BS ISO 4443-2022 pdf free download .Cryolite primarily used for the production of aluminium — Determination of elements — Wavelength-dispersive X-ray fluorescence spectrometric method using pressed powder tablets
6 Apparatus
6.1 Wavelength-dispersive X-ray fluorescence spectrometer (XRF), with vacuum path and equipped with crystals required as shown in Table 1.
6.2 Vibratory disc mill, with tray, ring and puck made of non-contaminating material. Tungstencarbide and chrome steel have been found to be satisfactory.
6.3 Tablet press, capable of providing 340 kN for 20 s.
6.4 Balance, with precision ±0,01 g.
6.5 Flat spatula.
7 Test procedure
7.1 Test specimen preparation
See ISO 1619 for guidance.
7.2 Test tablet preparation
7.2.1 Dry the sample to constant mass at (110 ± 2) °C. A typical drying time is 2 h.
7.2.2 Weigh 10,0 g of sample and put it into the mill. Then add 10 drops of acetone or ethyl alcohol and vibrate for 60 s to make the particle size below 45 μm fineness.
7.2.3 Transfer 2,0 g of milled sample to the tablet press, use boric acid backing to prepare the pressed tablet with a pressure of 340 kN and hold for 20 s. Tablet thickness should be a minimum of 4 mm, with a diameter of 40 mm.
7.2.4 Remove the tablets from the tablet press. Touch the edge of the tablets only during measurement.
Trim the edges. Avoid polluting the surface during X-ray measurement.
Always use the same mass and proportion of sample and reagents as for the calibration reference materials.
Results are particle-size dependent. Short milling times give larger spread in intralaboratory precision.
The particle size should be determined by using a suitable sieving technique. Erroneous data will be collected if analytical samples contain particles varying significantly in size that cause different beam penetration depth and a different surface roughness from those in the calibration reference samples.
The surface of the pressed powder tablet should be smooth and firm and should not drop out power after trimming. The measuring surface should not be mixed with boric acid.
7.3 X-ray fluorescence spectrometer application
7.3.1 Instrumental conditions
Follow the control setting and operation instructions of the spectrometer manufacturer, including monitoring and calibrating angles and monitoring and correcting for X-ray tube intensity.
Suggested conditions of measurement are given in Table 1. All measurements shall be made under vacuum. The Kα analytical lines are preferred. Use spectral lines overlap correction if required. Correct for background, using the lines recommended in Table 1.
7.3.2 Calibration and calibration reference materials The calibration reference materials are not specified in this method. The user of this document shall obtain suitable calibration reference materials, such as the China National Set GSB 04-2016-2006 series GFC01 to GFC06 for F, Al, Na, SiO 2 , Fe 2 O 3 , SO 4 , P 2 O 5 , CaO. 1) The X-ray fluorescence spectrometer application software is used to make a cryolite application on the XRF instrument and the set of calibration reference materials are analysed. Elemental concentrations in the calibration samples shall bracket the values expected in the analytical samples.
The number of calibration reference materials shall be six or more for each element. If six are not available, the number used shall be included in the test report.
Calibration is performed using the XRF instrument control software for application development and is not detailed in this document. If necessary, the instrument manufacturer should be consulted for recommendations on optimal tube anodes, crystal options and any concentration limit restrictions.
7.3.3 Verification of the calibration Reference sample tablets can be used daily for checking the instrument condition. Limits for acceptable deviation shall be established by the laboratory; if the deviation is unacceptable, the instrument shall be reviewed and, if necessary, recalibrated.
7.4 Monitoring of the sample for correction of instrumental drift Instrumental drift correction shall be performed regularly in accordance with the instrument manufacturer’s instructions to ensure that measured intensities are corrected for any spectrometer drift. If monitor samples are measured infrequently, then each batch of analysed samples shall be drift corrected.
7.5 Analyses, calculation and expression of results
The analysis shall be run on three tablets made from the same test portion. The triplicate measurements are averaged to give the concentration to be used in the test report.However, for any element, if any two results differ by more than twice the intralaboratory repeatability for that element as shown in Table 2, the analysis should be repeated.
8 Precision
8.1 General
The precision given in Table 2 was computed using ASTM E691. For details of the computation of the precision see References [3] and [4]. Annex B provides an example of how to use Table 2.BS ISO 4443 pdf download