Ultra-low level standard for concentration measurements
First Claim
1. A reference standard material for calibrating a concentration measurement apparatus, the reference standard material comprising:
- a substrate; and
a radioactive marker element detectable by the concentration measurement apparatus for calibration thereof, the radioactive marker element being on the substrate, having a known half-life, and in an amount sufficient for reliable detection of radioactive decay products thereof.
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Abstract
Concentration measurement equipment is calibrated by performing a concentration measurement on a reference standard sample which includes a radioactive marker element. Because a count of decay products can be correlated with the number of atoms of the radioactive marker element, a precise count of decay products of the radioactive marker element is used to calculate an otherwise unknown number of atoms of the radioactive marker element on the reference standard sample. The calculated number of atoms of radioactive marker element is then used to calibrate a concentration measurement of the radioactive marker element by the concentration measurement device. Suitable radioactive marker elements for use in calibrating concentration measurement equipment include Pm-147 and Tc-99. Materials, methods and systems in accordance with the teachings of the invention are useful for calibrating concentration measurements and measurement equipment, including Total X-ray Fluorescence (TXRF) and Time Of Flight-Secondary Ion Mass Spectroscopy (TOF-SIMS) measurements and measurement equipment.
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Citations
34 Claims
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1. A reference standard material for calibrating a concentration measurement apparatus, the reference standard material comprising:
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a substrate; and a radioactive marker element detectable by the concentration measurement apparatus for calibration thereof, the radioactive marker element being on the substrate, having a known half-life, and in an amount sufficient for reliable detection of radioactive decay products thereof. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for calibrating a concentration measurement apparatus, the method comprising the steps of:
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providing a reference standard sample including a radioactive marker element having a known half-life; measuring a flux of radioactive decay products from the reference standard sample; measuring a concentration of the radioactive marker element using the concentration measurement apparatus; and calculating a calibration adjustment to the concentration measured in the concentration measuring step using the known half-life of the radioactive marker element and the radioactive decay product flux measured in the flux measuring step. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. An apparatus comprising:
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a surface concentration measurement apparatus having a detector for generating a first signal indicative of a surface concentration measurement of an amount of a radioactive marker element on a reference standard sample; and a calibration subsystem coupled to receive the first signal and to supply a calibration correction to the first signal using, in accordance with radioactive decay equations, a known half-life of the radioactive marker element and a measured radioactive decay product flux. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34)
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Specification