• Sangita

      Articles written in Pramana – Journal of Physics

    • Relaxation intensity in some polyacrylates

      Manisha Gupta Sangita Madhuri Mathur Jagdish Shukla

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      Empirical formula suggested by Kita and Koizumi for evaluation of relaxation intensity in a limited range of frequency around the relaxation frequency for the Cole-Cole type distribution has been tested for poly butyl acrylate (PBA), Poly butyl methacrylate (PBMA) and poly isobutyl methacrylate (PiBMA).

      The relaxation intensity Δε is expressed in terms ofε″M, the dielectric loss maxima andW, the frequency separation for half, two thirds or three quarters ofε″M, in the form Δε=ε″M/[(C1/W)+C2+C3W], where the numerical constantsC1,C2,C3 are given for the respective type of relaxation.

    • Trace determination of uranium in fertilizer samples by total reflection X-ray fluorescence

      N L Misra Sangita Dhara Arijeet Das G S Lodha S K Aggarwal I Varga

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      Uranium is reported to be present in phosphate fertilizers. The recovery of uranium from the fertilizers is important because it can be used as fuel in nuclear reactors and also because of environmental concerns. For both these activities suitable method of uranium determinations at trace levels in these fertilizers are required. Studies have been initiated for such TXRF determination of uranium and the results are reported in the present paper. For TXRF determinations the fertilizer samples were processed with nitric acid and the uranium present in it was removed by solvent extraction using tri-n-butyl phosphate as the extractant. The organic phase containing uranium was equilibrated with 1.5% suprapure nitric acid to bring out uranium in aqueous phase. This aqueous phase was mixed with internal standard Y and the TXRF spectra were measured by depositing samples on float glass supports. The amounts of uranium in four fertilizer samples of Hungarian origin were determined by processing these TXRF spectra. Uranium concentrations in two fertilizer samples were found to be in the range of $4–6 \mu g/g$, whereas two fertilizer samples did not show the presence of uranium. The precision of the TXRF determination of uranium was found to be better than 8% ($1\sigma$).

    • Application of total reflection X-ray fluorescence spectrometry for trace elemental analysis of rainwater

      Sangita Dhara N L Misra

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      Applicability of total reflection X-ray fluorescence (TXRF) spectrometry for trace elemental analysis of rainwater samples was studied. The study was used to develop these samples as rainwater standards by the National University of Singapore (NUS). Our laboratory was one of the participants to use TXRF for this study. The rainwater sample obtained from NUS was analysed by TXRF and the trace elements Mn, Fe, Ni, Cu, Zn, V and Pb were determined as required by the NUS. The average precision was found to be within 16% and the TXRF-determined elemental concentrations of these elements were below $20 \mu g/l$. The average deviation of TXRFdetermined values from the certified values were 20% (excluding the deviation for Fe and V which were comparatively high). Apart from the above elements, S, K, Ca, Rb, Sr, Ba and Br were also determined by TXRF and were found to be in the range of 0.2 to 191 $\mu g/l$. TXRF-determined values of our laboratory played an important role in the certification of concentration of seven elements in this rainwater sample which was later developed as a rainwater standard.

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