advances in capillary column backflushing - · pdf file•no unpurged volumes ... fitting,...

ISCCE 2010ISCCE 2010 1

Advances in Capillary Column Backflushing

Matthew S. Klee, Ph.D.


Capillary Flow Technology Traits

•Ease of use - ruggedness•Inertness•Usability to > 350 oC•Excellent exclusion of air •No unpurged volumes •No porous materials into which compounds can dissolve ( peak tailing)

•Fast thermal response •No outgassing or shedding of particles


FS Tubing Connections – The Magic

Column 1 In

Restrictor 1

out to vent

Plate

Ferrule

Nut

Restrictor 2

or Column 2

Channel

Unique design provides rugged, reliable connections with minimal unswept volume and high inertness


Ferrule Sealing

Seal region

Square cut is not critical


Backflush Setup

1. Start with working method and reference sample/chromatogram2. Extract pertinent method information from current method 3. Select BF configuration4. Prepare hardware (next slide)5. Install columns 6. Determine pressure/flow settings, download and test stability7. Screen standard on new configuration8. Lock with migrated RTL calibration if RTL method9. Pick last peak of interest using graphical tool, from which BF timing

and conditions are recommended10. Verify BF works11. Fine tune BF conditions if necessary


Preparing hardware during setup

Assemble necessary HW & SW (e.g. PCM/EPC, CFT, Instrument Utilities SW)

Install any needed modules and accessory kits

Check frit (recommend “open/zero” frit)

Check/update PIDs (using instrument utilities SW)

Zero all used pressure control zones (inlet, EPC)

Decide if you need a split purge and install preferred version


EPC/PCM instability at low P or flow

•EPC and PCM modules were designed for most accurate and precise control at flows > 1 mL/min−Proportioning valve duty cycle should never be 0%−Symptoms are: long stabilization time, cycling P

•Some backflush configurations require flows of < 1 mL/min

•Adding a bleed ensures stable pressure control−Fixed bleed−Variable bleed


Basic Bleed Configuration

Purged Purged UnionUnionColumn 1 Column 2

Det

He supply

EPC1P2

IN

Oven

1/16” Swagelok tee

vent

restrictor


Purged 1/16” Union

For purged splitting, in-oven connections

Eliminates air infiltration and stagnant lines

Provides bleed path for EPC stabilization and dumping excess column flow


Fixed restrictor configuration using G2855-80582 This is inside oven, replacing

old Swagelok union

These are outside oven on top

Big one goes to Aux EPC

Use 1/16” straight Swagelok union with Vespel ferrules

Small one goes to vent (room, vacuum vent, split vent trap, etc.)

Let hang loose or vent using whatever connectors necessary according to user requirements


Cut off and remake the QuickSwap in-oven fitting, with tubing extending fully into union (past the purge point)


Fixed split with purged tube fitting

Column

MSDRestrictor

CFT

P1

S/S Inlet

Inlet EPC

P2

AuxEPC

Purged Tube Fitting

Outside oven

Use Vespel ferrules here

vent

Inside Oven


Variable split bleed saves the day

Provides necessary bleed to allow pressure control solenoids to operate well (> 1 mL/min)Maintains low flow even during high-pressure backflushUses normally unused pressure channel (EPC, Backpressure channel on PCM)Allows split flow to be turned OFF for leak checkingProvides the opportunity to program bleed flow for custom applications


Using 2nd EPC for Bleed During Run

Set P3 < P2

2 mL/min independent

of P2


Det

SV Trap

He supply

EPC1P2

IN

Oven

IN

EPC2P3

atmosphere1/16” Swagelok tee


Bleed OFF During Leak Check

0 mL/min


Det

SV Trap

He supply

EPC1P2

IN

Oven

IN

EPC2OFF


Variable restrictor configuration using G2855-80581 This is inside oven, replacing

old Swagelok union

These are outside oven on top

From Aux EPC 1 (purge feed line)

Use 1/16” straight Swagelok union with Vespel ferrules

Vent to split vent trap then to input of EPC 2


Post-Column BF with Variable Split

Column

MSDRestrictor

QuickSwap

P1

S/S Inlet

Inlet EPC

P2

AuxEPC 1

Purged Tube Fitting

Outside oven

Use Vespel ferrules here

AuxEPC 2

vent

trap

P3

Inside oven


Large-Volume Injection, Cool On-Column Solvent Vapor Exit

Not for the novice!


LVI COC SVE with Pre-Column Backflush to Vent 1

Vent

G3186B Purged Ultimate Union

COC

ColumnCoated

Vent

G3180B Purged 2-Way Splitter

EPC

Det

Pre-Columns

Uncoated


LVI COC SVE with Backflush of the column to Vent 2

EPCmakeup

G3180APurged Splitter

Column

COC

Retention Gap

Pre Column

G3182B Ultimate Union Det 1

Det 2

Vent

Purged Ultimate Union G3186,

G1472A


Conclusion

Capillary column backflushing has a large potential return – but requires some attention to detail to set up

Cost to implement backflushing is relatively low and is greatly facilitated by readily available instrument parts and accessories

advances in capillary column backflushing - · pdf file•no unpurged volumes ... fitting,...

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