Mass spectrometry
One extreme to
another
It takes a mix of ingenuity and engineering expertise to develop mass
spectrometers for use in extreme environments. Emma Davies investigates
TIM GRIFFIN, NASA
For Nasa, a leak of the cryogenic
propellants hydrogen and oxygen
during a space launch could spell an
explosive disaster. During routine
leak checks the engines are filled with
helium, and mass spectrometers used
to scan for any traces of escaping gas.
For scientists studying volcanoes,
increases in helium emissions can also
forecast a catastrophic event. So it
makes perfect sense for Nasa scientists
to collaborate on a mass spectrometry
project with Costa Rican researchers
measuring gas releases from the
craters of active volcanoes.
These days it’s not unusual to
find mass spectrometers being
used in extreme environments.
As the instruments become ever
more portable and robust they
are being taken to more
inhospitable environments
on Earth and in space.
Those working in
‘harsh environments’
tend to adapt and
build spectrometers
themselves so there
is much interest in
the work of other
scientists facing
similar challenges.
Helium high
When Tim Griffin,
chief of the polymer
and chemical
analysis branch at
Nasa’s Kennedy
Space Center in
42 | Chemistry World | May 2010
In short
 Nasa scientists are
helping develop mass
spectrometers for
monitoring volcanic
activity
 The Cassini spacecraft
currently touring Saturn
has mass spectrometers
on board
 The secrets of the
microbial communities at
the bottom of the ocean
are being revealed thanks
to mass spectrometry
Florida, US, got talking to a volcano
expert from the University of Costa
Rica at a conference, it soon became
clear that a collaboration would be
mutually beneficial. Nasa would
make technological advances while
the University of Costa Rica would
get closer to its long-term goal of
setting up small autonomous mass
spectrometers to monitor volcanic
activity. Griffin’s Nasa team has now
had two research stints in Costa
Rica and currently has proposals for
further work.
Helium forms beneath the Earth’s
surface as a by-product of radioactive
decay from heavier elements, and is
physically trapped there until volcanic
activity releases it. Even modest
increases in helium emissions indicate
that new fissures are forming in the
Earth’s crust and can forewarn of an
impending eruption.
Mass spectrometry is the only
analytical technique capable of
monitoring helium concentrations in
situ in real time and can give a good
idea of what is happening deep within
a volcano.
Griffin’s team at the Kennedy Space
Center has developed a portable mass
spectrometer (a linear quadrupole)
which can be taken to about 13km
above sea level. ‘This is a commercial
off-the-shelf unit but we built our own
sample delivery system and our own
sample chamber. We also did all the
control electronics and software in
house,’ recalls Griffin. While in Costa
Rica, he took one of the spectrometers
in a Cessna aeroplane (see left) and
flew through volcanic plumes above
all the major volcanoes, measuring
concentrations of helium, water,
CO2 and sulfur dioxide (some of the
most abundant gases released by
volcanoes). Researchers also drove
the system around the city of San
José in a 4x4 vehicle and carried it
on foot to the craters of the country’s
Turrialba and Miravalles volcanoes.
The Nasa team has a long history of
looking for the kinds of gases emitted
by volcanoes but the Costa Rican
project landed them with a series of
tough experimental and logistical
challenges.
www.chemistryworld.org
TIM GRIFFIN, NASA
‘The temperature – other than
it being so hot that it will melt your
sample tube – didn’t really prove to
be too much of an issue,’ says Griffin.
The biggest problem was dealing
with the high level of steam in the
volcanic environment, which would
swamp the mass spectrometer.
‘Water is a big issue everywhere,’ he
explains. Nasa normally purges areas
to remove moisture before taking
samples but this obviously couldn’t
be done at the volcanoes and so the
Nasa team came up with a new sample
delivery method. ‘We learnt a lot
about the instrumentation and came
up with ideas that we are looking to
incorporate into our new systems here
[at the Kennedy Space Center],’ says
Griffin.
Getting all of the equipment and
spares through customs proved one
of the biggest challenges for the
Nasa team. ‘Trying to plan for any
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contingency is a tough thing,’ Griffin
says. ‘It’s a small instrument but we
took a lot of equipment with us.’
Space spectrometers
Spares are not an option for Hunter
Waite, a space physicist at the
Southwest Research Institute in San
Antonio, Texas, US, who leads the
ion and neutral mass spectrometer
team for the Cassini space mission,
a collaboration between Nasa, the
European Space Agency, and the
Italian Space Agency. His team had to
build a quadrupole mass spectrometer
robust enough to operate unmanned
for years in space during Cassini’s tour
of duty around Saturn.
‘We design and build these
things to last a long time. We have
redundant filaments for the electron
ionisation source and a very robust
instrument,’ says Waite. ‘A really
good quadrupole mass spectrometer
Mass spectrometry
is being used to study
gases emitted from the
Turrialba volcano in
Costa Rica
‘Temperature
– other than it
being so hot it
will melt your
sample tube –
wasn’t much of
an issue’
in the lab might cost you about
$75 000 (£50 400). This cost over $20
million. You build it in a completely
different way. You design every bit
to be robust and you’re very careful
about part selection.’
The Cassini orbiter entered the
Saturn system in 2004 and has
since flown by Titan (its largest
moon) about 60 times and by the
small, icy Enceladus (Saturn’s sixth
largest moon) several times. ‘Each
time we go by we get a different set
of measurements from a different
position,’ says Waite.
The mission has already made
huge, widely reported discoveries on
Titan including vast methane lakes,
rocky shores, and wide expanses of
hydrocarbon sand dunes. Meanwhile,
a plume of ice particles was discovered
shooting from Enceladus. Cassini
completed its initial four-year mission
in 2008 and is now on the Cassini
Chemistry World | May 2010 | 43
NOAA OCEAN EXPLORER
MARK GARLICK/SCIENCE PHOTO LIBRARY
Mass spectrometry
Equinox mission, looking for signs of
seasonal climate changes in the Saturn
system.
The atmosphere on Titan is mainly
composed of nitrogen. There’s
also methane and hydrogen from
dissociation of the methane, then a
whole host of organic compounds.
‘We see things as complex as benzene,’
says Waite. ‘There’s a very, very rich
organic mixture that contains just
about every hydrocarbon that you
can imagine plus most of the nitriles
that you can imagine. This complexity
goes all the way through the mass
range of our mass spectrometer. And
it doesn’t stop there, it keeps going.’
Waite knows of the existence of
compounds with a molecular weight
of over 5000Da. ‘We can confirm their
presence with other instrumentation
but we can’t measure the composition
with the mass spectrometer because
we don’t have the mass range. If we go
back we’ll build a mass spectrometer
that has better resolution and a larger
mass range,’ he says.
His team is working on instrument
improvements and can now get
50 000 mass resolution quite easily
with time of flight mass spectrometry,
far exceeding the 100 mass resolution
with Cassini’s spectrometer.
Before they revisit Titan, Griffin
44 | Chemistry World | May 2010
wants to do some Earth-based ocean
studies in preparation for possible
future exploration of Kraken Mare,
a 400 000km2 hydrocarbon lake in
Titan’s northern hemisphere. ‘Going
to the oceans and testing some of this
mass spectrometry is a good start
so that we can develop membranes
that might be applicable for the inlet
system to allow the gas to permeate
through a membrane from liquid,’ says
Waite. ‘It’s a technique that has been
used in the oceans quite a bit,’ he adds.
Biomass in the basin
Peter Girguis, an expert in deep sea
organisms at Harvard University,
Cambridge, US, might
be just the man to
help. He uses mass
spectrometry
to study the
metabolic rates
of microbes
thousands of
metres under the
sea and has developed
a system for open data
sharing. His next research
expedition is to the North Pond
Basin, a valley in the underwater
mountain range the Mid-Atlantic
Ridge. He sees the project as a
unique opportunity for a group of
Cassini’s Huygens
probe, carrying a mass
spectrometer, was used to
study the composition of
Titan’s atmosphere
Underwater mass
spectrometry probes
have to operate in very
harsh environments
investigators to develop technologies
that are appropriate for remote
observatories. ‘Whether it’s the sea
floor or a mountain top or a hot spring
or Europa [one of Jupiter’s moons],
the core technologies are pretty
similar,’ he says.
Recent studies have pointed to
a thriving microbial community in
marine sediments in the parts of the
Earth’s crust that come to the surface
in the basins created by mid-ocean
ridges (the oceanic crust). Since about
80 per cent of the biosphere is deep
ocean – below 1000m in depth – the
biomass of deep sea microbes may
well exceed the total biomass on all
the continents, Girguis suggests.
His mass spectrometers will next
be in active service in hydrothermal
vents in the sea floor in the North
Pond Basin. The entire volume of
the Atlantic Ocean could circulate
through the basin every 5000 to
10 000 years, says Girguis. So
the microbes could have a
direct influence on ocean
chemistry. ‘The North Pond
site is unique in respect to
the distribution of oxygen
in the sediments,’ he adds.
‘Sediments in general are
anaerobic. For reasons that
we don’t fully understand
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PETER GIRGIUS, HARVARD UNIVERSITY, US
there seems to be quite a lot of oxygen
flowing around these sediments.
It’s interesting in terms of the
geochemistry and that makes it
interesting in terms of the microbes it
can support.’
This summer, the International
Integrated Ocean Drilling Program
will send its high-tech drill ship,
the JOIDES (Joint Oceanographic
Institutions for Deep Earth Sampling)
Resolution, to drill the bore holes
that Girguis needs for his research.
Next year, he and his team will go
out to set up the instruments. Then
it’s a question of finger crossing and
patience as they wait a full year before
they can return to collect the data.
another sample or turn itself off,
explains Girguis.
‘Our mass spectrometer gives
us the opportunity to go down and
measure the dissolved volatiles, from
oxygen and hydrogen to hydrogen
sulfide, methane and other alkanes,’
he says. ‘The thing I’m most proud of
is that it is made to be an open-source
instrument. I’m hoping that we can
foster the widespread use of these
instruments and other instruments
of oceanography.’
Mini MS
Tim Short, who runs the chemical
sensors group of the marine
technology program for US notfor-profit research company SRI
Spectrometer story
International, could perhaps benefit
Girguis has been working on mass
from the open-source approach. He
spectrometers since his PhD days.
has worked on many underwater
He started developing an underwater mass spectrometry projects, including
mass spectrometer while doing
developing ways to monitor pollutants
a postdoc at the Monterey Bay
in harbour water.
Aquarium Research Institute
One of his projects is with the
(MBARI), US, taking advantage of
Gulf of Mexico Hydrates Research
advances in the semiconductor world. Consortium, which monitors methane
‘We had to engineer an inlet system
hydrates on the sea floor (a potential
that would allow us to de-gas water
energy source but also a huge
at full ocean pressure and allow those greenhouse gas source). ‘We’re trying
gases to enter a high vacuum,’ recalls
to get information about why these
Girguis. Working with John Erickson, hydrates are so stable and why they
an MBARI engineer, Girguis designed
an inlet system where the pressure on
the membrane inlet is distributed to
a honeycomb-like titanium support
structure behind it, allowing gases to
pass through.
The hydrothermal vents where the
mass spectrometer needs to operate
are harsh environments. During
Girguis’ last experiment in the field
he took a mass spectrometer to look at
dissolved gases in water coming out
of hydrothermal vents in the sea floor
at 300˚C. Because of the pressure, the
water doesn’t boil, but it is still hot
and acidic enough to scorch a wooden
broom handle, says Girguis. His team
designed a titanium inlet system
that takes the water and cools it
down before delivering it to the mass
spectrometer.
For the North Pond project, the
researchers will insert a ‘string’ (a
pipe) into the drill hole. This will
contain instruments including oxygen
sensors cleverly designed in house
not to consume oxygen. The mass
spectrometer is encased in a titanium
bottle (about 1m long and 0.2m
diameter) and will sit atop the hole.
A pipe system will bring fluid up to
the mass spectrometer from different
depths. The mass spectrometer will
be programmed to turn on once every
hour, take a sample and analyse it
before ‘deciding’ whether to take
www.chemistryworld.org
‘The water
above vents in
the sea floor is
acidic enough to
scorch wood ’
Mass spectrometers in
robotic submarines are
being used to study vents
in the sea floor
become unstable,’ says Short.
Power supply to the mass
spectrometer limits the duration of
experiments in the field and Short’s
team is looking to reduce power
consumption. One way to do this is by
making smaller mass spectrometers.
Short hopes one day to make a mass
spectrometer the size of a mobile
phone but admits that such a device
is some way off.
When you reduce the size of a mass
spectrometer you typically lose mass
resolution or sensitivity, explains
Short. But by linking together a series
of identical ion traps, he and his team
hope to retain sensitivity. ‘We have
demonstrated that we can get decent
mass spectra out of single little traps.
Now we’re starting to work on making
large arrays of those traps,’ he says.
Mass challenge
Ben Langford, a postdoc at Lancaster
University, UK, could have done
with a miniature mass spectrometer
during fieldwork in the jungle in
Malaysian Borneo as part of the OP3
(Oxidant and Particle Photochemical
Processes) project (see Chemistry
World, March 2009, p40). It took
large numbers of people to haul three
large mass spectrometers through
the jungle and to put one up a tower
and one on a platform high in the
tree canopy. ‘We made meticulous
plans based on previous experience
– any component part that had
broken in the past we made sure
we had spares of,’ recalls Langford.
‘Within 30 minutes of switching the
instruments on all three had broken
with the same fault – a fault we had
never seen before.’
‘When you take a mass
spectrometer out into the field
anything can happen and it normally
does,’ says Langford. Taking
mass spectrometers into harsh
environments certainly requires
forward planning, a cool head and a
sense of adventure. There is much
that disparate groups working
in harsh environments can learn
from each other. ‘I personally
think it is important that biologists,
geochemists and geologists operate
with great synergy and collaboration
and understand that if one wants to
understand life and its relationship to
our environment, one cannot do that
by studying any one attribute alone,’
says Girguis. And the relationship
between extraterrestrial life and its
environment? We’ll leave that
one to Nasa.
Emma Davies is a science writer
based in Bishop’s Stortford, UK
Chemistry World | May 2010 | 45