BS ISO 23345:2021 pdf download – Jewellery and precious metals — Non destructive precious metal fineness confirmation by ED-XRF 5 Apparatus 5.1 ED-XRF, with the following specifications: — X-ray tube: adapted for precious metals analysis, minimum rating 50 kV and 40 W; — primary filter: adapted for precious metals analysis; — collimator: minimum 2 collimators, at least one <1 mm and one ≥1 mm; — camera: with magnification of the image of the measuring area; — detector: Si-PIN, SDD; — energy resolution: ≤160 eV (for Kα of Mn line), the lower eV value the better; — detectable elements: Z = 22 (Ti) to Z = 92 (U). 6 Procedure 6.1 Calibration 6.1.1 Calibration standards To calibrate the instrument for a specific alloy, calibration standards with the following features shall be used: — flat and clean surface of suitable size, with at least a diameter 5 times larger than the collimator used for measurement; — sufficiently thick (at least 0,5 mm); — homogeneous; — known exact composition; — composition of major and minor elements matching approximatively the sample to be analysed; trace elements may be ignored; a minimum of 3 standards shall be used, with the major element(s) composition covering a range up to 50 ‰. — minor elements below 5 ‰ do not need to be present in the standards but shall be declared in the calibration; they may be calibrated using the instrument maker’s calibration. EXAMPLE For the measurement of an alloy with Au = 750 ‰, the fineness of Au in the calibration standards may be 730 ‰, 750 ‰, and 770 ‰. 6.1.2 Method calibration The ED-XRF instrument (5.1) shall be specifically calibrated for each sample to be analysed. Each standard shall be analysed at least on 5 different positions. The standard deviation obtained for the measurements of each calibration standard shall not exceed 1,2 ‰ for the major element. Inter-element interference corrections should be applied. Analysis of the calibration standards, the reference material and the samples shall be performed using the same collimator size and using the same parameters (tube voltage, current, etc.). The largest possible collimator compatible with the sample target area should be used. 6.2 Verification 6.2.1 Reference material To verify the calibration, a reference material with the following features shall be used: — flat and clean surface of suitable size, with at least a diameter 5 times larger than the collimator used for...
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