Arsenic and inorganic arsenic detection ‘challenging’ for EU labs

By Joseph James Whitworth contact

- Last updated on GMT

The test looked at cadmium, lead, arsenic, mercury and inorganic arsenic in mushrooms.
The test looked at cadmium, lead, arsenic, mercury and inorganic arsenic in mushrooms.

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Arsenic and inorganic arsenic remain a detection challenge for a number of laboratories, according to proficiency testing.

The tests looked at the capability of labs to determine cadmium, lead, arsenic, mercury and inorganic arsenic in mushrooms. 

Results showed analytical capabilities to determine arsenic and inorganic arsenic had increased since the last tests in 2010. 

However the scores were not as good when compared to the other heavy metals analysed.

Heavy metal permitted levels

Maximum levels for heavy metals in mushrooms based on wet weight are set by the Regulation (EC) No. 1881/2006.

For common, oyster and shiitake mushroom the maximum levels are: 0.20 mg kg−1​ cadmium and 0.30 mg kg−1​ for lead. For other species the maximum level for cadmium of 1 mg kg−1​ applies.

No maximum levels have been set yet for inorganic arsenic and methylmercury, although they are the most toxic species of arsenic and mercury, respectively.

Since mushroom consumption has increased in the last years due to their nutritional properties, DG SANCO of the European Commission requested the EURL-HM test analytical capabilities of National Reference Laboratories (NRLs) to determine heavy metals in (shiitake) mushrooms.

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC) runs the International Measurement Evaluation Program (IMEP).

Two proficiency tests (PTs): IMEP-116 and IMEP-39 assessed the labs ability.

Participation in IMEP-116 was restricted to NRLs appointed by national authorities in EU member states. IMEP-39 was open to all laboratories.

Thirty-seven participants from 25 countries gave results in IMEP-116, and 62 laboratories from 36 countries reported for the IMEP-39 study.

Proficiency test findings

Laboratory results were rated with z- and zeta- scores in accordance with ISO 13528.

The percentage of satisfactory z-scores ranged from 81% (iAs) to 97% (total Cd) in IMEP-116 and from 64% (iAs) to 84% (total Hg) in IMEP-39​,” found the study.

Although no significant differences were seen, in general the better performing laboratories used microwave digestion with nitric acid and hydrogen peroxide for sample digestion; some quality assurance issues (e.g. having a quality system in place, being accredited, use of certified reference materials for validation and/or calibration purposes and taking part regularly in PTs); and having experience with this type of analysis/matrices.

In general, users of atomic absorption spectrometry (AAS)-based techniques reported lower values than those who used ICP-based techniques (ICP-MS and ICP-AES) for total arsenic mass fraction.

The lower values reported by participants using AAS-based techniques resulted in a significantly lower percentage of satisfactory z-scores (35%) when compared with those obtained by laboratories using ICP-based techniques (87%).

“However, this clustering of results on the basis of the technique used could be due to a non-quantitative digestion of the matrix without being related to the technique used.”

For inorganic arsenic determination, five out of the seven laboratories with satisfactory z​-scores in IMEP-39, used AAS-based techniques.

The technique used was not so significant for the total cadmium, lead and mercury mass fractions but the four lowest values reported for total cadmium used AAS or ET-AAS.

Source: Food Additives & Contaminants: Part A Volume 32, Issue 1, 2015

 Online ahead of print, DOI: 10.1080/19440049.2014.966336

Determination of total cadmium, lead, arsenic, mercury and inorganic arsenic in mushrooms: outcome of IMEP-116 and IMEP-39​”

Authors:  F. Cordeiro, T. Llorente-Mirandes, J.F. López-Sánchez, R. Rubio, A. Sánchez Agullo, G. Raber, H. Scharf, D. Vélez, V. Devesa, Y. Fiamegos, H. Emteborg, J. Seghers, P. Robouch and M.B. de la Calle

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