Determination of Tin by Hydride Generation AA

Importance of the Topic

The accurate determination of tin at trace levels is critical in environmental monitoring, industrial quality control, and toxicological studies. Hydride generation coupled with atomic absorption offers enhanced sensitivity and low detection limits for tin analysis, but conventional methods face challenges in standard stability, metal interferences, and pH dependency. This study addresses these limitations by developing a simplified and robust tin hydride generation protocol.

Objectives and Study Overview

This work aimed to investigate factors affecting tin hydride generation, including reagent stability, contamination, metal interferences, and pH effects. The primary goal was to introduce L-cysteine as an interference suppressor and to optimize reagent flows and acid matrices for a streamlined method. The optimized procedure was then applied to digested environmental samples to assess precision and accuracy.

Methodology and Instrumentation

This study employed a SpectrAA-400 with a VGA-76 Vapor Generation accessory for hydride generation and a GTA-96 platform atomizer for comparative graphite furnace atomic absorption (GFAAS). Critical reagents included NaBH₄ reductant, HNO₃ acid matrix, and L-cysteine. A new VGA-76 configuration used deionized water in the acid channel and 0.5% NaBH₄ with minimal NaOH in the reductant channel. Standards and samples were prepared in 1% HNO₃ and 1% L-cysteine without pH adjustment. GFAAS analyses utilized phosphate/magnesium and palladium modifiers for platform atomization.

Key Results and Discussion

Incorporating L-cysteine significantly improved standard stability over weeks, suppressed copper and other metal interferences, and produced linear calibration over a wide acid concentration range (0.2–2.5% HNO₃) with reproducibility better than 2% RSD. Calibration sensitivity reached 0.085 absorbance units at 5 µg/L Sn. Analysis of six digested environmental samples yielded spike recoveries of 86–100%. A mixed sample tested by both hydride generation and GFAAS showed close agreement (193 µg/L vs. 211 µg/L average).

Benefits and Practical Applications

• Enhanced sensitivity and signal stability for tin at part-per-billion levels.
• Reduced sample preparation by eliminating pH adjustment.
• Effective suppression of metal interferences using L-cysteine.
• Compatibility with environmental and industrial sample matrices.

Future Trends and Potential Applications

Emerging directions include coupling hydride generation with ICP-MS for multi-element analysis, developing portable systems for in-field monitoring, and refining speciation techniques to distinguish inorganic tin forms. Advances in microfluidic reagent mixing and automation may further streamline trace tin analysis.

Conclusion

The integration of L-cysteine into tin hydride generation protocols yields a simple, interference-resistant, and sensitive method suitable for challenging environmental samples. The approach minimizes pH constraints and enhances analytical reliability, offering a viable alternative to more complex atomic absorption techniques.

References

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