Flame AA Analysis of Cadmium (Cd) and Lead (Pb) in Simulated Seawater and Polished Rice Using Chelating Polymer Solid Phase Extraction

Significance of the Topic

The accurate determination of trace amounts of cadmium and lead in complex matrices such as seawater and food products is critical for environmental monitoring and food safety. Traditional solvent extraction methods are laborious and generate significant chemical waste. The integration of solid phase extraction using chelating polymer resins offers a greener, more streamlined approach to isolate and concentrate target metals prior to atomic absorption analysis.

Objectives and Study Overview

This study demonstrates the application of flame atomic absorption spectroscopy with preconcentration by chelating polymer solid phase extraction. Two sample types are evaluated: simulated seawater representing high salt matrices, and acid-digested polished rice as a food model. Key goals include assessing matrix removal efficiency, method sensitivity, accuracy, and suitability for routine analysis.

Methodology and Instrumentation

Sample Preparation

• Simulated Seawater: Used directly after stock solution preparation.
• Polished Rice: Two grams digested with nitric and perchloric acids on a hot plate, filtered and diluted to 100 milliliters.

Chelating Cartridge Conditioning and Extraction

1. Condition with 5 milliliters acetone, 10 milliliters 3 molar nitric acid, 20 milliliters distilled water, then 10 milliliters 0.1 molar ammonium acetate.
2. Load 100 milliliters sample adjusted to pH 5.6.
3. Rinse with 20 milliliters distilled water.
4. Elute analytes with 5 milliliters 3 molar nitric acid and dilute to 10 milliliters.

Instrumental Analysis

• Atomic Absorption Spectrometer: AA-7000 series with flame mode and D2 background correction.
• Flame: Air-acetylene.
• Measurement Wavelengths: 228.8 nanometers for Cd, 283.3 nanometers for Pb.
• Slit Width: 0.7 nanometers.

Main Results and Discussion

Matrix Removal Efficiency

• Na reduced from 10000 to 2 milligrams per liter.
• Mg reduced from 1300 to 0.6 milligrams per liter.

Sensitivity and Accuracy

• Simulated Seawater LLOQ: 0.0007 milligrams per liter for Cd and 0.02 milligrams per liter for Pb.
• Polished Rice LLOQ: 0.03 milligrams per kilogram for Cd and 0.8 milligrams per kilogram for Pb.
• Spike recoveries exceeded 95 percent in all tests.

The linear calibration curves and low detection limits demonstrate that chelating polymer SPE effectively preconcentrates Cd and Pb, while eliminating high-salt interferences prior to flame AA measurement.

Benefits and Practical Applications of the Method

• Reduced solvent use and waste generation compared to liquid–liquid extraction.
• Streamlined workflow suitable for high-throughput testing in environmental and food laboratories.
• Compatibility with flame AA, graphite furnace AA, ICP emission, and ICP mass spectrometry for extended application range.

Future Trends and Potential Applications

Advances may include automated on-line solid phase extraction integrated with atomic spectrometers, development of novel resin chemistries for broader target analyte range, and miniaturized systems for field deployable testing. Coupling with high-resolution ICP instruments could further improve detection capabilities for ultra-trace analysis.

Conclusion

The chelating polymer solid phase extraction method paired with flame atomic absorption on the AA-7000 delivers sensitive, accurate, and eco-friendly analysis of cadmium and lead in challenging matrices. This approach supports regulatory compliance and quality assurance in environmental monitoring and food safety testing.

Reference

Shimadzu Corporation. Application No. A479: Flame AA Analysis of Cadmium and Lead in Simulated Seawater and Polished Rice Using Chelating Polymer Solid Phase Extraction. First Edition May 2014.