Determination of Mercury, Methylmercury and Selenium

Overview

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Key numbers

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determined by HrGc/Ms. THg and MeHg concentrations ranged from 0.61 to 1.25 µg g−1 w.w. and
Citation: Storelli, A.; Barone, G.; approximately 50% of the concentration measured to avoid exceeding the PTWI. Nevertheless, the
proportion of MeHg respective to the total amount of Hg, from about 10% in phytoplankton
glauca (blue shark, n = 20), Squalus acanthias (picked dogfish, n = 38), Squalus blainville
(longnose spurdog, n = 26), Mustelus mustelus (smooth-hound, n = 32), Mustelus asterias
(starry smooth-hound, n = 30 ), Scyliorhinus canicula (lesser spotted dogfish, n = 49), Lamna
nasus (porbeagle, n = 20), Raja clavata (thornback ray, n = 41), Raja miraletus (brown ray,
n = 45), Raja asterias (Mediterranean starry ray, n = 50), Leucoraja circularis (sandy ray, n = 48),
NaCl 10% (w/v) was added to the sample, and the mixture was centrifuged (2400 rpm
extract was subjected twice to back-extraction with a 1% (v/w) cysteine aqueous solution.
reaction was carried out by adding 1 mL of saturated CuSO4 solution and 0.2 mL of 1% (v/w)
designed at 240 ◦ C. Helium (99.99%) was used as a carrier gas at a flow rate of 1.0 mL min−1 .
atopancreas (National Research Council of Canada). Replicate analyses (n = 3) (THg
blank value) and of quantification (LOQs: 10 SD blank value) were the following: LODs:
THg: 5 ng g−1 wet weight, MeHg: 0.03 ng g−1 wet weight, Se: 1 ng g−1 wet weight; LOQs:
As shown in Table 1, overall findings showed concentrations of THg and MeHg
for the MeHg/THg ratio, the percentages varied from 77.6% to 98.4% with an average of
88.5%. These results are in good agreement with the general assumption that most of the
Table 1. Total mercury (THg), methylmercury (MeHg), selenium (Se) concentrations expressed in
µg g−1 wet weight (means ± SD), percentages of methylmercury respect to THg and number of
scribe Se concentrations equal to 0.30 µg g−1 w.w. and in the range of 0.084–0.46 µg g−1
children (31,32). While THg intake is acceptable for the general population, it should not
weekly consumption of fish for a total population of 271.6 g week−1 , ranged from 1.91 to
In terms of species (Table 2), THg estimated intake was higher than the corresponding
reaching also 84% of established PTWI.
Table 2. Estimated weekly intakes (EWI: µg kg− 1 bw week− 1 ) of total mercury (THg) and methylmer-
50% than those measured to avoid exceeding the PTWI. However, emphasis needs to be
servings per week was considered. As seen in Table 2, the consumption of the studied
effects, but not more than one meal in a month of sharks and torpedinids (Table S2).
of the Hg, Se and selenium health benefit value (HBVSe). Table S2 MeHg concentrations, daily
1. United States Environmental Protection Agency (US EPA). Risk Based Concentration Table; United States Environmental Protection
1. United States Environmental Protection Agency (US EPA). Regional Screening Level (RSL) Summary Table (TR = 1E-06, HQ = 1);

Methods (brief)

for each species. THg and Se were analysed by atomic absorption spectrometry, while MeHg was
samples European Community limits for THg were surpassed, while for MeHg none of the fish had
in Southern Italy. Fish samples, separated by species, were placed in polythene bags, and
(n = 20) of about 100 g of muscle tissue were taken. For each species, a composite sample
aliquots of samples (about 2 g) were digested to a transparent solution with a mixture
of H2 SO4 –HNO3 (1:1). The sample solution was then cooled and diluted with double
Concentrations of THg and Se were quantified by atomic absorption spectrophotometer
For the quantification of MeHg, aliquots of the samples (about 0.5 g) were washed with
and the sample was added to ethylmercury chloride in methanol (100 µL internal standard)
NaCl 10% (w/v) was added to the sample, and the mixture was centrifuged (2400 rpm
After acidification of the collected cysteine extract with H2 SO4 (0.1 M), the derivatization
µL of the sample was injected in splitless mode at an injection temperature of 250 ◦ C. The
calibration standards, spiked samples and the certified material TORT-3 Lobster Hep-
10.9 ± 1.0 mg kg−1 dry weight), (% recovery = 96–101%). The limits of detection (LOD: 3 SD
blank value) and of quantification (LOQs: 10 SD blank value) were the following: LODs:
THg: 5 ng g−1 wet weight, MeHg: 0.03 ng g−1 wet weight, Se: 1 ng g−1 wet weight; LOQs:
standard is currently available, consequently the results obtained for muscle samples are
most of the studied fish samples contained concentrations exceeding the nationally or

Implications

This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.

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Verification notes

Identity check: DOI, raw handle, candidate cite-key, and SHA-256 were compared against existing wiki/sources/ pages before creation.
Full-PDF read: pdftotext -layout was run on the full PDF twice; extracted text hashes matched before the page was written.
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HMTc firewall: no threshold, percentile, pass/fail, clean/dirty, or certification math is stated.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised