A method for the analysis of methylmercury and total Hg in fungal matrices

A high-throughput, straightforward procedure for biomonitoring organomercury species in human hair

Mercury is a pervasive and concerning pollutant due to its toxicity, mobility, and tendency to biomagnify in aquatic and terrestrial ecosystems. Speciation analysis is crucial to assess exposure and risks associated with mercury, as different mercury species exhibit varying properties and toxicities. This study aimed at developing a selective detection method for organic mercury species in a non-invasive biomonitoring matrix like human hair. The method is based on frontal chromatography (FC) in combination with inductively coupled plasma mass spectrometry (ICP-MS), using a low pressure, homemade, anion exchange column inserted in a standard ICP-MS introduction system, without requiring high-performance liquid chromatography (HPLC) hyphenation. In addition to the extreme simplification and cost reduction of the chromatographic equipment, the proposed protocol involves a fast, streamlined and fully integrated sample preparation process (in contrast to existing methods): the optimized procedure features a 15-min ultrasonic assisted extraction procedure and 5 min analysis time. Consequently, up to 100 samples could be analyzed daily, making the method highly productive and suitable for large-scale screening programs in public and environmental health. Moreover, the optimized procedure enables a limit of detection (LOD) of 5.5 μg/kg for a 10 mg hair microsample. All these features undeniably demonstrate a significant advancement in routine biomonitoring practices. To provide additional evidence, the method was applied to forty-nine human hair samples from individuals with varying dietary habits successfully finding a clear correlation between methylmercury levels (ranging from 0.02 to 3.2 mg/kg) in hair and fish consumption, in line with previous literature data.

Analysis of polyhalogenated carbazoles and two related compounds in earthworms using a modified QuEChERS method with GC/MS and GC/MS/MS

A precise analytical method based on QuEChERS has been proposed for the concurrent determination of 11 polyhalogenated carbazoles (PHCZs), benzocarbazole (BZCZ), and 9H-carbazoles (CZ). The quantification was confirmed by gas chromatography using triple quadrupole tandem mass spectrometry (Shimadzu GC-MS/MS-TQ8040) and gas chromatography coupled mass spectrometry (Agilent 7890A-5973 GC-MS). The developed method was validated by testing the following parameters: linearity, instrument limit of detection (LOD), instrument limit of quantification (LOQ), method limit of detection (MLD), method limit of quantification (MLQ), matrix effect (ME), accuracy, and precision. All compounds showed good linearity in the range of 0.005-0.2 μg/mL with correlation coefficients higher than 0.992. The method demonstrated satisfactory recoveries (ranging from 71.21 to 105.04%) for most of the compounds with relative standard deviation precision (RSD) < 10.46%, except 3-BCZ (Recovery = 67.53%, RSD = 2.83%). The values of LOD and LOQ varied from 0.05 to 0.24 ng and 0.14 to 0.92 ng, respectively, while those of MLD and MLQ ranged from 0.02 to 0.12 ng/g wet weight (ww) and 0.07 to 0.45 ng/g ww, respectively. The developed method represents a reliable tool for the routine analysis of PHCZ congeners in invertebrate animals.

Feasibility study for mercury remediation by selenium competition in Pleurotus mushrooms

Mushrooms may incorporate significant levels of Hg making its consumption harmful to human health. Mercury remediation induced by Se competition in edible mushrooms represents a valuable alternative since Se plays effective roles against Hg uptake, accumulation, and toxicity. In this way, Pleurotus ostreatus and Pleurotus djamor were cultivated on Hg-contaminated substrate simultaneously supplemented with Se(IV) or Se(VI) under different dosages in this study. The protective role of Se was assessed taking into account morphological characteristics and Hg and Se total concentrations determined by ICP-MS, as well as proteins and protein-bound Hg and Se distribution by SEC-UV-ICP-MS, and Hg speciation studies (Hg(II) and MeHg) by HPLC-ICP-MS. Both Se(IV) and Se(VI) supplementation were able to recover the morphology mainly of Hg-contaminated Pleurotus ostreatus. The mitigation effects induced by Se(IV) stood out more than Se(VI) in terms of Hg incorporation, decreasing the total Hg concentration up to 96 %. Also, it was found that supplementation mainly with Se(IV) reduced the fraction of Hg bound to medium molecular weight compounds (17-44 kDa) up to 80 %. Finally, it was shown a Se-induced inhibitory effect on Hg methylation, decreasing MeHg species content in mushrooms exposed to Se(IV) (51.2 µg g^-1) up to 100 %.

Letter to the editor: Comment on "multiannual monitoring (1974-2019) of rare earth elements in wild growing edible mushroom species in Polish forests" by Siwulski et al. https://doi.org/10.1016/j.chemosphere.2020.127173. A recurring question - What are the real concentrations and patterns of REE in mushrooms?

Siwulski et al. (2020) investigated the occurrence of the lanthanides (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), scandium (Sc) and yttrium (Y) in 4 species of wild mushrooms, which were sampled over a 45 years period in Poland. The reported mean lanthanide concentrations for mushrooms were in the range from 539 to 1601 μg kg^-1 dry weight. These values are considered as highly elevated in the light of data published earlier for the same species, where the analytical results were assessed as not being biased by errors (these could arise from contamination of the samples with soil dust or unsuitable choice of analytical methodology including the use of unsuitable analytical instrumentation for measurement). It has long been established that the lanthanides are naturally distributed in ores, soil bedrock, soils, natural waters and plants in a pattern that reflects the Oddo-Harkins rule. This pattern is correspondingly reflected in fungi, including the same species and have been published earlier by other authors. However, when the individual lanthanide concentration data of B. edulis, I. badia, L. scabrum and M. procera from the study by Siwulski et al. are plotted, they do not display the expected sawtooth (zigzag) concentration pattern - in other words, the concentration data do not follow the Oddo-Harkins rule. Lanthanides are naturally found in very low concentration in foods including wild mushrooms. There is a striking lack of convergence in the results obtained for ICP-MS techniques, and the results obtained from ICP-OES measurement (as used by Siwulski et al.). If the reasons discussed here for anomalies in the reported lanthanides data hold true, how does this affect the data for other elements in mushrooms reported in the commented article?

Comment on "Worldwide basket survey of multielemental composition of white button mushroom Agaricus bisporus": The credibility of the concentration data reported for REE are questioned - are they reliable enough to be included in the database on nutrients in mushrooms?

The focus of this comment is on the Lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) which, together with Sc and Y are also called the rare earth elements (REE). Individual REE have similar chemical properties and can be treated as a group. They behave similarly in the environment and in food webs. However, the determination of REE in foods, including edible mushrooms is analytically very challenging. In study by Siwulski et al. (2020) concentrations were reported for Ce, Nd, Sm, La, Sm and Tm, but the others were not detected above the method quantification limit. The sum of Ce (340-2730 μg kg^-1 dw), Nd (10-1220 μg kg^-1 dw), Sm (10-420 μg kg^-1 dw), La (10-130 μg kg^-1 dw), Sm (10-420 μg kg^-1 dw), Tm (10-170 μg kg^-1 dw) in 32 samples of A. bisporus was in the range of 430-3510 μg kg^-1 dry weight. The first visible characteristic is a large difference in the concentrations of Ce, Nd, Sm, La and Tm between the A. bisporus samples and various wild species and cultivated Cyclocybe cylindracea and Pleurotus ostreatus. Secondly, there is no correspondence with the Oddo-Harkins order and the concentrations pattern of Ce, Nd, Sm, La and Tm reported for the A. bisporus samples. The pattern is clearly different from that observed in the wild mushrooms and the two cultivated species reported by other studies. The ICP-OES and also the low resolution ICP-MS determination of REE directly from a fungal digest can suffer from spectral interferences of different types including an effect of the matrix which have to be overcome in the course of reliable and controlled analysis of REE.

Comment on “Screening the Multi-element Content of Pleurotus Mushroom Species Using Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES)”

La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu are lanthanides, also referred to as “rare earth” elements (occurring at ultra-low concentration, i.e. each, at ppb or lower levels) in plant and animal foods including edible wild mushrooms. Could it be that lanthanides when collectively reported as a summed value (widely referred to as REE) are at relatively high concentrations because extremely high contributions from individual elements? REE elements naturally occur in environmental media such as the soil substrate in which plants and fungi grow in a characteristic pattern (Oddo-Harkins rule), with most of the available literature confirming the extension of this pattern in fungi. Abnormalities therefore need to be examined closely and resolved.

Rare Earth Elements in Boletus edulis (King Bolete) Mushrooms from Lowland and Montane Areas in Poland

Mining/exploitation and commercial applications of the rare-earth elements (REEs: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in the past 3 decades have raised concerns about their emissions to the environment, possible accumulation in food webs, and occupational/environmental health effects. The occurrence and distribution of REEs Y and Sc in the fruitbodies of Boletus edulis collected from geographically diverse regions in Poland were studied in 14 composite samples that were derived from 261 whole fruiting bodies. Individual REE median concentrations ranged from 0.4–95 µg kg⁻¹ dry weight (dw). The summed REE concentrations varied widely, with a median value of 310 µg kg⁻¹ dw and a range of 87 to 758 µg kg⁻¹. The Sc and Y median concentrations (dw) were 35 and 42 µg kg⁻¹, respectively. Ce, La, and Nd, with median values of 95, 51, and 32 µg kg⁻¹, respectively, showed the highest occurrence. B. edulis collected from a forested area formerly used as a military shooting range—possibly a historically contaminated site—had an elevated summed REE content of 1796 µg kg⁻¹. REE concentrations were generally low in Polish King Bolete. Dietary intake from a mushroom meal was negligible, posing no health risk to consumers.