Determination of Mercury in Mollusks

Mollusks can enrich pollutants in water bodies, which leads to excessive heavy metals in mollusks. The presence of heavy metals in the form has become an essential threat to mollusk food safety. These harmful substances can act on humans through the accumulation and amplification mechanism of the food chain, posing a potential threat to human health. Research on heavy metals in mollusks has focused on residue analysis and risk assessment. By analyzing the status of heavy metal contamination in mollusks and studying the effects and changes of food processing techniques on the degree of heavy metal contamination using in vitro digestion models, we aimed to evaluate the effects of processing methods on the safety of shellfish consumption.

Determination of Hg residues in mollusk samples

• Sample pretreatment

The samples were weighed accurately, added with aqueous tetramethylammonium hydroxide, shaken well, and placed in an oven at 90℃ to allow sufficient digestion, then transferred to a graduated tube after cooling, and fixed with the mobile phase (ammonium acetate and L-cysteine, added with ultrapure water, and pH adjusted to 7. 0 with ammonia).

• Hg detection method

The recoveries of methyl Hg in shellfish were between 90% and 110% by ICP-MS, the standard deviations were by the relevant detection standards and requirements. The linear correlation coefficients of the standard curves were all above 0. 9990.

• Evaluation method of Hg contamination in mollusk samples

The biological quality index method was used, and the single contamination index P_i was evaluated.

In the formula, P_i is the contamination index of heavy metal i, C_i is the measured value of heavy metal i in mollusks, and S_i is the evaluation standard of heavy metal i in shellfish. When P_i≤1, it means no contamination; when Pi>1 means contamination.

• Risk evaluation of heavy metal exposure to human

The risk assessment of human exposure to heavy metals was performed using the target risk factor (THQ) and target carcinogenic risk (TR) recommended by the US Environmental Protection Agency (US EPA), and THQ and TR were calculated as follows.

Efr is the exposure frequency; Edtot is the exposure duration; IR is the daily intake rate; C is the heavy metal residue in the edible fraction of shellfish; CPSo indicates the carcinogenic intensity index; BWa is the average body weight; Atn is the average exposure time: Atn = Edtot × 365 days/year; RfDo is the reference dose; Atm indicates the duration of a carcinogenic effect.

• Bioavailability analysis

The remaining digestate was adjusted to pH 5.0 with NaHCO₃ solution, added to the pancreatic-bile salt mixture, and shaken for 2 h at 37°C. The digestate was filtered and detected on ICP-MS and atomic fluorescence, respectively. The digest was filtered and detected on ICP-MS and atomic fluorescence.

Bioavailability = Available metal content/total metal × 100%

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