Substituting HF by HBF₄- an optimized digestion method for multi-elemental sediment analysis via ICP-MS/MS

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Geochemistry

Background:

• Accurate elemental mass fraction determination in sediments is crucial for assessing aquatic ecosystem health.
• Traditional methods using hydrofluoric acid (HF) for silicate decomposition pose toxicity risks and can lead to element precipitation.
• There is a need for safer and more efficient digestion protocols for comprehensive sediment analysis.

Purpose of the Study:

• To optimize a novel total digestion protocol for sediment analysis.
• To evaluate the efficiency of using tetrafluoroboric acid (HBF4) as a safer alternative to HF for silicate matrix decomposition.
• To analyze a wide range of elements in certified sediment reference materials using ICP-MS/MS.

Main Methods:

• Microwave acid digestion utilizing HBF4 for silicate decomposition.
• Analysis of 48 elements in four sediment reference materials (NIST SRM 2702, GBW 07313, GBW 07311, JMC-2) using ICP-MS/MS.
• Comparison of digestion efficiency using different acid mixtures with and without HBF4, focusing on trace metal recovery.

Main Results:

• The optimized protocol (5 mL HNO3, 2 mL HCl, 1 mL HBF4) achieved complete dissolution of reference materials.
• Quantitative recoveries (80-120%) were obtained for 34 elements across multiple reference materials.
• HBF4 usage avoided fluoride precipitation issues, improving recoveries for elements like Sr, Ba, and rare earth elements, and allowed direct ICP-MS measurement without special precautions.

Conclusions:

• The developed HBF4-based microwave digestion protocol offers a safe, efficient, and reliable method for total elemental analysis in sediments.
• This method enables accurate determination of trace and matrix elements with low limits of quantification.
• The protocol is suitable for routine environmental monitoring and geochemical studies of aquatic ecosystems.