Abstract. We present a technique that utilises a segmented flow coil
equilibrator coupled to a proton-transfer-reaction mass spectrometer to
measure a broad range of dissolved volatile organic compounds. Thanks to its
relatively large surface area for gas exchange, small internal volume, and
smooth headspace–water separation, the equilibrator is highly efficient for
gas exchange and has a fast response time (under 1 min). The system allows
for both continuous and discrete measurements of volatile organic compounds
in seawater due to its low sample water flow (100 cm3 min−1) and
the ease of changing sample intake. The equilibrator setup is both
relatively inexpensive and compact. Hence, it can be easily reproduced and
installed on a variety of oceanic platforms, particularly where space is
limited. The internal area of the equilibrator is smooth and unreactive.
Thus, the segmented flow coil equilibrator is expected to be less sensitive
to biofouling and easier to clean than membrane-based equilibration systems.
The equilibrator described here fully equilibrates for gases that are
similarly soluble or more soluble than toluene and can easily be modified
to fully equilibrate for even less soluble gases. The method has been
successfully deployed in the Canadian Arctic. Some example data from underway
surface water and Niskin bottle measurements in the sea ice zone are
presented to illustrate the efficacy of this measurement system.
Segmented flow coil equilibrator coupled to a proton-transfer-reaction mass spectrometer for measurements of a broad range of volatile organic compounds in seawater
