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- Title
A chemical ionization mass spectrometer for continuous underway shipboard analysis of dimethylsulfide in near-surface seawater.
- Authors
Saltzman, E. S.; De Bruyn, W. J.; Lawler, M. J.; Marandino, C. A.; McCormick, C. A.
- Abstract
A compact, low-cost atmospheric pressure, chemical ionization mass spectrometer ("mini-CIMS") has been developed for continuous underway shipboard measurements of dimethylsulfide (DMS) in seawater. The instrument was used to analyze DMS in air equilibrated with flowing seawater across a porous Teflon membrane equilibrator. The equilibrated gas stream was diluted with air containing an isotopically-labeled internal standard. DMS is ionized at atmospheric pressure via proton transfer from water vapor, then declustered, mass filtered via quadrupole mass spectrometry, and detected with an electron multiplier. The instrument described here is based on a low-cost residual gas analyzer (Stanford Research Systems), which has been modified for use as a chemical ionization mass spectrometer. The mini-CIMS has a gas phase detection limit of 220 ppt DMS for a 1 min averaging time, which is roughly equivalent to a seawater DMS concentration of 0.1nM DMS at 20°C. The mini-CIMS has the sensitivity, selectivity, and time response required for underway measurements of surface ocean DMS over the full range of oceanographic conditions. The simple, robust design and relatively low cost of the instrument are intended to facilitate use in process studies and surveys, with potential for long-term deployment on research vessels, ships of opportunity, and large buoys.
- Subjects
ATMOSPHERIC pressure; CHEMICAL ionization mass spectrometry; DIMETHYL sulfide; WATER vapor transport; OCEANOGRAPHY
- Publication
Ocean Science, 2009, Vol 5, Issue 4, p537
- ISSN
1812-0784
- Publication type
Article
- DOI
10.5194/os-5-537-2009