Achadu, OJodomo J.

Ayejuyo , O. O

English

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SIMULTANEOUS SPECTROPHOTOMETRIC DETERMINATION OF ALUMINIUM AND IRON  USING MICELLAR AIDED MIXED CHROMOGENIC REAGENTSAYEJUYO,  O. O and ACHADU*,  O.JChemistry Department, University of Lagos, Akoka Yaba, Lagos, Nigeria.Corresponding author email : ojodomo2000@yahoo.comAbstractSimple and novel spectrophotometric method is described for simultaneousdetermination of aluminium and iron. The method is based on the metal ion -complexes formed by aluminium and iron with mixed chromogenic reagents oforthophenanthroline and 8-hydroxyquinoline (oxine). The derivatives have absorptionmaxima at 400 nm and 510 nm respectively in the presence ofcetyltrimethylammonium bromide (CTAB) as micellar media (surfactant) maintainedat pH 5. Reaction conditions were optimized and the linear dynamic ranges fordetermination of aluminum and iron were found be 0.8 - 12 µg/mL and 0.6 - 8 µg/mLrespectively. The standard deviation (S.D) and coefficient of variation (CV) for thesimultaneous determination was 0.018 and 0.45% for aluminium and 0.03 and 1.5%for iron (II). The recoveries were between 102 % and 106 %, 101.2 % ad 104 % foraluminium and iron respectively at 95 % confidence level. The proposed methodwas successfully applied to the assay of aluminium and iron in rock minerals,lubricating oil and water samples. The results and paired t-test for the analyzedsamples were found to be in satisfactory agreement (shows no significant difference)with those acquired by the flame atomic absorption spectrophotometric (FAAS)technique.Keywords: Mixed chromogenic reagent, micellar media, Aluminum, Iron.IntroductionThe determination of trace amounts of aluminium and iron is important in industry,food products, potable water, metallurgy and environmental analytical chemistry.There is a growing need for procedures with high sensitivity and selectivity for thedetermination of aluminium and iron, because they have important roles in biologicalsciences and industry.[1]The role of trace and toxic levels of elements in human health has become animportant area of scientific research and hence much time and resources have beenput into the development of analytical techniques for single or simultaneousmulticomponent metals quantitation.[2]These two elements, iron and aluminium are usually present together in real andsynthetic samples. Therefore, it is important to measure them in the presence ofeach other. Among the most widely used analytical methods are those based on theUV-visible spectrophotometric techniques, due to both the simplicity and rapidness ofthe method.[3-5]Most techniques available for simultaneous assaying of aluminium and iron usuallyinvolve complex instrumentation, long analysis time and huge capital outlay. Forthese reasons, there is a growing need for simple, rapid, low cost and sensitivetechniques for the simultaneous quantitation of aluminium and iron.Spectrophotometric methods offer these advantages.This research work was aimed at developing a spectrophotometric techniquecapable of simultaneous determination of aluminium and iron. Since these metalsoccur together in environmental samples, biological and industrial wastes, it isimportant to measure them in the presence of each other. This work explores thepossibility of the method herein being used and well suited for the routine analyticalsimultaneous determination of these metals.Materials and MethodUV-Visible absorbance spectra were collected on a UV-VIS Spectronic D20+spectrophotometer, using a 5 cm quartz cell. Measurements of pH were made with aMetrohm hand held pH-meter.Flame atomic absorption spectrophotometry was carried out using Perkin-Elmer AAAnalyst with deuterium arc background correction. All solutions were prepared withdoubly distilled water. Chemicals used were of analytical grade.Prepared samples solution containing different concentrations of Al and Fe wereprepared by taking aliquots of the working standard solutions of the metals and mixedthoroughly.Under optimized conditions and at the respective wavelengths of maximumabsorption of the derivatives, 2 mL of prepared mixtures of iron and aluminium wasmeasured into 25 mL volumetric flasks and then treated with 2 mL of acetate buffersolution, 1mL ascorbic acid, 1mL of micellar solution and 2 mL of the mixedchromogenic reagent. The absorbance values were taken against reagent blank. Fewas taken at 510nm after 5 minutes and Al was taken at 400nm after 15 minutes. Theconcentrations of the metals in the prepared samples were evaluated from standardcalibration curves of Al and Fe standards respectively. The method of standardaddition was also used to determine the metals concentrations for samples withcomplex matrix.ResultsOptimization of Analytical VariablesVarious factors and conditions were optimized using the method of one at a timeand the results are shown in Table 1. These conditions were found and were usedto validate the applicability of the proposed method in the determination of iron andaluminium in real and complex environmental samples as shown in Table 2, 3 and4.Table 1.Shows selected analytical parameters obtained from optimization.Parameter Studied range Selected valueWavelength (nm) 300-700 400 (Al) and 510 (Fe)pH 3-8 5Time/h 0-72 5 mins (Fe) and 15 (Al)Mixed reagent (mL) 1-5 2Micellar solution (CTAB) 0.1-2.0/1-3 1/2Concn/vol (%/mL)Linear range (µg/mL) 0.1-12 0.6-8 (Fe) and 0.8-12 (Al)Mean recovery (%) - 100.03 (Fe) and 96.5(Al)Standard deviation - 0.030 (Fe) and 0.018 (Al)Coefficient of variation - 1.5 (Fe) and 0.45 (Al)Regression coefficient (R2) - 0.9972 (Fe) and 0.998(Al)Interferences Cu (II) and Fe (III)00.050.10.150.20.250.30.35380 430 480 530 580 630Wavelength(nm)Absorbance00.10.20.30.40.50.6380 430 480 530Wa v e l e ngt h( nm)Fig. 2 Absorption spectra of Aluminium-Oxine complex at pH 5 in micellar media00.10.20.30.40.50.60.70.8380 430 480 530 580Wavelength(nm)AbsorbanceFig. 3 Absorption spectra of Aluminium and Iron mixture complexes at pH 5 in micellar mediaSample                  No                                                     Found (µg/mL)________________________________________________________________________Proposed Method AAS _______________                     ______________Al                       Fe                         Al             Fe1*                                            1.06 ± 0.013             3.42 ± 0.052           0.996      3.5922**                                           ND                          0.1± 0.013              ND         0.1663***                                         3.26#± 0.028           7.22#± 0.182            3.15       7.522Table 3. Reproducibility of the proposed method.Present (µg/mL)Al3+     Fe2+4.00       2.004.00       2.004.00       2.004.00       2.004.00       2.00Found (µg/mL)Al3+     Fe2+4.01         1.983.98         2.004.02         1.973.99         2.024.02         2.01Mean (Found)Standard DeviationCoefficient of Variation4.004       1.9960.018       0.0300.45         1.50Added amount(µg/mL)               Found(µg/mL)                            Recovery ( %)       Al              Fe                                  Al                Fe                              Al             Fe_____________________________________________________________________                  5.00           3.00                              4.88              2.85                           97.6           95.01.00           1.00                              0.98               1.05                           98.0           105.02.50           6.00                              2.47               6.01                           98.8           100.1Mean Recovery                                                                                   96.5          100.03Table 4. Recovery Studies of the proposed methodDiscussionThe linear ranges were determined which was 0.6 - 8 µg/mL for iron (II), and 0.8 - 12 µg/mL for aluminium (III).The wavelengths of maximum absorption for the respective metal ion – complexes were found to be 400 nm and510 nm for Al and Fe (II) complexes in the presence of micellar solution of cetyltrimethyl ammonium bromide(CTAB). The relative standard deviation and coefficient of variation show that the method has good accuracy andprecision. A paired t-test was done for replicate determinations by the proposed method and the established flameatomic absorption spectrophotometric method (FAAS) and the result did not vary significantly. Good recoverieswere achieved for both metal ions; Fe was between 102 % and 106 %, while Al was between 101.2 % and 104 %.In order to check the accuracy of the method, several mixtures prepared using different concentration ratios of Al(III) and Fe (II) were analyzed using the proposed method. The metal ions were determined in five replicatemixtures, the standard deviation (SD) and coefficient of variation (CV) were found to be 0.018 and 0.45% for Al (III)and 0.03 and 1.5% for Fe (II) as shown in Table 3. The good agreements between amount present and amountfound for different compositions of the binary mixtures as shown in Table 4 are indicative of satisfactory accuracyand the precision of the proposed method. Interference studies carried out show no significant interferences fromanions of sulphate, phosphates and chlorides. Amongst metals tested, only Cu(II) and Fe(III) show littleinterferences.ConclusionThe determination of aluminium and iron in rock samples, lubricating oil sample and water samples and the closeagreements between the established method and the atomic absorption spectrophotometric method may indicatethe wide applicability and reliability of the method. This shows that the method can be well adapted for analyses ofcomplex environmental and biological samples. The high degree of reproducibility, valuable dynamic range,simplicity and relatively short experimental period of the proposed method permit the handling of a large number ofsamples. This research reports the simultaneous spectrophotometric determination of total iron and aluminium withthe use of mixed chromogenic reagents, thereby increasing the array of methods that are available for thesimultaneous determination of aluminium and iron. The proposed method has low cost, simplicity and greenprocess as added advantages.References1. Yang; J .G, and Li, Y. Q (1999). Spectroscopy and Spectroscopic Analysis. 19: 212.2. Greenwood, N. N.; Earnshow, A (1984) Chemistry of Elements; Oxford: New York. 122.3. Bowen, H.J.M (1982). Environmental Chemistry. (Royal Society of Chemistry, London). 6: 92.4. Kokot, S; Chen, S and Ni, Y. (2002). Spectrophotometric determination of metal ions in electroplating solution inthe presence of EDTA with the aid of multivariate calibration and artificial neural networks. Anal. Chim. Acta. 463:305-316.5. Youssef, Elsayed and Khalil, M.M.H. (1996). Simultaneous first derivative spectrophotometric determination ofiron (III) and molybdenum (VI) in cobalt-chromium and nickel-chromium alloys. Talanta 43: 583-588.Fig. 1 Absorption spectra of Iron-Phen complex at pH 5 in micellar mediaTable 2 . Determination of Aluminium and Iron in real samples by the proposed method and comparison with other method.*** Rock Sample                                      ǂ Mean value of three replicate determinations.**  Lube Oil Sample                                 # Measured in µg/g.* Lagoon Water Sample

Simultaneous Spectrophotometric determination of Aluminium and Iron using Micellar aided mixed Chromogenic reagent

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Simultaneous Spectrophotometric determination of Aluminium and Iron using Micellar aided mixed Chromogenic reagent

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