2, 10-dione dioxime or meso-HexaMethyl Propylene Amine Oxime (meso-HMPAO). This method is based on the formation of a stable 1 : 1 red-pink complex between copper(II) and meso-HMPAO in aqueous solution Absorption measurements were carried at 497 nm, with a molar absorptivity value of 338 L mol-1 cm-1. Beer's law was obeyed over the concentration range of 0.5-370 μg mL - 1 with a Sandell's sensitivity value of 0.18 μg cm - 2 . The proposed method has been successfully applied for determination of copper (II) in foodstuffs and pharmaceutical samples. The results obtained from this method are comparable with those obtained AAS.

Spectrophotometric Determination of Carbon Disulfide Using Bis(4-(4 -Nitrophenyl)azo-2-Nitrophenyl) Disulfide

Bis(4-(4′-nitrophenyl)azo-2-nitrophenyl) disulfide (NADS) has been synthesized for the first time and proposed for the indirect photometric determination of carbon disulfide by dithiocarbamic acid. The reaction, which involves the breaking of the disulfide bond with the formation of colored azothio anions, is carried out in a mixture of dimethylsulfoxide and n-butanol. The high value of the apparent molar absorptivity (2 × 105) is probably due to the autocatalytic character of the reaction. Using NADS, procedures for the determination of carbon disulfide in the atmospheric air of populated areas and in the model gas mixtures designed for the calibration of gas analyzers have been developed and certified. The procedures show high sensitivity and good reproducibility.

Spectrophotometric method for the determination of manganese with phenylfluorone in the presence of Triton X-100 and cetylpyridinium chloride in pharmacological preparations and vegetable fertilizers.

A simple and very sensitive method for the spectrophotometric determination of manganese in pharmacological preparations and vegetable fertilizers is proposed. The method is based on the formation of a blue coloured complex of Mn (II) with 9-phenyl-2,3,7-trihydroxy-6-fluorone (PF) in the presence of cetylpyridinium chloride (CP) and Triton X-100. Optimum concentrations of PF, CP, Triton X-100 and pH ensuring maximum absorbance were defined. The complex Mn(II)-PF-CP-Triton X-100 shows maximum absorbance at 591 nm with the molar absorptivity value 1.77x10(5 )L mol(-1 )cm(-1). The detection limit of the method is 0.004 microg mL(-1). The Beer's law is obeyed for manganese concentrations in the range 0.02-0.2 microg mL(-1). The effect of foreign ions was elucidated. The statistical evaluation of the method was carried out for six determination using 5 microg Mn and the following results were obtained: standard deviation 0.021, confidence interval 5.05+/-0.05 microg Mn. The method has been applied for the determination of manganese in pharmacological preparations (Biovital, Kinder Biovital) and vegetable fertilizers (Hydrovit 100, Florovit).

Extractive spectrophotometric determination of fluoroquinolones and antiallergic drugs in pure and pharmaceutical formulations.

A simple, rapid and sensitive spectrophotometric procedure has been proposed for the assay of fluoroquinolones viz., ciprofloxacin (CPF) and norfloxacin (NRF), and antiallergic drugs viz., methdilazine hydrochloride (MDH) and isothipendyl hydrochloride (IPH) in bulk and pharmaceutical formulations. The method is based on the reaction of selected drugs with Brilliant Blue G (BBG) in NaOAc-AcOH buffer of pH 4.0 for CPF and NRF or in neutral medium for MDH and IPH to give chloroform soluble ion-association complexes. The effects of various parameters have been studied. The ion-association complexes exhibited absorption maxima at 610 nm for CPF, at 614 nm for NRF and MDH, and at 612 nm for IPH. Beer's law plots were obeyed in the concentration ranges of 0.5-6.0, 0.4-8.0, 0.1-6.0 and 0.2-6.1 (mg ml(-1) for CPF, NRF, MDH and IPH, respectively, with correlation coefficients not less than 0.9969. Molar absorptivity values as calculated from the Beer's law data were found to be 2.86 x 10(4), 2.64 x 10(4), 3.13 x 10(4) and 5.51 x 10(4) mol(-1) cm(-1) for CPF, NRF, MDH and IPH, respectively. The influence of commonly employed excipients in the determination of the studied drugs has been studied. The results obtained by the proposed method were statistically validated.

A rapid and sensitive extractive spectrophotometric determination of copper(II) in pharmaceutical and environmental samples using benzildithiosemicarbazone.

Benzildithiosemicarbazone (BDTSC) is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of copper(II). BDTSC reacts with copper(II) in the pH range 1.0-7.0 to form a yellowish complex. Beer's law is obeyed in the concentration range 0.5-0.4 microg cm(-3). The yellowish Cu(II)-BDTSC complex in chloroform shows a maximum absorbance at 380 nm, with molar absorptivity and Sandell's sensitivity values of 1.63 x 10(4) dm3 mol(-1) cm(-1) and 0.00389 microg cm(-2), respectively. A repetition of the method is checked by finding the relative standard deviation (RSD) (n = 10), which is 0.6%. The composition of the Cu(II)-BDTSC complex is established as 1:1 by slope analysis, molar ratio and Asmus' methods. An excellent linearity with a correlation coefficient value of 0.98 is obtained for the Cu(II)-BDTSC complex. The instability constant of the complex calculated from Edmond and Birnbaum's method is 7.70 x 10(-4) and that of Asmus' method is 7.66 x 10(-4), at room temperature. The method is successfully employed for the determination copper(II) in pharmaceutical and environmental samples. The reliability of the method is assured by analyzing the standard alloys (BCS 5g, 10g, 19e, 78, 32a, 207 and 179) and by inter-comparison of experimental values, using an atomic absorption spectrometer.

TRANSPORT AND FRACTIONATION OF DISSOLVED ORGANIC MATTER IN SOIL COLUMNS

Dissolved organic matter (DOM) is a heterogeneous mixture of organic compounds that plays an important role in the movement of DOM-associated pollutants. In this study, transport and fractionation of DOM in soils was investigated in flow-through soil columns. Dissolved organic matter derived from spent mushroom substrate weathering was pumped through packed columns (2.5 cm × 10 cm) comprising a coarseloamy subsoil (mixed, semiactive, mesic Typic Hapludult), and effluents were monitored for changes in the composition of DOM. Effluent DOM was characterized for UV absorbance, molecular weight, acidity, and hydrophilicity. Transport through the columns resulted in preferential retention of specific DOM constituents as indicated by comparison with a Br - tracer. During the transport process, effluent DOM exhibited decreasing values of E 2 /E 3 (from 10.3 to 6.2), acidity (from 20.8 to 13.1 mmol c g -1 C), and hydrophilicity (39.0 to 28.4%), and increasing values of molar absorptivity (from 164 to 310 L mol -1 C cm -1 ) and number and weight-averaged molecular weight (from 1770 to 3150 and 2450 to 4180 Da, respectively). These results indicate that DOM fractions with higher molecular weight, higher molar absorptivity, lower E 2 /E 3 ratio, lower acidity, and lower hydrophilicity were adsorbed preferentially by soil minerals, whereas the inverse fractions were transported preferentially. The adsorbed DOM could not be completely desorbed by DOM-free background solution, indicating a strongly bound fraction. Sorptive fractionation of DOM during transport likely affects the transport behavior of DOM-complexed constituents.

Spectrophotometric Determination of Antiallergic Drug in Bulk Powder and in Its Pharmaceutical Formulations

Two simple, rapid and selective spectrophotometric methods have been described for the determination of promethazine hydrochloride (PMH) either in pure or pharmaceutical formulations. The methods are based on the formation of a green colored product with sulphanilic acid (SPA) in presence of N-bromosuccinimide (NBS) or a red colored, chloroform soluble product with p-nitroaniline (PNA) in presence of ceric ammonium sulphate (CAS). The chromogen formed has maximum absorption at 600 nm and at 510 nm with SPA and PNA, respectively. The optimum reaction conditions and other analytical parameters are evaluated. Beer's law is valid in the concentration range of 0.5–25 μg/mL (R= 0.9983) with SPA and 2–75 μg/mL (R = 0.9981) with PNA. Molar absorptivity values as calculated from the Beer's law data are 5.54 × 103 L/mol/cm and 3.05 × 103 L/mol/cm for SPA and PNA, respectively. The results are in good agreement with those of the official method. No interference was observed from common pharmaceutical excipients.

Analytical application of p-sulfonamidophenylazo-bis-acetoxime in the spectrophotometric determination of iron(III)

p-Sulfonamidophenylazobisacetoxime has been used for spectrophotometric determination of iron(III) at 405 nm, keeping the pH at 2.5-3.0. Beer's law is obeyed in the range (4 to 24) × 10 - 5 M. The molar absorptivity and Sandell's sensitivity values are 1853 dm 3 mol - 1 cm - 1 and 30.14 ng cm - 2 , respectively.

Spectroscopic study of dinitrophenol herbicide sorption on smectite.

Sorption of two dinitrophenolic herbicides, 4,6-dinitro-o-cresol (DNOC) and 4,6-dinitro-2-sec-butylphenol (DINOSEB) to smectite was studied using FTIR, HPLC, and quantum chemical methods. The high affinity of DNOC and DINOSEB for smectite surfaces was attributed to site-specific interactions with exchangeable cations and nonspecific van der Waals interactions with the siloxane surface. The positions of the nu(asym)(NO) and nu(sym)(NO) vibrational modes were perturbed by the exchangeable cations with similar changes occurring for both alkali and alkaline earth cations as a function of ionic potential. The cation-induced changes to the vibrational bands of the NO2 groups indicate that exchangeable metal cations are coordinated to -NO2 groups. Quantum chemical methods predicted a red-shift of the nu(asym)(NO) band and a corresponding blue-shift of the nu(sym)(NO) modes, as was observed experimentally. The nature of the smectite surface itself did not strongly influence the vibrational modes of sorbed DNOC or DINOSEB on the basis of a comparison of DNOC sorbed to three different smectites (K-SWy-2, K-SAz-1, and K-SHCa-1). FTIR spectra of DNOC and DINOSEB sorbed to a K-SWy-2 smectite were studied quantitatively using a modified form of Beers law. The FTIR-derived sorption isotherm of DNOC sorbed to K-SWy-2 was in good agreement with the isotherm derived from HPLC measurements. The molar absorptivity value of DNOC sorbed to K-SWy-2 smectite was 1.43 x 10(7) cm2/mol in good agreement with literature values for nitroaromatics (average value of 1.72 x 10(7) +/- 0.3 cm2/mol). On the basis of this value, the limit of detection using the FTIR method of approximately 5 microgDNOC g(clay) was determined. These two observations (sorption isotherms and molar absorptivity) provide a direct link between the macroscopic sorption results and the FTIR spectra.

Visible spectrophotometric determination of metal ions: the influence of structure on molar absorptivity value of copper(II) complexes in aqueous solution

In this study, the structure–absorptivity relationship problem is dealt with, on the basis of a considerable mass of data (117 complexes) concerning equatorial complexes of copper(II) in aqueous solution. Some spectrophotometric measurements have been carried out and as well as some molar absorptivity calculations on copper(II)–ammonia ( ε 640=77 M −1 cm −1 for the Cu(NH 3) 4 2+ species) and copper(II)–biuret ( ε 505=46 M −1 cm −1 for the Cu(C 2H 3N 3O 2) 2 2− species) systems have been made, in order to complete the quantitative information necessary for the discussion. It was found that the qualitative relationship between ε max and λ max, for the complexes in question is traceable back to a hyperbolic type of path; the dispersion of the data in the cartesian plane ( ε max, λ max) is analyzed and discussed. It has been found that the dissociated peptide nitrogen is, amongst those under study (namely: amino nitrogen; peptide nitrogen; imidazole nitrogen; carboxylate oxygen; alcoholate oxygen; hydroxide oxygen; water oxygen), that which corresponds to the major increase of ε max for copper(II). On the contrary, the one which corresponds to the minor increase is the imidazole donor (that is pyridine nitrogen of imidazole residue), which manifests the ability to lower the ε max values of the equatorial complexes of copper(II). Moreover, contrary to what has been previously demonstrated for λ max, for ε max it does not appear to be correct to schematize the ligand with its donor groups in order to assess spectrum–structure correlations. Consequently, this study contains a type of methodological proposal, even beyond the metal ion specifically in question, for the analyses of the selection criteria of the molecular characteristics that a ligand must possess in order to form a co-ordination compound of analytical interest with a determined metal ion.

Effect of solute-co-ordinating solvent interactions and temperature on the EPR and electronic spectra of bis(dithiophosphato)copper(II)

The self-redox reaction proceeding between two molecules of the complex bis(disubstituted-dithiophosphato)copper(II), Cu II( R 2-dtp) 2, is studied by EPR and UV–VIS spectroscopy in DMFA, DMSO and pyridine. The effect of temperature and disulphide concentration in the solutions is also evaluated. The EPR spectra show that the g-values of Cu II( R 2-dtp) 2 increase when it is dissolved in co-ordinating solvents, whereas the copper hyperfine splitting decreases compared to the corresponding values in non-co-ordinating solvents. Under the same conditions, a hypsochromic shift is observed in the maximal absorption at 420 nm of the electronic spectra which corresponds to the ligand-to-metal charge-transfer (LMCT) transition of the complex. The results are explained with the formation of axial or equatorial adducts between Cu II( R 2-dtp) 2 and the co-ordinating solvents used. On the other hand, the molar absorptivity of the LMCT band and the intensity of the EPR spectrum increase strongly with the nature of the used co-ordinating solvent, the time after dissolution and the quantity of added disulphide. Both also depend on the size and shape of remote ligand substituents and they increase in the order Me<Et<i-Pr. Beer's law is not obeyed immediately after dissolution of copper bis-dithiophosphate complexes. However, after standing for 24 h in the dark, DMFA solutions exhibit linear absorption/concentration dependence with ≈70% higher molar absorptivity. An additional increase of the LMCT band and EPR intensity is found after heating the solution up to 50 °C for a short time, as well as after addition of the corresponding disulphide of dithiophosphate [( RO) 2P(S)S–S(S)P( RO) 2] to the Cu II( R 2-dtp) 2 solution. As a result, the molar absorptivity value at the maximum of the LMCT band of Cu[(i-PrO) 2-dtp] 2 increases from 7.9×10 3 m −1 dm 3 cm −1 immediately after dissolution to 2.9×10 4 m −1 dm 3 cm −1. In DMSO and pyridine, the intensity of both the EPR signal and LMCT band of Cu II( R 2-dtp) 2 continuously decrease after the preparation of the solutions. A small increase is only observed immediately after the addition of the corresponding disulphide of dithiophosphate. While DMFA forms stable adducts with Cu[(i-PrO) 2-dtp] 2, adduct formation with DMSO and pyridine destroys the initial complex.

ON THE INTERACTION BETWEEN AZIDE AND MANGANESE IONS AT SEVERAL OXIDATION STATES

The interaction between azide and manganese ions, at several oxidation states (II, III, IV, V, VI and VII), has been investigated in aqueous medium at 25.0 ± 0.1°C and ionic strength 2.0 mol · L−1(NaClO4). Spectral data were obtained from absorbance measurements in order to calculate the molar absorptivity. The molar absorptivity values calculated, at 430 nm, for [Mn(N3)3],[Mn(N3)4]− and [Mn(N3)5]−2 were 230, 3,700 and 6,600 mol−1 · L · cm−1, respectively. Mn(IV) and Mn(V) are not stable in azide aqueous solution medium and spectral characteristics are similar to Mn(III)/N3− complexes. Additions of permanganate or manganese(VI) solution, as K2 MnO4, to several azide buffers solutions, N3−/HN3, have produced species which have shown similar spectral characteristics with at 438 nm.

Ultraviolet spectroscopy of anticonvulsant enaminones

The ultraviolet (UV) spectra of selected enaminones were determined in acidic, alkaline and neutral media and compared to their anticonvulsant activities. The wavelength of maximum absorption and molar absorptivity were compared with the anticonvulsant activity of the selected secondary and tertiary enaminones, and general inferences were made. The UV spectra of the enaminones had hypsochromic shifts in acidic media in comparison with neutral media. Generally, a small hypsochromic shift occurred in alkaline media when compared to the neutral solutions of the enaminones. The tertiary enaminones absorbed UV light at longer wavelength than the secondary enaminones in acidic, neutral and alkaline media. In particular, the tertiary enaminones displayed absorption at the higher end and secondary enaminones towards the lower end of the UV wavelength range 292–315 nm in aqueous media. Tertiary enaminones ( 30– 33) which were devoid of the NH proton were found to be uniformly inactive in a mouse model of electroshock seizures, while some secondary enaminones ( 1, 5– 8, 12, 16, 18, 20, 23– 25, 28 and 29) had anticonvulsant activity. Thus the NH group of secondary enaminones is very important for anticonvulsant activity, and this agrees with an already established trend in proton NMR spectroscopy. In addition, the para-substitution on the phenyl group in some enaminones result in higher molar absorptivity (ε) values that enhance anticonvulsant activity. These results indicate that the anticonvulsant activity of enaminones is not due to electronic effect alone, but is probably due to a combination of factors including electronic and steric effects, lipophilicity, and hydrogen bonding.

Spectrophotometric Method for the Determination of Cobalt with N,N?-Bis(2-Aminobenzoyl)Ethylenediamine

A simple and direct spectrophotometric method has been developed for the determination of cobalt(II) using N,N′-Bis(2-aminobenzoyl)ethylenediamine (Baben). The method is based on the colour reaction between Baben and cobalt(II) in borax buffer (pH 9.2). The studies are carried out at 470 nm at which the calculated value of molar absorptivity is found to be 1.102 × 104 L mol−1 cm−1. The system obeys Beer’s law over a wide range of concentration (2–20 μg/ml). The effect of interfering ions has been studied and the method was applied to the determination of cobalt in water, industrial effluents and in alloys and the results were highly satisfactory.

A highly sensitive spectrophotometric method for the determination of some phenothiazine antipsychotics using chloramine-T and indigocarmine.

A new simple, accurate and precise spectrophotometric method for the determination of six phenothiazine drugs in pure form and in dosage forms is described. The method is based on the oxidation of the studied drugs by a known excess of Chloramine-T in hydrochloric acid medium and subsequent determination of the unreacted oxidant by reacting it with indigocarmine in the same acid medium. The reacted oxidant corresponds to the drug content. The colored species exhibits maximum absorption at 610 nm. The apparent molar absorptivity values and Sandell sensitivity values are in the range 1.53 x 10(4)-2.96 x 10(4) l mol-1 cm-1 and 13.75-37.15 ng cm-2, respectively. The method is highly sensitive and suitable for 1-15 micrograms ml-1 concentrations with the detection limits being in the range, 0.0651-0.1724 microgram ml-1. The method was successfully applied to the studied drugs in their dosage forms. The results are reproducible within +/- 1% and compare favorably with those obtained by the procedures of the British Pharmacopeia.