DE2404618A1 - X-RAY FLUORESCENCE ANALYSIS DEVICE - Google Patents

Description

United States Atomic Energy Commission, Washington, D.C. 20545, UNITED STATES.

X-ray fluorescence analyzer.

The invention relates to a source holder collimator for encapsulating radioactive material and collecting the from emanations emanating from the material.

The determination of lead levels in biological samples is of Importance, for example, determining the level of lead in the blood of children who have ingested bits of paint dangerous lead levels can be reached. These lead levels go up to 0.08 mg% or more, whereas normal levels are between 0.02 mg% to 0.04 mg%, i.e. 0.2 ppm, where 0.02 mg% = 0.2 mg Pb / 100 g blood = 0.2 ug / ml

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Various devices and methods have been used to determine these levels of lead; for example known qualitative and / or quantitative chemical laboratory tests in order to determine unknown impurities in samples. place; however, these systems are expensive and time consuming and their accuracy depends on the training of those performing the experiments People from; In addition, these experiments require extensive processing of the samples, for example a prior chemical separation of the impurities from the sample.

The present invention overcomes these disadvantages and provides, in one embodiment, an annular fluorescent x-ray system which is a shaped toroidal sample shape around a radioactive low energy source used, which is shielded from an X-ray detector in close proximity to the sample. By correct Selection of the components - as described in detail below - the desired determination is achieved.

Briefly, according to one embodiment, the invention provides 360 ° irradiation of a shaped toroidal sample around a ring array of low energy radioactive material that is encapsulated and facing the x-ray detector Is shielded by a collimator that captures the primary emissions from the radioactive material away from the detector and collimated towards the sample, the latter lying in a plane passing through the ring arrangement and the formed toroidal shape Trial runs. The detector allows the desired X-ray fluorescence analysis, since it is shielded from the primary emissions of the radioactive material, but still more efficient Way, the secondary X-ray emissions from the sample, which are collimated by 360 ° through the specimen Primary emissions are generated by the ring array of radioactive material. According to one training it is radioactive Source provided which has a ring arrangement of spheres (spheres) encapsulated radioactive material of low energy,

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to selectively excite special X-rays ia the sample, means are provided which have a semiconductor detector to detect these X-rays for X-ray fluorescence analysis ascertain.

Thus, the present invention aims to provide low energy X-ray fluorescence analysis to indicate the detection of lead in blood, according to the invention a toroidal Sample is used which is irradiated around 3 60, so that there is a fast, accurate and simple system without the prior separation of lead from the sample is required.

For the prior art, reference is made to the following US patents referenced: 3,449,575; 2,479,882; 3,316,406; 2,797,333

Further advantages, goals and details of the invention emerge from the description of exemplary embodiments on the basis of FIG Drawing; in the drawing shows:

1 shows a partial plan view of the collimator according to an embodiment the invention;

Fig. 1a shows a detail of Fig. 1;

FIG. 2 shows a partial cross section along the line II-II in FIG. 1.

The present invention provides a portable apparatus for determining low levels of metal contaminants biological samples, whereby a minimum of sample preparation is required. According to an embodiment of the invention "normal" lead levels are determined in the blood, for example up to 0.02 mg%, and in this respect the invention allows Process and a device that can be used everywhere, i.e. independently of the laboratory, in the field for the examination of blood samples are usable with respect to lead. However, lead levels higher than 0.02 mg% can be found in blood or other specimens according to this Invention for research purposes or on an automatic Basis, as can be seen from the following discussion in the

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individual results. It is clear to the person skilled in the art that the inventive System also for the detection of trace elements in any sample formed in a bead ring, such as water, air purifying filters, etc. can be used.

It is known that fluorescence is used to detect elements can be used in a sample. In short, the X-ray fluorescence analysis method is that the Identify and measure the characteristics of the X-rays emitted by the atoms of the elements in the sample, namely when generating the excited states, the excited states of the atoms with the generation of vacancies in the normally occupied electronic energy levels or shells, i.e. the M, L or K energy shells are related. After generation Such vacancies lead to the subsequent re-adjustment of the electrons to the emission of special X-rays with known energies which are characteristic of the elements, the energy required to generate the vacancies is known and voids are generated by calibrated energy radiation sources, such as electrons, Protons, alpha particles or photons of sufficient energy to remove an electron from an electron shell of the atoms. Because the electronic energy levels or levels of all elements of the sample are discrete and a finite difference between them Levels between the elements of which it has made it possible to accurately measure the energies emitted during the excitation of the sample, identify many of the elements in a variety of samples.

Of the two previously known X-ray fluorescence analysis systems the energy dispersion method has certain advantages over the wavelength dispersion method the former according to the invention is used to create a portable Detector system. The energy dispersion method is very effective in eliminating the use of Refractive crystals and collimators that have been used in connection with the wavelength dispersion process, in addition, a detector, the output of which is a function of the energy emitted therein, is adjacent to the

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sample to be analyzed can be brought. By using this method with such a detector, the entire Spectrum of the X-rays generated in the sample measured by electronically sorting the detector pulses.

Applications of the energy dispersion method described, such as industrial applications for multi-element analysis of samples containing elements down to sodium in the periodic table are given in the following reference described: New York University Institute of Environmental Medicine Report NYU-3040 by Laurer, Kniep, Wrenn, and Eisenbud. The present invention uses the above-mentioned energy dispersion X-ray fluoroessence method for detection of lead in blood, using a donut-shaped blood sample, which is 360 ° through collimated primary emissions which pass through a collimator from a ring array of encapsulated radioactive source material in the center of the toroidal sample, the sample orbiting the collimator, around the detector against primary emissions shield from source material. As will be understood in detail below, an exemplary embodiment is used According to the invention, a special arrangement with a detector such as that recently developed Semiconductor detector, where the detector outputs are a function of the energy of the secondary X-ray emissions from the Sample generated therein by the primary emissions from the source. The invention uses, in one embodiment, a specific radioactive source in a compact one Arrangement to provide a portable device for the detection of lead in a blood sample, in quantitative and quantitative terms qualitative, without the need to separate the lead from the blood beforehand.

According to a preferred embodiment - compare the drawing - the device according to the invention has a Source holder 10 which is separate from a detector 24 which - as will be described below - emitted secondary Picks up and measures X-rays.

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The holder 10 consists of a ^ disk-shaped collimator 17, by a pair of trapezoidal metal collimators 34 and 34 'which, as shown, are assembled with beveled sides 38 and common bases 36 around an annular rectangular collator channel 42 in its edge 39, with a smaller inner annular channel 40 running concentrically with the channel 42. The channel 40 is filled with the source material 12 in a ring arrangement 14, which is described below. As will be described below, the edge 39 carries the blood sample 22 longitudinally a minor axis 41 in a sample retaining ring bead to be irradiated 52. A suitable material for the annular bead 52 is a white absorbent pad which has small pores Cellulose material, which forms an absorbent medium or blotting paper. In practice it was found that none from the outside Incoming interfering fluorescence peaks are generated by the absorbent material of the container bead ring 52 holding the blood. The ring 52 is held on the outer edge 39 by the collimator 17 by means of an interference fit.

From the configuration shown, it can be seen that the sample 22 can be arranged very close to the radiation source without the collimation being disturbed by the means 34 and 34 'is effected. The collimator 17 is made of a suitable material such as nickel, whatever provides proper shielding against radiation from source material 12.

Inside the rectangular channel 42 is an annular one Beryllium exit window 50 between the radioactive source material 12 disposed between the / channel 40 and the sample holding bead ring arranged to keep the radioactive source material within the channel 40 and also to act as a filter for the desired primary radiation from the source material to the blood sample.

The detector 24 is arranged within a cryostat 51 cooled by liquid nitrogen in order to generate an output variable 26 to generate and to determine the resolution properties of the

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writing Detektoxmacerials to maintain what the professional is readily understandable. The output variable 26 is used - as explained below - to generate a spectral analysis, through which the presence of lead can be determined and measured.

The collimator 17 is directly adjacent or on the cryostat 51 placed in contact with a beryllium window 49 which allows the sample within the container 52 X-rays emitted can run unhindered in the direction of the detector 24 in the manner indicated by the arrows. It it should be noted that the ring source holding channel 40, the ring beryllium window 50 and the ring sample holding container 52 are centered on the axis of rotation 23 and are all arranged in a common plane which is parallel to the window 49 in the cryostat 51 extends so that the detector 24 is effectively equidistant from all of the above elements of the assembly is held.

A suitable radioactive source material 12 which is a annular centered core device for use in channel 14 comprises an annular array of microspheres (Microspheres) that are approximately 250 microns in diameter

238 238

sit and consist of PuO-. Pu decays through alpha particle emission with a half-life of 86 years, so that renewal of this material is not necessary during the normal life of the device. The uranium-234 derivative of this isotope emits L-X-rays of 11.6 keV, 13.5 keV, 17.0 keV and 20.2 keV in approximately 13% of its decay. These X-rays are close to the L-absorption edge of the lead, which results in a substantial increase in the absorption by lead of the X-rays. The effect of the radiation from the PuO ₂ source material is to cause the lead present in the sample to emit secondary x-rays which can be detected by detector 24 and measured.

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A blood sample to be examined for lead is carried out during operation Capillary action is drawn into a hematocrit tube and then placed drop by drop into an absorbent material, which is designed in the form of the described blood container bead ring 52 so as to hold and shape or To achieve shaping of the blood sample. The annular bead is then inserted into the collimator 17 in the manner shown in the drawing. The radiation emanating from the source 12 is collected going radially outwards through the shape described, whereby the lead in the blood sample is excited. The detector 24 generates a spectrum analysis from which the amount of lead content is removable in the blood sample. It has been found that good results are obtained with exposure times of less than 1 minute can be achieved.

For calibration purposes, a standard lead solution can be added to a sample of lead-free blood of the same type from which then an aliquot is removed and centrifuged to separate the red blood cells containing 95% of the blood lead load. Centrifugation, for example in a centrifuge, effectively concentrates the lead in the sample a factor of about two. After circulating by centrifugation, it becomes the one containing the red blood cells Part dripped onto the container formed by the annular bead 52 and the detector can be used by conventional methods standardized radioactive source material and a single-channel analyzer. The following are examples specified for the invention.

EXAMPLES

One blood sample was used to detect only the flash-x-rays emanating therefrom, while others Perform fluorescence analyzes simultaneously to detect x-rays of different elements; the invention The selection of the materials and their arrangement in the form of an annular bead ensured that the sample annular bead was irradiated in the plane of the source around 360 °, even if the source is within 1mm of the sample surface and the sample is within 1mm of the Detector entrance window was brought. The fluorescent x-ray

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Radiation did not contribute to the lead x-ray energy region at, since the toroidal configuration of the present invention minimized scattering from the source structure, while the sample fluorescence / scatter ratio was maximized. It was found that without the described arrangement one of the significant contributions to the dark bumps in the dispersion fluorescence analysis due to both coherent and incoherent scattering of the primary excitation x-rays on the structural materials and the sample itself occurs.

It has become a high resolution semiconductor X-ray detector and self-performance is used. One detector used was a lithium drift silicon Si (Li) detector. These Detector type is described in US Patents 3,381,367 and 3,278,668 and has a silicon intrinsic region and a silicon intrinsic region Lithium drift region on what is known in connection with these detectors and the alternatively usable Ge detectors, wherein the latter described in the "Brookhaveri Nat. Lab. Report BNL 16610" are. Below about 16 keV, the 3 mm thick Si (Li) detector used had about 100% efficiency, and the The established L-shells x-rays of the lead were all-■ borrowed below this energy, with the lead X-rays, for example, energies of 14.762 keV (Ly), 12.620 keV (L.,), 12.611 keV (L.), 10.549 keV (L) or 10.448 keV (L.)

• ¹ 1 2

had.

The detector was housed in a vacuum-tight container with an X-ray entrance window and was used for instruction 5/1000 inch thick beryllium window 49, which for 100% permeability of the secondary characteristic X-rays from the blood sample above 10 keV was selected. In order to maintain superior dissolution properties, was the Si (Li) detector is cooled to liquid nitrogen temperatures.

The calibration curve used for the Si (Li) detector was with a

Co-source with photon energies of 6.399 keV, 7.057 keV and

14.40 keV produced. This provided an energy calibration where

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the center of the 10.5 keV Pb L X-ray peak im Channel 270 of the analyzer appeared.

2 The following instruments were used together with a 200 mm Si (Li) Detector 24 uses:

1. Preamplifier

2. Spectroscopic amplifier

An empty sample ring bulge provided a first multichannel analyzer output and thus a lead-free dark shock count. Then, when the bulges contained lead, they became qualitative and Quantitative channel output variables generated for that in the annular bead existing lead are characteristic.

The choice of actuator size was based on the two Resolution and geometric efficiency factors. The resolution was good enough to make one, if not both, of the am Most of the L-X-rays from lead present in the blood sample, i.e. 10.5 keV and 12.6 keV, versus other X-rays from the blood sample. The detector area was as large as possible in order to obtain maximum geometric efficiency.

Since the resolution obtainable from the Si (Li) detector is reversed As a function of its size, the size chosen was one dictated primarily by the other x-rays from the blood Compromise. Table I gives the normal values with ranges of the electrolyte content of the human blood:

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TABLE I. the
component Total blood count
of the same kind
(hunt / 100 ml) component Total blood count
same kind
(ug / 100 ml) lithium 1.9 (0.9-3.0) aluminum (21-94) manganese 4.040 (3580-4500) bromine 810 (330-1730) mercury 0.385 (0.16-0.51 calcium 9,700 phosphorus
(total) 35,000 chloride 295,000 potassium 168,000 chrome 3.5 Rubidium 303 (260-345) copper 98 (72-124) silicon 830 fluorine (11-45) silver traces gold 12th sodium 200,000 iodine 9.7 (2.5-16.9) sulfur
(total) 1.928 iron (45,500-52,300) tin 13th lead 29 (18-49) zinc 880 (480-1280)

was
A large number of elements in the blood sample, all of which could more or less contribute to matrix effects in the sample, nonetheless require rubidium (approximately 300 micrograms / 100 ml), bromine (approximately 800 micrograms / 100 ml) and zinc (approximately 900 Micrograms / 100 ml) the most careful consideration with regard to their possible spectral interference with the lead tips in the output signals generated by the detector.

It has been found in practice that K ^ and K ^ of bromine at 11.9 keV and 13.4 keV and the 15.1 keV and 13.35 keV K ^ and K ₀ ^ peaks of rubidium the 14.7 keV L ^ and 12.6 keV L ^ x-rays of lead in the blood sample clasped, while the bromine (11.9 keV) and 9.6 keV K 4 x-rays of zinc surrounded the 10.5 keV L ^ x-rays of lead. Due to the small amount and the close proximity to the K / 3 X-rays of the rubidium, the L ^ X-rays of the lead were avoided and the detector analyzed the remaining K ^ (10.5 keV) and L a (12.6 keV) X-rays instead of lead, both of which are possible by about 900 eV opposite

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Interference x-rays were separated. The minimum resolution was thus 350 eV (full width of the peak at 1/2 maximum

2
Height). For this purpose, a 200 mm Si (Li) detector with guaranteed resolutions of <300 eV (full width of the tip at 1/2 maximum height) at 5.9 keV Mn K. energy was used. The actual system had a guaranteed resolution of 270 eV, full width of the tip at 1/2 maximum height, (5.9 keV), using 6.4 keV Fe K ₀ ^ X-rays at 280 eV (full width of the tip at 1/2 maximum height) has been checked. An actual system used was an Ortec Model No. 7016-16270 of Oak Ridge, Tennessee, USA.

With regard to safety considerations in the portable device In this example, the source was generally held to strengths on the order of millicurie, which, however, did the available primary output emissions to the order of

7 R
10 to 10 photons / second limited. In order to obtain an isotope source with the correct emissions for the required effective excitation of the sample, same-sized

Pu microspheres (microspheres) from FuO «with diameters of

250 microns is found useful, although larger or smaller diameter sources can be used. This sphere size has an activity per sphere according to the following table II-

TABLE II

Volume = 4/3 iTr ³ = 4.2 (1.25 χ 10 ~ ² cm) ³ = 8.15 χ 1O ~ ⁶ cm ³

Mass of Pu = 8.15 χ 10 cnT χ 7.35 gm / cirr ⁵

= 6.0 χ 10 gm Pu

²³⁸ Pu activity = 6.0 10 ~ ⁵ gm χ 17.5 Ci / gm

= 105 χ 10 ~ ⁵ Ci
or κ 1.0 mCi / 250 μ sphere PuO "

This gives an activity of 25 m Ci in a 2 mm diameter circle, which forms the minor axis of the ring arrangement of the radioactive microspheres, i.e. the encapsulated pellets.

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The sources were advantageously free from interfering radiation and had a reasonable cost. A Plutionium-238 source decays through alpha particle emission with a half-life of 86 years, while the uranium-234-derivative L X-rays of 11.6 keV, 13.5 keV, 17.0 keV and 20.2 keV in approximately 13% of its Decays emitted. The uranium L-X-rays are 2.5 χ larger

109
than those of Cd.

An actual source used was a 4 mm diameter 20 m Ci source from Amersham-Searle, the five 1 mm diameter

238

bead-shaped pellets were used, each 4 m Ci Pu sandwiched between 0.5 mm for a total activity of 20 mi Ci Contained copper washers. A source of the Mound Laboratories

ο O Q

had Pu spheres in the form of PuO ₂ from 50 microns to 400 microns in diameter, with the desired 250 micron spheres having activity per sphere as calculated above. By arranging the microspheres as shown in the drawing it is possible to obtain 25 m Ci of activity in a 2 mm diameter circle.

To the lowest possible detection limit with the one described Maintaining x-ray flux optimized the design of the ring source, holder, and collimator of this invention source-sample-detector geometry by placing the sample close to the detector to maximize detector efficiency, where at the same time minimizing the number of x-rays transmitted directly from the source to the detector, the controller and Minimizes fluorescence from structural materials around the source and maximizes the fluorescence / scattering ratio of the sample will. In addition, the annular bead-like design of the source-sample geometry according to the invention brings about a scattering for the excitation photons at the best angles to increase the energy increment between the lead x-rays and scatter interference and to reduce the number of scattered photons.

To this end, the blood sample was shaped into a bead ring shape so as to create a bead ring-shaped target that irradiates around 60 degrees became. The bead rings have an 8 mm outer diameter

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knife and a 4.2 mm inner diameter cut to the

to slide the sample lightly over the 4 mm source. The crosshairs holding the / source in place also held the annular bead in place its location around the beryllium exit window, which is provided in the collimator for the source in the collimation space is.

During manufacture, the bead ring was held on a 4.2 mm diameter shaft with a base mounting arrangement, cut from a polytetrafluoroethylene rod to which blood does not adhere. A filter paper-like toroidal one Absorbent element 0.8 mm thick was formed into an annular bulge, whereupon, after adding the blood sample, the annular bulge under a Heat lamp was dried while the shaft was stationary. Sufficient drying took place within 3 to 4 minutes, whereupon the bead was ready for fluorescence analysis and around a ring array of encapsulated radioactive pellets was arranged, which were arranged as a hollow central core close to the sample by 360 °, while the sample from the source through shielded the collimator, but was close to the detector around 360. This arrangement allows the sample to be irradiated in the source plane around 360 °, while the source is within a distance of approximately 1 mm from the surface of the Sample lay and the sample was approximately 1 mm from the Be entry window 49 of the detector cryostat 51 was arranged. The detector position within of the cryostat was set by the manufacturer to a minimum distance of 5 mm from the window entrance of a vacuum-tight Container cryostat 51 set.

In the toroidal configuration of this example, a 1 mm collimation space between the source and the sample prevented the direct transmission of the source emissions from the source to the detector, and by placing the source within the sample external structural or construction material eliminated, thereby limiting the scattering interference to the sample itself while minimizing the amount of scatter and fluorescence from the Edges of the source holder, formed by the collimator, was generated. In addition, the collimator was made of nickel, so that

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its fluorescent X-rays did not cause interference with the 10.5 keV Pb region. Because of the described by the Structure and the collimator with respect to the detector-induced direction of the source emissions, the scattering was predominant 90, so that the reduction in the number of photons scattered at this angle in the energy range of interest and the increased energy separation between the Pb fluorescence energies were exploited.

increased energy separation between the 90 ° scatter and the

It has been found that this construction thus minimizes the dark shocks due to the scattering and fluorescence of the external structural materials as the analyzer output is increased by the closest possible neighborhood from both the source-sample and sample-detector. Geometric efficiency estimates for those in this Example training used were "approximately 11% for source to sample and 10% for sample to detector with an 8 mm

Diameter loading entrance window / on the cryostat, as in the drawing shown. Due to the symmetry of the source and sample, the sample-detector efficiency can be increased by 20% with correct use can be increased by two of the detectors described.

The system sensitivity and the detection limit for the measurement of lead in blood using the described 20 m Ci Amersham-Searle source was obtained by adding known amounts standardized lead solution to measured amounts of "normal" blood. The standard lead solution used contained 1000 ppm or 1 milligram Pb / ml. One tenth of a ml of the standard solution, i.e. 100 micrograms of Pb were added to 10 ml of blood to make a 100 micrograms / 10.1 ml = 9.9 micrograms / ml = 9.9 ppm Prepare containing solution. 9 blood solutions were prepared, each containing 0.5; 1.0; 2.0; 3.3; 4.3; 5.0; 6.2; 7.4; and 9.9 ppm Contained lead.

Blood samples for counting rate determinations were prepared in annular bulges using aliquots of 75 microliters of each of the nine solutions that were dripped into the annular bead and dried.

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Ten 1-minute counts were made for each of the samples, from which the mean standard deviations were calculated, which were considered to be representative of the counting speed of these Sample to be viewed. The mean count rate of a 75 microliter aliquot of "normal" blood with none added lead, also counted ten times, was then subtracted from the 9 samples. The resulting curve was considered straight Line calculated (p = 0.994) at a slope of 29.7 cpm / ppm.

The following table III summarizes the above results:

Time
(Min.)

TABEL III (pg%) - (yig) 59 0.089 (ppm) Determination limit 42 0.063 0.59 (jig / ml) 26th 0.040 0.42 0.59 19th 0.028 0.26 0.42 15th 0.023 0.19 0.26 11 0.016 0.15 0.19 0.11 0.15 0.11

The portable device described above can maintain normal levels of lead in blood with minimal sample preparation within one determine short analysis time; This device can be used in the field for monitoring, as a research device and / or in automatic systems are used. With regard to the basic parameters of this system, i.e. background sensitivity, Detection limits and drift (baseline and gain) each of these systems is identical, while the instrumentation is different is. The monitoring system generates a yes / no decision (the power supply is not considered here) and works with only one amplifier, one single-channel analyzer and one dial-time readout device. That Research system is used for quantitative measurements and is equipped to monitor the entire energy range from approximately 2 keV to 20 keV. The latter requires an additional Multi-channel analyzer. For automatic operation is

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an automatic printer and a point marker for the Consideration of the spectrum added. In the case of automatic operation with the monitoring system, there would be overnight operation added an automatic printer scale device.

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Claims (7)

- 18 P ATENT ON SPEECH j X-ray fluorescence analysis device for the detection of lead in the blood of children with a radioactive source for irradiating a sample and for generating secondary reaction products which are determined according to the lead in the sample,
marked by a bead ring-shaped sample ring (22) around 360 irradiated by a radioactive source in the ring within the sample ring and a shield between the source and the detector for collimating the radiation from the source to the sample and away from the detector. 2. Device in particular according to claim 1, characterized by centered first core means comprising a ring arrangement radioactive material in a plane form to primary emissions from the radioactive material, disc-shaped second means having a holder with a groove around the Forming outer edge around to hold, contain and encompass the ring assembly of radioactive material, and to the primary emissions of it to the outside in the groove collimate in a direction from the center of the ring assembly away in the plane of the ring assembly, further with bead ring-shaped third means an annular container form in order to bring the biological sample into a corresponding shape, and this container on the axis of rotation of the Ring arrangement is formed around the groove, and finally fourth means form a detector, which is adjacent to the bead-ring-shaped third means and shielded from the emissions of the radioactive material is by the disc-shaped second means. 3. Apparatus according to claim 2, characterized in that the characteristic secondary emissions are X-rays given off by the atoms of the metal element due to the generation of excited states by the 409831/0901 Primary emissions, and wherein the fourth means is an x-ray fluorescence detector for the x-rays given off by the metal. 4. Apparatus according to claim 2, characterized in that the characteristic secondary emissions are X-rays that are emitted by the atoms of the metal element and indeed as a result of the generation of excited states in these by the primary emissions incident on them in the biological Sample in the third means, the fourth means distinguishing the characteristic secondary emissions, and although by energy dispersion as a measure of the amount of the element present in the biological sample, the fourth means generate an output variable as a function of the energy contained in them by the characteristic secondary emissions was deposited. 5. Apparatus according to claim 2, characterized in that the fourth means comprise a semiconductor, namely a silicon, germanium or lithium drift semiconductor detector, and wherein means are provided to provide an output proportional to the energy of the characteristic secondary emissions which are received by the detectors from the biological sample. 6. The device according to claim 2, characterized in that blood is used as a biological sample, which by Lead as a metal element is contaminated, and the fourth means on the characteristic secondary emissions of the lead respond to produce an output proportional to the amount of lead in the biological sample. 7. The device according to claim 2, characterized in that the fourth means respond to characteristic -Sekundäremissions, which are 10.5 and 12.6 keV K ^ _- X-rays to generate an output proportional to the amount of lead. 409831/0901 8. The device according to claim 2, characterized in that the fourth means have a vacuum-tight container, which is cryogenically cooled, and that a beryllium window is provided for the fourth means, and wherein the fourth means serve to select and determine the secondary emission characteristics of the lead contamination in a biological sample. 9. Apparatus according to claim 2, characterized in that the 238
■ first means Pu is to generate primary emissions in the energy range of the L absorption zone of the lead, and to characterize 7 to provide 8 static secondary emissions in the range of 10 to 10 photons per second for determining the fourth means. A 09831/0901