Microsoft Word C038497e doc Reference number ISO 15202 3 2004(E) © ISO 2004 INTERNATIONAL STANDARD ISO 15202 3 First edition 2004 11 15 Workplace air — Determination of metals and metalloids in airbor[.]
General definitions
A chemical agent refers to any chemical element or compound, whether occurring naturally or produced through work activities This includes substances that may not be intentionally created or marketed.
3.1.2 measuring procedure procedure for sampling and analysing one or more chemical agents in the air and including storage and transportation of the sample
TWA concentration concentration of a chemical agent in the atmosphere, averaged over the reference period
NOTE A more detailed discussion of TWA concentrations has been published by the American Conference of Government Industrial Hygienists [3]
3.1.4 limit value reference figure for concentration of a chemical agent in air
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NOTE An example is the Threshold Limit Value (TLV) for a given substance in workplace air, as established by the ACGIH [3]
3.1.5 reference period specified period of time stated for the limit value of a specific chemical agent
NOTE Examples of limit values for different reference periods are short-term and long-term exposure limits, such as those established by the ACGIH [3]
3.1.6 workplace defined area or areas in which the work activities are carried out
Analytical definitions
3.2.1 blank solution solution prepared by taking a reagent blank, laboratory blank or field blank through the same procedure used for sample dissolution
A blank solution may require additional processing, such as the incorporation of an internal standard, if the sample solutions undergo similar procedures to create test solutions suitable for analysis.
A calibration blank solution is prepared without adding any stock or working standard solution, resulting in an analyte concentration of zero.
Calibration solutions are prepared by diluting stock or working standard solutions, ensuring that the analyte concentrations are appropriate for calibrating the analytical instrument.
NOTE The technique of matrix-matching is normally used when preparing calibration solutions
A field blank filter undergoes the same handling procedure as a sample, but it is not used for actual sampling Instead, it is loaded into a sampler, transported to the sampling site, and then returned to the laboratory for analysis.
3.2.5 laboratory blank unused filter, taken from the same batch used for sampling, that does not leave the laboratory
3.2.6 linear dynamic range range of concentrations over which the calibration curve for an analyte is linear
NOTE The linear dynamic range extends from the detection limit to the onset of calibration curvature
3.2.7 reagent blank solution containing all reagents used in sample dissolution, in the same quantities used for preparation of laboratory blank, field blank and sample solutions
3.2.8 sample dissolution process of obtaining a solution containing all analytes of interest present in a sample, which might or might not involve complete dissolution of the sample
3.2.9 sample preparation all operations carried out on a sample after transportation and storage to prepare it for analysis, including transformation of the sample into a measurable state, where necessary
3.2.10 sample solution solution prepared from a sample by the process of sample dissolution
A sample solution may require additional procedures, such as dilution or the incorporation of an internal standard, to prepare a test solution suitable for analysis.
3.2.11 stock standard solution solution used for preparation of working standard solutions and/or calibration solutions, containing the analyte(s) of interest at a certified concentration(s) traceable to national standards
3.2.12 test solution blank solution or sample solution that has been subjected to all operations required to bring it into a state in which it is ready for analysis
NOTE 1 “Ready for analysis” includes dilution and/or the addition of an internal standard
The blank test solution serves as the reference solution, while the sample test solution is the analyzed sample, provided that neither solution undergoes any additional processing prior to analysis.
A working standard solution is created by diluting stock standard solutions to achieve analyte concentrations that are more appropriate for preparing calibration solutions than those found in the original stock solutions.
ICP-AES definitions
3.3.1 axial plasma end-on plasma plasma that is viewed end-on by the optical detection system
3.3.2 background correction process of correcting the intensity at an analytical wavelength for the intensity due to the underlying spectral background
3.3.3 background equivalent concentration concentration of an analyte that results in an emission signal of an intensity equivalent to the background emission signal at the analytical wavelength
3.3.4 corrosion-resistant sample introduction system sample introduction system that features a nebulizer, spray chamber and torch injector tube that are resistant to corrosion by hydrofluoric acid
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Excitation interference occurs when the sensitivity of a measurement changes due to variations in plasma conditions, particularly when a calibration or test solution matrix is introduced into the plasma.
ICP torch device used to support and introduce sample into an ICP discharge
NOTE An ICP torch usually consists of three concentric tubes, the outer two usually made from quartz
ICP high-temperature discharge generated in flowing argon by an alternating magnetic field induced by a radio- frequency (RF) load coil that surrounds the tube carrying the gas
3.3.8 injector injector tube centre tube innermost tube of an ICP torch, through which the sample aerosol is introduced to the plasma
NOTE The injector is usually made of quartz or ceramic material
The inner argon flow in a nebulizer is crucial as it directs the flow of argon gas, which carries the sample aerosol through the injector and into the plasma.
NOTE The inner argon gas flow rate is typically 0,5 l⋅min −1 to 2,0 l⋅min −1
Inter-element correction is a spectral interference correction technique that involves subtracting the emission contributions from interfering elements, which emit at the same wavelength as the analyte This process is carried out after measuring the concentrations of the interfering elements at different wavelengths, ensuring accurate analysis of the analyte's emission.
3.3.11 intermediate argon flow auxiliary argon flow flow of argon gas that is contained between the intermediate and centre (injector) tubes of an ICP torch
NOTE The intermediate argon gas flow rate is typically 0 l⋅min −1 to 2,0 l⋅min −1
3.3.12 internal standard reference element non-analyte element, present in all solutions analysed, the signal from which is used to correct for matrix interferences or improve analytical precision
3.3.13 internal standardization reference element technique technique that uses the signal from an internal standard to correct for matrix interferences
The load coil is a length of tubing wound around the end of an ICP torch, which connects to the radio-frequency (RF) generator This component is essential for inductively coupling energy from the RF generator to the plasma discharge.
3.3.15 matrix interference matrix effect non-spectral interference interference of a non-spectral nature caused by a difference between the matrix of the calibration and test solutions
The matrix-matching technique is employed to reduce the impact of matrix interferences on analytical results This method involves preparing calibration solutions that align the concentrations of acids and other significant solutes with those found in the test solutions.
3.3.17 nebulizer device used to create an aerosol from a liquid
3.3.18 outer argon flow plasma argon flow coolant argon flow flow of argon gas that is contained between the outer and intermediate tubes of an ICP torch
NOTE The outer argon flow is typically 7 l⋅min −1 to 15 l⋅min −1
3.3.19 pneumatic nebulizer nebulizer that uses high-speed gas flows to create an aerosol from a liquid
3.3.20 radial plasma plasma that is viewed from the side by the optical detection system
The spray chamber device, positioned between a nebulizer and an ICP torch, is designed to filter aerosol droplets by size, allowing only the finest droplets to enter the plasma while larger droplets are either drained or pumped away as waste.
3.3.22 spectral interference interference caused by the emission from a species other than the analyte of interest
Transport interference occurs due to variations in viscosity, surface tension, or density between calibration and test solutions This discrepancy leads to changes in nebulizer efficiency, ultimately affecting the amount of analyte that reaches the plasma.
NOTE A transport interference can be due to a difference in dissolved solids, type and concentration of acid, etc., between the calibration and the test solutions
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3.3.24 ultrasonic nebulizer nebulizer in which the aerosol is created by flowing a liquid across a surface that is oscillating at an ultrasonic frequency
〈radial plasma〉 position in a radial plasma from where the emission measured originates
NOTE The viewing height is generally given as the distance, in millimetres, above the load coil
〈axial plasma〉 horizontal and vertical adjustment of an axial plasma to establish optimum viewing conditions, such that only emission from the central channel of the plasma is measured
Statistical terms
3.4.1 analytical recovery ratio of the mass of analyte measured when a sample is analysed to the known mass of analyte in that sample, expressed as a percentage
3.4.2 bias consistent deviation of the results of a measurement process from the true value of the air quality characteristic itself
〈of a measuring procedure or of an instrument〉 quantity used to characterize as a whole the uncertainty of a result given by an apparatus or measuring procedure
NOTE The overall uncertainty is calculated based on a combination of bias and precision, usually in accordance with Equation (1) and is expressed as a percentage: ref ref
− + × (1) where x is the mean value of results of a number (n) of repeated measurements; x ref is the true or accepted reference value of concentration; s is the standard deviation of the measurements
3.4.4 precision closeness of agreement of results obtained by applying the method several times under prescribed conditions NOTE Adapted from ISO 6879 [5]
3.4.5 true value value which characterizes a quantity perfectly defined in the conditions which exist when that quantity is considered
NOTE The true value of a quantity is a theoretical concept and, in general, cannot be known exactly; see EN 1540 [4]
〈of measurement〉 parameter associated with the result of a measurement that characterizes the dispersion of the values that could reasonably be attributed to the measurand
NOTE 1 The parameter can be, for example, a standard deviation (or a given multiple of it), or the width of a confidence interval
Measurement uncertainty consists of various components, which can be assessed through statistical analysis of measurement results, characterized by standard deviations Additionally, some components are derived from assumed probability distributions based on prior experience or information, also represented by standard deviations The ISO Guide to the Expression of Uncertainty in Measurement (GUM) categorizes these assessments as Type A and Type B evaluations of uncertainty.
4.1 Airborne particles containing metals and metalloids are collected using the method specified in
4.2 The collected sample and the filter are then treated to dissolve the metals and metalloids of interest using one of the sample dissolution methods specified in ISO 15202-2
4.3 The resultant solutions are analysed for the metals and metalloids of interest using the inductively coupled plasma atomic emission spectrometry method specified in this part of ISO 15202
The entire measuring procedure outlined in ISO 15202-1, ISO 15202-2, and this section of ISO 15202 must adhere to applicable international, European, or national standards, such as EN 482 and EN 13890, which define the performance requirements for measuring chemical agents in workplace air.
During the analysis, use only reagents of recognized analytical grade and only water as specified in 6.1
6.1 Water, complying with the requirements for ISO 3696 grade 2 water (electrical conductivity less than
0,1 mS⋅m −1 and resistivity greater than 0,01 MΩ⋅m at 25 °C)
For optimal results, it is advisable to use ultrapure water sourced from a purification system, ensuring a resistivity greater than 0.18 MΩ⋅m, commonly indicated by manufacturers as 18 MΩ⋅cm.
6.2 Ammonium citrate solution, 17 g⋅l −1 (NH 4 ) 2 HC 6 H 5 O 7 and 5 g⋅l −1 C 6 H 8 O 7 ⋅H 2 O, prepared in accordance with B.4.2 of ISO 15202-2:2001
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NOTE This solution is required only when soluble nickel compounds are to be determined (see B.6.1.3 of ISO 15202- 2:2001)
6.3 Mineral acids, concentrated, of various types, as required for preparation of matrix-matched calibration solutions (see 6.6.2)
The concentration of the metals and metalloids of interest shall be less than 0,1 mg⋅l −1
NOTE It might be necessary to use mineral acids of higher purity in order to obtain an adequate quantification limit for some metals and metalloids
6.3.1 Nitric acid (HNO 3 ), concentrated, ρ ≈ 1,42 g⋅ml −1 , mass fraction ≈ 70 %
Concentrated nitric acid is highly corrosive and oxidizing, and its fumes can irritate the respiratory system It is crucial to prevent skin or eye contact and to avoid inhaling the fumes Always wear appropriate personal protective equipment, such as gloves and safety glasses, when handling both concentrated and dilute nitric acid.
6.3.2 Hydrochloric acid (HCl), concentrated, ρ ≈ 1,18 g⋅ml −1 , mass fraction ≈ 36 %
Concentrated hydrochloric acid is highly corrosive, and its vapour can irritate the skin, eyes, and respiratory system To ensure safety, it is essential to wear appropriate personal protective equipment, such as gloves and safety goggles, when handling both concentrated and diluted hydrochloric acid Always work with open containers of concentrated hydrochloric acid in a fume hood to prevent exposure to harmful vapours Additionally, be cautious of pressure build-up in stoppered flasks when mixing hydrochloric acid with water due to its high vapour pressure.
6.3.3 Sulfuric acid (H 2 SO 4 ), concentrated, ρ ≈ 1,84 g⋅ml −1 , mass fraction ≈ 98 %
Concentrated sulfuric acid is highly corrosive and can cause severe burns, so it is crucial to avoid skin and eye contact Always wear appropriate personal protective equipment, such as gloves and safety goggles, when handling sulfuric acid, whether concentrated or diluted Exercise extreme caution during the dilution process, as it is highly exothermic Never add water directly to sulfuric acid, as this can lead to violent reactions; instead, always add sulfuric acid to water to ensure safety.
6.3.4 Perchloric acid (HClO 4 ), concentrated, ρ ≈ 1,67 g⋅ml −1 , mass fraction ≈ 70 %
Concentrated perchloric acid is highly corrosive and oxidizing, and its fumes can irritate the skin, eyes, and respiratory system It is essential to avoid direct contact and inhalation of the fumes Always wear appropriate personal protective equipment, such as gloves and a face shield or safety spectacles, when handling both concentrated and dilute forms of this acid.
6.3.5 Hydrofluoric acid (HF), concentrated, ρ ≈ 1,16 g⋅ml −1 , mass fraction ≈ 48 %
Concentrated hydrofluoric acid is extremely toxic and can cause severe burns upon skin contact, inhalation, or ingestion It is crucial to avoid any contact with skin or eyes and to prevent inhalation of vapors Always use appropriate personal protective equipment, such as gloves and face shields, when handling hydrofluoric acid, whether concentrated or diluted Work with open vessels in a fume hood and be aware of the serious nature of hydrofluoric acid burns before starting any work Keep hydrofluoric acid burn cream containing calcium gluconate on hand at all times while working with this substance and for 24 hours afterward In the event of contamination, wash the affected area thoroughly with water and apply the cream, seeking immediate medical attention if an accident occurs.
Hydrofluoric acid can cause a delayed burning sensation upon exposure, which may not be felt for several hours Even relatively dilute solutions 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 be worn underneath suitable rubber gloves to provide added protection for the hands
To prepare a solution, begin by adding about 700 ml of water to a 1,000 ml volumetric flask Next, carefully introduce 100 ml of concentrated nitric acid into the flask and swirl the mixture to ensure proper blending After allowing the solution to cool, dilute it to the mark with additional water, then stopper the flask and mix thoroughly.
6.5 Stock standard solutions, for preparation of calibration solutions
6.5.1 Single-element stock standard solutions
To prepare calibration solutions, utilize commercial single-element standard solutions with certified concentrations that are traceable to national standards Ensure that the range of standard solutions encompasses all relevant metals and metalloids at appropriate concentrations, typically 1,000 mg⋅l\(^{-1}\) or 10,000 mg⋅l\(^{-1}\) Always adhere to the manufacturer's expiration date or recommended shelf life for optimal accuracy.
To prepare single-element stock standard solutions, utilize high purity metals or their salts, ensuring that the preparation procedure is appropriate for its intended use Calibration of any equipment employed must be traceable to national standards For optimal storage, use a suitable container, such as a polypropylene bottle, and limit the storage duration to a maximum of one year.
6.5.2 Multi-element stock standard solution(s)
To prepare calibration solutions, utilize one or more commercial multi-element standard solutions with certified concentrations that are traceable to national standards These solutions should encompass all relevant metals and metalloids at appropriate concentrations, generally ranging from 10 mg⋅l\(^{-1}\).
1 000 mg⋅l −1 , depending on the sensitivity of the emission lines to be measured Observe the manufacturer's expiration date or recommended shelf life
To prepare a working standard solution for metals and metalloids, select suitable concentrations between 1 mg⋅l\(^{-1}\) and 100 mg⋅l\(^{-1}\), based on the sensitivity of the emission lines Accurately pipette the required volume of single-element or multi-element stock standard solutions into a labeled volumetric flask Add a suitable mineral acid to ensure analyte stability, then dilute with water almost to the mark, mix, and allow to cool to room temperature Finally, dilute to the mark with water, mix thoroughly, and store in a polypropylene bottle for up to one month.
When preparing working standard solutions, it is crucial to select analytes that are chemically compatible to prevent spectral interferences Additionally, the choice of mineral acid type and volume must be made with care to maintain the stability of the analytes.
Method development
Develop and validate a method for analyzing airborne particulate matter samples, following ISO 15202-2, that is compatible with available ICP-AES instruments Begin the method development process using the default instrument conditions recommended by the manufacturer Consult standard texts, manufacturer manuals, and relevant international, European, or national standards for guidance on ICP-AES method development.
ISO 15202 outlines guidelines applicable to various ICP-AES instruments, including both simultaneous and sequential types equipped with photomultiplier or solid-state detector systems While certain principles are universally relevant for method development across all instruments, many parameters are specific to individual instruments or categories.
8.1.2 Requirement for the quantification limit
For each metal and metalloid of interest, determine a value for the lower limit of the analytical range that will be satisfactory for the intended measurement task
To assess compliance with the limit values outlined in EN 482 [6], utilize Equation (2) to determine the minimum quantity of the metal or metalloid required for quantification at a concentration of 0.1 times its limit value.
L low is the required lower limit, in micrograms, of the analytical range of the metal or metalloid;
The limit value (L V) for the metal or metalloid is measured in milligrams per cubic metre The design flow rate (q v) of the sampler is specified in litres per minute, and the minimum sampling time (t min) is defined in minutes for the sampling process.
To determine the necessary quantification limit in milligrams per litre, divide the specified lower limit of the analytical range, measured in micrograms, by the volume of the test solution, expressed in millilitres.
According to ISO 15202-1:2000, when calculating the minimum sampling time for sample collection using the equation in section 8.1.4, it is essential that the concentration of each metal or metalloid on the filter exceeds the lower limit of the analytical range, given that its air concentration is greater than 0.1 times the limit value during sampling.
For certain measurement tasks, it may be essential to achieve quantitative measurements below 0.1 times the limit value; therefore, an appropriate lower value should be incorporated into the equation provided.
When measuring, it is crucial to acknowledge the impact of known spectral interferences For each relevant analytical wavelength, consult existing literature and previous experiences to evaluate how the intensity of these interferences relates to the limit values of both the interferents and the metals and metalloids being analyzed.
For compliance testing of limit values, an interferent at ten times its limit will result in a positive bias exceeding 0.1 times the analyte's limit value.
L V,i is the limit value, in milligrams per cubic metre, of the interferent;
L V,a is the limit value, in milligrams per cubic metre, of the analyte; ρa is the apparent analyte concentration, in milligrams per litre, caused by interferent concentration of
If the total potential interferences exceed 0.1 times the analyte's limit value, consider using an alternative analytical wavelength or implementing interelement corrections.
NOTE 1 Inter-element correction is not normally necessary for measurements made to test compliance with limit values
For certain measurement tasks, it may be necessary to acquire quantitative measurements at concentrations lower than 0.1 times the limit value; therefore, a suitable lower value should be substituted into Equation (3).
NOTE 3 Inter-element correction is best avoided, if possible, by selecting an alternative analytical wavelength that is free from or less prone to interference
8.1.4 Axial or radial viewing of the plasma
When choosing between an axial plasma instrument and a radial plasma instrument, or a dual-view instrument capable of both orientations, it is essential to determine the most suitable configuration for the specific measurement task Depending on the analytical wavelengths, utilizing the axial plasma may yield better results for certain measurements, while the radial plasma may be more effective for others.
NOTE Axial viewing of the plasma might be necessary to obtain the required quantification limits (see 8.1.2), but it is more susceptible than radial viewing to spectral interferences
When selecting a sample introduction system, it is essential to consider the required sensitivity and the characteristics of the test solution matrix Typically, the standard system provided by the instrument manufacturer will suffice for most applications.
NOTE 1 If the spectrally pure test solutions contain hydrofluoric acid, it will be necessary to use a corrosion-resistant sample introduction system
Ultrasonic nebulizers offer greater sensitivity compared to traditional pneumatic nebulizers, including cross-flow and concentric types However, they are susceptible to corrosion from hydrofluoric acid and typically have longer wash-out times Despite these drawbacks, ultrasonic nebulizers can be advantageous for achieving lower quantification limits, especially when measuring metals or metalloids with low limit values or short sampling durations.
Hydride generation for elements like arsenic, antimony, selenium, and tellurium, along with cold vapor generation for mercury, offers lower quantification limits compared to other sample introduction methods However, these techniques are not included in ISO 15202 standards.
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Instrument performance checks
The user shall perform regular visual checks to ensure the instrument and ancillaries are in good order before commencing work Follow the instrument manufacturer's recommendations
Further guidance is given in Annex A
8.2.2 Performance checks and fault diagnostics
Daily performance checks are essential to ensure the ICP-AES instrument operates at an acceptable standard If there are suspicions of malfunction, more thorough fault diagnostics should be employed Always adhere to the manufacturer's recommendations for optimal performance.
Further guidance is given in Annex B
A comprehensive series of performance checks, often referred to as QUID (a procedure for Quality Control and Identification of Malfunctions of ICP emission spectrometers), has been described in the literature; see
Reference [12] This can be used to supplement the performance checks and fault diagnostics recommended by the instrument manufacturer
A short version of QUID is described in Annex C.
Routine analysis
When handling concentrated or dilute acids, it is crucial to wear appropriate personal protective equipment, such as gloves and safety glasses, to ensure safety Additionally, refer to the WARNING notices in section 6.3 for further guidance The addition of internal standards is discussed in section 8.3.1.
When employing internal standards, it is essential to add the same concentration to all solutions being measured, including calibration solutions, blank test solutions, sample test solutions, interference check solutions, and quality control solutions.
To incorporate internal standards into measurements, a known volume of a single-element stock standard solution can be pipetted into each solution, such as adding 100 µL of the stock standard to 10 mL of the sample Alternatively, internal standards can be mixed with the sample during introduction using a two-channel peristaltic pump, T-piece, and mixing coil In this case, it is essential to prepare an internal standard solution at the appropriate concentration by diluting the single-element stock standard solution accordingly.
To ensure accurate results, set up the ICP-AES instrument according to the manufacturer's guidelines and the specified method Allow the instrument to warm up for the recommended 30 to 60 minutes before beginning analysis During this warm-up period, it is beneficial to aspirate a calibration blank solution into the plasma to maintain consistent plasma conditions throughout the analysis.
To perform calibration, aspirate the calibration solutions into the plasma in ascending order of concentration and measure the emission for each solution Utilize the instrument's computer to create a calibration function for the relevant metals and metalloids, ideally employing linear regression It is advisable to subtract the emission intensity of the calibration blank solution from the emission intensities of the other solutions.
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Calibration solutions should ensure that the calibration function passes through the origin If the correlation coefficient, R², for any of the metals and metalloids of interest is below 0.999, the calibration process must be repeated.
If the R² value is less than 0.999, it may be feasible to eliminate an incorrect calibration point and reprocess the data to achieve an acceptable calibration However, it is essential to adhere to the minimum number of calibration solutions specified in section 6.6.2.
Aspirate the blank and sample test solutions, prepared according to ISO 15202-2, into the plasma and conduct emission measurements for each solution Utilize the stored calibration function to determine the concentrations of the relevant metals and metalloids.
After the initial calibration, it is essential to analyze both the calibration blank solution and a mid-range calibration solution at least every 20 test solutions If the concentration of a metal or metalloid in the continuing calibration blank exceeds three times the instrumental detection limit, or if there is a change greater than ± 5% in the concentration of a metal or metalloid during calibration verification, corrective actions must be taken These actions include using the instrument software to adjust for sensitivity changes or suspending analysis to recalibrate the spectrometer Subsequently, it is necessary to reanalyze the test solutions affected by the sensitivity change or, if reanalysis is not feasible, to reprocess the data accordingly.
When incorporating inter-element correction in the method, it is essential to analyze interference-check solutions to ensure the effectiveness of the correction procedure for each analytical wavelength The acceptance criteria stipulate that the apparent analyte concentration must align with an air concentration that is below 0.1 times the relevant limit value.
Analyze reagent blank and laboratory blank solutions according to the specifications in section 8.5.1.1, along with quality control solutions outlined in section 8.5.2.1 Utilize the results to effectively monitor the performance of the method as detailed in sections 8.5.1.2 and 8.5.2.2.
When reviewing the results, it is essential to assess the relative standard deviation of each outcome If any result exhibits a relative standard deviation that is considerably higher than anticipated, based on the measured concentration, it is advisable to repeat the analysis for the affected solution.
NOTE When the measured concentration for a metal or metalloid is well above its quantification limit, it can reasonably be expected that the relative standard deviation will be < 1 %
If the concentration of any metals or metalloids in a sample test solution exceeds the upper limit of the calibration range, dilute the solution appropriately, ensuring matrix matching if needed, and reanalyze Be sure to document the dilution factor used Alternatively, consider utilizing a different analytical wavelength for the analysis.
Estimation of detection and quantification limits
8.4.1 Estimation of the instrumental detection limit
To estimate the instrumental detection limit for each metal or metalloid of interest, follow the procedures outlined in sections 8.4.1.2 and 8.4.1.3 under the specified analytical conditions It is essential to repeat this estimation whenever there are changes in the experimental conditions.
An instrumental detection limit is useful for monitoring changes in instrument performance, but it should not be confused with a method detection limit Typically, the instrumental detection limit is lower than the method detection limit, as it focuses solely on the variability of individual instrument readings without accounting for variability introduced by the sample matrix.
To prepare a test solution with metal or metalloid concentrations close to their expected instrumental detection limits, dilute the working standard or stock standard solutions by an appropriate factor Ensure to follow the same procedure used for calibration preparation.
To determine the instrumental detection limit for each metal or metalloid of interest, conduct a minimum of ten consecutive emission measurements on the test solution Calculate the detection limit by taking three times the sample standard deviation of the mean concentration value.
An alternative method for estimating the instrumental detection limit is to analyze a calibration blank solution that is fortified with the relevant metals and metalloids at concentrations that cover the expected detection limit.
8.4.2 Estimation of the method detection limit and the quantification limit
To determine the method detection limit and quantification limit for each metal or metalloid of interest, follow the procedures outlined in sections 8.4.2.2 and 8.4.2.3 under the specified analytical conditions It is essential to repeat this estimation whenever there are significant changes in the experimental conditions.
To ensure accurate testing, prepare a minimum of ten laboratory blank test solutions using unused filters identical to those employed for sample collection, as specified in ISO 15202-1 Adhere to the sample-dissolution procedure outlined in ISO 15202-2 for the preparation of these test solutions.
Emission measurements should be conducted on the test solutions, and the method detection limit and quantification limit for each metal or metalloid of interest must be calculated as three times and ten times the sample standard deviation of the mean concentration values, respectively.
Quality control
8.5.1 Reagent blanks and laboratory blanks
Carry reagent blanks and laboratory blanks throughout the sample preparation and analytical process as outlined in ISO 15202-2 Prepare and analyze these blanks at a frequency of at least one per 20 samples or a minimum of one per batch.
If reagent and laboratory blank results are unexpectedly high compared to prior data, it is essential to investigate potential contamination from laboratory processes or the sampling filter batch Taking appropriate corrective measures will help prevent future occurrences.
To ensure method accuracy during the sample preparation and analytical process outlined in ISO 15202-2, it is essential to carry spiked samples and spiked duplicate samples throughout the entire procedure These samples, which consist of filters with known amounts of metals and metalloids added, help estimate percent recovery relative to the true spiked value Spiking can be achieved by adding known volumes of a working standard solution, ensuring the amounts fall within the instrument's linear dynamic range It is crucial that the working standard solution is prepared from stock standard solutions sourced differently than those used for calibration Quality control solutions should be prepared and analyzed at a frequency of at least one per batch.
20 samples or a minimum of one per batch
To ensure the effectiveness of the method, it is essential to monitor performance by creating control charts that display the relative percent recoveries and the relative percent differences between spiked samples and their duplicates If quality-control results show that the method is outside the control range, it is crucial to investigate the underlying causes, implement corrective actions, and repeat the analysis if needed For further guidance on utilizing quality-control charts, refer to ASTM E 882-87.
Certified reference materials (CRMs) for the relevant metals and metalloids should be analyzed before the routine application of the method to ensure that the percent recovery aligns satisfactorily with the certified values.
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If laboratories carry out metal and metalloid in air analysis on a regular basis, it is recommended that they participate in a relevant external quality assessment or proficiency testing scheme.
Measurement uncertainty
Laboratories should estimate and report measurement uncertainty following GUM guidelines The process begins with creating a cause-and-effect diagram to identify sources of random and systematic errors These errors are then estimated or determined experimentally and compiled into an uncertainty budget The combined uncertainty is multiplied by a coverage factor, typically recommended as 2, to yield an expanded uncertainty that provides approximately 95% confidence in the calculated value.
NOTE 1 References [16] and [17] describe the application of cause-and-effect analysis to analytical methods
Measurement precision is influenced by various terms that contribute to random variability, which can be assessed using quality-control data The error linked to instrumental drift can be estimated by assuming a rectangular probability distribution, calculated by dividing the allowable drift before recalibrating the instrument.
NOTE 3 Systematic errors include, for example, those associated with method recovery, sample recovery, preparation of working standard solutions, dilution of test solutions, etc
When multiple emission lines are measured for any analytes, results should be processed according to the protocol outlined in section 8.1.6.2 to obtain a single result for each metal and metalloid of interest.
9.2 Calculate the mean concentration of each of the metals and metalloids of interest in the blank test solutions
9.3 Calculate the mass concentration of each metal or metalloid in the air sample at ambient conditions, using Equation (4):
The equation \( V \rho_M = \rho_{M,0} \times V - \rho_{M,1} \times V \) describes the relationship between the calculated mass concentration of a metal or metalloid in an air sample at ambient conditions (\( \rho_M \)), the mean concentration in field blank test solutions (\( \rho_{M,0} \)), and the concentration in the sample test solution (\( \rho_{M,1} \)) The mass concentration is measured in milligrams per cubic meter, while the concentrations in the test solutions are expressed in milligrams per liter.
V is the volume, in litres, of the air sample (see 8.4.3 of ISO 15202-1:2000);
V 0 is the volume, in millilitres, of the field blank test solutions;
V 1 is the volume, in millilitres, of the sample test solution;
9.4 If it is necessary to recalculate metal and metalloid in air concentrations to reference conditions (see
According to section 8.1.3.1 of ISO 15202-1:2000, the mean atmospheric temperature and pressure should be calculated by averaging the measurements taken at the beginning and end of the sampling period Subsequently, apply a temperature and pressure correction to the concentrations of metals and metalloids in air, as determined in section 9.3, using Equation (D.1).
Method detection limits and quantification limits
Method detection limits and quantification limits are influenced by various factors such as sample preparation techniques, selected analytical wavelengths, the type of analytical instrumentation, instrument operating parameters, and blank variability In the validation process, these limits were established by preparing blank test solutions from mixed cellulose ester membrane filters, utilizing the closed-vessel microwave digestion procedure outlined in ISO 15202-2:2001.
Annex G, and analysing them using a method established following the procedure described in this part of
ISO 15202 provides results in micrograms per liter for a specific range of metals and metalloids, as illustrated in Table 2, which exemplifies the achievable method detection limits and quantification limits.
It is important to determine method detection limits and quantification limits under the test conditions used following the instructions given in 8.4
Table 2 — Achievable method detection limits and quantification limits
Plasma viewing Method detection limit àg/l
The quantification limits for various elements are as follows: Antimony has a limit of 206,836 µg/L with axial measurements of 13 and 43 Arsenic is at 193,696 µg/L with axial values of 19 and 62 Beryllium shows a limit of 313,042 µg/L with radial measurements of 0.3 and 0.9 Cadmium is quantified at 228,802 µg/L with axial values of 2.8 and 9.5 Chromium has a limit of 267,716 µg/L with radial measurements of 3.3 and 11 Cobalt is at 228,616 µg/L with axial values of 2.3 and 7.7 Copper shows a limit of 324,752 µg/L with radial measurements of 15 and 50 Indium is quantified at 230,606 µg/L with axial values of 10 and 33 Iron has a limit of 259,939 µg/L with radial measurements of 14 and 46 Lead is at 220,353 µg/L with axial values of 10 and 33 Manganese shows a limit of 257,610 µg/L with radial measurements of 1.0 and 3.1 Nickel is quantified at 221,648 µg/L with radial values of 10 and 34 Selenium has a limit of 196,026 µg/L with axial measurements of 17 and 55 Tellurium is at 214,281 µg/L with axial values of 28 and 94 Tin shows a limit of 189,927 µg/L with radial measurements of 63 and 210 Vanadium is quantified at 309,310 µg/L with radial values of 1.2 and 4.2 Yttrium has a limit of 371,029 µg/L with radial measurements of 0.6 and 2.1 Finally, zinc is at 206,200 µg/L with radial values of 15 and 51.
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Upper limits of the analytical range
The upper limit of the useful analytical range is determined by the linear dynamic range of the spectrometer under the analytical conditions established in 8.1.
Bias and precision
The sample dissolution methods outlined in ISO 15202-2 are generally effective for most applications, ensuring negligible analytical bias However, they may not be suitable in every case According to EN 13890, the mean analytical recovery for measuring metals and metalloids in airborne particles must be at least 90% If there is uncertainty regarding the adequacy of the chosen dissolution method, ISO 15202-2 mandates an evaluation of its effectiveness Should the analytical recovery fall below 90%, an alternative dissolution method must be explored Thus, the analytical bias is anticipated to remain within a maximum of 10%.
The coefficient of variation (CV) due to analytical variability, denoted as CV(analysis), is influenced by factors such as the selected analytical wavelength, the instrumentation used, and the operating parameters of the instrument Laboratory experiments have determined the figures of merit for CV(analysis) across a range of metals and metalloids Test solutions were prepared by spiking filters with specific amounts of these elements and digesting them using the closed-vessel microwave procedure outlined in ISO 15202-2:2001 The analysis followed the established method in ISO 15202, revealing that CV(analysis) typically ranges from 2% to 5% for metal and metalloid concentrations exceeding ten times the method detection limit.
Overall uncertainty of sampling and analysis methods
Laboratory experiments have confirmed that the measuring procedure outlined in ISO 15202 meets the performance requirements specified in EN 482 for overall measurement uncertainty when comparing with limit values The study focused on a selected range of metals and metalloids, utilizing the closed-vessel microwave digestion method as per ISO 15202-2:2001 For 8-hour time-weighted average limit values in the UK, the procedure satisfied EN 482 requirements for all metals and metalloids except tellurium, which required a minimum sampling time of 2 hours Additionally, for 15-minute short-term exposure limit values, the procedure met the EN 482 requirements for all selected metals and metalloids at a typical sampling flow rate of 2 l⋅min −1.
CEN has established general requirements for measuring chemical agents in workplace atmospheres as outlined in EN 482 The standard specifies upper limits of acceptability for overall uncertainty across various measurement tasks, serving as a guideline for this International Standard Notably, CEN's requirements are less stringent for screening measurements compared to those intended for limit value comparisons Additionally, measurements made within the range of 0.1 to 0.5 times the exposure limit value have an overall uncertainty threshold of less than 50%, while those in the range of 0.5 to 2.0 times the exposure limit value require an overall uncertainty of less than 30%.
NOTE 2 The metals and metalloids covered in the method performance experiments are As, Be, Cd, Cr, Co, Cu, Fe, In,
Spectral interferences
In the validation of this method, the potential for spectral interferences was carefully evaluated, as outlined in section 8.1.3 It was determined that no spectral interference correction was needed for measurements taken at the chosen analytical wavelengths Nonetheless, it remains crucial to assess the necessity of interference correction based on the specific test conditions, following the guidelines provided in section 8.1.8.
Test records
Comprehensive records of the performed tests must be maintained, including: a confidentiality statement for the supplied information; complete identification of the air sample, detailing the sampling date, location, sample type (personal or static), individual identifier or location for static samples, a brief description of work activities during sampling, and a unique sample identification code; a reference to ISO 15202-3:2004; details of the sampler, filter, and sampling pump used; information on the flowmeter, including calibration standards and conditions; the start and end times of the sampling period, its duration, mean flow rate, and atmospheric conditions; the volume of air sampled; the name of the sample collector; the time-weighted average mass concentration of metals and metalloids in the air sample; the sample dissolution method; and analytical variables for calculating results, including concentrations in blank and sample solutions, volumes, and dilution factors.
The article outlines essential requirements for reporting in analytical procedures, including the types of instruments used for sample preparation and analysis, along with their unique identifiers It emphasizes the need to provide estimated instrumental detection limits, method detection limits, and quantification limits under working analytical conditions, as well as measurement uncertainty in accordance with the GUM Additionally, it mentions the inclusion of quality control data upon customer request, any operations not specified in the International Standard, and the names or unique identifiers of the analysts Finally, it highlights the importance of documenting the date of analysis and any inadvertent deviations, unusual occurrences, or notable observations.
Laboratory report
The laboratory report shall contain all information required by the end user, regulatory authorities and accreditation organizations
Guidance on maintenance of ICP-AES instrumentation
A maintenance contract is advisable for the following reasons
Maintenance and/or calibration of certain instrument components could be beyond the capability of the laboratory
Instrument upgrades (software and hardware) are often included in maintenance packages
It might not be possible to obtain spare parts and other consumable items from sources other than the manufacturer
Certain accreditation systems require users to have a maintenance contract
When considering a maintenance contract, it's essential to evaluate the service level provided, response times, the expertise of service engineers, and the duration of manufacturer support for the instrument, including access to spare parts and consumables.
It is advisable to maintain an instrument log book to record the following information:
details of service contracts and contacts;
instrument usage (who has used the instrument and for how long);
details of faults and replacement of user-serviceable parts
It is advisable to follow manufacturer's guidelines regarding maintenance Failure to comply with such guidelines might invalidate maintenance contracts
The following checks should be carried out periodically:
air filters: Check for overload Remove and wash/dry or replace if clogged
To ensure optimal performance of your cooling system, regularly inspect the filter and verify that all connections are secure Additionally, monitor the levels of water, antifreeze, and fungicide, and look for any signs of corrosion around metal couplings For detailed guidance, consult the manual specific to your system.
Ensure gas lines are secure by checking for loose connections and leaks, as well as inspecting for kinks It's important to verify the performance of inline filters and oil traps, and to check inlet pressures For specific details, refer to the instrument manual.
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exhaust system: Check for loose connections, kinks and possible leakages in flexible exhaust ducting
Verify the performance of the ventilation system Consult a ventilation expert if necessary Refer to instrument manual for specific details
The following instrument checks should be carried out:
peristaltic pump tubing: Check for depressions and flat spots on tubing daily and/or before analysis
New tubing will require a breaking-in period Ensure that suitable chemically resistant tubing is used Performance checks can be carried out volumetrically using a graduated cylinder and stopwatch
other tubing: Periodically visually check connectors Check for blockages and deposits
Check for potential kinking and snagging of tubing if it is connected to an autosampler and associated robotic arm
nebulizer: Periodically visually check that the nebulizer is not clogged Check o-ring seals and couplings between the nebulizer/spray chamber and the spray chamber/torch
spray chamber: Periodically, visually check the spray chamber to ensure that it is clean and that the waste is draining efficiently into the waste container
Regularly monitor the liquid level in the waste container, especially if not automatically checked by instrument software Ensure smooth waste flow from the spray chamber to the drain, and inspect the waste tubing for kinks and deposits Additionally, verify that the various types of waste within a single drain are compatible, as different applications may necessitate distinct waste systems.
Regularly inspect the waste container and empty it before it overfills If the waste includes hydrofluoric acid, add calcium carbonate (CaCO₃) or boric acid (H₃BO₃) to complex the fluoride Additionally, ensure that the drain tubing from the spray chamber is properly positioned to prevent blockages from solids.
autosampler and other sample introduction accessories:
Periodically check the components and interfaces with the instrument Follow the manufacturer's guidelines
Regularly inspect the torch and its mounting alignments, ensuring the injector tube is free from accumulated deposits Verify the position of the injector tube and examine the quartz torch body for any signs of devitrification or residue build-up, especially when handling high matrix or organic solvent samples Check o-rings and seals for potential leakages, and confirm the spatial alignment of the torch relative to the load coil Always adhere to the manufacturer's guidelines for cleaning or replacing the injector and torch as necessary.
torch box: Periodically check for signs of corrosion or leakage
RF generator: Periodically check for signs of corrosion Likewise check for corrosion in components of the plasma-initiation system A service engineer might be required for specialized checks
Regular maintenance of the spectrometer is essential, including periodic checks and cleaning or replacement of purge windows Operators may need to perform wavelength calibration routines at set intervals, and specialized checks may require the assistance of a service engineer.
computer: Periodically back up data files, clean out unwanted files and check network connections
Examples of performance checks and fault diagnostics
A straightforward daily test for plasma involves introducing a solution with at least 1,000 mg⋅l\(^{-1}\) of an element that generates a distinct "bullet" in the center of the ICP discharge The appearance of this bullet signifies that the sample aerosol is successfully reaching the plasma, while its vertical position serves as an indicator of the gas flow and RF power settings in use, particularly for radial plasma Sodium and yttrium are recommended elements for conducting this test.
Emission counts for a specific element concentration serve as a valuable diagnostic tool, primarily for trend analysis rather than as a definitive measure of performance, due to daily variations in these counts.
The background equivalent concentration reflects the sensitivity of an emission line relative to the emission background at the same wavelength An elevated concentration may signal issues with the efficiency of the sample introduction system, though other factors could also contribute to this anomaly.
The short-term precision of repeat measurements of a strong emission line serves as an indicator of the noise linked to sample introduction Additionally, the precision of an argon emission line can act as a diagnostic tool for assessing the performance of the RF generator.
The emission intensity ratio of an ion line to that of an atom line serves as a diagnostic tool for assessing the relative excitation conditions in plasma Specifically, the Mg(II) 280 nm to Mg(I) 285 nm line intensity ratio is recommended for this purpose These ion/atom ratios are influenced by factors such as RF power, nebulizer flow, and viewing height, making them useful for ensuring consistent excitation conditions It is crucial to conduct analyses under specific conditions when applying interference correction factors or utilizing stored calibration curves.
Dispersive instruments experience varying degrees of drift, making proper wavelength calibration of the spectrometer essential before analysis In many cases, this calibration is automatically handled by the software at the start of the analysis.
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Procedure for quality control and identification (QUID) of malfunctions of inductively coupled plasma atomic emission spectrometers
To ensure optimal analytical performance and instrument maintenance in an ICP system, users should implement systematic verification actions Drawing from established research on drift diagnostics, resolution measurements, ionic to atomic line intensity ratios, detection limits, and figures of merit, a comprehensive procedure has been proposed to assess analytical performance, manage key components of the ICP apparatus, and identify any potential system deterioration.
A flow chart corresponding to the procedure, Quality Control and Identification of Malfunctions, called QUID, is given in Figure C.1
Figure C.1 — Flow chart of the QUID procedure
Table C.1 lists the elements in the test protocol along with their ionization and excitation energies Barium is included for its two narrow lines, which are effective for measuring resolution in the UV and visible spectrum, particularly the Ba(II) 455 nm line, noted for having the lowest sum of ionization and excitation energies Additionally, magnesium is featured due to the useful ratio of intensities between its ion and atom lines for monitoring energy transfer The signal-to-background ratio (SBR) is also considered.