Intesity m/z=15 [Amps]

Underwater cryotrap - membrane inlet system (CT-MIS) for

improved in situ analysis of gases by mass spectrometry.

gases by mass spectrometry.

Torben Gentz & Michael Schlüter

Alfred Wegener Institute for Polar and Marine Research Bremerhaven, Germany

Presented at the 8thWorkshop on Harsh Environment Mass Spectrometry, St Petersburg, FL September 20, 2011

Outline

• Background

• Motivation

• Design of the Cryotrap

• Redesign of the sample inlet compartment

Mass spectrometer, cryotrap, under water pump

• Field applications

• Summary

Background

Worldwide distribution of gas flares and seepages.

[

^{P M}

#

* X Y _ S G D

!

( M V _ o n _S e a Pockmarks Active submarine Mud Volcanos

Improved online and onside methods are required for the detection of gas flares, seepages as well as the calculation of mass fluxes of methane released from the seafloor.

Man-made gas releases

Hydroacoustic and visual detection of gas release

Hugh, colourfull impression Small source area with steep gas gradients

Gas release at the Hakon Mosby Mud Volcano, Barent Sea continental slope Acoustic “image” of gas

bubble plumes in the water column.

Gas release in the North Sea

Diameter of gas release: 5 cm

Water column and sediment sampling

Phase separation (gas phase from aqueous phase):

Gas analysis by gas chromatography

Gas analysis:

State of the art

Headspace technique for analysis of

discrete samples

Problems:

-time consuming, -coarse spatial and

temporal resolution

Need for new methods

HydroC, Contros Mets, Franatech

Mono-parameter instruments

HydroC, Contros

Nereus/Kemonaut,

by R. Camilli, H.F. Hemond Mets, Franatech

Inspectr200-200, AML, by T. Short and G. Kibelka

R. Camilli, H. Hemond, Trends Anal. Chem. 23 (2004) 307.

Short, R. T. and others, J Am Soc Mass Spectr 12 (2001). : 676-682.

Poly-parameter instruments

Motivation: getting

rite of the water vapor

Water vapor

is the main gas that permeates through this membrane?

70 times magnification 320 times magnification

is the main gas that permeates through this membrane?

For several applications including investigations of natural as well as manmade gas seepages there is a strong demand for:

1. Improve detection limit

2. “Security System“ in case of membrane rupture

•Downgrades the detection limit

•Affects on the ionization effency

•Could cause condensation in the analytical line

•Downgrades the life time of the filament

• Indicate a high pressure in the analytical line

First step: Shipboard Cryo-Trap coupled to the Inspectr200-200

y = 2,0412E-13x + 4,0236E-11 R² = 0,9985

0.00E+00 1.00E-10 2.00E-10 3.00E-10

0 200 400 600 800 1000 1200

Intesity m/z=15 [Amps]

CH4 [nmol L^-1 ]

Calibration MS 09.06.2008

Schlueter, M., and T. Gentz. 2008.

Application of Membrane Inlet Mass Spectrometry for Online and In Situ Analysis of Methane in Aquatic Environments.

J Am Soc Mass Spectr 19: 1395-1402.

Improved detection limit:

From > 100nmol L^-1 to 16 nmol L^-1CH₄ Inspectr200-200

External membrane inlet system

Cryo-trap: Dewar flask with -100 °C ethanol Cooling Thermostats or liquid nitrogen

Improved signal noise ratio at m/z 15 Higher ionisation effency

High emission at the ion source

How to get a Cryo-Trap System to operate under water?

Requirements for under water applications:

(1) temperatures below -85°C have to be reached, (2) a small waste-heat production is required,

(3) the energy consumption has to be below 10 W, (4) large quantity of water vapor need to be trapped (5) service life time of more than 10 hours is favorable (5) service life time of more than 10 hours is favorable

(6) a short cool down time below 60 min is necessary, and (7) the system should be robust, of small dimensions and low

weight

The system was intended to be designed for application with different sensor systems (IR,MS) and for “non lab” environments.

Peltier element and stirling cooler.

Requirements:

(1) temperatures below -85°C have to be reached, (2) a small waste-heat production is required,

(3) the energy consumption has to be below 10 W,

Micro Stirling Cooler, Ricor K508 Peltier element, Whatson Marlow, MI4040

Comparison…

Temperature [°C]

-20 0 20 40 60 80 100

Temperarture [°C]

-20 0 20 40 60 80 100

Heat sink

Peltier element: 80 W at 6.8 V.

Stirling cooler: 6 W at 24 V

Time [min]

0 5 10 15 20 25

Temperature [°C]

-100 -80 -60 -40 -20

B

Peltier element, Whatson Marlow, MI4040

-85°C

25

Micro Stirling Cooler, Ricor K508

Time [min]

0 150 300 1200 1300

Temperarture [°C]

-100 -80 -60 -40 -20

A

Cooling side

-85°C

1300

Temperature [°C]

0 20 40

Water vapor [Amps]

1.5e-7 1.8e-7 2.0e-7 5e-4

6e-4

Temperature Water vapor Pressure

Performance of the cryo-trap

Requirements:

(4) large quantity of water vapor need to be trapped (5) service life time of more than 10 hours is favorable (6) a short cool down time below 60 min is necessary

96% 98%

Time [min]

0 25 50 75 100 125 150 175 200 1325

Temperature [°C]

-100 -80 -60 -40 -20

0

Water vapor [Amps]

2.5e-8 5.0e-8 7.5e-8 1.0e-7 1.3e-7 1.5e-7

Pressure [Torr]

0 1e-4 2e-4 3e-4

4e-4 ^Pressure

Under water Cryo-Trap

Requirements:

(7) The system should be robust, of small dimensions and low weight

Analyzer unit

Connection to the sensor unit Cooler unit Membrane unit Specifications:

Length: 290mm

Outer diameter: 190mm

Max depth: 200m

Inner diameter: 180mm

Weight: 5.1 kg

Material: Aluminum

Cooling area: 20mm

Cryo-Trap and redesign

Design of the Inspectr200-200 (AML)

Redesign of the Cryo trap & UWMS

Analyzer unit MIS & Gear pump Sample inlet

Sensor unit (dry) CT-MIS (sample unit)

1/8“ Capillary Heater control Power supply

Application in harsh environments

Deployment of the under water gas analyser system

How to find and

investigate gas flares?

500m Hydroacoustic in the

water column

Multibeam echosounding:

High resolution bathymetrie of the seafloor

Under water observation and measurements

280m

280m

500m Gas release

4 x 5 m

Under water gas analyser, sampler and observing system

• Camera / Spot light

• Syringe sampler

• Energy supply

• Bubble counter

• CT-UWMS

• CTD

•Oxygen optode

•Turbity sensor Mode of deployment:

Towed system by research vessel Mobile underwater platforms

3D-concentration field of CH ₄

Gas Bubbles CH

[nM/L]

This 24000 points allows calculation of budgets, gas fluxes etc.

Summary

Under water cryo trap membrane inlet system for underwater and other harsh environment:

• improves detection limits

• reduce the internal pressure significantly

• expand the lifetime of the analyser

• secure the analyser for inflowing water

• is easily to adapt to other sensors

The improved detection limit of the UWMS by the CT enhanced the computation of mass budgets as well as the search for gas

flares, since small CH₄

concentration gradients are guiding to the gas flares.

• is easily to adapt to other sensors

Thank you for your attention

Torben.Gentz@awi.de

www.awi.de