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  • Author or Editor: N. Siddique x
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Abstract  

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.

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Abstract  

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 |z-score|> 3.

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Abstract  

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.

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Abstract  

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.

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Summary

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 (R F 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 r 2 = 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.

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Abstract  

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.

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Abstract  

Tuna fish flesh homogenate, IAEA-436, was received under the IAEA Analytical Quality Control Services (AQCS) intercomparison programme. Instrumental neutron activation analysis (INAA) was used to determine Al, As, Br, Ca, Ce, Cl, Co, Cr, Cs, Eu, Fe, Hg, K, Mg, Mn, Na, Rb, Se, Sb, Sm, and Zn in this proposed reference material (RM). IAEA-407 (Fish Homogenate) and NIST-SRM-1572 (Citrus Leaves) were used for quality assurance (QA) purposes. Due to the very low levels of most elements in IAEA-436, large discrepancies were observed between our results for IAEA-436 and data cited by the IAEA.

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Abstract  

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.

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