Authors:E. Obiajunwa, Adeleke Adebajo, and Olanrewaju Omobuwajo
The energy-dispersive X-ray fluorescence (EDXRF) spectroscopy has been used for the determination of essential and trace elements" contents of some twenty Nigerian medicinal plants. The accuracy and precision of the technique were assured by analyzing the European Community Bureau Reference Standard BCR 62 (Olive Leaves). Fourteen elements, namely K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Se, Br, Rb, Sr were detected with toxic heavy metal such as Cd, As, Pb, Hg were detected in the samples. The ranges of elemental concentrations varied from 7.7.104 to 1.6 mg/kg in the herbs. The results show that many of these plants contain elements of vital importance for human metabolism and prevention and healing of diseases.
Authors:R. Herrera, J. Denison, V. Spate, A. Gudiño, C. Baskett, I. Dubman, M. Mason, E. Bohl, A. Williams, T. Nichols, M. Glascock, and J. Morris
The University of Missouri Research Reactor Center (MURR) has been one of the premier providers of neutron activation analysis (NAA) to the high purity materials industry for the past 20 years. Over the last two decades, significant advances in contamination control in the manufacturing process and the development of alternate analytical techniques have challenged the NAA community to keep pace. This paper presents an overview of the High Purity Materials Analysis Program at MURR. Specifically we present trends in the trace element concentrations that we have observed in our laboratory over the past 10 years and compare our experience with the relevant literature. The prospects for the future success of NAA and the methodological changes required for satisfying the industry's need will be discussed.
Authors:Ch. Jesús, F. Socorro, and M. Rodríguez de Rivera
In the calorimeters used for the determination of thermodynamical properties of liquid environments, the mixture takes place when injecting liquid in the mixture zone, this injection incorporates an additional calorific power that is a function of the volumetric heat capacity of the injected liquid and the injection flow. In this article, it is rewritten Tian's equation including this additional power to relate correctly the experimental output to the mixture enthalpy. It is applied Tian's equation, once it has been corrected, to two types of calorimeters: flow-microcalorimeters and isothermal titration calorimeters. In this second case, it has been taken into account the classical operating mode (titration) and the continuous liquid injection mode. Tian's equation, completed with all the energetic terms additional to the mixture process, is of great interest for the scientific and academic community because it allows to explain, in a simple and effective way, the operation of these instruments.
Authors:X. Wang, W. Zimmermann, K. Ng, A. Chakraboty, and J. Keller
This article presents results of the experimental investigation on the adsorption of the water vapor on silica gel. Two independent
experimental methods has been used, viz. the constant-volume-variable-pressure (CVVP) system and variable pressure thermogravimetry
(TG). Results from these two methods are compared with each other. Also the isosteric heat of adsorption of this system has
been determined from the equilibrium data. The silica gels investigated here are Fuji Davison type 'A' and type 'RD'. Adsorption
isotherm of water vapor have been measured under a variety of conditions all referring to chiller operation cycles, i.e. temperatures
from 303 to 358 K and pressures from 500 to 7000 Pa. The data collected from the two independent experiments compare very
favorably with each other and their trends are consistent with those of the adsorption chiller manufacturer. This lends significant
weight to our experimental data on silica gel+water systems as being valuable to the adsorption chiller manufacturers and
the scientific community.
Authors:M. Suşeska, M. Rajiş, S. Matečiş-Mušaniş, S. Zeman, and Z. Jalový
TNAZ (1,3,3-trinitroazetidine) is a relatively new, powerful, steam castable, strained ring explosive. Owing these characteristics
it is of considerable interest to the energetic material community. A relatively high vapour pressure, volume contraction
and formation of shrinkage cavities in the solidification of its melt may be considered as some of its disadvantages. The
kinetics and heats of TNAZ sublimation and evaporation were studied by the non-isothermal and isothermal thermogravimetry
method. The activation energy of 94-102 kJ mol-1 was found for TNAZ sublimation, while the activation energy of 60-81 kJ mol-1 was found for TNAZ evaporation. The enthalpy of TNAZ sublimation at the melting temperature was found to be 95 kJ mol-1, and the enthalpy of TNAZ evaporation equals 66 kJ mol-1.
Authors:K. Inn, Zhichao Lin, Zhongyu Wu, C. McMahon, J. Filliben, P. Krey, M. Feiner, Chung-King Liu, R. Holloway, J. Harvey, I. Larsen, T. Beasley, C. Huh, S. Morton, D. McCurdy, P. Germain, J. Handl, M. Yamamoto, B. Warren, T. Bates, A. Holms, B. Harvey, D. Popplewell, M. Woods, S. Jerome, K. Odell, P. Young, and I. Croudace
In 1977, the Low-level Working Group of the International Committee on Radionuclide Metrology met in Boston, MA (USA) to define the characteristics of a new set of environmental radioactivity reference materials. These reference materials were to provide the radiochemist with the same analytical challenges faced when assaying environmental samples. It was decided that radionuclide bearing natural materials should be collected from sites where there had been sufficient time for natural processes to redistribute the various chemically different species of the radionuclides. Over the succeeding years, the National Institute of Standards and Technology (NIST), in cooperation with other highly experienced laboratories, certified and issued a number of these as low-level radioactivity Standard Reference Materials (SRMs) for fission and activation product and actinide concentrations. The experience of certifying these SRMs has given NIST the opportunity to compare radioanalytical methods and learn of their limitations. NIST convened an international workshop in 1994 to define the natural-matrix radionuclide SRM needs for ocean studies. The highest priorities proposed at the workshop were for sediment, shellfish, seaweed, fish flesh and water matrix SRMs certified for mBq per sample concentrations of 90 Sr, 137 Cs and 239 Pu + 240 Pu. The most recent low-level environmental radionuclide SRM issued by NIST, Ocean Sediment (SRM 4357) has certified and uncertified values for the following 22 radionuclides: 40 K, 90 Sr, 129 I, 137 Cs, 155 Eu, 210 Pb, 210 Po, 212 Pb, 214 Bi, 226 Ra, 228 Ra, 228 Th, 230 Th, 232 Th, 234 U, 235 U, 237 Np, 238 U, 238 Pu, 239 Pu + 240 Pu, and 241 Am. The uncertainties for a number of the certified radionuclides are non-symmetrical and relatively large because of the non-normal distribution of reported values. NIST is continuing its efforts to provide the ocean studies community with additional natural matrix radionuclide SRMs. The freeze-dried shellfish flesh matrix has been prepared and recently sent to participating laboratories for analysis and we anticipate receiving radioanalytical results in 2000. The research and development work at NIST produce well characterized SRMs that provide the world's environment-studies community with an important foundation component for radionuclide metrology.
Antibiotic extraction from solid matrices is generally complicated unlike aqueous phases. Consequently, increasing the extraction efficiency of antibiotics from solid matrices has received a great concern. Therefore, the main objective of this study was to determine three macrolide antibiotics; tylosin (TYL), spiramycin (SPIR), and erythromycin (ERY) in buffaloes’ meat using the recommended method of thin-layer chromatography-bioautography (TLC-B) after some modifications. Antibiotics were extracted by 0.2% metaphosphoric acid-methanol (6:4, 7p/7p), and then the extracts were cleaned up using an Oasis HLB cartridges (200 mg). The recovery ratios at 0.5, 1, and 2 maximum residue limits (MRLs) with high precision were 84.19–92.22%, 83.09–89.42%, and 84.89–90.28%, respectively. The detection limits were 12, 45, and 2 ng g−1 for TYL, SPIR, and ERY, respectively. Forty-five samples of Egyptian buffaloes’ meat were analyzed using the adapted method. Only 9 and 5 samples out of the 45 samples were positive for TYL and ERY, respectively, with mean concentrations of 42.59 and 31.21 (ng g−1) which were lower than the permitted MRLs recommended by the European community.
Within the framework of the Protection of the Environment programme of the JRC-Ispra of the European Community, research on trace metal exposure and health effects is concerned primarily with the toxicological assessment of present levels of trace metals in the tissues of exposed and unexposed populations. Main activities are: (1) microdetermination of trace elements in human tissues in order to generate an accurate and reliable data base on the levels and biochemical forms of trace metals in differently exposed humans; (2) metabolism and biochemical mechanisms involving trace metals to assess the toxicological significance of the current levels of the elements in the human body. Few selected applications related to the different steps of the biochemical toxicology research are shown. They concern the long-term behaviour of trace metals at the target tissues of laboratory animals, the biological monitoring of vanadium in workers during maintenance operations at an oil fired power plant for energy production, and the biochemical mechanism of methylation of arsenic in vivo.
An examination of year-long, in-home radon measurement in Colorado from commercial companies applying typical methods indicates
that considerable variation in precision exsts. This variation can have a substantial impact on any mitigation decisions,
either voluntary or mandated by law, especially regarding property sale or exchange. Both long-term exposure (nuclear track
greater than 90 days), and short-term (charcoal adsorption 4–7 days) exposure methods were used. In addition, periods of continuous
monitoring with a highly calibrated alpha-scintillometer took place for accuracy calibration. The results of duplicate commercial
analysis show that typical results are no better than ±25 percent with occasional outliers (up to 5 percent of all analyses)
well beyond that limit. Differential seasonal measurements (winter/summer) by short-term methods provide equivalent information
to single long-term measurements. Action levels in the U.S. for possible mitigation decisions should be selected so that they
consider the measurement variability; specifically, they should reflect a concentration range similar to that adopted by the
The National Physical Laboratory is the national standards laboratory of the UK and is charged with maintaining primary measurement
standards in the UK. These include standards in the field of ionising radiation and, in common with other National Standards
Laboratories, NPL develops and maintains absolute standards of radioactivity. These are used to calibrate secondary standard
instruments and also to prepare traceable standards of radioactivity at levels appropriate to the user community. Over the
past eight years NPL has run a series of six environmental radioactivity measurement intercomparisons, aimed at evaluating
the capabilities of laboratories measuring environmental radioactivity in the UK. This paper reviews the general progress
made over the years by the participating laboratories with reference to those laboratories who are accredited by the United
Kingdom Accreditation Service (UKAS). The first exercises made clear that (1) there was no account taken of cascade summing
effects in γ-ray spectrometry measurements by many laboratories, (2) the calibration standards used, in some cases, were completely
inappropriate for the work being undertaken, and (3) the nuclear decay data utilised by many laboratories (and in some cases,
supplied by reputable manufactures) were either of an old vintage or incorrect. Over the years, the situation has changed
somewhat in that participants are more aware of the pitfalls of measuring radioactivity. Finally, the effect that this has
had on NPL's activities in the area of radionuclide metrology will also be described.