The IAEA conducted the IAEA-CU-2006-06 Proficiency Test (PT) on “The determination of major, minor and trace elements in ancient
Chinese ceramic” in 2006. The results of this PT showed that of the 21 analytes reported by our laboratory 9 failed the precision
criteria. Therefore the results reported by our laboratory along with the results of other laboratories which carried out
analysis using neutron activation analysis (NAA) were studied. It was found that the major factor contributing towards data
falling in the “Warning” category, failing the precision criteria was the high uncertainties cited in the certificates of
the reference materials (RMs) used for quantification of data. In this regard, it is recommended that synthetic standards
should be prepared and used on a routine basis especially for the measurement of the elements K, Eu, Lu, Ta, Tb and Yb.
A proficiency test (PT) exercise was offered by the International Atomic Energy Agency (IAEA) for major, minor and trace elements
in Chinese ceramic reference material (IAEA-CU-2006-06). Neutron activation analysis (NAA) laboratory at PINSTECH, Pakistan
participated in the exercise and submitted the results for 28 elements. The aim of participation was to develop a suitable
methodology for accurate measurement of as many elements as possible in ceramic material using a low power reactor (PARR-2)
as this would help future investigation in a project on the authenticity of art objects, for provenance, conservation and
management of ancient cultural heritage of the country. After receiving the final report of the PT exercise, a critical review
of our data and final scoring of each element is made to check the suitability of our methodology and reliability of the acquired
data. Most of the reported results passed different statistical evaluation criterion such as relative bias, z-score and u-scores and ratio of our results and IAEA target values. One element (Yb) falls in the unacceptable range of relative bias
and z-scores. Hf and Tb showed slightly high z-scores within the questionable range. Ho, Mo and Sn were determined during this study but their results were not submitted
to the IAEA. The confidence of accuracy observed for most of the elements in ceramic material has made it mandatory to report
their results as information values.
A study was undertaken to assess the air quality of Lahore by the elemental analysis of air conditioner (AC) filter dust samples
collected from 15 different commercial sites. Samples were prepared using the Leeds Public Analyst Method and were analyzed
using instrumental neutron activation analysis (INAA) for up to 31 elements. The elements Al, As, Ba, Ce, Co, Cr, Cs, Fe,
Hf, K, La, Lu, Mn, Na, Nd, Rb, Sc, Sm, Sn, Ta, Th, Yb and Zn were detected in all 15 samples whereas the remaining elements
have been detected in fewer samples; i.e. Mg, Sb and Tb were detected in 14 samples, Br and V in ten samples, U in nine samples
and Ca and Ti in eight samples only. Al, Ca, Fe, K, Mg and Na were determined in all samples at percentage levels. The concentrations
of most elements were found to lie around the mean values for the 15 samples studied and were not orders of magnitude different.
However the concentrations of Ca, Mg, Sn and Zn were found to be more variable and were found to be dependant on activities
such as construction, fruit and vegetable handling, tin plating and transport, respectively.
The International Atomic Energy Agency Marine Environmental Laboratory (IAEA-MEL) conducted an intercomparison exercise for
the “Trace elements and methyl mercury in fish scallop: IAEA-452” in 2009. The Neutron Activation Analysis (NAA) laboratory
at PINSTECH, Pakistan took part in this exercise. Comparison with the IAEA results showed that of the 18 elements reported
to the IAEA 7 had unacceptable z-scores while the data for two elements was questionable (2< |z-score| <3). Upon investigation it was discovered that the large number of elements having unacceptable z-scores was due to human error and the greater difficulty in analyzing biological samples which have low amounts of trace
elements. Therefore selection of values corresponding to matrix matched reference materials (RMs), such as IAEA-436 and IAEA-407,
and to non-interfering peaks the results obtained became comparable to the IAEA results with only the result for As having
Authors:M. Amir, A. Ahmad, N. A. Siddique, M. Mujeeb, S. Ahmad, and W. A. Siddique
A new simple, accurate, selective, precise, economical and stability-indicating high-performance thin layer chromatographic method for the analysis of diosgenin in callus and rhizome of Dioscorea deltoidea was developed and validated. The method was developed on TLC aluminium plates precoated with silica gel 60F254 using solvent system petroleum ether-isopropanol (12:1, v/v), which gives a compact spot of diosgenin (RF value 0.76 ± 0.02). Densitometric analysis of diosgenin was carried out in the absorbance mode at 366 nm after spraying with methanolic sulphuric acid. The linear regression analysis data for the calibration plots showed good linear relationship with r2 = 0.991 and 0.995 for diosgenin with respect to peak height and peak area, respectively, in the concentration range of 100–1000 ng per spot. The limits of detection and quantification for diosgenin were 16.58 and 50.25 ng per spot. The proposed method was applied for determination of diosgenin in rhizome of D. deltoidea (0.047% w/w) as well as in in vitro culture (callus) (0.092% w/w). Statistical analysis proves that the method is repeatable, selective and accurate for the estimation of diosgenin in D. deltoidea. The developed method effectively resolved the diosgenin in D. deltoidea; hence, it can be employed for routine analysis as a stability indicating method.
Authors:M. Arshed, N. Butt, M. Siddique, and M. Anwar-ul-Islam
Mössbauer study of the rust formed on SS-304 exposed to sea water for about 30 d indicates that ferrihydrite and -FeOOH are formed as corrosion products, the cause of corrosion being the presence of chloride ions in sea water. Ferrihydrite is found to exhibit two doublets at 300 K while at 80 K it exhibits a doublet and a sextet. This is contrary to earlier studies in which it was reported that at 80 K ferrihydrite is fully magnetically ordered and exhibits a sextet only.
Authors:M. Arshed, M. Anwar-ul-Islam, M. Siddique, and N. Butt
The corrosion of mild steel as a result of 3 years of immersion in deionized water, using Mössbauer results, indicates that -FeOOH, -FeOOH and Fe3O4 are formed as corrosion products. This study shows that purified water will produce -FeOOH only when the exposure time is long. It is proposed that ferrihydrite, which is formed as an intermediate corrosion product, is converted to -FeOOH, which in turn is converted to -FeOOH and Fe3O4.
Authors:N. Siddique, Sabiha-Javied, S. Waheed, and M. Tufail
Analysis of geological materials requires the use of matrix specific reference materials (RMs). Phosphate rocks (PR), the
basic ingredient of phosphate fertilizers, are very important in agriculture. A project was undertaken to study the PRs of
the Hazara Deposits of Pakistan. Due to the unavailability of phosphate rock reference materials (PR-RMs) with a large number
of certified elements, validation of the results was problematic when carrying out elemental analysis of PR samples and their
derived products. Therefore a parallel study was performed to determine the composition of three phosphate based RMs; BCR-RM-032
(Natural Moroccan Phosphorite), IAEA-434 (Phosphogypsum) and PRH (a local PR-RM from the Hazara Deposits of Pakistan). Instrumental
Neutron Activation Analysis was used for this purpose and more than 30 elements including rare earth elements were determined
in the three PR samples.
Authors:S. Waheed, N. Siddique, M. Arif, M. Daud, and A. Markwitz
Size fractionated PM2.5 and PM2.5–10 airborne particulates collected from the airport housing society site in Rawalpindi were characterized using the non destructive
ion beam analysis method. Proton induced X-ray emission and Proton induced gamma ray emission were employed to quantify 28
trace elements in fine and coarse filter samples. The average PM2.5 and PM2.5–10 masses were found to be 15.7 and 144 μg/m3, respectively which, when combined exceed the Pakistani limit for PM10 of 100 μg/m3. The average black carbon (BC) content was found to be 3.49 and 5.95 μg/m3 corresponding to 23.8 and 4.30% of the fine and coarse masses, respectively. The reconstructed mass (RCM) was calculated
for both particle modes using 5 pseudo sources, namely soil, sulfate, smoke, sea salt and BC. It was found that 5 sources
could account for 80.6 and 49.0% of the fine and coarse masses, respectively. The low value of RCM for the coarse mode may
imply a much higher organic content. The major sources contributing to the fine mode were soil, sulfate and BC. Similarly
for the coarse mass fraction it was found that soil was the major source whereas the sulfate and BC sources did not contribute