H. Verheul

Incorporation routes of elements into human hair; implications for hair analysis used for monitoring

A study has been made on the incorporation of some trace elements and minerals into human hair by measuring their distributions across hair diameters. For this study the Particle Induced X-ray Emission (PIXE) technique using the proton microbeam of the Vrije Universiteit of Amsterdam has been applied. Results of measurements on single hair strands at different positions in the root and outside the skin provide evidence that the elements not only can enter the cortex via the matrix but also via the hair root sheaths. Moreover, there are indications that the distribution of an endogenous element is not always homogeneously spread over a cross section of the hair. Endogenous Fe and Pb seem to be peaked on the periphery of the hair by natural means, while the elements S,Zn and Cu of the samples measured are found to be distributed homogeneously across the hair diameter. The consequences for hair analysis in use for monitoring the trace elements status of an individual are discussed.

Experimental comparison of synchrotron radiation with other modes of excitation of X rays for trace element analysis

Abstract Monochromated synchrotron radiation (SXRF), 17.5 keV photons from an X-ray tube (XRF) with Mo anode and 3 MeV protons (PIXE) were used to excite X-ray spectra from thin samples of standard reference materials. Relative detection limits derived from these X-ray spectra were calculated to compare the different excitation modes. XRF shows the highest detection limits, while protons and synchrotron radiation monochromated to 16.5 keV are comparable. Much lower detection limits (down to 0.1 ppm) are experimentally shown with synchrotron radiation monochromated to 9.1 keV. Results are in agreement with theoretical predictions. The advantage of the polarization of the synchrotron radiation has been discussed theoretically and shown experimentally.

On the incorporation of trace elements into human hair measured with micro-PIXE

Abstract A study has been made on the incorporation of trace elements into human hair by measuring concentration distributions across hair diameters of selected samples using the Amsterdam proton microbeam. Because hair is considered as a recording filament, reflecting metabolic changes over a period of time, a hair of a young mother was plucked 4 months after delivery of her first child. No change in the Zn and Cu concentrations correlated with the period of gestation was observed. A strong increase of Ca in the distal end must be attributed to outside contamination. From a study of a hair root, including the root sheaths, it is found that the method of incorporation of sulfur (minor element) differs strikingly from the behaviour of the trace elements Zn, Cu, Fe and Ca. The Zn and Cu distributions provide evidence of a, not yet reported, transversal transcellular input route, in which the root sheaths play an important role. From the results it is deduced that Zn and Cu seem to be distributed homogeneously by nature, while Fe, present at a high level in the root sheaths, seems to be peaked by nature on the periphery. The results are discussed against the background of the range of values of concentrations of certain elements found in the literature.

A proton microbeam under construction

Abstract A proton microbeam is presently being assembled in our laboratory. A description of the various components and systems will be given, such as slit systems, magnetic lenses and the target chamber, including detectors, microscope and target scanning intruments. The figure of 2 μm is a critical lower limit in every respect. It represents both the accuracy of the positioning of the target and the resolving power of the microscope. It is therefore also a practical lower limit to the useful beam spot size.

Elemental trace analysis in serum using proton-induced X-ray flourescence

Abstract In order to perform a study of changes in concentrations of trace elements into the sera of nephritic patients, PIXE is applied to this type of samples. For six elements calibration curves are measured using distilled water solutions and also using the technique of standard addition to show the influence of matrix effects. To calculate these matrix effects a computer code is developed. A comparison is made between results obtained with protons, deuterons and alpha-particles of 2.5, 5.0 and 10.0 MeV respectively. In most samples more than ten elements are quantitatively determined. For two elements the results are compared with results of other analytical techniques such as atomic absorption sctroscopy.

The influence of matrix effects on absolute analysis using pixe

Abstract Theoretical calculations have been made to correct measured K X-ray intensities for the following matrix effects: slowing down of the protons, absorption of characteristic X-rays in the target, electron induced X-ray emission and X-ray induced X-ray emission. Typical examples of results of the calculations are given.

On the proton microbeam of the Vrije universiteit, Amsterdam, and its applications

Abstract The proton microbeam set-up at Amsterdam has been in operation since January 1981. The main features of the equipment are presented as well as the results of beam profile measurements. The performance of the set-up will be illustrated by means of preliminary results of measurements on hair and arteries.

Fluorine determination in hamster tooth germs

The delayed 52+ → 12+ nuclear transition of fluorine (Eγ = 197 keV, t12 = 87 ns) emitted after the 19F(p,p′ γ)19F reaction, has been used to measure the influence of fluoride administration on tooth development in vivo. The method used has the advantage of an improved peak to background ratio for the detection of fluorine if measurements are performed anticoincident with the cyclotron burst. Besides the registration of fluoride distributions, also bulk elements like P and Ca have been measured to correlate the detected fluorine distributions with some specific morphological structures in hamster tooth germs.

Determination of carbon contents in the iron meteorites Toluca and Algarrobo

Abstract The nuclear microprobe at the cyclotron of the Vrije Universiteit in Amsterdam, The Netherlands, was employed for a study of the iron meteorites Toluca and Algarrobo. Samples were irradiated with ~ 0.4 nA of 1.4 MeV deuterons. Carbon was detected by measuring the proton spectrum of the 12 C(d, p) 13 C nuclear reaction. The X-ray spectrum of Fe and Ni was measured simultaneously. Area scans of squares approximately 1 × 1 mm 2 were made with beam size approximately 20 × 20 μm 2 . Spots chosen for the analysis contained areas of taenite, plessite and martensite surrounded by kamacite. Our area scans show clearly that regions of martensite are more C-rich than those of plessite and taenite with lowest C intensity in kamacite. At this point it is still impossible to determine the C-concentrations absolutely with good precision due to possible C-contamination during the target preparation and/or the C-deposition on the irradiated spot during the measurement. However, minimal concentrations of carbon in plessitic and martensitic areas were calculated assuming that all the C counts in kamacite areas come from contamination and using a Fe-C standard with 0.8% C. Further improvements of the technique are planned, including measuring immediately after polishing samples with Al 2 O 3 , as well as employing a cold trap inside of the irradiation chamber to reduce carbon deposition during measurement.

A new way of assignment of concentrations in pixe analysis

Abstract A new method of assignment of element concentrations in trace-element analysis is proposed. The concentrations in thin samples ( t 2 ) are determined by measuring the characteristic X-ray yield and the sample-mass derived from the energy-loss of the beam while passing a thin target. It is shown that the energy-loss is accurately determined by the γ-yield of the 1013 keV γ-radiation of the 27 Al(p, p′γ) 27 Al reaction induced by a 3.0 MeV proton-beam in an Al-beam stop behind the target. This feature has been confirmed experimentally with targets of various thicknesses using a 3.0 MeV proton beam of mm 2 dimensions. First results of the use of a proton microbeam are presented and discussed.