ISO 5889 Manganese Ores and Concentrates - Determination of Aluminium, Copper, Lead and Zinc Contents - Flame Atomic Absorption Spectrometric Method

The standard “ISO 5889 Manganese ores and concentrates - Determination of aluminium, copper, lead and zinc contents - Flame atomic absorption spectrometric method” developed by the International Organization for Standardization (ISO) describes a flame atomic absorption spectrometric method for the determination of aluminium, copper, lead and zinc contents of manganese ores and concentrates. This method is applicable to the following concentration range:

0,1 percent to 4,0 percent aluminum
0,005 percent to 1,0 percent copper
0,005 percent to 1,0 percent lead
0,005 percent to 0,25 percent zinc

It is recommended that this standard be considered together with the standard “ISO 4297 Manganese ores and concentrates - Chemical analysis methods - General instructions”. This standard contains general instructions for chemical analysis methods of manganese ores and concentrates.

This testing method is generally based on the following principles:

Decomposition of a test piece by treatment with hydrochloric and nitric acids.
Filtration of insoluble residues after evaporation.
Storage of the filtrate as mother solution.
Incineration of the filter containing the residue.
Treatment with hydrofluoric and sulfuric acids.
Fusion with fusion mix.
Dissolving solutes in hydrochloric acid
Combining the resulting solution with the mother solution.
Aspiration of the solution into the flame of an atomic absorption spectrometer using an air/acetylene burner for copper, lead and zinc and a dinitrogen oxide/acetylene burner for aluminium.
Comparison of the absorbance values obtained with the values obtained from the calibration solutions.

In addition to ordinary laboratory apparatus, the following equipment is also used in these tests:

Platinum crucible.
Atomic absorption spectrometer equipped with air/acetylene and dinitrogen oxide/acetylene burners.

The atomic absorption spectrometer used in this method is considered satisfactory if it meets the following criteria:

Minimum sensitivity: The absorbance of the highest calibration solution must be at least 0,3.
Curve linearity: The slope of the calibration curve (expressed as the change in absorbance) covering the upper 20 percent concentration range should not be less than 20 of the slope value of the lower 0,72 percent concentration range determined in the same manner.
Minimum stability: The absorbance standard deviation of the most concentrated calibration solution and the absorbance standard deviation of the zero calibration solution should be less than 1,5 percent and 0,5 percent, respectively, of the mean absorbance value of the most concentrated solution, each calculated from a sufficient number of replicate measurements.

The atomic absorption spectrometer should preferably be connected to a chart recorder or digital readout device and should be capable of measuring absorbance at wavelengths given in the standard.

The ISO 4296-1 standard is valid for sampling manganese ores. The ISO 4296-2 standard is valid for sample preparation.

For safety reasons, the manufacturer's instructions must be followed for igniting and extinguishing the dinitrogen oxide-acetylene flame to avoid possible explosion hazards. Also, tinted safety glasses should be worn when the flame is burning.

Approximately 2 g of test sample is used in the tests.

When decomposing the test piece, the test piece is transferred to a 200 ml crusher, moistened with water, dissolved in 40 ml of hydrochloric acid while heating, keeping the volume constant by adding water. After decomposition of the test piece, 2 ml of nitric acid (is added, the solution is boiled until nitrogen oxides cease to develop, then the solution is evaporated to dryness. 10 ml of hydrochloric acid is added to the dry residue and evaporated to dryness again. The salts are redissolved by heating with 10 ml of hydrochloric acid and 20 ml of hot water is added. The residue is filtered through a medium-textured filter paper containing a little filter pulp. All adhering particles are carefully removed with a glass rod with a rubber tip and the beaker is washed with water. The filter paper is washed with the residue with hot hydrochloric acid, then with hot water until the yellow color of the filter paper disappears. The filtrate (mother solution) is separated.

In preparing the test solution, the solution is transferred to a 200-ml single-mark volumetric flask, diluted to the mark with water and mixed. This solution is used for aluminum contents up to 1,50 percent, copper contents up to 0,1 percent, lead in all concentration ranges and zinc contents up to 0,025 percent. For aluminum contents over 150 percent, zinc contents over 0,025 percent and copper contents over 0,1 percent, an aliquot of this solution is transferred to a 100-ml single-mark volumetric flask, a corresponding amount of the background solution is diluted to the mark with water and mixed.

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