Continuous Arsine Detection Using a Peltier-Effect Cryogenic Trap To Selectively Trap Methylated Arsines

Area of Science:

• Analytical Chemistry
• Environmental Science

Background:

• Hydride generation (HG) is crucial for eliminating matrix interferences in arsenic speciation.
• Cryogenic trapping (CT) using liquid nitrogen (LN2) is a common method for separating volatile arsines based on boiling points.

Purpose of the Study:

• To develop and evaluate a novel thermoelectric cryogenic trap for arsenic speciation analysis.
• To replace traditional liquid nitrogen cooling with a more efficient and continuous operation method.

Main Methods:

• A thermoelectric cryogenic trap utilizing Peltier modules and a polytetrafluoroethylene (PTFE) body was designed.
• Arsines were separated based on their boiling points within the trap, with specific compounds trapped on a sorbent bed.
• Atomic fluorescence spectrometry was used for the detection of arsenic species.

Main Results:

• The thermoelectric trap successfully trapped methylarsines (CH3AsH2 and (CH3)2AsH) while allowing AsH3 to pass through.
• The limit of detection (LOD) for inorganic arsenic was 1.1 ng/g with a recovery of 101.0 ± 1.1%.
• Monomethylarsonic acid and dimethylarsinic acid showed minimal interference, with recoveries of 0.2 ± 1.2% and -0.3 ± 0.5%, respectively.

Conclusions:

• The thermoelectric cryogenic trap offers an effective alternative to LN2-based CT for arsenic speciation.
• Continuous operation of the thermoelectric trap enhances analytical throughput and maintains high accuracy.
• The method demonstrates good selectivity and minimal interference from common arsenic compounds.