Automated Method for the Sensitive Analysis of Volatile Amines in Seawater

Area of Science:

• Marine Chemistry
• Analytical Chemistry
• Biogeochemistry

Background:

• Methylamines (MAs) are polar, volatile, nitrogen-containing organic compounds crucial to the marine nitrogen cycle.
• Accurate analysis of MAs is challenging, hindering a comprehensive understanding of their occurrence and ecological significance.
• Existing analytical methods often lack the sensitivity and throughput required for detailed marine studies.

Purpose of the Study:

• To develop and validate an automated headspace solid-phase microextraction (HS-SPME) method for analyzing methylamines in seawater.
• To enhance sensitivity and sample throughput compared to existing analytical techniques for MAs.
• To apply the developed method to quantify MAs in Southern Ocean seawater samples.

Main Methods:

• An automated HS-SPME technique coupled with gas chromatography and nitrogen phosphorus detection (GC-NPD) was employed.
• Optimization of SPME conditions including temperature, equilibration, and extraction parameters.
• Method validation for sensitivity, detection limits, and sample throughput using seawater matrices.

Main Results:

• The method demonstrated significantly higher sensitivity towards trimethylamine (TMA) (6-24 times) compared to dimethylamine (DMA) and monomethylamine (MMA).
• Detection of DMA and TMA was achieved using small seawater volumes (2.5-10 mL), with detection limits of 6.6 nM and 4.1 nM respectively.
• The method exhibited 4-6 times greater sample throughput and was classified as 'practical' with a BAGI score of 62.5.

Conclusions:

• The developed automated HS-SPME-GC-NPD method provides a standardized and efficient approach for methylamine analysis in seawater.
• This advancement facilitates more accurate quantification of MAs, enabling deeper insights into their role in marine nitrogen cycling.
• The method successfully quantified DMA and TMA in Southern Ocean samples, demonstrating its applicability in real-world marine environments.