Determining element concentrations in samples
AssigneeOrtec Incorporated
InventorRainer Rolle
Life of this patent
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Abstract
The invention provides a method and apparatus for determining the concentration of an element such as a heavy metal in a matrix of a material such as rock by the X-ray or gamma-ray fluorescence technique. It allows the use of this technique where a sample to be analyzed has a rough or jagged surface. The effect of the rough surface is eliminated by adjusting the distance between the source and/or detector from the sample so that the rate of detection of radiation in a reference energy band is maintained constant for all samples, including reference samples used for calibration. The reference band is at least partly outside the band or bands characteristic of the element sought.
Claims26
A method of determining the concentration of an element in a sample which has a rough surface comprising the steps of:
- A. irradiating at least one calibration sample of known concentration of the element to excite rdiation from the element in a known energy band characteristic of the element and
- i. measuring such radiation to establish a relationship between the measured characteristic radiation and the concentration of the element, and
- ii. measuring under substantially the same geometrical conditions of irradiation and detection as in step A.i., the rate of emission of detected radiation in a reference energy range, said reference energy range being relatively wide compared to said characteristic band such that the ratio of the characteristic radiation to reference range radiation is small, such rate establishing a reference value for that range;
- and
- B. irradiating the rough surfaced sample to be analyzed,
- i. first measuring the rate of emission of detected radiation from that sample in said reference energy range, while varying the geometrical conditions of irradiation and detection until the measured rate of detected radiation in the reference energy range is equal to the established reference value, and
- ii. then, under the same geometrical conditions for which said measured rate of detected radiation in the reference energy range equaled said established reference value in step B.i., measuring the excited radiation of that sample in only the characteristic band, and from such measurement and the established relationship, determining the concentration of the element in that sample.
A method of determining the concentration of an element in a plurality of samples, some of which have a rough surface comprising the steps of:
- A. irradiating at least one calibration sample of known concentration of the element to excite radiation from the element in a known energy band characteristic of the element and
- i. measuring such radiation to establish a relationship between the measured characteristic radiation and the concentration of the element, and
- ii. measuring under substantially the same geometrical conditions of irradiation and detection as in step A.i., the rate of emission of detected radiation in a reference energy range, said reference energy range being relatively wide compared to said characteristic band such that the ratio of the characteristic radiation to reference range radiation is small, such rate establishing a reference value for that range;
- and
- B. irradiating a rough surfaced sample to be analyzed, and
- i. first measuring the rate of emission of detected radiation from that sample in said reference energy range, while varying the geometrical conditions of irradiation and detection until the measured rate of detected radiation in the reference energy range is equal to the established reference value, and
- ii. then, under the same geometrical conditions for which said measured rate of detected radiation in the reference energy range equaled said established reference value in step B.i., measuring the excited radiation of that sample in only the characteristic band, and from such measurement and the established relationship, determining the concentration of the element in that sample.
Dependencies are inferred from the claim text.