Underwater Mass Spectrometry: Developments and Calibration

Underwater Membrane Mass
Spectrometry: Developments and
Calibration
Ryan J. Bell, R. Timothy Short, Strawn K. Toler,
Friso H.W. van Amerom, Peter G. Wenner, and
Robert H. Byrne
SRI International
&
University of South Florida
College of Marine Science

Acknowledgements
• Faculty, staff and students at SRI International, the
Center for Ocean Technology and College of
Marine Science.
• Funding from U.S. Office of Naval Research
(ONR) Grant No. N00014-03-1-0479 and
Contract No. N00014-07-C-0720.
• Skidaway Institute of Oceanography
• Google Maps

In Situ Underwater Membrane
Introduction Mass Spectrometry at USF
& SRI International
1. Description of Underwater Membrane Introduction MS
2. Calibration Methodology
3. Surface Contour Deployments
4. Depth Profile Deployments
5. Benthic Moored Deployments

MS: Versatile Chemical Sensor
• Trace Elements
• Isotope Ratios
• Pollutants/VOCs
• Dissolved Gases
• Proteins/Amino Acids
• Bacterial Signatures
No configuration valid for all analytes

Membrane Introduction Mass Spectrometry
(MIMS)
Ion source
Electron impact
Mass-filter
Quadrupole
Detector
Electron multplier
Membrane
e -
+
+
Ion and
fragments
Mass-scan

Simultaneous Detection of Multiple Analytes
• Dissolved Gases
– e.g. Nitrogen, Oxygen, Argon, Carbon Dioxide,
Methane, Hydrogen Sulfide
• Volatile Organic Compounds
– e.g. Toluene, Benzene, Dimethyl Sulfide,
Chloroform
• Larger MW Compounds with Modification
– e.g. PCBs, Pesticides, Drugs, Toxins

Principle Features of UMS
Type
Linear quadrupole mass filter
Mass range
200 amu
Inlet System
Membrane introduction system
Power consumption 100 Watts
Voltage of operation 24 VDC or 110 VAC
Deployment time Configuration dependent
Dimensions ∅ 19 cm (7.5”)
L 105 cm (41’’)
Weight
33 kg (72.7 Lb)
Depth
>1000 m
DSL tether range ~1600 m (1 mile)

New 200 amu In Situ Mass Spectrometer
Microcontroller
Embedded PC
MS electronics box
200 amu linear quadrupole in
vacuum housing w/ heating jacket
Turbo pump
MIMS probe
Roughing pump

Membrane Assembly

Calibration - Instrument Parameters
• Physical parameters that affect instrument response:
– Detector settings
– Filament settings
– Membrane geometry
– Residual gas
– Membrane temperature
– Sample velocity
Constant during deployment
– Hydrostatic pressure
Variable during deployment

Laboratory Calibration - Pressure and
Concentration
• An HPLC pump and back pressure regulator allow control of
hydrostatic pressure for pressure calibrations
• Two solutions with known gas
concentrations are mixed at
various ratios to allow for
intermediate concentrations and in
situ automated calibration

Calibration Results
Nitrogen (m/z 28)
Oxygen (m/z 32)
Methane (m/z 15)
Calibration Normalized at 200atm 1atm Response (78% N2, vs Pressure 21% O2, 1% (atm) CH4) 2/18/05
2/18/05
Instrument
Normalized
Response
Response
(A)
Instrument Response (A)
1.00E-07 1.20 1.0000E-07
9.00E-08 9.0000E-08
1.00
8.00E-08 8.0000E-08
7.00E-08 7.0000E-08
0.80
6.00E-08 6.0000E-08
5.00E-08 0.60 5.0000E-08
4.00E-08
4.0000E-08
0.40
3.0000E-08
3.00E-08
Oxygen
y = 1.742E-10x + 2.143E-08
R 2 = 9.999E-01
Oxygen
y = 7.056E-11x + 1.690E-08
R 2 = 9.994E-01
Nitrogen
y = 1.821E-10x + 5.175E-09
R 2 = 9.999E-01
2.0000E-08
R 2 = 9.939E-01
2.00E-08 0.20
1.0000E-08
1.00E-08
y = 1.593E-10x + 1.573E-10
Methane
y R= 2 6.512E-11x = 9.995E-01+ 7.765E-11
0.00 0.0000E+00
Methane
R 2 = 9.962E-01
0.00E+00
0 100 200 300 400 500 600
0 0 100 50 200 100 300 150 400 200 500 250 600
Concentration (umole/kg)
Hydrostatic Concentration Pressure (umole/kg) (atm)
Methane
Nitrogen
Nitrogen
Oxygen y = 7.176E-11x + 3.614E-09

Calibration Results - Pressure

Field Calibration
• Three or more field samples are sparged at constant
temperature with gas standards of various concentrations.
• Each standard is sampled prior to deployment
Field Baseline Determinations
• Oxygen baseline is determined by the addition of sodium
sulfite to solution.
• Carbon dioxide baseline is determined by the addition of
sodium carbonate to solution.

Field Baseline Determination
• Baselines for nitrogen, argon, and methane, are determined
by stopping the sample pump, whereupon sample in
contact with the membrane is completely degassed
• Pump stop method is compared to sampling of boiling water
for baseline determination.

Stopping Sample Pump
• Comsol Multiphysics (finite element) model of sample degassing
during stopped sample flow at the membrane surface
40 mm
2.5 mm
Vacuum
Membrane
Membrane
16x Scale

Pre-Deployment Calibration

1.00E-07
1.00E-08
1.00E-09
1.00E-10
1.00E-11
1.00E-12
0 100 200 300 400 500 600 700
Scan #
2 . 2 e - 1 0
2 . 0 e - 1 0
1 . 8 e - 1 0
1 . 6 e - 1 0
1 . 4 e - 1 0
1 . 2 e - 1 0
1 . 0 e - 1 0
8 . 0 e - 1 1
6 . 0 e - 1 1
4 . 0 e - 1 1
2 . 0 e - 1 1
0 . 0
1 7 : 0 0 F r id a y
0 2 0 0 0 4 0 0 0 6 0 0 0 8 0 0 0 1 0 0 0 0 1 2 0 0 0 1 4 0 0 0 1 6 0 0 0 1 8 0 0 0
S c a n N u m b e r ( 7 s e c / s c a n )
1 7 :0 0 S a tu rd a y
Deployment Methods
W a s t e W a t e r I n f lu e n t
m / z 9 1
Intensity (Amps)
AUV
USV
Moored
Intensity
ROV
Depth Profiling
Diver

Lake Maggiore Chemical Surveys
O 2
Ar
CO 2
• Mass spectrometer deployed
aboard an unmanned surface
vehicle
• Mapping variation of
dissolved gas ion intensities
• Develop surface contour maps
based on gas ion intensity data
• Carbon dioxide & oxygen
data displayed

Lake Maggiore, St Petersburg, FL
O 2 and CO 2 are inversely correlated in areas of
active photosynthesis and respiration
m/z 32 - Oxygen
m/z 44 - Carbon Dioxide

Hillsborough River, February 2007

Hillsborough Deployment Method

Hillsborough Deployment Method

300
Oxygen Time Series
Conc. (mmole/kg)
250
200
150
100
50
0
YSI Dissolved Oxygen Sensor
MS m/z 32
MS m/z 32 - Argon Corrected
2:24 PM 3:21 PM 4:19 PM 5:16 PM 6:14 PM
Time

Oxygen
3 : 2 1 P M 4 : 1 9 P M 5 : 1 6 P M
296 mmole/kg
157 mmole/kg

Oxygen at Sulfur Springs

Carbon Dioxide
204 mmole/kg
3:21 PM 4:19 PM 5:16 PM
151 mmole/kg

Methane
3 : 2 1 P M 4 : 1 9 P M 5 : 1 6 P M
2.33 mmole/kg
1.39 mmole/kg

Depth Profiles in The Gulf of Mexico
• Vertical profiles of dissolved
gases with underwater mass
spectrometer in Gulf of Mexico
• Mount instrument on custom
frame along with CTD, DO and
pH Sensors
• Communicate with instrument
through standard UNOLS CTD
tether using Seabird Modem
• Determine dissolved gas
concentrations from mass spec
data with the aid of a portable
calibration unit

Depth Profiles in The Gulf of Mexico
Depth Profile Deployment Method

Depth Profile Data (Florida Shelf)
Profile obtained while sampling the water column
Profile obtained while sampling a standard solution

Correction Method: • Normalized m/z 17
• Normalized standard solution cast
• Corrected using to laboratory data
Alternative Techniques:

Depth Profile Data (Miss. Coast)
Argon Corrected

Benthic Boundary Layer (Georgia Coast)
• R/V Savannah
• Benthic Chamber (30m)
• R2 Navy Tower

Benthic Boundary Layer (Georgia Coast)

Benthic Boundary Layer (Georgia Coast)

Benthic Boundary Layer (Georgia Coast)
O2 Conc. (mmole/kg)
180
160
140
120
100
80
60
40
20
0
Oxygen
Carbon Dioxide
Argon
0 20 40 60 80 100 120 140
Time (min)
30
25
20
15
10
5
0
CO2 and Ar Conc. (mmole/kg)

Benthic Boundary Layer (Georgia Coast)
O2 Conc. (mmole/kg)
180
160
140
120
100
80
60
40
20
0
Oxygen
Carbon Dioxide
Argon
Noon 6 pm Midnight 6 am
0 5 10 15 20
Time (hrs)
30
25
20
15
10
5
0
CO2 and Ar Conc. (mmole/kg)

Future Plans for Underwater MS
• Continued Deployments
• Alternative Sampling Interfaces
– Wider range of analytes
• Unattended Operation/ Full Ocean Depths
– Ocean Observatories
• Extreme MS Miniaturization
– MEMS Microfabrication

Questions, mateys?

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Tue Sep 18, 2007 10:11am BSTEmail This Article |Print This Article |
RSS [-] Text [+] Begin: Story Text
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The basics
Ahoy!
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Bilge rat
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Hornpipe
Lubber
Smartly

Argon Time Series
16
14
Conc. (mmole/kg)
12
10
8
6
4
2
Calculated Saturated Argon
MS m/z 40
0
2:24 PM 3:21 PM 4:19 PM 5:16 PM 6:14 PM
Time