Speciation analysis of lead in seafood using short-column ion chromatography coupled with ICP-MS

Lead pollution in marine environments is largely attributed to human activities such as mining, fossil fuel combustion, and waste incineration. Once introduced into the environment, lead undergoes various physical and chemical transformations via global biogeochemical cycling. Marine organisms can absorb and accumulate lead, posing a significant risk to human health through seafood consumption.

Accurate evaluation of lead in seafood requires distinguishing between different lead species, particularly due to their varying toxicities. Organic lead compounds such as trimethyl lead (TML) and triethyl lead (TEL) are significantly more toxic than inorganic lead (Pb²⁺). Several hyphenated techniques using ICP-MS have been employed for lead speciation, including gas chromatography (GC), liquid chromatography (LC), and capillary electrophoresis (CE). However, GC-ICP-MS and CE-ICP-MS require complex interfaces and derivatization steps. Conventional HPLC-ICP-MS approaches often rely on expensive columns, increasing overall analysis costs.

To address these limitations, the researchers developed a more economical method using ion chromatography (IC) with low-cost guard columns for separating lead species. A critical component of speciation analysis is the extraction of lead species from seafood without altering their forms. The team introduced a microwave-assisted extraction protocol suitable for a variety of seafood types, including fish, shellfish, and seaweed.

Samples were freeze-dried and ground into powder. Approximately 100 mg of each sample was mixed with 6.0 mL of 12 mM EDTA solution in a 50 mL Teflon jar, incubated at room temperature for 6 hours, then subjected to microwave-assisted extraction at 120°C for 30 minutes. After cooling, the extract was centrifuged, and the residue was re-extracted using the same method. The combined supernatants were filtered (0.45 µm) and diluted up to fivefold with ultrapure water before IC-ICP-MS analysis.

Figure: IC-ICP-MS chromatograms for Pb standard solutions containing 0.10, 0.25, 0.50, 1.00, 2.00, 5.00 and 10.0 ng/mL lead

Three lead species—Pb²⁺, TML, and TEL—were successfully separated using two consecutive Zorbax-300SCX strong cation-exchange guard columns, achieving baseline separation within 10 minutes. The method demonstrated high precision and accuracy, with recoveries ranging from 94% to 105%, relative standard deviations (RSD, n=5) below 6%, and detection limits between 0.60 and 0.72 ng Pb/g dried seafood.

The analysis revealed species-specific lead distributions: seaweed and shellfish contained only Pb²⁺, while fish samples showed both Pb²⁺ and TML.

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last time modified: April 14, 2025