Atomic Absorption Spectrometric Procedure Research Articles

Spectrophotometric and atomic absorption spectrometric determination of cephalexin and cephradine in dosage forms

This paper describes two simple, sensitive and selective spectrophotometric and atomic absorption spectrometric (AAS) procedures for the determination of two compounds of cephalosporins (Cephalexin monohydrate and Cephradine). These procedures are based on the formation of ion-pair complexes between the drugs and ammonium reineckate. The formed precipitates are quantitatively determined either spectrophotometrically or by AAS procedures. The methods consist of reacting drugs with Reinecke's salt in an acidic medium at a temperature of 25 ± 2°C. The spectrophotometric procedure (procedure I) is based on dissolving the formed precipitate with acetone. The volume was completed quantitatively and absorbance of the solution was measured at 525 nm against blank. Also, the AAS procedures (procedure II) are quantitatively determined directly or indirectly through the chromium precipitate formed or the residual unreacted chromium in the filtrate at 358.6 nm. The optimum conditions for precipitation have been carefully studied. Beer's law is observed for the studied drugs in the ranges 0.1-1.5 mg mL-1 or 5-70 μg mL-1 using spectrophotometric or AAS methods, with correlation coefficients ≥ 0.9965, respectively. Both procedures I and II were accurate and precise when applied to the analysis of the cited cephalosporins in different dosage forms with good recovery percent ranged from 98.90 ± 0.94 to 100.15 ± 0.97 without interference from additives.

Retention of inorganic arsenic by coryneform mutant strains

The natural resistance mechanisms of corynebacteria to respond to the environments containing high levels of arsenic were successfully adopted to develop inexpensive and selective extractants for submicrogram amounts of arsenic. Kinetic and equilibrium characteristics were evaluated, and a preliminary exploration of the capability of these strains to be used for arsenic speciation was also made in this work. Three kinetics models were used to fit the experimental data. It was found that the pseudo-first-order kinetics model was not quite adequate to describe the retention process, while the intraparticle diffusion and the pseudo-second-order kinetics models provide the best fits. The equilibrium isotherm showed that the retention of arsenic was consistent with the Langmuir equation and that the Freundlich and Dubinin–Radushkevich models provided poorer fits to the experimental data. The maximum effective retention capacity for arsenic was about 15.4 ng As/mg biomass. The amount of arsenic retained was directly measured in the biomass by forward planning a slurry electrothermal atomic absorption spectrometric procedure.

DETERMINATION OF DILTIAZEM HCI AND DOTHIEPIN HCI THROUGH COMPLEX FORMATION

Simple, sensitive and accurate spectrophotometric and atomic absorption spectrometric procedures were developed for the determination of both diltiazem and dothiepin hydrochlorides in pure forms and in pharmaceutical preparations. The first method was based on the formation of ion-pair complexes between the two drugs and tropeolin oo using extractive procedures. The complex showed absorption maxima at 477 nm. Beer's Law was obeyed in the concentration range of (4-20) and (1.6-16) µgml-1 for diltiazem and dothiepin hydrochlorides respectively. The second method was based on formation of a ternary complex between (copper (II), rose bengal and drug). This complex was extracted with methylene chloride and measured at 555 nm. Beer's Law was obeyed in concentration range (24-80) and (16-32) µgml-1 for diltiazem and dothiepin hydrochlorides, respectively. The third method depends on determination of copper content of the formed complex using atomic absorption procedure, Beer's Law was obeyed in concentration range (16-24) and (32-68) µg ml-1 for dothiepin and diltiazem hydrochlorides respectively. The proposed methods hold their accuracy and precision welt when applied to the determination of diltiazem and dothiepin in their dosage forms.

Colorimetric and Atomic Absorption Spectrometric Methods for the Determination of Hyoscine N-Butylbromide in Pharmaceutical Formulations Using Cobalt (II) and Chromium (III) Thiocyanate Complexes

Two simple and sensitive colorimetric and atomic absorption spectrometric procedures have been established for determination of hyoscine N-butylbromide (Hyo.Br) in pure form and in pharmaceutical formulation. The methods are based on formation of an insoluble coloured ion-associate between the examined drug and tetrathiocyanatocobaltate (CoTC) or hexathiocyanatochromate (CrTC). The first method involves extraction of Hyo-CoTC and Hyo-CrTC ion-associates with methylene chloride and isobutyl alcohol, followed by measuring the absorbance at 630 and 557 nm, respectively. Optimization of the extraction conditions is investigated. Beer's law is obeyed in the concentration ranges 144.20-865.20 and 72.00-640.00 μg/ml using CoTC and CrTC, respectively. The molar absorptivities, Ringbom ranges, Sandell sensitivities and quantification and detection limits are also calculated. The second method is based on measuring the absorbance of the excess cobalt or chromium in the aqueous solution, after precipitation of the drug, at 240.7 and 357.9 nm using atomic absorption spectrometer, respectively. Linear application ranges, characteristic concentrations and detection limits of Hyo.Br are 0.404-1.617 mg/ml, 16.11 and 10.78 μg/ml in the case of CoTC, while 0.040-0.283 mg/ml, 29.50 and 2.70 μg/ml in the case of CrTC. The present methods have been successfully applied for the determination of the drug in commercial dosage form. The data obtained by the developed methods are compared with the official one.

Determination of zinc in tissues of normal and dystrophic mice using electrothermal atomic absorption spectrometry and slurry sampling

An electrothermal atomic absorption spectrometric procedure for zinc determination in animal tissues is first optimized and then used to measure the metal content of different tissues from normal and dystrophic mice. The procedure involves minimal manipulation of the sample to overcome the severe contamination problems normally associated with the measurement of low zinc levels. The samples (recommended amount 10 mg) are slurried in 2 ml of a 10-mM tetramethylammonium hydroxide solution containing 0.1 g/100 ml silicone antifoam. After mild heating at 60 °C for 10 min and homogenization for 1 min, the suspensions are submitted to a 10-fold dilution and then injected into the electrothermal atomizer. Calibration is carried out using aqueous standard solutions of zinc prepared in the same suspension media. The reliability of the whole procedure is verified using three certified reference materials.

Cinchocaine hydrochloride determination by atomic absorption spectrometry and spectrophotometry

Two sensitive spectrophotometric and atomic absorption spectrometric procedures have been developed for determination of cinchocaine hydrochloride (Cin.Cl) in pure form and in pharmaceutical formulation. The spectrophotometric method was based on formation of an insoluble colored ion-associate between the cited drug and tetrathiocyanatocobaltate (CoTC) or hexathiocyanatochromate (CrTC) which dissolved and extracted in an organic solvent. The optimal experimental conditions for quantitative extraction such as pH, concentration of the reagents and solvent were studied. Toluene and iso-butyl alcohol proved to be the most suitable solvents for quantitative extraction of Cin-CoTC and Cin-CrTC ion-associates with maximum absorbance at 620 and 555 nm, respectively. The optimum concentration ranges, molar absorptivities, Ringbom ranges and Sandell sensitivities were also evaluated. The atomic absorption spectrometric method is based on measuring of the excess cobalt or chromium in the aqueous solution, after precipitation of the drug, at 240.7 and 357.9 nm, respectively. Linear application ranges, characteristic masses and detection limits were 57.99–361.9, 50.40 and 4.22 μg ml –1 of Cin.Cl, in case of CoTC, while 37.99–379.9, 18.94 and 0.81 μg ml –1 in case of CrTC.

Determination of selenium in infant foods using electrothermal atomic absorption spectrometry with direct slurry sample introduction

Abstract Slurry sampling electrothermal atomic absorption (SS ETAAS) was applied to the development of a sensitive and precise method for selenium determination in infant foods without sample pretreatment. Suspensions prepared in a medium containing 0.1% Triton X-100, 0.5 or 5% v/v concentrated HNO3 were directly introduced into the furnace. The accuracy of the procedure was confirmed by analysis of a standard reference material and comparison with hydride generation atomic absorption spectrometric (HGAAS) procedure. The characteristic mass is 44 pg and detection limit 0.43 μg·l−1.

Colourimetric and atomic absorption spectrometric determination of some f luoroquinolone derivatives

Three simple, accurate, sensitive and selective procedures for the determination of ten fluoroquinolones (amifloxacin, ciprofloxacin hydrochloride, difloxacin hydrochloride, enoxacin, enrofloxacin, lomefloxacin hydrochloride, lovefloxacin, norfloxacin, ofloxacin and pefloxacin mesylate) were described. Procedures I and II are based on the formation of ion-pair complexes between the drugs and ammonium reineckate reagent in an acidic medium at 25 ±2°C and the formed precipitates are quantitatively determined either colourimetrically (procedure I) or by atomic absorption spectrometrically (procedure II). Procedure I is based on dissolving the formed precipitate with acetone, the volume was completed quantitatively and the absorbance of the solution was measured at 527 nm against pure solvent blank. The formed precipitates on the atomic absorption spectrometric procedure (procedure II) are quantitatively determined either directly or indirectly through the chromium precipitate formed or the residual un-reacted chromium in the filtrate at 358.6 nm and the optimum conditions for precipitation have been carefully studied. Procedure Ill is based on the reaction of the studied drugs with 2,2-diphenyl-1-picrylhydrazyl reagent (DPPH). The latter is employed to abstract a hydrogen atom from the drugs thereby promoting a process of radical coupling. This results in a reduction of the violet color of DPPH with the formation of the yellow colored 2,2-diphenyl-1-picrylhydrazine (DPPH2). The decrease in the intensity of the violet color is used to measure the concentration of the drugs. All measurements are made at λ = 520 nm on methanolic solutions of the reagent and drugs. Beer's law is obeyed for the studied drugs in the range 2-36 µg ml−1 with correlation coefficients not less than 0.9992. All procedures hold well accuracy and precision when applied to the analysis of the cited fluoroquinolones in different dosage forms with good recovery percent ranged from 98.88±0.40 to 100.99±0.44 without interference from additives.

On-line preconcentration and determination of cobalt by chelating microcolumns and flow injection atomic spectrometry

A simple and sensitive flow injection analysis–atomic absorption spectrometric procedure is described for the determination of cobalt. The method is based upon on-line preconcentration of cobalt on a microcolumn of 2-nitroso-1-naphthol immobilized on surfactant coated alumina. The trapped cobalt is then eluted with ethanol (250 μl) and determined by flame atomic absorption spectrometry. The analytical figures of merit for the determination of cobalt are as follows: detection limit (3 S), 0.02 ng ml −1; precision (RSD), 2.8% for 20 ng ml −1 and 1.7% for 70 ng ml −1 of cobalt; enrichment factor, 125 (using 25 ml of sample). The method has been applied to the determination of cobalt in water samples, vitamin B 12 and B-complex ampoules and accuracy was assessed through recovery experiment and independent analysis by furnace AAS.

Cadmium determination in biological samples by direct solid sampling flame atomic absorption spectrometry

A direct solid sampling flame atomic absorption spectrometric procedure for trace determination of cadmium in biological samples has been developed. Test samples (0.05–2.00 mg) were ground and weighed into small polyethylene vials, which were connected to the device for solid sample introduction into a conventional air/acetylene flame. Test samples were carried as a dry aerosol to a quartz cell, placed between the burner and the optical path, which had a perpendicular entrance and a slit in the upper part. The atomic vapor generated in the flame produced a transient signal that was totally integrated within 1 s. The effect of operating conditions and the extent of grinding on the analytical signal were evaluated. Background signals were always low and a characteristic mass of 0.29 ng Cd was obtained. Calibration was performed using different masses of solid certified reference materials. Results obtained for certified and in-house reference materials were typically within the 95% confidence interval of the certified and/or reference value, and the precision, expressed as relative standard deviation, was between 3.8 and 6.7%. The proposed system is simple and it might be adapted to conventional atomic absorption spectrometers allowing the determination of Cd in more than 80 test samples per hour, excluding weighing.

Spectrophotometric and AAS determination of ramipril and enalapril through ternary complex formation

Two sensitive, spectrophotometric and atomic absorption spectrometric procedures are developed for the determination of two antihypertensive agents (enalapril maleate and ramipril). The spectrophotometric procedures for the two cited drugs are based on ternary complex formation. The first ternary complex (copper(II), eosin, and enalapril) was estimated by two methods; the first depends on its extraction with chloroform measuring at 533.4 nm. Beer's law was obeyed in concentration range from 56 to 112 μg ml −1. The second method for the same complex depends on its direct measurement after addition of methylcellulose as surfactant at the pH value 5 at 558.8 nm. The concentration range is from 19 to 32 μg ml −1. The second ternary complex (iron(III), thiocyanate, and ramipril) was extracted with methylene chloride, measuring at 436.6 nm, with a concentration range 60–132 μg ml −1. The direct atomic absorption spectrometric method through the quantitative determination of copper or iron content of the complex was also investigated for the purpose of enhancing the sensitivity of the determination. The spectrophotometric and atomic absorption spectrometric procedures hold their accuracy and precision well when applied to the determination of ramipril and enalapril dosage forms.

Colourimetric and AAS determination of cephalosporins using Reineck's salt

Two simple, accurate, sensitive and selective procedures for the determination of eight cephalosporins are described. These procedures are based on the formation of ion-pair complexes between the drugs and ammonium reineckate, the formed precipitates are quantitatively determined either colourimetrically or by atomic absorption spectrometrically. The methods consist of reacting drugs with Reinecke's salt in an acidic medium at 25±2°. The first colourimetric procedure (procedure I) is based on dissolving the formed precipitate with acetone, the volume was completed quantitatively and the absorbance of the solution was measured at 525 nm against pure solvent blank. Also, the formed precipitates on the atomic absorption spectrometric procedure (procedure II) are quantitatively determined directly or indirectly through the chromium precipitate formed or the residual unreacted chromium in the filtrate at 358.6 nm. The optimum conditions for precipitation have been carefully studied. Beer's law is obeyed for the studied drugs in the range 5–35 μg ml −1 with correlation coefficients ≮0.9989. Both procedures I and II hold well accuracy and precision when applied to the analysis of the cited cephalosporins in different dosage forms with good recovery percent ranged from 98.7±0.90 to 100.1±0.74 without interference from additives.

Determination of Cr(VI) in welding fumes by anion-exchange fast protein liquid chromatography with electrothermal atomic absorption spectrometric detection.

The applicability of an anion-exchange fast protein liquid chromatographic-electrothermal atomic absorption spectrometric procedure (FPLC-ETAAS) was investigated for the determination of Cr(VI) in welding fumes after alkaline extraction of aerosols loaded on filters. Gas tungsten arc welding (GTAW) of stainless steel was applied. Samples of welding fumes were collected during regular welding on polycarbonate membrane filters of 8 microm and 0.4 microm pore size (inhalable and respirable aerosols). Alkaline extraction (2% NaOH-3% Na2CO3) of filters in a heated ultrasonic bath was applied to leach Cr from the airborne particulate matter. 0.5 cm3 of sample extract was then injected onto an anion-exchange FPLC column. Tris-HCl buffer (0.005 mol dm(-3), pH 8.0) and the same buffer with NaCl (0.5 mol dm(-3)) were employed in gradient elution (15 min, flow rate 1 cm3 min(-1)). The separated Cr species were determined "off line" by ETAAS in 0.5 cm3 fractions. Cr(VI) was reproducibly and quantitatively eluted from 12.0 to 13.0 min with a maximum peak at 12.5 min. Good repeatability of measurement (+/-3.0%) of alkaline extracts was obtained for Cr(VI). The LOD (3s) was found to be 0.035 microg m(-3) Cr(VI), when 2 m3 of aerosols were collected on the filter. Validation of the procedure was performed by spiking alkaline extracts and by the analysis of standard reference material CRM 545, Cr(VI) in welding dust loaded on a filter. The technique was successfully applied for the determination of Cr(VI) in welding fumes.

Determination of Mercury in Sewage Sludges by Slurry Sampling Electrothermal Atomic Absorption Spectrometry

An electrothermal atomic absorption spectrometric procedure was developed for the determination of mercury in sewage sludge, in which the samples were suspended in a solution containing hydrofluoric and nitric acids. Silver nitrate (4%, m/v) and potassium permanganate (3%, m/v) were incorporated as matrix modifiers, and aliquots were directly introduced into the graphite furnace. A fast-heating program with no conventional pyrolysis step was used. The detection limit for mercury in a 50 mg/mL suspension was 0.1 microg/g. Calibration was performed by using aqueous standards. An analysis of certified reference materials confirmed the reliability of the procedure.

Determination of trace impurities in some nickel compounds by flame atomic absorption spectrometry after solid phase extraction using Amberlite XAD-16 resin

A simple flame atomic absorption spectrometric (FAAS) procedure for the determination of lead, bismuth, gold, palladium and cadmium as impurities in Raney nickel and nickel oxide was developed using a preconcentration step on an Amberlite XAD-16 resin packed column. Lead, bismuth, gold, palladium and cadmium were quantitatively recovered and separated from a solution containing 1 M HCl and 0.3 M NaI by the column system. Effects of the various parameters such as reagent concentrations, sample volume, matrix effects, etc. have been investigated. Under optimized conditions, the relative standard deviation of the combined method of sample treatment, preconcentration and determination with FAAS (n = 7) is generally lower than 12%. The limit of detection (3s, n = 20) was between 10–270 ng/g. The results were used for separation and preconcentration of five trace elements from nickel matrices.

Determination of hexavalent chromium in lime-treated sewage sludge by anion-exchange fast protein liquid chromatography with electrothermal atomic absorption spectrometry detection

The applicability of an anion-exchange fast protein liquid chromatographic–electrothermal atomic absorption spectrometric procedure (FPLC-ETAAS) was investigated for the determination of trace amounts of Cr(VI) in lime-treated sewage sludge. Samples of sewage sludge and sludge mixed with sawdust (volume ratio 1 + 1) with a pH of 8.0 and 7.8, respectively, as well as their mixtures with 5% of quicklime with a pH of 12 were analysed. Liming was applied for sludge stabilisation and disinfection. TRIS–HCl buffer (0.005 mol dm−3, pH 8.0) and the same buffer with NaCl (0.5 mol dm−3) were employed in gradient elution (15 min, flow rate 1 cm3 min−1). The separated Cr species were determined ‘off line’ by ETAAS in 0.5 cm3 fractions. It was experimentally proven that Cr(VI) was reproducibly and quantitatively eluted from 12.0 to 13.0 min with a maximum peak at 12.5 min. The repeatability of measurement for a standard solution of 25.0 ng cm−3 of Cr(VI) was found to be 4.0% and the LOD 1.5 ng cm−3 of Cr(VI). The technique was successfully applied for the determination of Cr(VI) in lime-treated sewage sludge. In aqueous extracts of untreated sewage sludge Cr(VI) was not detected. In aqueous extracts of lime-treated sewage sludge Cr(VI) was determined 48 h after liming [the concentration was about 200 ng g−1 Cr(VI)] and was monitored over a time span of six months. The validation of the procedure was performed by analysis of a certified reference material, spiking of samples (recoveries from 93 to 101%) and comparative analysis of Cr(VI) in the fraction eluted at 12.5 min by the ion chromatography thermal lens spectrometry technique. The applied FPLC-ETAAS procedure was found to be a reliable and sensitive technique for the determination of traces of Cr(VI) in lime-treated sewage sludge and investigation of oxidation–reduction processes of Cr. The LOD for sludge samples analysed was 20 ng g−1 of Cr(VI) and the repeatability of measurement 6.5%.

Organic palladium and palladium-magnesium chemical modifiers in direct determination of lead in fractions from distillation of crude oil by electrothermal atomic absorption analysis

Platinum reforming catalysts are easily poisoned by increased levels of lead, therefore a sensitive atomic absorption spectrometric procedure for lead determination in fractions from crude oil distillation was developed. Lead was present in organic form in the samples analysed therefore the behaviour of various lead compounds (Pb-alkylarylsulphonate, Pb-4-cyclohexanobutyrate, tetraethyllead, Pb in fuel oil) was studied. The best procedure for the determination of lead in different petroleum products, including those containing asphaltenes includes a pretreatment with iodine and methyltrioctylammonium chloride, followed by the use of an organic Pd-Mg modifier. Under these conditions an effective matrix removal is possible at a pyrolysis temperature up to approximately 1100°C and the behaviour of lead present in different forms is unified. The characteristic mass is 11–12 pg Pb, corresponding to a detection limit of 0.25 ng g −1 for 20 μl sample solution. This can be lowered by multiple injection.

Spectrophotometric and atomic absorption spectrometric determination of certain cephalosporins

Two sensitive spectrophotometric and atomic absorption spectrometric procedures are developed for the determination of certain cephalosporins (cefotaxime sodium and cefuroxime sodium). The spectrophotometric methods are based on the charge-transfer complex formation between these drugs as n-donors and 7,7,8,8-tetracyano-quinodimethane (TCNQ) or p-chloranilic acid (p-CA) as π-acceptors to give highly coloured complex species. The coloured products are measured spectrophotometrically at 838 and 529 nm for TCNQ and p-CA, respectively. Beer’s law is obeyed in a concentration range of 7.6–15.2 and 7.1–20.0 μg ml −1 with TCNQ, 95.0-427.5 and 89.0-400.5 μg ml −1 with p-CA for cefotaxime sodium and cefuroxime sodium, respectively. The atomic absorption spectrometric methods are based on the reaction of the above cited drugs after their alkali-hydrolysis with silver nitrate or lead acetate in neutral aqueous medium. The formed precipitates are quantitatively determined directly or indirectly through the silver or lead content of the precipitate formed or the residual unreacted metal in the filtrate by atomic absorption spectroscopy. The optimum conditions for hydrolysis and precipitation have been carefully studied. Beer’s law is obeyed in a concentration range of 1.9–11.4 and 1.78–8.90 μg ml −1 with Ag(I), 14.2–57.0 and 13.3–53.4 μg ml −1 with Pb(II) for cefotaxime sodium and cefuroxime sodium, respectively (for both direct and indirect procedures). The spectrophotometric and the atomic absorption spectrometric procedures hold well their accuracy and precision when applied to the analysis of cefotaxime sodium and cefuroxime sodium dosage forms.

Spectrophotometric and atomic absorption spectrometric determination of ramipril and perindopril through ternary complex formation with eosin and Cu(II)

Two sensitive, spectrophotometric and atomic absorption spectrometric procedures are developed for the determination of ramipril and perindopril. Both methods are based on the formation of a ternary complex, extractable with chloroform, between copper(II), eosin and the two cited drugs. Spectrophotometrically under the optimum condition, the ternary complexes showed an absorption maximum at 535 nm, with apparent molar absorptivities of 6.55 and 4.00×10 3 mol −1cm −1 and Sandell’s sensitivities of 5.80×10 −2 and 1.04×10 −1μg cm −2 for perindopril and ramipril, respectively. The solution of ternary complex obeyed Beer’s law in concentration ranges 10–60 and 20–100 μg ml −1 for perindopril and ramipril, respectively. The proposed method was applied to the determination of the two cited drugs in pharmaceutical tablets. The atomic absorption spectrometric method, directly through the quantitative determination of copper content of the organic extract of the complex, was also investigated for the purpose of enhancing the sensitivity of the determination. The spectrophotometric and atomic absorption spectrometric procedures hold their accuracy and precision well when applied to the determination of ramipril and perindopril dosage forms.

Flow injection on-line preconcentration and flame atomic absorption spectrometric determination of iron, cobalt, nickel, manganese and zinc in sea-water

A rapid and sensitive flow injection analysis–atomic absorption spectrometric procedure is described for the determination of iron, cobalt, nickel, manganese and zinc based upon on-line preconcentration on a microcolumn packed with C18 material. These metals were complexed with 5,7-dichlorooxine from weakly acidic or neutral solutions in the flow system and adsorbed on the column. The preconcentrated elements were eluted with acidified methanol (pH ≥ 2) and injected directly into the nebulizer for atomization in an air–acetylene flame for measurement. The retention efficiency was better than 98%, resulting in sensitivity enhancement factors of 60, 80, 80, 80 and 60 for a 1 min preconcentration time for iron, cobalt, nickel, manganese and zinc, respectively. The respective detection limits were 4.0, 1.0, 1.0, 0.5 and 0.5 ppb, respectively. The throughput of samples was 30 h–1, with a loading time of 1 min. The method was applied to sea-water samples.