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Biomedical subjects

A R Byrne

Publications and source records attributed to A R Byrne.

At least 19 recordsLinked to original sources

The validation of Kayzero-assisted NAA in Budapest, Rez, and Ljubljana via the analysis of three BCR certified reference materials.

After installation and calibration of k0-assisted NAA in three Central European research institutes (AEKI-Budapest, NPI-Rez, and IJS, Ljubljana), its validation was established via the analysis of three BCR certified reference materials. The matrices of choice were: CRM 277 estuarine sediment, CRM 038 coal fly ash from pulverized coal, and CRM 101 spruce needles. For some elements, e.g. Zn, Cd, and Hg, the analyses were not only performed instrumentally (INAA), but also in the radiochemical mode (RNAA). The work was performed in the framework of a European Copernicus Project.

Carbon↗

Installation and calibration of Kayzero-assisted NAA in three Central European countries via a Copernicus project.

An account is given of the installation and calibration of k0-based NAA--assisted by the DSM Kayzero/Solcoi software package--at the KFKI-AEKI, Budapest, the NPI, Rez and the IJS, Ljubljana. Not only the calibration of the Ge-detectors and the irradiation facilities are discussed, but also other important topics such as gamma-spectrometric hard- and software, QC/QA of the IRMM-530 Al-Au flux monitor and the upgrade of the Kayzero/Solcoi code. The work was performed in the framework of a European Copernicus JRP, coordinated by the Laboratory of Analytical Chemistry, Gent, with DSM Research, Geleen, as the industrial partner.

Journal Article↗

Preliminary study on the determination of selenium compounds in some selenium-accumulating mushrooms.

Using various chromatographic techniques (size exclusion, anion exchange, and cation exchange) combined with several detectors (neutron activation analysis and atomic fluorescence spectrometry), an attempt was made to characterize selenium compounds in some edible, selenium-accumulating mushrooms (Albatrellus pes-caprae and Boletus edulis). The mushrooms contained mostly low-molecular-weight (6 kDa) selenium compounds. After proteolysis, only a small fraction of the extractable selenium could be identified as selenite (3.0-9.2%, Albatrellus pes-caprae), selenocystine (minor, Albatrellus pes-caprae; 7.5%, Boletus edulis), or selenomethionine (1.0%, Boletus edulis), leaving the form of the bulk still to be elucidated.

Agaricales↗

Applicability of neutron activation analysis (NAA) in quantitative determination of some essential and toxic trace elements in food articles.

Accurate and reliable data on microgram and nanogram quantities of some essential and toxic elements in most food articles are very scarce. Neutron activation analysis (NAA), with its essentially blankfree advantage, is a valuable approach in the field of determination of trace elements in different foodstuffs and diets. Accordingly, various radiochemical (RNAA) and instrumental (INAA) approaches have been developed in our laboratory for the element As, Cd, Co, Cu, Hg, I, Mo, Ni, Sb, Se, Sn, Th, U, V, and others, and verified by the analysis of compositionally appropriate certified reference materials.

Animals↗

Preliminary studies on arsenic species in some environmental samples.

Arsenic compounds have been determined in some environmental samples from the German Environmental Specimen Bank (ESB) (marine mussels, freshwater mussel and fish, sea-gull eggs) and certified reference materials (DORM-1, DOLT-1, NBS Oyster Tissue) after separation by open column cation and anion exchange chromatography by two different methods of total arsenic determination in separated fractions (instrumental neutron activation analysis or hydride generation atomic absorption spectrometry). Arsenobetaine has been identified as the major species in all the different materials.

Journal Article↗

Determination of trace amounts of selenium in poultry feedstuffs by gas chromatography.

In view of the importance of establishing reliable selenium concentration levels in different kinds of feedstuffs, the purpose of this work was to develop optimum experimental conditions for the isolation and GC determination of selenium as its chelate with 4-nitro-1,2-diaminobenzene. It was shown that ignition of the sample in an oxygen flask followed by reduction of Se(VI) to Se(IV) and the formation of 5-nitro-2,1,3-benzoselenadiazole chelate in HCl medium is a relatively rapid procedure giving a low blank value and allowing the determination of selenium in commercial feedstuffs and similar biological samples. The method was validated by the analysis of suitable certified or standard reference materials.

Animal Feed↗

Comprehensive RNAA of cadmium, cobalt, nickel, and copper using 109Cd, 57Co, and reactor-produced 67Cu as radioisotopic yield monitors.

An existing radiochemical NAA procedure for Cd, Co, and Cu was improved to allow determination of individual radiochemical yields by the radioisotopic tracer technique, thus eliminating errors owing to variable recovery. 109Cd was used as tracer for Cd determination via 115Cd/115mIn, 57Co for Co via 60Co, and potentially for Ni via 58Co, whereas as a novelty 67Cu, produced by reactor irradiation of ZnO of natural isotopic composition (by the 67Zn [n,p] 67Cu reaction) was used for Cu via the indicator nuclide 64Cu. The simple production and purification of 67Cu by anion exchange is described. Results for biological RMs are given and discussed.

Animals↗

Some improvements in the quality of NAA procedures and the reliability of the results.

After considering the need for quality control in NAA, the concept of quality in NAA procedures themselves is discussed, and some important factors identified. Two approaches to improve quality are then described in more detail. The first concerns the unique ability of NAA using different isotopic reactions and different modes (INAA/RNAA) to provide independent data sets in the same laboratory, thus allowing internal validation or crosschecking. The second discusses the need for chemical yield measurements in RNAA and the advantages of the radioisotopic tracer technique. Some recent advances and further possibilities for this use of tracers are listed.

Neutron Activation Analysis↗

Prompt and delayed NAA techniques for the characterization of specimen bank materials.

The combined application of instrumental-, radiochemical- and prompt gamma neutron activation analysis to two spruce shoot materials from the German Environmental Specimen Bank (ESB) resulted in information on 50 elements, covering more than 50% of the total mass. Comparison of the element concentrations in the 'fingerprint' mode clearly indicated a different status of heavy metal pollution at the two distinct collecting sites.

Environmental Monitoring↗

Vanadium levels in hair and blood of normal and exposed persons.

Vanadium was determined by both instrumental neutron activation analysis (INAA) and NAA with radiochemical separation (RNAA) in hair of normal children and of children potentially exposed by accidental drinking of vanadium contaminated water (long-term, low-dose exposure). Vanadium hair levels in the two groups did not differ significantly and were in the range 46-313 micrograms/kg (median 98 micrograms/kg) and 24-235 micrograms/kg (median 88 micrograms/kg for the normal and exposed groups, respectively. Using RNAA with proven reliability at the ultratrace level, vanadium was determined in whole blood of the exposed and normal children, normal adults and workers professionally exposed to vanadium in a factory producing vanadium pentoxide. Significantly increased vanadium concentrations were found in blood of exposed children (range 0.018-0.239 micrograms/l, median 0.078 micrograms/l) compared to normal children (range 0.024-0.226 micrograms/l, median 0.042 micrograms/l), while no differences could be detected between blood vanadium levels of normal children and normal adults (range 0.032-0.095 micrograms/l, median 0.056 micrograms/l). Preliminary results for vanadium in blood of occupationally highly exposed persons showed values 2-4 orders of magnitude higher than in normal adults.

Adult↗

Some considerations regarding reference materials and their role in environmental monitoring. Plenary lecture.

After a brief introduction indicating the principal function of reference materials (RMs) in ensuring that the analytical measurement programme is performing reliably, the availability, different types and sources of information on RMs are described. Next, the correspondence of available RMs to present sample demands is discussed, particularly with regard to the adequacy of matrices and analytes, the availability of RMs for 'difficult' trace elements, and the preparation and certification of speciation RMs. The role of RMs in quality control is indicated, and their usage and certain problems which can thereby arise, including total dissolution, homogeneity and their representativeness in relation to samples, are discussed. The application of truly representative RMs in low-level trace element work, as a means of quality control of sampling and storage procedures, is mentioned. Strategies open to the analyst in the total absence of certified RMs are presented, and the importance of publication of independent results by alternative methods for such materials, as a means of establishing consensus values, is stressed. In the situation where results for a particular analyte obtained by different groups for the same (but not identical) biomedical or environmental system differ markedly, a progressive multi-stage exchange scheme is proposed, which is designed to reveal whether the differences arise from analytical factors, sampling effects or real system differences.

Environmental Monitoring↗

Rapid radiochemical neutron activation analysis for iodine in urine by different separation techniques.

In the present work on radiochemical neutron activation analysis for the determination of iodine in urine samples, the performance of three different radiochemical separation techniques, namely, direct extraction, use of an iodinated ion-exchange resin column and Schöniger combustion, were intercompared and validated. The practical advantages of the iodinated-resin technique make it most suitable for the rapid routine determination of iodine in urine. It was further verified by participation in an international intercomparison run of urine analysis, and used in a pilot study on iodine determination in the urine of 171 Slovenian schoolchildren, where it gave results in good agreement with the catalytic method.

Child↗

Preliminary study of the effects of some physical parameters on the stability of methylmercury in biological samples.

The effects of storage conditions (long-term storage of wet samples in a deep-freeze or thermal cycling), freeze-drying and gamma-irradiation at 1 and 5 Mrad on the stability of methylmercury in some biological samples were investigated. Methylmercury was determined by volatilization separation followed by gas chromatography and by ion-exchange separation of inorganic and organic species followed by measurement by cold vapour atomic absorption spectrometry (CVAAS). Total mercury was determined by CVAAS. Biological samples studied included fish and shellfish tissues, human hair and blood samples and appropriate reference materials. From the preliminary results obtained it can be concluded that fresh and dried fish muscle and fish certified reference materials show good stability with time and against temperature cycling. Shellfish and blood should not be repeatedly frozen and unfrozen otherwise possible losses of methylmercury can occur. Losses of methylmercury of up to 30% from wet mussels occurred on prolonged storage in a deep-freeze. Gamma-irradiation reduced the methylmercury content of the fish and shellfish only for hake (Merluccius merluccius). Further experiments should be carried out to confirm this and to investigate if this effect is species dependent. Apparent losses of methylmercury on freeze-drying of blood need to be reconfirmed on further samples.

Animals↗

Minor and trace elements in human milk from Guatemala, Hungary, Nigeria, Philippines, Sweden, and Zaire. Results from a WHO/IAEA joint project.

Concentrations of As, Ca, Cd, Cl, Co, Cr, Cu, F, Fe, Hg, I, K, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Se, Sn, V, and Zn were determined in human whole milk samples from Guatemala, Hungary, Nigeria, Philippines, Sweden, and Zaire; in most of these countries, three groups of subjects representing different socioeconomic conditions were studied. Analytical quality control was a primary consideration throughout. The analytical techniques used were atomic absorption spectrophotometry, atomic emission spectrometry with an inductively coupled plasma, colorimetry, electrochemistry, using an ion-selective electrode and neutron activation analysis. The differences between median concentrations of Ca, Cl, Mg, K, Na, and P (minor elements) were lower than 20% among the six countries. Among trace elements, concentrations observed in Filipino milk for As, Cd, Co, Cr, Cu, F, Fe, Mn, Mo, Ni, Pb, Sb, Se, and V were higher than for milk samples from other countries. The remaining five countries showed a mixed picture of high and low values. In the case of at least some elements, such as, F, I, Hg, Mn, Pb, and Se, the environment appears to play a major role in determining their concentrations in human milk. The nutritional status of the mother, as reflected by her socioeconomic status, does not appear to influence significantly the breast milk concentrations of minor and trace elements. Significant differences exist between the actual daily intakes observed in this study and current dietary recommendations made by, for example, WHO and the US National Academy of Sciences. These differences are particularly large (an order of magnitude or more!) for Cr, F, Fe, Mn, and Mo; for other elements, such as, Ca, Cu, Mg, P, and Zn, they amount to at least a factor 2. In the opinion of the present authors, these findings point to the need for a possible reassessment of the dietary requirements of young infants with respect to minor and trace elements, particularly for the elements Ca, Cr, Cu, F, Fe, Mg, Mn, Mo, P, and Zn.

Democratic Republic of the Congo↗

Uranium content of blood, urine and hair of exposed and non-exposed persons determined by radiochemical neutron activation analysis, with emphasis on quality control.

Recent reviews have highlighted the diversity (and sparsity) of data for uranium concentrations in body fluids, bone and soft tissues, and it is unclear to what extent this reflects genuine geographical or biological variations. In the present work, a very sensitive radiochemical neutron activation analysis technique (detection limit, 1-2pg g-1) was applied to an exploratory study of uranium levels in hair, urine and blood of non-exposed and occupationally exposed persons. Since quality control in much previous work has been somewhat neglected, this aspect was emphasized by the use of a wide range of suitable reference materials, by standard addition experiments, and by care in sampling and sample handling. For controls, typical levels found in hair, urine and blood were 10 ng g-1, 10 and 5 ng l-1, respectively. The urine values correspond to the lower end of the literature data, while for blood our value is about two orders of magnitude lower than the presently quoted level. In the case of occupationally exposed persons, it was found that hair shows some promise as an indicator of exposure.

Hair↗