P. G. Wenner †‡ R.J. Bell†‡; F.H.W. van Amerom†; S.K. Toler†; M.L. Hall†; R.T. Short†

Center for Ocean Technology†, College of Marine Science‡

University of South Florida, St. Petersburg, FL

P. G. Wenner, R. J. Bell, S. K. Toler, F.H.W. van Amerom, M. L. Hall and R. T. Short and R.H. Byrne

University of South FloridaCollege of Marine Science

Center for Ocean Technology

Determination of dissolved gas concentrations in natural waters using

an in-situ, membrane inlet mass spectrometer

Fifth Workshop on Harsh Environment Mass Spectrometry

September 20-23, 2005 Lido Beach, Sarasota, Florida

ContentsContents

•• Instrument Design and FunctionInstrument Design and Function

•• Recent DeploymentsRecent Deployments

•• CalibrationCalibration

•• New Instrument DevelopmentNew Instrument Development

•• SummarySummary

Instrument Design and Function

Underwater Mass Spectrometry at USFUnderwater Mass Spectrometry at USF

~1600 m (1 mile)Real-time tether range

>1000 mDepth

33 kg (72.7 Lbs.)Weight

L 105 cm (41”)

Ø 19 cm (7.5”)Dimensions

Configuration dependentDeployment Time

24 VDC or 110 VACSupply Voltage

88 WattsPower Consumption

Membrane IntroductionInlet System

200 amuMass Range

Linear quadrupole mass filterType

USF Underwater Mass SpectrometerUSF Underwater Mass Spectrometer

Ethernet Hub Embedded PC Roughing Pump Housing

Microcontroller

Turbo Pump

MIMS Probe Sample Pump Mass Spec Electronics

Turbo Pump Controller Board

High Pressure Membrane InletHigh Pressure Membrane Inlet

Sintered rod supporting PDMS

Sample Flow

Thermocouple

Cartridge Heater

To MSMembrane

•• PDMS membrane permeable to low molecular weight, nonPDMS membrane permeable to low molecular weight, non--polar polar compoundscompounds

•• Membrane supported by machined 1/16” sintered Membrane supported by machined 1/16” sintered HastelloyHastelloy rodrod•• Inserted thermocouple allows for direct measurement of sample Inserted thermocouple allows for direct measurement of sample

temperaturetemperature•• Sample flowSample flow--over configurationover configuration

FlowFlow--through Membrane Inletthrough Membrane Inlet

•• Brass probe based on original Scott Bauer design from MIMS TechnBrass probe based on original Scott Bauer design from MIMS Technology, ology, Inc.Inc.

•• Sample flowSample flow--through configurationthrough configuration

•• Successfully deployed to 30 meters depthSuccessfully deployed to 30 meters depth

•• Greater response observed for flowGreater response observed for flow--through inlet through inlet 11

•• Attempt to develop highAttempt to develop high--pressure version of this inletpressure version of this inlet

1LaPack, M.A., The Theory and Practice of Membrane Extractions, PhD Dissertation, 1994.

Target Analytes for Underwater MIMSTarget Analytes for Underwater MIMS

• Volatile Organic Compounds Benzene, Toluene, Xylene, Dimethyl sulfide, etc.(very low ppb, ~1-5 min response)

• Gases CH4, N2, O2, CO2, Ar, etc. (very low ppm, ~10 sec response)

• Semi-Volatile CompoundsNapthalene, PAHs, Pesticides, etc.(low ppb, ~5-20 min response)

Recent Deployments

SaanichSaanich Inlet DeploymentInlet Deployment

•• The inlet is located just north The inlet is located just north of Victoria, BCof Victoria, BC

•• Maximum Depth: 225 metersMaximum Depth: 225 meters

•• There is a ledge at 70 m There is a ledge at 70 m located at the northern mouth located at the northern mouth of the inletof the inlet

•• The ledge restricts bottom The ledge restricts bottom water circulation and turnoverwater circulation and turnover

•• Bottom waters are anoxic Bottom waters are anoxic with the presence of reduced with the presence of reduced species, species, ieie. CH. CH44,, HH22SS

α

β

0.0

0.2

0.4

0.6

0.8

1.0

53500 54000 54500 55000 55500 56000 56500 57000 57500 58000 58500

0

50

100

150

200

m/z 40

m/z 44

Depth

m/z 44

m/z 32

m/z 34

Nor

mal

ized

resp

onse

m/z 15

Saanich Inlet Time Series

14:52 15:08 15:24 15:40 15:56 16:12Time of Day

Depth (m

)

SaanichSaanich Inlet Depth ProfilesInlet Depth Profiles

• Sharp increase m/z 44, 15

• Sharp decrease m/z 32

• Chemocline @ 100 m

Gulf of Mexico Cruise, April 2005Gulf of Mexico Cruise, April 2005

•• Vertical profile with mass spec Vertical profile with mass spec to 500 m depthto 500 m depth

•• Mount instrument on shipboard Mount instrument on shipboard rosetterosette

•• Communicate with instrument Communicate with instrument through standard UNOLS CTD through standard UNOLS CTD tether to which rosette is tether to which rosette is attachedattached

•• Determine dissolved gas Determine dissolved gas concentrations from mass spec concentrations from mass spec data with the aid of a portable data with the aid of a portable calibration unitcalibration unit

Calibration Calibration -- MethodMethod

• Shipboard apparatus allows in-field sample preparation and calibration

•• Two solutions with known but Two solutions with known but different gas concentrations different gas concentrations are mixed at various ratios to are mixed at various ratios to allow for intermediate allow for intermediate concentrations and concentrations and automated automated calibrationcalibration

Gulf of Mexico, April 26 2005, Cast 1, m/z 40

0

1E-13

2E-13

3E-13

4E-13

5E-13

6E-13

2767 2817 2867 2917 2967 3017 3067 3117

Scan #

Inte

nsity

Mass Spec in the water holding @ 5 meters

Mass Spec descending @ ~ 2 meters/sec

Scan: 3113: microcontroller string indicates a problem; Depth: 370 meters

tp 259 mA, Hum 38%tp 1003 mA, Hum 56%tp 1545 mA, Hum 134%tp 1628 mA, Hum 139%

Scan 3130: sample pump shuts down

Sample flow integrated thermocouples Sample flow integrated thermocouples

Thermocouple

Sample Flow

Type-T thermocouple wire

1/16” ID SS 316 tubing

Thermocouple tip encased in vacuum epoxy

Thermocouple

Cartridge Heater

Thermocouple/microcontroller connectionThermocouple/microcontroller connection

Thermocouple leads

F-16 mite microcontroller

Salt residue from seawater leak

Hillsborough River, June & July 2005Hillsborough River, June & July 2005

Hillsborough River State Park

USF College of Marine Science

Hillsborough River Deployment; June 16 - 18, 2005 m/z 40 Trace w/ High Pressure Membrane Probe

0.00E+00

5.00E-11

1.00E-10

1.50E-10

2.00E-10

2.50E-10

3.00E-10

3.50E-10

4.00E-10

4.50E-10

6550 8550 10550 12550 14550 16550 18550 20550 22550

Scan #

Inte

nsity

Friday, June 17, 2005; 11:52 am

Saturday, June 18, 2005; 12:29 pm

System modifications to System modifications to eliminate signal degradationeliminate signal degradation

••Replace flowReplace flow--over membrane inlet over membrane inlet with flowwith flow--through inletthrough inlet

•• Cure PDMS at 450Cure PDMS at 45000 F for 4 hoursF for 4 hours

Hillsborough River Deployment, July 19 - 21, 2005 m/z 40 Trace

0.00E+00

1.00E-09

2.00E-09

3.00E-09

4.00E-09

5.00E-09

6.00E-09

1400 3400 5400 7400 9400 11400

Scan #

Inte

nsi

ty

July 19, 2005; 5:43 pm

July 20, 2005; 1:06 pm

Calibration

Calibration Calibration -- Instrument ParametersInstrument Parameters

•• Physical parameters that effect instrument Physical parameters that effect instrument response:response:

–– Detector settingsDetector settings–– Filament settingsFilament settings–– Membrane constructionMembrane construction–– Membrane temperatureMembrane temperature–– Sample velocitySample velocity

–– Hydrostatic pressureHydrostatic pressure

Constant during deployment

Variable during deployment

Calibration - Permeation theory

Flux = A.S.D.(dC/dx)

Fick’s Law Flux ∝ instrument responseA is membrane surface areaS is permeate solubilityD is permeate diffusion rate (cm2/s)dC/dx is concentration gradient

Membrane

xPermeate Stream

(Vacuum)Sample Feed

C

C’

C’.S

Flux = A.S.D.(dC/dx)

1.00

1.20

1.40

1.60

1.80

2.00

2.20

35 37 39 41 43 45 47 49 51 53 55

Nitrogen

Water

Carbon Dioxide

OxygenArgon

Nor

mal

ized

Res

pons

e

Temperature (°C)

Normalized Response vs. Temperature

• Approximately linear in our temperature range

• Fixed temperature important for quantification of many analytes

Normalized Response vs. Sample Velocity

Nitrogen

Argon

Oxygen

Carbon Dioxide

Nor

mal

i zed

Res

pons

e

Sample flow velocity (cm/s)

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

• Strong boundary layer develops at low sample velocities

• Fixed flow velocity important for quantification of many analytes

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 50 100 150 200

Normalized Response vs. PressureNitrogen Response (m/z 28)

Modified Free Volume Model

D = Dd + Dh*exp(-b*P)

Dual Sorption Model

D = Dd + Dh/(1+b*P)~Dd, Dh and b are functions of T~

Nor

mal

ized

Res

pons

e

Hydrostatic Pressure (atm)

• Strong dependence on pressure, especially more polar compounds

• Not practical fix for pressure; response must be calibrated

Calibration - Screenshot

Calibration at 1atm (78% N2, 21% O2, 1% CH4) 2/18/05

y = 1.742E-10x + 2.143E-08R2 = 9.999E-01

y = 1.821E-10x + 5.175E-09R2 = 9.999E-01

y = 1.593E-10x + 1.573E-10R2 = 9.995E-010.0000E+00

1.0000E-08

2.0000E-08

3.0000E-08

4.0000E-08

5.0000E-08

6.0000E-08

7.0000E-08

8.0000E-08

9.0000E-08

1.0000E-07

0 100 200 300 400 500 600

Concentration (umole/kg)

Inst

rum

ent R

espo

nse

(A)

Methane

Oxygen

Nitrogen

Normalized Response vs Pressure (atm) 2/18/05

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 50 100 150 200 250

Hydrostatic Pressure (atm)

Nor

mal

ized

Res

pons

e

Nitrogen

Oxygen

Methane

Oxygen (m/z 32)

Methane (m/z 15)

Nitrogen (m/z 28)

Calibration at 200atm (78% N2, 21% O2, 1% CH4) 2/18/05

y = 7.056E-11x + 1.690E-08R2 = 9.994E-01

y = 7.176E-11x + 3.614E-09R2 = 9.939E-01

y = 6.512E-11x + 7.765E-11R2 = 9.962E-010.00E+00

1.00E-08

2.00E-08

3.00E-08

4.00E-08

5.00E-08

6.00E-08

7.00E-08

8.00E-08

9.00E-08

1.00E-07

0 100 200 300 400 500 600

Concentration (umole/kg)

Inst

rum

ent R

espo

nse

(A)

Methane

Oxygen

Nitrogen

New Instrument Development

Next Generation InNext Generation In--Situ Mass SpecSitu Mass SpecRedesign of microcontroller with expanded capability

Embedded PC upgrade with 1 GHz processor running 170 Mb embedded XP OS

Modular carriage makes for easier disassembly of component systems

Integrated system allows for removal of external pressure vessel without compromising vacuum

Redesigned vacuum chamber with heating jacket allowing for bakeout of chamber

Roughing pump mounted on dampers, reducing noise and vibration

Greenland -- the final frontier.... This is the voyage of Tim and Pete in a kayak. Their 10-day mission: to explore strange new harsh environments, to seek out new challenges and new applications. To boldly go where no mass spectrometrist has gone before.

SummarySummary•• The inThe in--situ mass spectrometer was successfully deployed situ mass spectrometer was successfully deployed

to depths of >200 meters in to depths of >200 meters in SaanichSaanich InletInlet

•• Gulf of Mexico and Hillsborough River deployments Gulf of Mexico and Hillsborough River deployments exposed problems and opportunitiesexposed problems and opportunities

•• Calibration of mass spec ion intensities with dissolved Calibration of mass spec ion intensities with dissolved gas concentrations underway with much yet to be donegas concentrations underway with much yet to be done

•• Development of new inDevelopment of new in--situ mass spec will address situ mass spec will address shortcomings of present systemshortcomings of present system

•• Kayaking in Greenland is funKayaking in Greenland is fun

AcknowledgementsAcknowledgements•• David Fries, Gottfried David Fries, Gottfried KibelkaKibelka, Chad , Chad

LembkeLembke, Scott Samson, Charlie , Scott Samson, Charlie CullinsCullins, Charlie Jones, Joe , Charlie Jones, Joe KolesarKolesarand Eric and Eric SteimleSteimle (University of South (University of South Florida)Florida)

•• Richard Hildebrand, O. Manuel Richard Hildebrand, O. Manuel UyUy(Johns Hopkins University, Applied (Johns Hopkins University, Applied Physics Lab)Physics Lab)

•• Jean Whelan (Woods Hole Jean Whelan (Woods Hole Oceanographic Institute)Oceanographic Institute)

•• Michael Michael WhiticarWhiticar (University of (University of Victoria)Victoria)

•• Funding from U.S. Office of Naval Funding from U.S. Office of Naval Research (ONR) Grant No. N00014Research (ONR) Grant No. N00014--0303--11--04790479