A miniaturized cryogenic trap design for collection of arsanes

Abstract

A new miniaturized design of a cryogenic trap for collection of arsanes generated from inorganic and methyl-substituted arsenic species was developed. The detection was performed by atomic absorption spectrometry. The miniaturization of the cryogenic trap was achieved by replacing the commonly used quartz U-tube (45cm long, 2.5/4.3mm i.d./o.d., packed with chromosorb) by a U-shaped quartz capillary (U-capillary, 20cm long, 0.53/0.65mm i.d./o.d.). The type and material of the gas phase dryer, an essential part of the cryotrapping system, were necessary to optimize to prevent blockage of the U-capillary by frozen water and to prevent loss of arsanes. A cartridge with solid NaOH was found as the best solution because of a higher absorbing efficiency of water compared to commonly used nafion membrane. The diameter of the NaOH beads was found as a crucial parameter influenced loss of arsane.Processes during the cryotrapping procedure with the U-tube and U-capillary were investigated by 73As radioactive indicator and arsane trapping and volatilization efficiency were quantified. Trapping and volatilization efficiency of 100% were found in the U-tube as well as in the U-capillary. Relevant experimental parameters for the collection in the U-capillary (carrier gas flow rate, column length and capacity) were studied. Finally, miniaturized, simple and commercially available design of the cryogenic trap based on non-polar fused silica capillary successfully performed the collection procedure of arsanes.