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Home ›› About Speciation ›› Speciation News

Chromium speciation analysis for samples containing organic materials

(05.09.2024)

Chromium speciation analysis is crucial because Cr(VI) is highly toxic and carcinogenic, whereas trivalent chromium (Cr(III)) is generally considered less harmful and, in some cases, beneficial for the glucose metabolism. The toxicity of Cr(VI) is the reason for legislation meant to limit the human exposure. For this reason, different kind of samples from the human environment are analyzed for the presence of Cr(VI). As it is the case with all oxidation species, these species can be easily converted by changing pH and redox conditions during sampling and sample pretreatment. Sample pretreatment is challenging for solid samples, since chromium has to be extracted for most speciation techniques calling for liquid samples.

The speciation analysis of hexavalent chromium (Cr(VI)) in presence of organic materials is especially complex and challenging due to several factors:

1. Matrix Effects

Complex Organic Matrices: Organic materials, such as biological tissues, plants, or complex environmental samples (like soils rich in organic matter), contain a variety of organic compounds that can interfere with the extraction and detection of Cr(VI). These matrix components can bind to Cr(VI) or Cr(III), altering their speciation and making accurate quantification difficult.
Interference from Organic Compounds: Organic compounds in the sample can lead to various polyatomic interferences affecting chromium signal of ICP-MS detection.

2. Instability of Cr(VI)

Redox Instability: Cr(VI) is highly reactive and can be easily reduced to Cr(III) in the presence of reducing agents found in organic materials. This redox instability means that Cr(VI) can change its oxidation state during sample handling, storage, or analysis, leading to an underestimation of Cr(VI) levels.
pH Sensitivity: The speciation of chromium is pH-dependent. In organic matrices, pH variations can cause Cr(VI) to convert to Cr(III), especially under acidic conditions. Maintaining a consistent and appropriate pH during the extraction and analysis is challenging but crucial for accurate speciation.
Control of Environmental Factors: Temperature, light, and oxygen levels can affect the stability of Cr(VI) during sample preparation and analysis. Ensuring consistent environmental conditions is difficult but necessary to prevent speciation changes.
Storage Conditions: Cr(VI) can be unstable during storage, particularly in organic matrices that may contain reducing agents. Ensuring the preservation of Cr(VI) during storage (e.g., by freezing or adding stabilizers) is essential, but not always straightforward.

3. Analytical Challenges

Extraction Efficiency: Extracting Cr(VI) from organic materials without altering its speciation is challenging. Conventional extraction methods, such as using alkaline solutions, might not be effective for all types of organic matrices, or they may cause partial reduction of Cr(VI) to Cr(III).
Specificity of Analytical Techniques: The selectivity of extraction methods is not sufficient for differentiating Cr(III) from Cr(VI). Techniques like ion chromatography (IC) coupled with UV detection, or high-performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS), are commonly used for Cr(VI) analysis. However, these techniques require careful calibration and method validation to distinguish between Cr(VI) and Cr(III) in complex organic matrices.
Detection Limits and Sensitivity: The sensitivity of the analytical method is critical, particularly when Cr(VI) is present at low concentrations in the presence of large amounts of Cr(III). Achieving low detection limits without compromising accuracy is a significant challenge.
Contamination and Analyte Loss: During sample preparation, contamination from laboratory equipment (e.g. metallic parts of the HPLC system) or reagents can introduce Cr(VI) or reduce Cr(VI) to Cr(III), skewing results. Additionally, improper handling can lead to the loss of Cr(VI) through volatilization or adsorption onto surfaces.
Lack of Certified Reference Materials: There is a shortage of certified reference materials for Cr(VI) in organic matrices. This lack of standards makes it difficult to validate methods and ensure accurate and reproducible results.

Summary

In summary, the speciation analysis of hexavalent chromium in organic materials faces significant challenges due to matrix effects, the instability of Cr(VI), analytical limitations, and issues related to sample preparation, storage, and method validation. Addressing these challenges requires careful optimization of extraction methods, strict control of environmental conditions, and the development of standardized protocols and reference materials.

Reports about the presence of Cr(VI) in biological materials such as body fluids (blood, milk, urine), food, plant materials, organic fertilizers, etc. often lack the necessary selectivity and fail to address the challenges mentioned above. On the other hand, researchers having used sophisticated methods for speciation analysis taking care for possible interconversions were often not able to detect Cr(VI) in such materials above the detection limit. Actually, spiking experiment have shown, that Cr(VI) added to such sample types gets reduced to Cr(III) in short time.

Michael Sperling

Related studies addressing the analytical challenges for chromium speciation

Ge Song, Honglian Tan, Chuhan Cheng, Peng Li, Xinyang Sun, Yuling Zhou, Yong Fang, Development of a Fast Method Using Inductively Coupled Plasma Mass Spectrometry Coupled with High-Performance Liquid Chromatography and Exploration of the Reduction Mechanism of Cr(VI) in Foods, Toxics, 12 (2024) 325. DOI: 10.3390/toxics12050325

Marina Saraiva, Petru Jitaru, Jens J. Sloth, Speciation analysis of Cr(III) and Cr(VI) in bread and breakfast cereals using species-specific isotope dilution and HPLC-ICP-MS, J. Food Compos. Anal., 102 (2021) 103991. DOI: 10.1016/j.jfca.2021.103991

M. Saraiva, R. Chekri, A. Leufroy, T. Guerin, J.J. Sloth, P. Jitaru, Development and validation of a single run method based on species specific isotope dilution and HPLC-ICP-MS for simultaneous species interconversion correction and speciation analysis of Cr(III)/Cr(VI) in meat and dairy products. Talanta, 222 (2021) 121538. DOI: 10.1016/j.talanta.2020.121538

M. Saraiva, R. Chekri, T. Guerin, J.J. Sloth, P. Jitaru, Chromium speciation analysis in raw and cooked milk and meat samples by species-specific isotope dilution and HPLC-ICP-MS. Food Addit. Contam. Part A, 38/2 (2021) 304–314. DOI: 10.1080/19440049.2020.1859144

Radka Pechancová, Jiří Gallo, David Milde, Tomáš Pluháček, Ion-exchange HPLC-ICP-MS: A new window to chromium speciation in biological tissues, Talanta, 218 (2020) 121150. DOI: 10.1016/j.talanta.2020.121150

Radmila Milacic, Janez Scancar, Cr speciation in foodstuffs, biological and environmental samples: Methodological approaches and analytical challenges - A critical review, Trends Anal. Chem., 127 (2020) 115888. DOI: 10.1016/j.trac.2020.115888

O. Mihai, M.S. Kawamoto, K.L. LeBlanc, P. Grinberg, A.R. d.A. Nogueira, Z. Mester, Determination of chromium picolinate and trace hexavalent chromium in multivitamins and supplements by HPLC-ICP-QQQ-MS. J. Food Compos. Anal., 87 (2020) 103421. DOI: 10.1016/j.jfca.2020.103421.

R. Pechancova, T. Pluhacek, D. Milde, Recent advances in chromium speciation in biological samples, Spectrochim. Acta Part B, 152 (2019) 109–122. DOI: 10.1016/j.sab.2018.12.008.

Z.F. Chen, X. Guan, Y.S. Zhao, Morphology analysis of hexavalent chromium reduction to trivalent chromium with syrup under different pH conditions. Appl. Water Sci., 9 (2019) 187. DOI: 10.1007/s13201-019-1070-1.

R. Pechancová, T. Pluháček, J. Gallo, D. Milde, Study of chromium species release in blood and joint effusion utilizing HPLC-ICP-MS, Talanta, 185 (2018) 370–375. DOI: 10.1016/j.talanta.2018.03.100.

E.M. Hamilton, S.D. Young, E.H. Bailey, M.J. Watts, Chromium speciation in foodstuffs: a review, Food Chem., 250 (2018) 105–112. DOI: 10.1016/j.foodchem.2018.01.016.

F. Seby, V. Vacchina, Critical assessment of hexavalent chromium species from different solid environmental, industrial and food matrices, Trends Analyt. Chem., 104 (2018) 54–68. DOI: 10.1016/j.trac.2017.11.019.

B. Finley, P.K. Scott, M.E. Glynn, D. Paustenbach, E. Donovan, K.A. Thuett, Chromium speciation in the blood of metal-on-metal hip implant patients, Toxicol. Environ. Chem. 99 (2017) 48–64. DOI: 10.1080/02772248.2016.1148904.

A. Di Laura, P.D. Quinn, V.C. Panagiotopoulou, H.S. Hothi, J. Henckel, J.J. Powell, F. Berisha, F. Amary, J.F.W. Mosselmans, J.A. Skinner, A.J. Hart, The chemical form of metal species released from corroded taper junctions of hip implants: synchrotron analysis of patient tissue, Sci. Rep. 7 (2017) 10952. DOI: 10.1038/s41598-017-11225-w.

M. Chrysochoou, K. Reeves, Reduction of hexavalent chromium by green tea polyphenols and green tea nano zero-valent iron (GT-nZVI). Bull. Environ. Contam. Toxicol., 98 (2017) 353–358. DOI: 10.1007/s00128-016-1901-9.

Fanny Hernandez, Fabienne Séby, Sandrine Millour, Laurent Noël, Thierry Guérin, Optimisation of selective alkaline extraction for Cr(VI) determination in dairy and cereal products by HPIC–ICPMS using an experimental design, Food Chem., 214 (2017) 339–346. doi: 10.1016/j.foodchem.2016.07.099

K. Pyrzynska, Chromium redox speciation in food samples, Turk. J. Chem., 40 (2016) 894–905. DOI: 10.3906/kim-1606-5.

Y.A. Lin, S.J. Jiang, A.C. Sahayam, Y.L. Huang, Speciation of chromium in edible animal oils after microwave extraction and liquid chromatography inductively coupled plasma mass spectrometry. Microchem. J., 128 (2016) 274–278. DOI: 10.1016/j.microc.2016.05.001.

F.B. de Souza, H. de Lima Brandão, F.V. Hackbarth, A.A.U. de Souza, R.A.R. Boaventura, S.M. A.G.U. de Souza, V.J.P. Vilar, Marine macro-alga Sargassum cymosum as electron donor for hexavalent chromium reduction to trivalent state in aqueous solutions. Chem. Eng. J., 283 (2016) 903–910. DOI: 10.1016/j.cej.2015.08.038.

Z.F. Chen, Y.S. Zhao, J.W. Zhang, J. Bai, Mechanism and kinetics of hexavalent chromium chemical reduction with sugarcane molasses. Water Air Soil. Pollut., 226 (2015) 363. DOI: 10.1007/s11270-015-2629-6.

K.M. Shah, P.D. Quinn, A. Gartland, J.M. Wilkinson, Understanding the tissue effects of tribo-corrosion: uptake, distribution, and speciation of cobalt and chromium in human bone cells, J. Orthop. Res. 33 (2015) 114–121. DOI: 10.1002/jor.22729.

V. Vacchina, I. de la Calle, F. Seby, Cr(VI) speciation in foods by HPLC-ICP-MS: investigation of Cr(VI)/food interactions by size exclusion and Cr(VI) determination and stability by ion-exchange on-line separations, Anal. Bioanal. Chem., 407 (2015) 3831–3839. DOI: 10.1007/s00216-015-8616-3.

B. Novotnik, T. Zuliani, J. Scancar, R. Milacic, Content of trace elements and chromium speciation in Neem powder and tea infusions, J. Trace Elem. Med. Biol., 31 (2015) 98–106. DOI: 10.1016/j.jtemb.2015.04.003.

B. Novotnik, T. Zuliani, J. Scancar, R. Milacic, Chromate in food samples: an artefact of wrongly applied analytical methodology? J. Anal. Atom. Spectrom., 28 (2013) 558–566. DOI: 10.1039/c3ja30233d.

A.J. Hart, P.D. Quinn, B. Sampson, A. Sandison, K.D. Atkinson, J.A. Skinner, J.J. Powell, J.F.W. Mosselmans, The chemical form of metallic debris in tissues surrounding metal-on-metal hips with unexplained failure, Acta Biomater. 6 (2010) 4439–4446. DOI: 10.1016/j.actbio.2010.06.006.

Related studies reporting the presence of Cr(VI) in samples containing natural organic matter

Arthur Felipe Burg, Graciela Marini Hiedrich, Ana Barbosa Viana, Valderi Luiz Dressler, Chromium Speciation in Organic Fertilizers by Spectrophotometry, Quim. Nova, 48/3 (2025) e-20250043. DOI: 10.21577/0100-4042.20250043

B.-H. Chen, S.-J. Jiang, A.C. Sahayam, Determination of Cr(VI) in rice using ion chromatography inductively coupled plasma mass spectrometry. Food Chem. 324/15 (2020) 126698. DOI: 10.1016/j.foodchem.2020.126698

M.W. Mathebula, K. Mandiwana, N. Panichev, Speciation of chromium in bread and breakfast cereals. Food Chem., 217 (2017) 655–659. DOI: 10.1016/j.foodchem.2016.09.020.

Hamid Shirkhanloo, Mehri Ghazaghi, Hassan Z. Mousavi, Chromium speciation in human blood samples based on acetylcysteine by dispersive liquid–liquid biomicroextraction and in-vitro evaluation of acetyl cysteine/cysteine for decreasing of hexavalent chromium concentration, J. Pharm. Biomed. Anal., 118 (2016) 1–8. DOI: 10.1016/j.jpba.2015.10.018

E. Vieira, M.E. Soares, M. Kozior, Z. Krejpcio, I.M. Ferreira, M.L. Bastos, Quantification of total and hexavalent chromium in lager beers: Variability between styles and estimation of daily intake of chromium from beer. J. Agr. Food Chem., 62 (2014) 9195–9200. DOI: 10.1021/jf502657n.

Shizhong Chen, Shengping Zhu, Yuanyuan He, Dengbo Lu, Speciation of chromium and its distribution in tea leaves and tea infusion using titanium dioxide nanotubes packed microcolumn coupled with inductively coupled plasma mass spectrometry, Food Chemistry 150 (2014) 254–259. doi: 10.1016/j.foodchem.2013.10.150

Khakhathi L. Mandiwana, Nikolay Panichev, Svetlana Panicheva, Determination of chromium(VI) in black, green and herbal teas, Food Chemistry 129 (2011) 1839–1843. doi: 10.1016/j.foodchem.2011.05.124

M.E. Soares, E. Vieira, M.D. Bastos, Chromium speciation analysis in bread samples, J. Agric. Food Chem. 58 (2010) 1366–1370. DOI: 10.1021/jf903118v.

H.J. Wang, X.M. Du, M. Wang, T.C. Wang, O.Y. Hong, B. Wang, M.T. Zhu, Y. Wang, G. Jia, W.Y. Feng, Using ion-pair reversed-phase HPLC ICP-MS to simultaneously determine Cr(III) and Cr(VI) in urine of chromate workers, Talanta 81 (2010) 1856–1860. DOI: 10.1016/j.talanta.2010.03.059.

Abayneh A. Ambushe, Robert I. McCrindle, Cheryl M. E. McCrindle, Speciation of chromium in cow's milk by solid-phase extraction/dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS), J. Anal. At. Spectrom., 24/4 (2009) 502-507. DOI: 10.1039/b819962k

Róbert Kovács, Aron Béni, Roland Karosi, Csilla Sógor, József Posta, Investigation of chromium content in foodstuffs and nutrition supplements by GFAAS and determination of changing Cr(III) to Cr(VI) during baking and toasting bread, Food Chem., 105/3 (2007) 1209-1213. DOI: 10.1016/j.foodchem.2007.02.030

Maria E. Soares, Maria L. Bastos, Margarida Ferreira, Selective Determination of Chromium (VI) in Powdered Milk Infant Formulas by Electrothermal Atomization Atomic Absorption Spectrometry after Ion Exchange, J. AOAC International, 83/1 (2000) 220-223.

J. Lameiras, M. Elisa Soares, M. Lourdes Bastos, M. Ferreira, Quantification of total chromium and hexavalent chromium in UHT milk by ETAAS, Analyst, 123 (1998) 2091–2095. doi: 10.1039/a804700f