X-ray or gamma ray systems or devices – Specific application – Diffraction – reflection – or scattering analysis
Reexamination Certificate
2001-07-20
2002-12-17
Porta, David P. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Diffraction, reflection, or scattering analysis
C378S046000
Reexamination Certificate
active
06496562
ABSTRACT:
The present invention relates to the discrimination and classification, by means of X-ray fluorescence analysis, of chemical substances whose X-ray fluorescence lines cannot be detected and which therefore cannot be classified by energy dispersive X-ray fluorescence analysis (EDXRFA) alone, through the packaging and without having to take a sample.
A fast check of the identity of laboratory chemicals is necessary in many situations. This is primarily true in chemical companies within the context of so-called returned material stream management. In this case, returned material stream means chemicals which are taken back after having been returned to the chemical works by end-users or wholesalers.
Under the circular economy law, every returned material stream is to be regarded as waste until a control procedure has plausibly characterized every returned material stream. Only then can the returned material stream be categorized as a product, or raw material, secondary raw material or definitively as waste.
After the chemicals have been taken back, they are correspondingly documented, inspected in terms of their composition and then re-used as secondary raw materials in production where appropriate.
Energy dispersive X-ray fluorescence analysis (EDXRFA) is a fast analysis method for qualitative and quantitative determination of elements in substances. The determination is carried out via evaluation of the X-ray fluorescence lines. The X-ray fluorescence lines of elements with atomic numbers between 21 and 92 can be detected through a PE (polyethylene) container and allocated. However, elements with atomic numbers between 1 and 20 make up a large proportion of substances. It is not possible to characterize these elements, and therefore these substances, using conventional EDXRFA evaluation (X-ray fluorescence line determination and evaluation) owing to the lack of X-ray fluorescence lines.
Information about the substance and its composition can be obtained via the coherent (Rayleigh scattering) and incoherent (Compton scattering) scattering of X-rays in the substance. Correlations between the average atomic number and the ratio between coherent and incoherent scattered radiation are known, and are described for example by H. Kunzendorf in Nuclear Instruments and methods, 99 (1972) 611-612. The matrix correction, based on inelastic scattered radiation, for X-ray fluorescence lines is used by various EDXRFA suppliers for quantative evaluation.
It is therefore an object of the present invention to characterize and discriminate from one another, without risk and without other additional analysis methods and without having to take a sample, substances whose X-ray fluorescence lines cannot be detected and which therefore cannot be classified by energy dispersive X-ray fluorescence analysis (EDXRFA) alone.
It has now been found, surprisingly, that it is also in fact possible to employ energy dispersive X-ray fluorescence analysis for classifying and identifying chemical substances with atomic numbers 1 to 20, specifically by the application of multivariate statistical methods to the measurement signals obtained for the entire Compton and Rayleigh scattering range.
Previously, these substances whose X-ray fluorescence lines cannot be detected, but which only have a Compton and Rayleigh scattering range, could not be discriminated from one another but were instead assigned together to an allocation field. If it was desired to ascertain more accurately which individual elements or substances were present, it was necessary to carry out other conventional analyses.
The invention therefore relates to a method for classifying and identifying, by means of energy dispersive X-ray fluorescence analysis, chemical substances whose X-ray fluorescence lines cannot be detected and which therefore cannot be classified by energy dispersive X-ray fluorescence analysis (EDXRFA) alone, which is characterized in that the sample to be analysed is
a) positioned in front of the measurement opening in a sample chamber in an X-ray fluorescence system, then measured, and
b) classified and identified by application of multivariate statistical methods to the measurement signals obtained, i.e. for the Compton and Rayleigh scattering range,
in its original packaging or per se without prior processing in a sample vessel.
As multivariate statistical methods, principal component analysis (PCA) is applied for detecting differences of the substances and/or regularized discriminance analysis (RDA) is applied for discriminating and classifying the substances.
As already mentioned, checking the identity of laboratory chemicals is particularly important when chemicals are taken back. As statistics show, it is primarily small packagings which are sent back in large quantities to chemical plants. Substances in small packagings are therefore often documented and analysed in small-packaging sorting systems (SSS). In the case of analysing different substance streams, each individual substance needs to be analysed in its packaging. Opening the packaging and taking a sample must not be performed in the room where the sorting system is and the analyses are carried out, because of the risk to people and the environment which should be avoided when dealing with old chemicals (Circular economy law and waste avoidance law (Krw-/AbfG) 1994 (BGBl. I, 1354); regulation No. 259/93 of the council for monitoring and control of the movement of waste in, into and out of the European Community 1993 (ABl. L 30, 1); regulation governing the introduction of the European waste catalogue (EAK regulation) 1996 (BGBl. I, 1428); regulation governing the determination of waste requiring special monitoring (BestbüAbfV) 1996 (BGBl. I 1366); regulation governing the determination of recyclable waste requiring special monitoring (BestbüAbfV) 1996 (BGBl. I 1377); second general administrative order concerning the waste law (TA Abfall) 1991 (GMBl. p. 139, corr. 496); regulation governing the protection of hazardous substances (GefStoffV) 1993 (BGBl. I 1782)). Energy dispersive X-ray fluorescence analysis (EDXRFA) has crystallized as a suitable method for analysis through unopened packaging.
The analysis is hence preferably carried out through the packaging, in which case a variety of packaging materials (glass or polyethylene packaging) may be present and need to be taken into consideration correspondingly during the allocation.
When inspecting these substances, complete identification of the substances including information about the main and subsidiary constituents is not required. Plausible allocation of the substance spectrum recorded through the packaging to the spectrum of the substance name written on the packaging label is, however, expected. This type of analysis is referred to as allocation analysis.
Substances which contain elements with an atomic number (AN)>22 (Ti) can, depending on the packaging size, be characterized through PE packaging with the aid of their element lines. The peak detection, peak parameter determination (peak position, width at half maximum and area) as well as the subsequent checking of the XRFA data against the information in the database, take place automatically. A further innovation is that these substance groups can also be discriminated substantially better using multivariate statistical methods. To that end, the X-ray fluorescence range of the element with an AN>22 and the Compton and Rayleigh scattering range are calculated using the multivariate statistical methods.
As already mentioned, however, elements with atomic numbers between 1 and 20, which do not have detectable X-ray fluorescence lines, make up a large proportion of substances. It is not possible to characterize these elements, and therefore the substance (e.g. between NaCl and NaCN or K
2
CO
3
and KF), using conventional EDXRFA evaluation owing to the lack of X-ray fluorescence lines. The XRFA measurement of such substances only provides scattered-radiation spectra which do not permit evaluation with conventional EDXRFA evaluation. These substances ha
Henrich Alexander
Hoffmann Peter
Itzel Hans-Helmut
Ortner Hugo
Gemmell Elizabeth
Merck Patentgesellschaft mit Beschrankter Haftung
Millen White Zelano & Branigan P.C.
Porta David P.
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