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Utilizing NeSSI™ for Analytical Applications. Dave Veltkamp* Brian Marquardt* Charlie Branham † *Center for Process Analytical Chemistry (CPAC) University of Washington, Seattle WA † Grad Student from Bart Kahr’s group in Chemistry, UW. CPAC Project Overview.

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utilizing nessi for analytical applications

Utilizing NeSSI™ for Analytical Applications

Dave Veltkamp*

Brian Marquardt*

Charlie Branham†

*Center for Process Analytical Chemistry (CPAC)

University of Washington, Seattle WA

† Grad Student from Bart Kahr’s group in Chemistry, UW

cpac project overview
CPAC Project Overview
  • Goal is to support NeSSI related development within CPAC
    • Developing platforms and demo applications
    • Support PI and student use in research programs
  • Promote and support wider NeSSI adoption and use
    • Web based support
    • Interaction with NeSSI community
    • Legal umbrella for cooperative development
old nessi gas vapor system

NeSSI substrate with 3 MFC’s

  • 2 bubblers for vapor generation

1 MFC Controls N2 dilution flow

Single inlet line (N2)

Outlet lineto flow cell

Standard Ace Glass impingers

2 MFCs Control N2 flow to bubblers

Old NeSSI Gas/Vapor System
optical flow cell
Optical Flow Cell
  • Flow cell is a simple cross fitting
    • 6-around-1 fiber optic for source and collection
    • Delrin rod with sensing compound coated on end
  • Multiple crosses can be chained together for screening several compounds at once
  • Optical detection using simple reflectance optical measurement
    • Ocean Optics USB2000 VIS spectrometer (350-1000 nm)
    • 405 nm blue LED excitation
    • Compound fluorescence signal in region 600-900 nm
vapochromatic response
Vapochromatic Response

Full spectrum response of the 0%, 10%, and 50% bubbler flow samples used to make the PLS model showing both the change in intensity and shift in peak maximum with changing benzene concentration.

vapochromic 1 response
Vapochromic #1 Response

* MFC #3 run at 5% FF rather than 50% FF

bubbler results benzene conc
Bubbler Results (Benzene Conc.)

Benzene concentration (ppm) calculated from the weight loss experiment data as a function of bubbler flow rate (%FF N2)

new gas sensor testing system
New Gas Sensor Testing System
  • More capability to generate analytical vapors, gas blending, and on-line dilution of vapor streams for method development work
  • This system delivered by CORCOR Tech to UM last week and will facilitate collaboration with Kent Mann
reconfiguration of cpac nessi system
Reconfiguration of CPAC NeSSI™ System
  • Our Swagelok NeSSI™ system proven to be very easy to change to suit needs
    • Replaced bubblers with permeation tubes and oven
    • Changed to look at CO2 in N2 blending
    • Changed to look at O2 and moisture in air
    • Investigation of flow, mixing, and dead volumes
  • Used to evaluated new analytical instruments in CPAC lab
    • ASI microFast GC – 2 column GC with trap injection
    • Aspectrics EP-IR mid infrared spectrometer with gas cell
  • LabVIEW software developed to automate experiments
schematic of system
Schematic of System
  • Needed to design system with multiple (3) dilution stages
    • Somewhat complex flow paths to minimize dead volumes
  • Had to compromise automated vs. manual control of N2 flows in first two stages
    • Lack of additional MFCs required manual metering valves
system flows
System Flows
  • By closing valves and using the MFCs as flow meters, all flows can be measured
  • Closing off the N2 flows (SV2 and MFC2) and waste valves (PV3 and PV4) allows flow thru bubbler to be measured
    • MFC3 and MFC1 set to “valve open” setpoint
  • All flow streams and legs of system can be flushed by N2
dilution flows
Dilution Flows
  • 1st dilution of bubbler flow at input to MFC 3
    • Most of flow goes to waste, MFC setpoint typically 1-5%
    • N2 flow regulated by waste needle valve
  • 2nd dilution at outlet port of MFC 3
    • Again most of flow going to waste, MFC 1 set to 1-5%
    • N2 and 2nd diluted sample flows set by needle valves PV2 and PV4
  • 3rd dilution at output port of MFC 1
    • N2 flow controlled by MFC 2
  • Important to balance pressures and flows to avoid unexpected flow conditions – some tweaking required!!
aspectrics ep ir instrument
Aspectrics EP-IR Instrument
  • 128 channels from 2.50 to 5.00 microns (4000-2000 cm-1)
    • Each channel approx 19.7 nm wide “band pass”
    • Also a 256 channel model available
  • Runs at an acquisition frequency of 100 scans (rotation) per second
    • Real-time data collection of fast events
    • High averaging for low LOD applications
  • Small size and rugged construction
    • Only moving part is the encoder disk
    • Suitable for high vibration process environments
    • No hygroscopic parts
  • Several optical configuration of sampling cell/accessories possible
  • Powerful on-line embedded chemometrics software
aspectrics ep ir with gas cell
Aspectrics EP-IR with Gas Cell





Gas cell

Glow source

asi microfast gc
  • System on loan from ASI as part of WTC project with Infometrix
  • Programmed temperature gas chromatograph using
    • Syringe or valve inlets to a flash evaporator.
    • Sample delivery to an adsorbent trap for concentration
    • Desorbtion and delivery to twin capillary columns
    • Temperature programmed column elution
    • Detection by simultaneous flame ionization detectors (FID).
    • Trace levels down to low parts per billion can be measured.
  • Compact and easy to setup chromatography
    • Weight on the order of 12 pounds
    • Size on the order of a shoe box
    • Speed of analysis on the order of 10 times faster than competitors
  • Very easy to use
    • Trap injection makes it simple to use and automate
    • Really more like a spectrometer or sensor in operation
      • Even non-chromatographers can use it!!
asi microfast gc1

dual columns and heater assembly





end of



head of








FID Manifold

Back Panel







Sample Inlet


FID Vents



glass liner

V4(n open)


Trap &














@ 40psi





electronic pressure regulators

Pneumatic Manifold




Vacumn Pump



pump vent

micro fast gc column details


column #1100 micron IDDB-5

Columnsoven sheath~1mm ID

column #2100 micron IDDB-1701


column heater sheath

microFAST GC™ Column Details

3 meter column length

microfast gc analytical cycle
microFAST GC™ Analytical Cycle

Typically 2-3 minutes

Sample Time

Trap pre-purge time

Column cool-down time

Equilibrate time

Injection time

Trap cool-down time

Trap preheat time

Trap cleanout time

Column separation time

Adjustable parameters that affect analysis – lots of tuning potential

example benzene chromatograms
Example Benzene Chromatograms

Not very demanding chromatography – but convenient reference method

experiment blending co 2 with n 2
Experiment: Blending CO2 with N2
  • Goal was to characterize the NeSSI™ system, software control, and the EP-IR gas cell data collection
    • Series of step changes in MFC setpoints for CO2 dilution
    • Different hold times (delay) between setpoint changes
    • Series repeated 5½ times
  • Bubbler replaced with CO2 from tank
  • Results show very good reproducibility and control of the gas blending system
    • Dynamic response consistent with expectations
    • No dead volume issues
co 2 blending experimental design
CO2 Blending Experimental Design

Note: MFC #2 offset by 90%FF, numbers on plot represent step hold time

step times and spectral response
Step times and Spectral Response

CO2 setpoints inverted & offset for clarity

Note: Total flow = 250 sccm, volume of cell ~ 210 ml – so about 1-2 min exchange time (lag) seems about right

nessi permeation tubes

dilution flow

NeSSI™ Permeation Tubes
  • Used a stainless steel condenser as “oven” for permeation tubes
    • Removed condenser core and replaced with permeation tubes
    • Mounted in single-port ½” adapter to direct N2 up thru oven
    • Second ¼” adapter block returns flow into NeSSI™
    • Temperature maintained by flowing water thru jacket from heater/chiller
  • Permeation tubes made in-house
    • Teflon tubing sealed at both ends
    • Made different tubes for water, benzene, and toluene vapors
permeation tube results
Permeation Tube Results
  • Water permeation tube study
    • Vapochrome compound (Kafty)
    • Oven temp. set at 50°C
    • MFC flow rate set at 10%, 20%, 30%, 40%, and 50% for 30 min
    • Spectra taken at each flow rate
  • Benzene permeation tube
    • Vapochrome compound (#4)
    • Oven temp. set at 30°C
    • MFC flow rate set at 0%, 10%, 20%, 30%, 40%, and 50% for 30 min
    • Spectra taken at each flow rate
conclusions and future work
Conclusions and Future Work
  • Setup of NeSSI™ Vapor Platform complete (for now)
    • LabVIEW software developed and tested
    • Flow dynamics tested and characterized
    • New vapor generation ideas to be tested
  • New instrumentation interfaced and tested
    • Both Aspectrics EP-IR and ASI microFAST GC™ valuable additional tools for monitoring gas mixing and delivery
    • Additional applications from Sponsors welcome
  • Vapochromic compound testing continuing
    • Moisture, CO2, O2 and BTEX sensors testing underway
    • Additional screening and analytical performance testing planned
  • Plan to get back to some microreactor work
    • Parker NeSSI™ system for reactant and product streams
    • Microreactor components from Microglass & IMM on hand
  • Fuel cell studies with Eric Stuve and Chem. E. students planned
  • WTC Project with Infometrix on Process GC interfaced to NeSSI™