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Metals (chromium, copper and their compounds) [Air Monitoring Methods, 2012]

  1. K. Pitzke,
  2. M. Jaschke,
  3. J.-U. Hahn

Published Online: 15 OCT 2012

DOI: 10.1002/3527600418.am744047e0013

The MAK Collection for Occupational Health and Safety

The MAK Collection for Occupational Health and Safety

How to Cite

Pitzke, K., Jaschke, M. and Hahn, J.-U. 2012. Metals (chromium, copper and their compounds) [Air Monitoring Methods, 2012]. The MAK Collection for Occupational Health and Safety. 159–172.

Publication History

  1. Published Online: 15 OCT 2012

Method number1
ApplicationAir analysis
Analytical principleICP emission spectrometry (ICP-OES)
Completed inMarch 2009

1 Summary

This analytical method permits the determination of chromium, copper and their compounds in the air at the workplace in a concentration range from 2.4 µg/m3 to 240 µg/m3. A suitable pump draws a defined volume of air through a particle filter (membrane filter) for the sampling procedure. The metals contained in the retained dust (in this case chromium, copper and their compounds) are quantitatively determined by means of simultaneous ICP emission spectrometry after acidic digestion.

2 Characteristics of the method

Precision:

Chromium

Standard deviation (rel.) s = 1.35–2.12%

Confidence interval u = 22%

In the concentration range from c = 0.05–5.0 mg/L and n = 6 determinations

Copper

Standard deviation (rel.) s = 1.80–2.89%

Confidence interval u = 24%

In the concentration range from c = 0.05–5.0 mg/L and n = 6 determinations

Limits of quantification:

Chromium

27.1 µg/m3 at an air sample volume of 0.42 m3

Copper

27.1 µg/m3 at an air sample volume of 0.42 m3

217 µg/m3 at an air sample volume of 0.05 m3

Recovery:

Chromium η > 0.99 (> 99%)

Copper η > 0.99 (> 99%)

Sampling recommendation:

Sampling time: 2 h

Sample flow rate: 210 L/h

Short-term exposure value for copper:

Sampling time: 0.25 h

Sample flow rate: 210 L/h

Chromium [CAS No. 7440-47-3]

Chromium is a shiny silver metal (atomic mass 51.99 g/mol, melting point ≈ 1890 °C, boiling point ≈ 2670 °C). Chromium and its compounds have many different uses. In the case of hard-chrome plating chromium is applied to steel, aluminum or copper by galvanization as a protection against abrasion. Chromium is used as component of alloys in corrosion-resistant and heat-resistant steels and non-ferrous alloys. The principal area of use for chromium compounds is in chrome tanning with chromium(III) salts such as Cr2(SO4)3 or Cr(OH)SO4 (basic chromium sulfate). These are not considered as a health hazard. After the tanning process, the leather has absorbed approximately 1.5 to 3% of Cr2O3. Chromium(VI), which is harmful to health, is formed during the chrome tanning process in the presence of fats with high proportions of unsaturated fatty acids. Therefore the best protection against chromium(VI) is to use suitable stuffing agents and to perform post-tanning with vegetable material such as extracts of bark, fruits or leaves containing tannin [1].

Chrome tanning in two vats with dichromate solution and then thiosulfate solution is no longer common due to the toxicity of chromium(VI) compounds. In the List of MAK and BAT Values as well as TRGS 900 chromium(VI) compounds are classified as Category 2 carcinogens [2, 3]. The detailed documentation of the toxicity of chromium(VI) compounds is found in “Toxikologisch-arbeitsmedizinische Begründungen von MAK-Werten” [4]. Chromium(III) compounds have an Occupational Exposure Limit (OEL) of 2 mg/m3 as the respirable fraction; for short-term exposure they are classified in Peak Limitation Category I with an excursion factor of 1 [3]. In the List of MAK and BAT Values chromium(III) compounds have been assigned to Section II b [2]. The detailed documentation of the toxicity of chromium(III) compounds is found in the “Toxikologisch-arbeitsmedizinische Begründungen von MAK-Werten” [5].

Copper [CAS No. 7440-50-8]

Copper is a relatively soft pale reddish metal (atomic mass 63.55 g/mol, melting point ≈ 1083 °C, boiling point ≈ 2595 °C). Copper is a component of many alloys such as brass, nickel silver or red brass, bronze (cast alloys). On account of its good conductivity it is used in cables and connections, in electrical and electronic components (transformers, contacts, circuit boards), also in alloys with e.g. beryllium. Copper compounds are used in paint pigments or galvanic surface coatings.

The currently valid MAK value for copper and its inorganic compounds is 0.1 mg/m3 as the respirable fraction. For short-term exposures it is classified in Peak Limitation Category II with an excursion factor of 2 [2]. The detailed documentation of the toxicity of copper and its inorganic compounds is found in the “Toxikologisch-arbeitsmedizinische Begründungen von MAK-Werten” [6]. At present no Occupational Exposure Limit is given in TRGS 900 [3].

Examiner: R. Meyer zu Reckendorf

1 General principles

  1. Top of page
  2. General principles
  3. Equipment, chemicals and solutions
  4. Sampling and sample preparation
  5. Operating conditions for ICP-OES
  6. Analytical determination
  7. Calibration
  8. Calculation of the analytical result
  9. Evaluation of the method
  10. References

This analytical method permits the determination of chromium, copper and their compounds in the air at workplaces in a concentration range from 2.4 µg/m3 to 240 µg/m3. A suitable pump draws a defined volume of air through a particle filter (membrane filter) for the sampling procedure. The metals contained in the retained dust (in this case chromium, copper and their compounds) are quantitatively determined by means of simultaneous ICP emission spectrometry after acidic digestion.

2 Equipment, chemicals and solutions

  1. Top of page
  2. General principles
  3. Equipment, chemicals and solutions
  4. Sampling and sample preparation
  5. Operating conditions for ICP-OES
  6. Analytical determination
  7. Calibration
  8. Calculation of the analytical result
  9. Evaluation of the method
  10. References

2.1 Equipment

For sampling:

  • Pump for personal sampling with a flow rate of 3.5 L/min, e.g. GilAir-5 EX, GSM GmbH, Neuss, Germany

  • Personal sampling device for dust collection, sampling head GSP-BIA, e.g. GSM GmbH, Neuss, Germany

  • Membrane filter, diameter 37 mm, pore size 0.8 µm, cellulose nitrate, e.g. Sartorius AG, Göttingen, Germany

  • Gas meter or volumetric flow meter

For sample preparation and analysis:

  • Aluminum heating block thermostat with external time/temperature control, operating range up to 200 °C, e.g. from Gebr. Liebisch GmbH & Co, Bielefeld, Germany

  • Graduated digestion vessels with air cooler made of quartz glass (diameter 19 mm, maximum volume 25 mL) with ground connections (NS 19/26), acid-proof, 0.2 mL graduation, e.g. from VWR International GmbH, Langenfeld, Germany

  • Stoppers made of polyethylene for the digestion vessels (NS 19/26), e.g. from Pöppelmann GmbH & Co, Lohne, Germany

  • Glass rods (diameter approx. 4 mm), made of quartz glass fitted with replaceable end pieces of PTFE tube, e.g. from VWR International GmbH, Langenfeld, Germany

  • 5 L bottle made of PFA with PTFE dispenser for rinsing the air cooler, e.g. Optifix HF Dispenser, 30 mL, from Poulten & Graf GmbH, Wertheim, Germany

  • Ceramic tweezers to transfer the membrane filters to the digestion vessels, e.g. Plano, W. Plannet GmbH, Wetzlar, Germany

  • ICP emission spectrometer, e.g. ICP-OES with CCD (charge-coupled device detector): Optima 5300DV, PerkinElmer LAS GmbH, Rodgau, Germany

  • Autosampler, e.g. Autosampler SC-14, Elemental Scientific Inc., Omaha, USA

  • Continuous-load peristaltic pump, e.g. IPC-N, Ismatec Laboratoriumstechnik GmbH, Wertheim-Mondfeld, Germany

  • Sample inlet system with cooler, e.g. PC3 with Peltier cooler, Elemental Scientific Inc., Omaha, USA

  • Nebulization chamber made of PFA, e.g. PFA cyclone nebulization chamber for PE Optima 5300DV, Elemental Scientific Inc., Omaha, USA

  • Nebulizer made of PFA, e.g. concentric OpalMist PFA nebulizer, AHF Analysentechnik AG, Tübingen, Germany

  • Mixing chamber made of PEEK, T-piece with 1/16 fitting, e.g. from YMC Europe GmbH, Schermbeck, Germany

  • Ultrapure water system, e.g. from Wilhelm Werner GmbH, Leverkusen, Germany

  • Measuring cylinders made of PFA, 500 mL, 100 mL, 50 mL, e.g. from VIT-LAB GmbH, Seeheim-Jugenheim, Germany

  • Volumetric flasks made of PFA for the standard and calibration solutions with screw caps and ring marks, 500 mL, 100 mL, 50 mL, e.g. from VIT-LAB GmbH, Seeheim-Jugenheim, Germany

  • Adjustable piston pipettes, e.g. Gilson Pipetman Ultra U1000, volume range 200 to 1000 µL, Gilson Inc., Middleton, USA

  • Adjustable repeater pipette, e.g. Stepper 411, Socorex ISBA S.A., Ecublens, Switzerland

  • Disposable polypropylene vessels with screw caps and 5 mL graduation, nominal volume 50 mL, e.g. from Greiner Bio One GmbH, Frickenhausen, Germany

  • Disposable polypropylene vessels with screw caps and 1 mL graduation, nominal volume 15 mL, e.g. from Greiner Bio One GmbH, Frickenhausen, Germany

Note: In order to keep the blank value low in the case of higher sample throughput, all the reusable vessels should be cleaned e.g. in a suitable washing machine with consecutive acidic, alkaline and neutral solutions and, after subsequent treatment with hot ultrapure water, they should be dried at room temperature.

2.2 Chemicals

  • Hydrochloric acid, 30% with a low metal content, e.g. Suprapur, Merck KGaA, Cat. No. 1.00318, Darmstadt, Germany

  • Nitric acid, 65% with a low metal content, e.g. Suprapur, Merck KGaA, Cat. No. 1.00441, Darmstadt, Germany

  • ICP multiple-element standard solution IV, 1000 mg/L, e.g. Certipur, Merck KGaA, Cat. No. 1.11355.0100, Darmstadt, Germany

  • Rubidium ICP standard, 1000 mg/L as RbNO3 in HNO3 (2 to 3%), e.g. Certipur, Merck KGaA, Cat. No. 1.70346.0100, Darmstadt, Germany

  • Scandium ICP standard, 1000 mg/L as Sc2O3 in HNO3 (7%), e.g. Certipur, Merck KGaA, Cat. No. 1.70349.0100, Darmstadt, Germany

  • Cesium nitrate, 99.999% (metals basis), e.g. from Alfa Aesar, Cat. No. 038617, Karlsruhe, Germany

  • ICP multiple-element standard solution VIII, 100 mg/L, e.g. Certipur, Merck KGaA, Cat. No. 1.09492.0100, Darmstadt, Germany

  • Argon (purity at least 99.996 %).

  • ICP plasma standard chromium, 1000 mg/L, e.g. from Alfa Aesar Specpure®, Cat. No. 38728, Karlsruhe, Germany

  • ICP plasma standard copper, 1000 mg/L, e.g. from Alfa Aesar Specpure®, Cat. No. 13867, Karlsruhe, Germany

  • High Speed Steel Standard with a certified metal content, British Chemical Standard, Article No. 241/2, Middlesbrough, UK

  • Chromium(III) nitrate nonahydrate, e.g. Merck KGaA, Cat. No. 1.02481.0250, Darmstadt, Germany

  • Copper sulfate, e.g. Merck KGaA, Cat. No. 1.02791.0250, Darmstadt, Germany

  • Ultrapure water, specific resistance ≥ 17 MΩ × cm at 25 °C

2.3 Solutions

The following solutions are prepared using the chemicals listed in Section 2.2:

  1. Acidic digestion mixture: 2 parts by volume of nitric acid (65%) and 1 part by volume of hydrochloric acid (25%) [7].

    Preparation of digestion mixture: 
    Ultrapure water:130 mL
    Nitric acid (65%):1400 mL
    Hydrochloric acid (30%):570 mL

  2. Rinsing solution for the ICP-OES (˜1% HNO3) 50 mL of nitric acid (65%) are dissolved in approx. 5 liters of water.

  3. Standards and additional solution:

    The additional solution is composed of an ionization buffer as well as the internal standard solutions of scandium and rubidium.

    The use of ionization buffers is advisable in the case of samples of unknown composition. When selecting the internal standard, it is important to ensure that these elements are not present in the calibration, control and sample solutions [8].

    A cesium solution serves as an ionization buffer. To prepare it, 3.68 g of CsNO3 are first dissolved in some ultrapure water that has been previously placed in a 500 mL volumetric flask. Then a pipette is used to transfer 1.5 mL each of the 1000 mg/L scandium and rubidium initial solutions to the volumetric flask, 10 mL of 65% HNO3 are added, and the flask is filled to its nominal volume with ultrapure water. The concentration of cesium is 5 g/L. The concentration of the internal standards in the additional solution is 3 mg/L in each case.

    The sample solution and the additional solution are continuously mixed together with a peristaltic pump in a mixing chamber before they reach the nebulizer. The diameters of the pump tubes ensure that the supply of the additional solution is in a ratio of 1:3 to the sample.

  4. Control sample for the precision:

    A standard with a concentration in the middle of the working range of the calibration (cf. Table 1) is used as a control sample for confirmation of the precision within an analytical series.

  5. ICP-OES instrumental test standard:

    ICP multiple-element standard VIII, with concentrations of 0.05 mg/L and 1.0 mg/L, serves as a control sample for the accuracy of the calibration.

    To prepare it, 25 or 500 µL of the ICP instrumental test standard are pipetted into a suitable 50 mL vessel that already contains a few milliliters of ultrapure water, and the vessel is filled to its nominal volume with ultrapure water.

2.4 Calibration solutions

The calibration solutions shown in Table 1 are prepared using the chemicals listed in Section 2.2. Before preparation of the calibration solutions, ICP multiple-element standard solution IV is diluted to concentrations of 100 mg/L (stock solution 1) or 10 mg/L (stock solution 2). For this purpose 10 mL or 1 mL of this standard solution as well as 3 mL of nitric acid are pipetted into a 100 mL PFA volumetric flask, and the flask is then filled to its nominal volume with ultrapure water.

A few milliliters of ultrapure water are placed in 50 mL PFA volumetric flasks. Then aliquots of the stock solutions (see Table 1) are added with a pipette, and the flasks are filled to their nominal volume with ultrapure water.

Table 1. Concentrations of the calibration solutions
Stock solutionsVolume of the stock solutionMixture volumes (with ultrapure water)Calibration solutions
[mg/L][mL][mL][mg/L]
1002.5505
1000.5501
1000.25500.5
    
 100.5500.1
 100.25500.05
 100.05500.01

The stability of the calibration solutions must be checked and in case of any doubt they must be freshly prepared every working day; the matrix of the dilutions must be adjusted to the matrix of the stock solution if necessary.

3 Sampling and sample preparation

  1. Top of page
  2. General principles
  3. Equipment, chemicals and solutions
  4. Sampling and sample preparation
  5. Operating conditions for ICP-OES
  6. Analytical determination
  7. Calibration
  8. Calculation of the analytical result
  9. Evaluation of the method
  10. References

3.1 Sampling procedure

A cellulose nitrate membrane filter (see Section 2.1) is inserted into the sampling head of the dust collection device (GSP), and a pump is connected. Stationary or personal sampling can be carried out. The air sample is drawn through the membrane filter by a flow-regulated pump at a flow rate of 3.5 L/min. After 2 hours of sampling, this is equivalent to an air sample volume of 0.42 m3. The sample carrier is subsequently removed from the sampling head and sealed with the designated caps.

After sampling, the flow rate must be tested for constancy. If the deviation from the adjusted flow rate is ≥ ± 5%, it is advisable to repeat the measurement.

3.2 Sample preparation

Ceramic tweezers are used to transfer the loaded membrane filter to a 25 mL quartz glass digestion vessel, and a glass rod is used to push it down to the bottom of the vessel. Then 10 mL of the acidic digestion mixture are added, an air cooler is fitted to the vessel and the solution is boiled for two hours in a thermostatically controlled aluminum heating block at 130 °C under reflux. After cooling, 10 mL of ultrapure water are cautiously added via the reflux cooler, and the mixture is brought to the boiling point again to achieve homogenization. After cooling, the air cooler and the glass rod are removed, the digestion vessel is sealed with a polyethylene stopper and the volume of the sample solution is read off. The solution is then analyzed by ICP.

A blank value determination is performed with each sample series. For this purpose at least one filter that has not been used for sampling is subjected to the entire sample preparation and analyzed.

To prepare the sample dilutions for the quantitative analysis, a few milliliters of ultrapure water are placed in suitable graduated 15 mL polypropylene vessels, a pipette is used to add an aliquot of the acidic digestion mixture, and the vessels are filled to 10 mL with ultrapure water.

4 Operating conditions for ICP-OES

  1. Top of page
  2. General principles
  3. Equipment, chemicals and solutions
  4. Sampling and sample preparation
  5. Operating conditions for ICP-OES
  6. Analytical determination
  7. Calibration
  8. Calculation of the analytical result
  9. Evaluation of the method
  10. References
Apparatus:ICP emission spectrometer, ICP-OES with CCD (charge-coupled device detector): Optima 5300DV, PerkinElmer LAS GmbH, Rodgau, Germany
Plasma parameters:

Plasma: 13 L/min

Auxiliary gas flow rate: 0.2 L/min

Nebulizer gas flow rate: 0.65 L/min

RF power: 1400 Watt

Flow rate (sample):0.40 mL/min
Nebulizer system:

Nebulizer chamber: PFA cyclone nebulizer chamber for PC3 sample inlet system, with cooling

Nebulizer: Concentric PFA nebulizer e.g. OpalMist, AR30-07-PFA02

Injector:

Material: Sapphire

Inner diameter: 2 mm

Plasma view:Axial
Measured wavelength:Chromium: 267.716 nm, 283.566 nm
 Copper: 324.755 nm, 224.701 nm
Measured solutions:

An aliquot of the sample solution is diluted at least 1 : 4 (v/v).

If the measurement result is outside the linear range of the calibration function, further dilutions, e.g. 1 : 20 and 1 : 100 (v/v) must be prepared.

5 Analytical determination

  1. Top of page
  2. General principles
  3. Equipment, chemicals and solutions
  4. Sampling and sample preparation
  5. Operating conditions for ICP-OES
  6. Analytical determination
  7. Calibration
  8. Calculation of the analytical result
  9. Evaluation of the method
  10. References

An autosampler transfers the prepared sample at a flow rate of 0.40 mL/min to the ICP emission spectrometer, and analysis is performed under the conditions stated in Section 4.

6 Calibration

  1. Top of page
  2. General principles
  3. Equipment, chemicals and solutions
  4. Sampling and sample preparation
  5. Operating conditions for ICP-OES
  6. Analytical determination
  7. Calibration
  8. Calculation of the analytical result
  9. Evaluation of the method
  10. References

The calibration solutions described in Section 2.4 are used to obtain the calibration functions. The calibration solutions are introduced into the ICP emission spectrometer at a flow rate of 0.40 mL/min, and analysis is carried out under the operating conditions stipulated in Section 4. The intensities are determined from the peak heights, which are plotted versus the corresponding concentrations. The calibration curves are linear in the investigated concentration ranges.

7 Calculation of the analytical result

  1. Top of page
  2. General principles
  3. Equipment, chemicals and solutions
  4. Sampling and sample preparation
  5. Operating conditions for ICP-OES
  6. Analytical determination
  7. Calibration
  8. Calculation of the analytical result
  9. Evaluation of the method
  10. References

The data evaluation unit calculates the concentration of chromium and copper in the workplace air from the concentration of the substances in the measured solution. The data evaluation unit uses the calculated calibration functions for this purpose. The concentrations of the metals in the workplace air are calculated from the measured concentrations, taking the corresponding dilutions and the air sample volume into account.

The concentration by weight of the analyte is calculated using equation 1:

  • mathml alt image(1)

where:

ρis the concentration by weight of the analyte in the air sample in mg/m3
Cis the concentration in the measured solution in µg/L
CBlankis the concentration of the blank value in µg/L
0.001is the conversion factor [µg [RIGHTWARDS ARROW] mg]
fvis the dilution factor (as a rule the dilution is 1 : 4)
Vis the volume of the sample solution in L
VAiris the air sample volume (calculated from the flow rate and the sampling time) in m3

8 Evaluation of the method

  1. Top of page
  2. General principles
  3. Equipment, chemicals and solutions
  4. Sampling and sample preparation
  5. Operating conditions for ICP-OES
  6. Analytical determination
  7. Calibration
  8. Calculation of the analytical result
  9. Evaluation of the method
  10. References

The characteristics of the method were calculated as stipulated in EN 482 [9].

8.1 Precision

In order to determine the precision, membrane filters are spiked with different masses of the dissolved metals, dried and subjected to all the steps of the sample preparation and analysis as described in Sections 3.2 and 4. For this purpose six filters are spiked with different concentrations of chromium and copper in each case, dried and subjected to digestion. Standard solutions of chromium and copper are used as starting solutions (see Section 2.2). The results are shown in Tables 2 and 3.

Table 2. Standard deviation (rel.) for n = 6 determinations for chromium
Spiked mass of chromiumConcentration*Standard deviation (rel.)
[µg][µg/m3][%]
  • *

    The concentration is calculated on the basis of a 2-hour sampling period at a flow rate of 3.5 L/min

 8.4 202.12
421001.88
842001.35
Table 3. Standard deviation (rel.) for n = 6 determinations for copper
Spiked mass of copperConcentration*Standard deviation (rel.)
[µg][µg/m3][%]
  • *

    The concentration is calculated on the basis of a 2-hour sampling period at a flow rate of 3.5 L/min

 4.2 102.89
21 501.83
421001.80

8.2 Recovery

The analytical recovery is defined as 100% according to EN 13890 on the basis of the sample preparation described above (restricted to those metals and compounds that are soluble in the stipulated system) [10, 11]. The sample preparation method was checked with certified chromium and copper compounds. For this purpose 70 mL of the acidic digestion mixture were added to 75 mg of the High Speed Steel Standard, 8.5 of mg copper sulfate and 25 mg of chromium nitrate nonahydrate in each case, and these mixtures were subjected to the entire digestion process. The solutions prepared in this manner were visually free of particles.

The quantitative analysis resulted in a recovery of η = 1.08 for copper from the High Speed Steel Standard and η = 1.06 for chromium. A recovery of η =  0.99 was achieved for copper from copper sulfate and η = 0.99 for chromium from chromium nitrate nonahydrate. The results are shown in Table 4.

Table 4. Recovery for chromium and copper
StandardAnalyteRecovery
[η]
Copper sulfateCu0.99
High Speed Steel StandardCu1.08
Chromium nitrate nonahydrateCr0.99
High Speed Steel StandardCr1.06

8.3 Limits of quantification

During development of the method the limit of quantification was determined as stipulated in DIN 32645 according to the blank value method [11]. Ten membrane filters that had not been used for sampling were subjected to the entire sample preparation process for this purpose. The mean for the blank value, which is caused by the filters, reagents and vessels used, as well as the corresponding standard deviation were determined and inserted in the following equation 2 to calculate the limit of quantification [12]:

  • mathml alt image(2)

where:

XBGis the limit of quantification in mg/L
inline imageis the mean value for the blank value measurements in mg/L
sis the standard deviation (rel.)
kis the selected factor (k = 10)

The limits of quantification for chromium and copper are listed in Tables 5 and 6.

Table 5. Limits of quantification for chromium and copper for n = 10 determinations
AnalyteMeasured wavelengthMean blank value inline imageStandard deviation (rel.) of the blank values in the sample solutionLimit of quantification XBG in the sample solution
[nm][mg/L][mg/L][mg/L]
Cr267.7160.0180.0550.57
Cr283.5630.0360.0670.71
Cu324.7520.0270.0920.95
Cu224.7000.0140.0560.57
Table 6. Limits of quantification for chromium and copper in the sampled air for n = 10 determinations
AnalyteMeasured wavelengthLimit of quantification for 2 h sampling time*Limit of quantification for 0.25 h sampling time**
 [nm][µg/m3][µg/m3]
  • *

    0.42 m3 air sample, 20 mL sample solution, dilution factor 4

  • **

    0.05 m3 air sample, 20 mL sample solution, dilution factor 4

Cr267.71627.1
Cr283.56333.8
Cu324.75245.2362
Cu224.70027.1217

8.4 Storage stability

The storage period of the loaded membrane filter should not exceed one month.

8.5 Selectivity

The selectivity of the method depends largely on the selection of the wavelength and thus on spectral interference. The reasons for spectral interferences are e. g. the emission lines from interferents and molecules in the sample matrix. In the case of overlapping lines and relevant intensities of the interferents an inter-element correction can be carried out, in which a linear correction factor is calculated. The correction factor is determined with individual element standards in concentrations of at most 100 mg/L. Experiments showed that more highly concentrated standards can precipitate in the mixing chamber or in the nebulizer. For samples with a high salt concentration it is advisable to use another nebulizer, such as a Babington nebulizer. In this case the limit of quantification is expected to increase by a factor of 2.

Changes in the excitation conditions in the plasma due to change of the electron density lead to non-spectral interference. This interference is decisively compensated by the addition of the cesium ionization buffer. In both cases dilution of the sample results in measurement conditions with less interference. An increase in the quantification limit must be accepted as a consequence.

References

  1. Top of page
  2. General principles
  3. Equipment, chemicals and solutions
  4. Sampling and sample preparation
  5. Operating conditions for ICP-OES
  6. Analytical determination
  7. Calibration
  8. Calculation of the analytical result
  9. Evaluation of the method
  10. References
  • 1
    Falbe J, Regitz M (eds.) (1993) Roempp Chemie Lexikon, Georg Thieme Verlag, Stuttgart.
  • 2
    Deutsche Forschungsgemeinschaft (2011) List of MAK and BAT Values 2011. Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area, Report No. 47. Wiley-VCH, Weinheim.
  • 3
    TRGS 900 (2006) Arbeitsplatzgrenzwerte. Revised and supplemented: GMBl 2011 No. 10, pp. 193–194, www.baua.de
  • 4
    Henschler D (ed.) (1992) and its compounds. Occupational Toxicants – Critical Data Evaluation for MAK Values and Classification of Carcinogens, Vol. 3: 101122. Wiley-VCH, Weinheim.
  • 5
    Greim H (ed.) (2009) Chrom(III)-Verbindungen. Gesundheitsschädliche Arbeitsstoffe, Toxikologisch-arbeitsmedizinische Begründungen von MAK-Werten, 46th issue. Wiley-VCH, Weinheim.
  • 6
    Greim H (ed.) (2006) Copper and its inorganic compounds. The MAK Collection for Occupational Health and Safety, Part I: MAK Value Documentations, Vol. 22: 4372. Wiley-VCH, Weinheim.
  • 7
    Hebisch R, Fricke H-H, Hahn J-U, Lahaniatis M, Maschmeier C-P, Mattenklott M (2005) Sampling and determining aerosols and their chemical compounds. In: Parlar H, Greim H (eds.) The MAK Collection for Occupational Health and Safety, Part III: Air Monitoring Methods, Vol. 9: 240. Wiley-VCH, Weinheim.
  • 8
    Montaser A, Golightly DW (eds.) (1992) Inductively Coupled Plasmas in Analytical Atomic Spectrometry, Second Edition, VCH Publishers, Inc., New York.
  • 9
    DIN EN 482 (2006) Workplace atmospheres – General requirements for the performance of procedures for the measurement of chemical agents. Beuth Verlag, Berlin.
  • 10
    EN 13890 (2010) Workplace atmospheres – Procedures for measuring metalloids in airborne particles – Requirements and methods. Beuth Verlag, Berlin.
  • 11
    DIN 32645 (2008) Chemical analysis – Decision limit, detection limit and determination limit under repeatability conditions – Terms, methods, evaluation. Beuth Verlag, Berlin.
  • 12
    BGI 505-0 (2003) Von den Berufsgenossenschaften anerkannte Analysenverfahren zur Feststellung der Konzentrationen krebserzeugender Arbeitsstoffe in der Luft in Arbeitsbereichen – A. Allgemeiner Teil. Carl Heymanns Verlag KG, Köln.