Effects of Gamma Radiation on Iron (III) Complex with Sodium salicylate in Aqueous Solutions
M.F. Barakat, M.El-Banna
1 Nuclear and Radiological Regularity Authority,
National Center of Radiation Research and Technology,
Atomic Energy Authority, Nasr City, Post Code 11762, P.O. Box 7551, Cairo, Egypt Fax: 2287603
ABSTRACT
In the present work, the radiation induced color bleaching of aqueous solutions of Iron- salicylate complex has been studied. The structure of the iron- salicylate complex has been studied. It was found that the molar ratio of the formed complex determined was 1: 1.5. The color bleaching of the complex solutions upon irradiation was followed spectrophotometrically and the % color bleaching was calculated and was plotted against the applied gamma irradiation doses. The obtained relationships consisted of two linear sections, the first between 0-2 kGy while the second section extends between 2-6 kGy. These relationships were used as calibration curves to determine the unknown irradiation dose.
Key words: Gamma irradiation/ Sodium salicylate / Iron / Metal complex / spectrophotometry.
INTRODUCTION
Several studies on radiolysis of complex compounds in aqueous solutions have been reported (1-6). For example, the radiolysis of some complexes of copper (II), cobalt (II) and nickel (II), in aqueous systems containing mixed ligands was studied and it was observed that some of the complexes decomposed by gamma irradiation while others did not (3, 4).
Roy et al., studied the effect of gamma radiations on aqueous solutions of thymine in the presence and absence of metronidazol as well as its Cu (II) and Ni (II) complexes under different conditions (7). It was found that the degradation of thymine increased when Cu (II) and Ni (II) complexes with metronidazol were subjected to gamma irradiation. Moreover, the metal complexes in presence of metronidazol showed high rate of oxidation of thymine-OH radical, and in the case of the Cu (II) complex, Cu (II) was reduced to Cu (I). The two reactive sites i.e. the metal and the ligand are subjected to the effect of the radiolytic products of water i.e. OH, H., e-aq... etc. (7)
Abou-Sekkina and Elsheikh followed the effect of gamma radiations on the 2,6-N,N'-dilamoyl-diaminopyridine (dbapH) and 2,6-N,N'-diacetyldiaminopyridine (daapH), Co(daapH)2Cl2, Ni(dbapH)2Cl2, and Ni(daapH)2Cl2 at doses from 1kGy to 10 MGy using infrared absorption measurements. The compounds and complexes investigated were arranged in a descending order of their decreasing stability towards gamma radiations (8).
Sugimori and Tsuchihashi studied the radiation chemistry of some aqueous metal salicylate complexes, and found that chelated Fe (III) and Cu (II) effectively increase the decarboxylation of salicylic acid (9).
In the present work, radiolysis of the Fe (III) salicylate complex has been studied. The effect of irradiation dose on the color bleaching of the complex in aqueous solutions has been carried out. The possibility of using the color bleaching curve in determining unknown gamma irradiation dose has also been investigated.
EXPERIMENTAL
A – Materials
a- Sodium salicylate.(2-(HO)C6H4CO2Na) was obtained from El Nasr Pharmaceutical Company, Egypt, M.W. 160.11, m.p. 200°C.
b- Ferric sulphate (Fe2 (SO4)3 .5 H2O), Fe( III) was obtained from El Nasr Pharmaceutical Company, Egypt, M.W. 489.96.
c- Double distilled water was used allover the work.
B – Methods
a- Formation of Fe (III) complex with Sodium salicylate.
Aliquots of 0.1, 0.3, 0.4 and 0.5 ml of aqueous 10-2M Fe (III) solutions were mixed with increasing amounts of aqueous 10-2M sodium salicylate solutions, and the mixtures obtained were completed to the mark with water in 5ml volumetric flasks. The absorbance of the resultant complex solutions was measured spectrophotometrically and the results obtained are shown in figure 1.
b- Applicability of Beer’s law to the iron complex solution.
A stock concentrated solution of the complex compound was prepared from which solutions with varying concentrations of the complex were prepared by dilution to be used for testing the applicability of Beer’s law. The optical density of complex solutions with different complex concentrations was measured and the values obtained were plotted against the corresponding concentrations. The plot showed a good linear relationship with a correlation coefficient 0.9863 and a slope of 0.915.
c- Preparation of irradiated samples.
Iron (III) salicylate complex solutions to be irradiated were prepared by adding 50 ml of 10-2 M sodium salicylate to 33.3 ml of 10-2 M Fe (III) and completing the solution to the mark in a 100 ml volumetric flask. 3 ml aliquots of the stock complex solution were introduced into well stoppered glass irradiation vials (1.5 cm in diameter and 5 cm in height). The irradiation tubes were subjected to gamma radiations at different irradiation doses.
Irradiation was carried out using the Canadian Co-60-gamma cell type 400 at the National Center of Radiation Research and Technology, Cairo, Egypt. Frequently, the operator used a Reference Alanine Dosimeter supplied by the National Physical Laboratory, UK, to determine the irradiation dose. The applied doses were determined each day by calculation.
d- Apparatus
Spectrophotometric measurements were carried out using a single beam T60 UV-VIS spectrophotometer, using glass cells with optical path length of 1 cm. The absorbance of the complex solutions was measured against the aqueous solution of Sodium Salicylate as a blank. All measurements of optical density were carried out immediately after irradiation.
e- Color bleaching measurements:-
Gradual color bleaching was observed upon subjecting the complex compound solution to increasing gamma-radiation doses. The % color bleaching was determined using the following equation:
% Color bleaching = ×100 (1)
Where A0 and Ax are the absorbance of the complex samples at zero dose and after being subjected to a dose x, respectively (10).
RESULTS AND DISCUSSIONS
Fe (III) ions form with aqueous sodium salicylate solution a violet colored complex. The absorption spectrum of the ferric sulphate-sodium salicylate complex solution showed a single absorption maximum at 525 nm.
The structure of the iron salicylate complex was determined by the molar ratio method. The absorbance of the solutions formed by adding increasing amounts of sodium salicylate to different Fe (III) ions solutions were determined and plotted against sodium salicylate concentrations. The results are shown in figure 1. From these results, it could be deduced that the structure of the formed complex involves the formation of 1: 1.5 iron: salicylate complex.
Fig. 1: Absorbance change of samples prepared by increasing sodium salicylate concentrations on four different Fe (III) solutions at λmax. 526 nm.
a- 0.2×10-3M Fe (III) b- 0.6×10-3M Fe (III)
c- 0.8×10-3M Fe (III) d- 1×10-3M Fe (III)
By appropriate dilutions of the stock complex solution, different concentrations of the complex solution within the range up to 3.5×10-3M were prepared, and their absorbance was measured and plotted against the Fe (III) concentration. A linear relationship was obtained as shown as figure 2. These results demonstrate the applicability of Beer’s law, the correlation coefficient of the obtained results, determined by linear regression analysis, was 0.9863 And the molar absorption coefficient of the complex equals 8.88 ×102 mol-1dm3cm-1.
Fig. 2: Absorbance-Concentration relationship of Fe (III) salicylate-complex.
Fig.3: Absorbance change of Fe (III) complex compound with sodium salicylate on applying different gamma irradiation doses.
The effect of gamma irradiation on the complex solutions was performed by introducing 3ml aliquots of the stock iron complex solution containing 3×10-3M Fe (III) into the irradiation tubes. After irradiation at increasing doses the absorbance was measured and plotted against the irradiation dose. The results are given in figure 3. From these data it is clear that the color of the complex decays almost completely at doses slightly greater than 2 kGys.
Fig. 4: % Color decay curve of Fe (III) complex compound with sodium salicylate.
The % color decay values were calculated at different doses for the irradiated complex samples and were then plotted against the corresponding irradiation doses. The results are given in figure 4. A broken line was obtained consisting of two linear sections the first between 0-2 kGy (correlation coefficient 0.9622) while the second section extends between 2-6 kGy (correlation coefficient 0.7154) but with a rather lower slope. This probably indicated that the rather rapid decay of complex up to ~ 2 kGy leads to the formation of another less sensitive product to irradiation which underwent gradual decay up to 6 kGy.
The linear section of % color bleaching-irradiation dose plot, shown in figure 4, could be used as a calibration curve for determining unknown irradiation doses.
The possibility of evaluating the irradiation doses given to some test samples subjected to different unknown γ-irradiation dose was investigated. Thus, several test complex samples consisting of 3 ml of the iron-salicylate complex containing 3×10-3M Fe (III) were subjected to different unknown gamma irradiation doses predetermined by the operator of the gamma source. The % color decay values of the irradiated test samples were calculated as described before by equations and by using the calibration curve, the corresponding irradiation dose was determined for each sample. The mean irradiation dose was then calculated for all unknown test samples. The results obtained for a series of irradiated samples at different doses are given in table 1.
Table (1): Results of unknown dose determination using aqueous solution of Fe (III) Sodium salicylate complex.
No. of test samples / Applied unknown doses, kGy / Determined dose, kGy / % Difference from calculated doseMean / ± Standard deviation
4 / 0.5 / 0.57 / ± 0.12 / 14
9 / 1 / 1.02 / ± 0.14 / 2.0
7 / 1.2 / 1.19 / ± 0.14 / -15
9 / 1.4 / 1.42 / ± 0.02 / 1.4
6 / 1.52 / ± 0.03 / 8.6
9 / 1.5 / 1.46 / ± 0.10 / -2.7
9 / 1.6 / 1.69 / ± 0.09 / 5.6
7 / 1.8 / 1.84 / ± 0.07 / 2.2
4 / 2 / 1.74 / ± 0.025 / -13
6 / 1.89 / ± 0.02 / -5.5
9 / 1.92 / ± 0.05 / -4.0
5 / 2.5 / 2.36 / ± 0.14 / -5.6
From these results it is clear that the iron (III) - salicylate complex could be used for determining unknown gamma irradiation doses. The deviation of the results obtained from the actual dose values applied was within the range 2-15 %. This shows clearly that Fe (III) - salicylate aqueous solutions could be used for unknown dose evaluation with in the dose range 0-2 kGy.
CONCLUSIONS
1- The iron-salicylate complex formed was a1:1.5 complex.
2- The obtained relationship between absorbance of 3×10-3M Fe (III) and gamma irradiation doses show that the color decays gradually almost completely at doses slightly greater than 2 kGys.
3- The iron-salicylate complex system could be used for unknown irradiation dose evaluation within the dose range 0-2 kGys.
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تأثيرات أشعة جاما على أيون الحديد الثلاثى مع صوديوم ساليسيليت فى المحاليل المائيه
محمود بركات، ماجده البنا
هيئة الرقابه النوويه و الأشعاعية
المركز القومى لبحوث و تكنولوجيا الإشعاع
هيئة الطاقه الذريه -مدينة نصر-الرقم البريدى:11762 صندوق بريد :7751 القاهره-مصر
الملخص
تم فى هذا العمل دراسة تأثير الإشعاع الجامى على زوال لون مركب الحديد مع الساليسيليت فى المحاليل المائيه. و تمت دراسة تركيب مركب الحديد مع الساليسيليت، وقد وجد أن نسبة تركيب المركب هى 1:1.5
وتم قياس زوال لون محاليل المركب عند التعرض للإشعاع على جهاز الطيف الضوئى، وتم حساب نسبة زوال اللون ودراسة العلاقه بين نسبة زوال لون المركب مع الجرعات الإشعاعيه المستخدمه . و تبين أن هذه العلاقه خطيه و مكونه من مقطعين ، الأول يقع فى المدى 0-2 كيلوجراى، بينما الثانى 2-6 كيلو جراى. و قد أستخدم المقطع الأول من هذه العلاقه لتقدير قيمة الجرعات الجاميه المجهوله بين صفر-2 كيلوجراى.
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