Assessment of contamination and nutritional deficiency in ready-made baby foods available in local market using neutron activation analysis technique

Abstract

The present studies have been carried out for the determination of nutritional and toxic elements and also to estimate the natural radioactivity concentrations in some locally available baby foods using the nuclear reactor based Neutron Activation Analysis (NAA) technique. For NAA, 15 samples having about 75 mg of each were prepared in two folds followed by the standard protocol of NAA for short and long irradiation. Two Certified Reference Materials (CRMs) namely, IAEA-Soil-7, IAEA-SL-1 and one Standard Reference Material (SRM) NIST-1633b Coal Fly Ash were prepared in the same way. The CRMs were used to control the quality of analysis, whereas the SRM was used to quantify the elements using relative method. In short irradiation scheme, individual irradiation of 15 samples and 3 CRMs was performed in the pneumatic transfer system Rabbit Irradiation Channel of the TRIGA reactor for 1 min with the thermal power of 250 kW for the determination of Al, Ca, Mg, Mn, Ti, V, etc. In case of long irradiation, all the samples, CRMs and the SRM were irradiated simultaneously in the same irradiation channel for 7 minutes with the thermal power of 2.4 MW for determination of Na, K, Fe, Cr, Th, U, Zn, etc. All the irradiated samples and CRMs were counted individually using the HPGe spectrometry system with different decay intervals depending on the half-lives of the interested elements. For quantification, the relative standardization approach was applied. The natural activity was measured for determination of 238U, 232Th, their daughters and 40K in all the 15 samples, using gamma spectrometry system. For this analysis, about 70g of each sample was packed in a plastic pot and kept shielded for about 4 weeks before counting to retain secular equilibrium between the daughters and parents of 238U and 232Th decay series. Counting of each sample was performed for 20,000 sec on the surface of the HPGe detector. For quantification, a calibration curve was constructed using Al2O3 based 226Ra standard (800 Bq). For quality control, 4 CRMs namely, IAEA-Soil-6, IAEA-375, IAEA-152 and IAEA-414 were also packed and counting was taken for them in the same way as of the sample. An experiment was designed and conducted to determine the correction factors due to variation of density and chemical compositions of the samples, CRMs and the standard. In some cases lower nutritional values were obtained compared to the quoted values. The total dose rates and Radium Equivalent Activity were also determined in the samples. These revealed that the radiation dose rate is approximately ground level and are within the range of safe limit.