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  • Author or Editor: I. H. Qureshi x
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Summary  

Extensive use of coffee, by one-third of world's population, entails the evaluation of trace element contents in it. Instrumental neutron activation analysis (INAA) was successfully employed to determine the concentration of 20 trace elements (essential, toxic and nonessential) in four samples of coffee beans of various origins and two instant coffee brands most commonly consumed in Pakistan. This study provides the base-line values of certain toxic and essential elements in coffee. The daily intake of essential and toxic elements through coffee was estimated and compared with the recommended values. The cumulative intake of Mn is four times higher than the recommended value and that of toxic elements is well below the tolerance limits.

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Abstract  

Trace amounts of boron present as impurity in steel can be accurately determined by measuring the α-yield in10B (n,α)7Li reaction, since this reaction has a very high cross section for thermal and epithermal neutrons while natural boron contains significant isotopic abundance of10B. The α-particles produced during10B (n,α)7Li nuclear reactions can be detected by solid state nuclear track detectors (SSNTDs) and the boron content and its distribution can be determined in a sample. The technique involves the simultaneous irradiation of unknown and known samples with thermal neutrons and recording the reaction products in SSNTDs as α-tracks. The α-tracks in the detectors are counted with the aid of an optical microscope after chemical etching. Boron concentration and distribution in the unknown sample is determined by counting and comparing the track density with that of standard sample of known boron concentration. The technique of SSNTDs has been applied by us to determine the distribution of trace amount of boron in commercial alloy steel using LR-115, CA80-15, CN-85 and CR-39 detectors. All these detectors pose various problems during reactor irradiation and etching. However, CR-39 has been found to be suitable for determining the magnitude and distribution of boron in steel. A brief description of the method and the optimum irradiation and etching conditions of various detectors for α-track revelation along with results for the estimation of boron in alloy steel are described in this paper.

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