Sequential Determination of Cd, Cu, Pb, Co and Ni in Marine Invertebrates by Zeeman Graphite Furnace Atomic Absorption Spectroscopy

Significance of the Topic

Marine invertebrates are key indicators in biomonitoring programs to assess bioavailable metal levels in aquatic environments. Understanding metal accumulation in organisms such as zooplankton and benthos provides insight into biogeochemical cycling, potential toxic exposures, and anthropogenic impacts on ecosystems. Precise multi‐element analysis of limited biomass samples supports prospective monitoring and ecological risk assessment.

Study Objectives and Overview

The study aimed to develop and optimize a sequential, multi‐element graphite furnace atomic absorption spectroscopy (GFAAS) method with Zeeman background correction using the Agilent SpectrAA‐880 instrument. Target analytes included Cd, Co, Cu, Ni, and Pb in marine invertebrate tissues. Certified reference materials (Tort‐2 lobster hepatopancreas and CRM 278R mussel tissue) were used for method validation and performance evaluation.

Methodology

• Sample preparation: Freeze‐dried samples homogenized; ~10 mg digested with 100 µL HNO₃ at 80 °C for 3 h; diluted to 2 mL and adjusted to 3.25% HNO₃.
• Calibration: 4–5 standard levels prepared by auto‐mix; concentration calibration with New Rational algorithm; Reslope checks every ten samples.
• Quality assurance: GLP compliant; blanks, replicate precision (CV 1–5%); limits of detection calculated as mean blank plus 2.6×SD; daily QC charts and statistical tests (Lilliefors, ANOVA/Welch, Student‐Newman‐Keuls).

Used Instrumentation

• Agilent SpectrAA‐880 Zeeman AAS with GTA‐110 graphite furnace atomizer
• Programmable Sample Dispenser (PSD) for micro‐volume handling
• Nitrogen gas (grade 5.0) and chemical modifiers: 0.4 mg/mL Pd(NO₃)₂ and 2 g/L Mg(NO₃)₂
• Rinse solution: 0.002% Triton X-100 and 0.065% HNO₃; slitted lids to minimize evaporation

Main Results and Discussion

• Recovery rates between 90% and 107% for all elements in both reference materials.
• Detection limits ranged from 0.10 mg/kg (Cd) to 3.5 mg/kg (Cu) dry weight, suitable for trace analysis.
• QC charts over multiple days showed no significant drift; statistical evaluation confirmed method stability and reproducibility.
• Peak appearance times matched between standards and samples, indicating negligible matrix effects.

Benefits and Practical Applications

• Enables accurate, low‐volume analysis of multiple trace metals in small biomass samples.
• Reduces analysis time and resource use through sequential multi‐element determination.
• Supports biomonitoring of aquatic ecosystems, baseline studies, and bioaccumulation experiments.

Future Trends and Opportunities

• Integration with high‐throughput automation and hyphenated techniques for expanded element coverage.
• Advances in sample digestion to improve detection limits and homogeneity in micro‐samples.
• Application to broader environmental matrices and real‐time monitoring of metal bioavailability.

Conclusion

The optimized GFAAS method on the Agilent SpectrAA‐880 delivers precise, accurate, and stable multi‐element analysis of Cd, Co, Cu, Ni, and Pb in marine invertebrates. Its low detection limits and robust QC demonstrate suitability for environmental biomonitoring, even with minimal sample biomass.

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