BS ISO 13546:2021 pdf download – Copper concentrates — Determination of mercury content — Cold vapour atomic absorption spectrometric method
5.13 Hydroxylamine hydrochloride solution, 20 g/l. Add 2 g of hydroxylamine hydrochloride (5.3) to 100 ml of deionized water.
5.14 Mercury trapping solution. Add 10 g of potassium permanganate (5.2) to 100 ml of water and mix well. This reagent is used to oxidize mercury vapour to its Hg 2+ state and trap it in solution.
5.15 Nitric acid solution, diluted (1+9).
5.16 Mercury standard solution A, 100 µg/ml. Weigh 0,1354 g of mercury (II) chloride (5.4) into a 250 ml beaker and dissolve in 100 ml of nitric acid (5.5). Quantitatively transfer to a 1-l volumetric flask with water. Mix and store in a labelled glass container. Alternatively, use a suitable high-quality commercial standard solution.
5.17 Mercury standard solution B, 10 µg/ml. Pipette 10 ml of mercury standard solution A (5.16) into a 100-ml volumetric flask containing 10 ml nitric acid (5.5). Dilute to volume with water. Mix and store in a labelled volumetric flask. Prepare the solution monthly.
5.18 Mercury standard solution C, 0,1 µg/ml. Pipette 10 ml of mercury standard solution B (5.17) into a 1-l volumetric flask containing 100 ml of nitric acid (5.5). Dilute to volume with water. Mix and store in a labelled volumetric flask. The solution should be freshly prepared. 6 Apparatus All laboratory glassware and equipment shall be free of mercury contamination. Use ordinary laboratory apparatus, including pipettes and volumetric flasks conforming with the specifications of ISO 648 and ISO 1042, respectively, and the following:
6.1 Analytical balance, sensitive to 0,1 mg.
6.2 Magnetic stirrers.
6.3 Laboratory glassware, of class A conforming with ISO 385, ISO 648, ISO 1042 and used in accordance with ISO 4787.
6.4 Atomic absorption spectrometer, equipped with a mercury hollow cathode lamp or electrodeless discharge lamp or a continuum radiation source. WARNING — Follow the manufacturer’s instructions to avoid possible explosion hazards when igniting and extinguishing the air-acetylene flame and possible burning from the hot electric furnace. Wear tinted safety glasses whenever the atomic absorption spectrometer is in operation. Good ventilation is necessary to prevent poisoning by mercury hydride. The atomic absorption spectrometer used in this method shall meet the following criteria:
a) Minimum sensitivity: the absorbance of the highest concentration calibration solution (see 8.7) is at least 0,5 µg/ml. b) Graph linearity: the slope of the calibration graph covering the top 20 % of the concentration range (expressed as a change in absorbance) is not less than 0,7 of the value of the slope for the bottom 20 % of the concentration range determined in the same way.
c) Minimum stability: the standard deviation of the absorbance of the most concentrated calibration solution and that of the zero-calibration solution, each being calculated from a sufficient number of repetitive measurements, are less than 1,5 % and 0,5 %, respectively, of the mean value of the absorbance of the most concentrated solution.
The use of a strip-chart recorder, digital readout device or both is recommended to evaluate criteria a), b) and c) and for all subsequent measurements.
Parameters will vary with each instrument.
6.5 Stopwatch.
6.6 Hotplate.
7 Sampling and sampling preparation
7.1 Test sample
Prepare an air-equilibrated test sample and a hygroscopic moisture test sample in accordance with ISO 9599.
Mercury can evaporate from samples at elevated temperatures, so a separate chemical analysis sample shall be prepared as described in ISO 12743:2021, 16.2.
7.2 Test portion
Taking multiple increments, extract the test portion from the test sample as specified in Table 1 and weigh to the nearest 0,1 mg. At the same time as the test portions are being weighed for analysis, weigh test portions for the determination of hygroscopic moisture in accordance with ISO 9599.
8 Procedure
8.1 Number of determinations
Carry out the determinations at least in duplicate in accordance with Annex A, independently, on each test sample.
NOTE The expression “independently” means that the second and any subsequent result is not affected by previous results. For this particular analytical method, this condition implies that the repetition of the procedure is carried out either by the same operator at a different time or by a different operator including, in either case, appropriate recalibration.
8.2 Blank test Carry out a blank test in parallel with the analysis using the same quantities of all reagents but omitting the test portion. The purpose of the blank test in this method is to check the quality of reagents. If a significant value is obtained as a result of the blank test, check all reagents and repeat the analysis.