© ISO 2012 Workplace air — Determination of metals and metalloids in airborne particulate matter by inductively coupled plasma atomic emission spectrometry — Part 2 Sample preparation Air des lieux de[.]
Soluble metal and metalloid compounds
To obtain results for comparing soluble metal or metalloid compounds with limit values, utilize the sample dissolution method outlined in Annex B Prepare test solutions for analysis according to the procedure specified in ISO 15202-3.
If it is confirmed that no insoluble compounds of the relevant metals or metalloids are present in the workplace or produced during processes, prepare test solutions for analysis according to ISO 15202-3 Utilize one of the sample dissolution methods for total metals and metalloids outlined in Annexes C through H, and compare the results with the limit values for the soluble metals or metalloids in question.
The methods outlined in Annexes C through H are not exclusively designed for soluble metal or metalloid compounds Nevertheless, they can serve as an alternative to the method in Annex B under the specified circumstances, particularly if this option is more convenient.
Total metals and metalloids and their compounds
To compare results with limit values for total metals, metalloids, or their compounds, it is essential to choose an appropriate sample dissolution method from Annexes C to H Consider the suitability of each method for dissolving the specific metals and metalloids present in the test atmosphere, as well as the availability of necessary laboratory equipment.
9.2.2 Use the selected sample dissolution method to prepare test solutions for analysis of total metals and metalloids and their compounds by the method specified in ISO 15202-3.
Mixed exposure
— for comparison with limit values for soluble metal and/or metalloid compounds and with limit values for metals and/or metalloids and their insoluble compounds, or
For comparing soluble metal and metalloid compounds with the limit values for total metals and metalloids and their compounds, refer to the guidelines outlined in sections 9.3.2 and 9.3.3.
9.3.2 Use the sample dissolution method specified in Annex B to prepare test solutions for the determination of soluble metal and metalloid compounds by the method specified in ISO 15202-3.
To determine total metals, metalloids, and their compounds, select an appropriate sample dissolution method as outlined in section 9.2 This method should be applied to treat any undissolved material from the soluble metal and metalloid compounds process (refer to B.6.6.1) and prepare test solutions for analyzing metals, metalloids, and their insoluble compounds according to ISO 15202-3.
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Action to be taken if there is doubt about the effectiveness of the selected sample
When there is uncertainty about the effectiveness of a selected sample dissolution method for achieving the required analytical recovery of metals and metalloids from materials in the test atmosphere, it is essential to assess its suitability for that specific application This can be done by analyzing a bulk sample of known composition that closely resembles the materials present in the workplace, such as a certified reference material For soluble metals and metalloids, the best approach to determine analytical recovery is to analyze filters that have been spiked with a solution containing a known mass of the soluble compound of interest.
When designing an experiment to assess the effectiveness of a sample dissolution method, it is crucial to consider that the particle size of the bulk sample can significantly impact dissolution efficiency Additionally, microgram quantities of relatively insoluble materials tend to dissolve more readily than milligram quantities.
If the analytical recovery falls below the minimum acceptable threshold of 90% with a coefficient of variation under 5%, as outlined in EN 13890, it is essential to explore alternative sample dissolution methods These methods may not be detailed in ISO 15202, provided that their analytical recovery can be shown to comply with EN 13890 standards.
10.1.3 Do not use a correction factor to compensate for an apparently ineffective sample dissolution method, since this might equally lead to erroneous results.
Action to be taken when particles have become dislodged from the filter durin g transportation 7
When opening filter transport cassettes or samplers, it is important to check for any dislodged particles that may have occurred during transportation If such evidence is found, wash the internal surfaces of the cassette or sampler in the sample dissolution vessel to recover the material Prior to analysis, notify the sample originator about the condition of the sample upon receipt, allowing them to decide whether it should be analyzed.
Action to be taken regarding sampler wall deposits
Before opening filter transport cassettes or samplers, it is essential to recognize that particles may have settled on the interior walls during the sampling process Consideration should be given to the necessary actions to ensure these particles are included in the sample For more details, refer to Annex J.
11.1 Record details of all reagent sources (lot numbers) used for sample preparation.
When documenting laboratory procedures, it is essential to record specific details of the apparatus used for sample preparation This includes noting the serial numbers of equipment, especially when multiple items of the same type are present in the lab.
11.3 Record any deviations from the specified methods.
11.4 Record any unusual events or observations during sample preparation.
normative) Action to be taken when there is visible, undissolved, particulate material after
Safety precautions to be observed when using hydrofluoric and perchloric acids
A.1 Special precautions to be observed when using hydrofluoric acid
A.1.1 Take extreme care when using hydrofluoric acid Ensure that the nature and seriousness of hydrofluoric acid burns is understood before commencing work with this substance.
Hydrofluoric acid exposure may not cause an immediate burning sensation, which can take several hours to manifest Even dilute solutions of hydrofluoric acid can be absorbed through the skin, leading to serious effects comparable to those from concentrated acid exposure.
When using hydrofluoric acid, it is recommended that a pair of disposable gloves is worn underneath suitable rubber gloves to provide added protection for the hands.
Always carry hydrofluoric acid burn cream containing calcium gluconate when working with hydrofluoric acid and for 24 hours afterward In the event of skin contamination, wash the area thoroughly with water and apply the cream Seek immediate medical attention if an accident occurs Remember that calcium gluconate cream has a limited shelf life and should be replaced before its expiration date.
A.2 Special precautions to be observed when using perchloric acid
Perchloric acid can create explosive compounds when it interacts with organic materials and various metal salts To safely dissolve samples using this acid, it is crucial to eliminate any organic substances beforehand, which can be achieved by heating them with nitric acid prior to the addition of perchloric acid.
A.2.2 Do not allow perchloric acid solutions containing high concentrations of metal salts to boil dry, as solid perchlorates are shock-sensitive and can explode.
When conducting sample dissolution with perchloric acid, it is essential to use a specialized fume cupboard equipped with a scrubbing system This setup effectively removes acid vapors from exhaust gases, thereby minimizing the risk of potentially explosive materials accumulating in the ducts.
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Sample dissolution method for soluble metal and metalloid compounds
B.1.1 This annex specifies a method for the dissolution of soluble metal and metalloid compounds using a suitable leach solution.
B.1.2 The method is applicable in all instances, except when use of a specific leach solution or leach conditions, or both, is prescribed in National Standards or Regulations.
Metals with established limit values for soluble compounds, as referenced in sources [15] and [16], are detailed below, along with the applicable sample dissolution method specified in this annex.
Aluminium Molybdenum Platinum Silver Tungsten
Barium Nickel Rhodium Thallium Uranium
NOTE 1 The above list is based upon the applicability of the sample dissolution procedure reported in References [18],
[19] and [20], with adaptation based on expert judgement Furthermore, the list is not comprehensive and the procedure will be effective for some metals and metalloids that are not listed.
The dissolution method outlined in this annex is applicable for soluble zinc compounds, such as determining zinc chloride levels in the presence of zinc oxide found in galvanizing fume.
B.2 Effectiveness of the sample dissolution method
Soluble compounds of metals and metalloids are defined by the specific leach solutions and conditions used in their measurement methods Solubility, except for very soluble or insoluble compounds, can vary based on factors such as the leach solution, particle size, solute/solvent ratio, pH, and temperature Therefore, the sample dissolution method is crucial for obtaining accurate results.
The sample dissolution method for soluble compounds outlined in ISO 15202 can yield inaccurate results if the soluble compound interacts with the filter material or contaminants, leading to the formation of insoluble compounds For instance, soluble silver compounds may show low recovery rates when filtered through chloride-contaminated filters Therefore, it is crucial to consider chemical compatibility when selecting filters for soluble compound samples, as detailed in ISO 15202-1 If potential compatibility issues are suspected, it is advisable to conduct tests to ensure satisfactory analytical recovery prior to sample collection Additionally, exposure to light can also result in low recoveries for soluble silver compounds.
B.3.1 Soluble metal and metalloid compounds are dissolved by treating the filter and collected sample with a suitable leach solution and agitating in a water bath at 37 °C ± 2 °C for 60 min.
B.3.2 The resultant sample solution is filtered through a membrane filter to remove undissolved particulate material and to produce a test solution for analysis using the method specified in ISO 15202-3.
B.4.2 Nitric acid (HNO3), concentrated, as specified in 7.2.
Usual laboratory apparatus and in particular the following.
B.5.1 Disposable gloves, as specified in 8.1.
B.5.2.1 Beakers, 50 ml capacity, of a form that is compatible with filters of the diameter used in the sampler, for preparation of test solutions.
NOTE Beakers are not required if the leach step is carried out in the sampler (see Note 2 in B.6.2.2).
For optimal results in sample dissolution methods outlined in ISO 15202, it is advisable to dedicate a set of beakers specifically for this purpose Beakers that are heavily contaminated may not be adequately cleaned using the method described in section 8.2 Therefore, if these beakers are to be utilized, it is highly recommended to clean them under the test conditions prior to use by incorporating the necessary reagents and following the specified sample dissolution procedure.
B.5.2.2 One-mark volumetric flasks, 10 ml capacity for preparation of test solutions.
10 ml volumetric flasks are unnecessary when preparing test solutions in graduated test tubes or when using a syringe filter to remove undissolved material.
B.5.3 Disposable test tubes, polypropylene, graduated, 10 ml capacity, with push-fit closures and preferably compatible with the auto sampler tube racks of the ICP-AES instrument.
NOTE Test tubes without graduation are satisfactory if the samples are made up in volumetric flasks (see B.6.3.4).
B.5.5 Piston operated volumetric apparatus, as specified in 8.4, for dispensing leach solution (see B.6.2.2, B.6.3.2, B.6.3.3, B.6.4.1 and B.6.4.2).
B.5.6 Water bath, with temperature control, and preferably equipped with integral sample shaker.
For optimal mixing in a water bath without an integral sample shaker, a waterproof magnetic stirrer can be positioned at the bottom This setup allows for effective stirring of sample solutions using polypropylene-encapsulated magnetic followers.
NOTE Suction filtration equipment is not required if disposable syringe filters are used to remove undissolved particulate from the sample solutions (see B.6.4).
B.5.7.1 Suction filtration apparatus, typically a water-operated or electrically driven vacuum pump, connected to a conical flask fitted with a filter funnel/support assembly (see Figure B.1).
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NOTE Alternative suction filtration apparatus is commercially available that permits simultaneous vacuum filtration of multiple sample solutions.
B.5.7.2 Membrane filters, of a diameter suitable for use with the suction filtration apparatus (B.5.7.1).
When selecting membrane filters, it is crucial to consider potential reactions between the analyte and the filter material or any contaminants present Additionally, it is important to choose filters that are preferably soluble in the sample preparation methods used for determining total metals and metalloids.
B.5.8.1 Syringes, disposable, polypropylene, 5 ml capacity, suitable for use with disposable syringe filters (B.5.8.2).
NOTE Disposable syringes are not required if suction filtration equipment is used to remove undissolved particulate from the sample solutions (see B.6.3).
B.5.8.2 Syringe filters, disposable, polypropylene, incorporating a suitable membrane filter (e.g polypropylene) with a pore size of 0,8 àm or less, for use with disposable syringes (B.5.8.1).
NOTE Disposable syringe filters are not required if suction filtration equipment is used to remove undissolved particulate from the sample solutions (see B.6.3).
B.6.1.1 Except when national standards or regulations specify otherwise, use water (B.4.1) to leach the sample filter.
When measuring the soluble compounds of a specific metal or metalloid, it is essential to adhere to the instructions outlined in national standards or regulations These guidelines may specify particular leach solutions or leach conditions that must be utilized.
NOTE It is advisable to wear disposable gloves (B.5.1) during sample preparation, for personal protection and in order to avoid the possibility of contamination from the hands.
Example of a suction filtration apparatus
To begin, open the filter transport cassettes, sampler filter cassettes, or samplers, and carefully transfer each filter into a labeled 50 ml beaker using clean flat-tipped forceps Ensure to follow the same procedure for the blank filters.
NOTE If the leach is carried out in the sampler (see Note 2 in B.6.2.2), there is no need to remove the filter.
Accurately pipette 5 ml of leach solution into each beaker If the sampler type allows airborne particles to adhere to the internal surfaces, use the leach solution to carefully wash any particulate material into the beaker.
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