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Conversion of Agilent EI GC/MSD Systems

From Helium To Hydrogen Carrier Gas

Bruce D. Quimby, Ph.D.GPD Solutions Groupand Harry F. Prest, Ph.D.GC/MS Research and Development

October 9, 2012

C&EN Webinar

Question: Have You Ever Tried Converting Your GC/MS From Helium To Hydrogen Carrier Gas?

Answer 1: “No. Never thought of trying it. Too busy.”

Answer 2: “We did that several years ago. It took some effort, but it has been working fine.”

Answer 3: “We tried it once. The results were horrible and confusing! We had a very high background, high noise, and very bad peak shapes. After 4 days, we went back to helium.”

October 9, 2012C&EN Webinar

2

Introduction: Converting from He to H2 Carrier Gas

Many GC/MS users are considering changing from helium to hydrogen carrier gas due to price/availability problems with helium.

– Read Chemical and Engineering News - July 16, 2012 (2-34)

This talk describes the steps recommended for converting EI GC/MS methods.

It is important to recognize the differences with using hydrogen carrier. Time should be allotted for adapting the method, optimization, and resolving potential problems. Areas that will need attention include:

– choice of supply of H2– remove/bypass carrier gas filter (may be re-installed later if needed)– GC/MSD hardware changes– choosing new chromatographic conditions– potential reduction in signal-to-noise ratio (2-5x)– changes in spectra and abundance ratios for some compounds– activity and reactivity with some analytes


3

Introduction: Converting from He to H2 Carrier Gas

Methods that will generally require less optimization include analytes that are:

– “durable” compounds– at higher concentrations– analyzed with split injections– derivatized

Methods that will generally require more optimization include analytes that are:

– “fragile” compounds – at trace concentrations

Allow time for necessary updates to SOPs and validation


4

5

H2 Safety


Letter from Agilent Safety Engineer: Describes H2Safety Features of Agilent GCs


6

Designed for Reliability – H2 Safety

Safety ShutdownWhen gas pressure set points are not met, the valve and heater are shut off to prevent explosion

Flow Limiting FritIf valve fails in open position, inlet frit limits the flow

Oven ON/OFF SequenceFan purges the oven before turning on heater to remove any collected H2

Explosion TestGC and MS designed to contain parts in case of explosion


7

Safety First: Read This Before You StartG3170-90010


8

9

Source of H2 Carrierand

Plumbing


9

Source of Hydrogen: Use a Hydrogen Generator

Higher initial expense than cylinders, much lower cost over timeVery clean H2, >99.9999% availableMore consistent puritySafety considerations

– H2 is only generated at needed pressure (like 40 psig)– Flow is limited (like 250 mL/min)– Auto-shutdown if set point pressure cannot be maintained– Minimal stored gas (like 50 mL at 40 psig) of H2 at any one time

Make sure to buy a good one with a low spec for water and oxygen


10

This is an example of the type of generator to use for H2 carrier gas.

Look for generators with a >99.9999% specification and low individual specs on water and oxygen.


Hydrogen Generation

11

Plumbing the Instrument

Chromatographic quality stainless steel tubing is often recommended for H2plumbing and is probably the best choice if available. Users may have to follow local codes or internal company guidelines.

We have also used new 1/8th copper that has been cleaned for GC use.

Dirty tubing will cause huge contamination problems, as H2 appears to carry dirt out of metal more than He does.

Don’t use really old copper tubing, as it becomes brittle and can break.

Note that MSD leak checks will not always find big outgoing leaks. Leak check when complete with electronic leak detector.

When plumbing a H2 generator, start out with no traps. Only add traps if needed. Make sure the water and oxygen levels are low enough.


12

Split Vent and Septum Purge Vent Should be Connected to Exhaust


13

MS Components Required for Conversion:

Magnet and Draw Out Lens


14

Check the Magnet in the 5975

If the magnet in the 5975 does NOT have a serial number along the left edge (as viewed through the source window), it is suitable for use with Helium, but not Hydrogen.

If not, please contact your Agilent service engineer to change it to a Helium and Hydrogen compatible magnet before converting the system to H2 carrier.

Note: All 5973 magnets are compatible with both He and H2


15

Replace the Standard 3 mm Draw Out Lens With the Optional Hydrogen Draw Out Lens

G2589-20045Hydrogen Draw Out Plate, Inert

Standard 3 mmDraw Out Plate, Inert


16

Choosing a Column and Method Conditions


17

MSD Pumping Capacity for H2 is Less than for HeThis Limits Column Choice

These are approximate values for the 5975. Maximum flow of H2 to maintain reasonable source pressure:

– Performance turbo: 2 mL/min– Standard turbo: 1 mL/min– Diffusion pump: 0.75 mL/min– Pressure pulsing: turbo < 3 mL/min, diffusion < 2.5 mL/min

It is very helpful to have an ion gauge on the MS to monitor the vacuum vs. column flow.

Try to avoid flows that produce pressures higher than 5 x 10-5 torr. You can get useful data above this pressure, but performance may start to degrade


18

Guidelines for Choosing Column Dimensions and Flows for Method Converted from He to H2

Determine max flow of H2 into MS that will give source pressure of 5 x 10-5

torr or less source pressure. This is your max column flow.

Choose column dimensions at initial oven temp of method to give:− a flow < max column flow for vacuum pump− a flow > min column flow for efficiency− an inlet pressure of at least 5 psig

Keeping a temperature ramp of the same number of °C/void time will give similar elution order. Use the Agilent method translator for this.

These are only approximate guidelines. Sometimes you may have to deviate from them.


19

Van Deemter CurvesIf the flow of He or H2 is too low, you loose efficiency MUCH FASTER than if it is too high. This is why operating at or above minimum linear velocity is important.

Use 35 cm/sec as minimum for H2


20

Column Choice

When in doubt (or a hurry) use:− Use 20m x 180 um column and set constant flow at 0.3-0.5 mL/min. − Try to get a linear velocity of at least 35 cm/sec

Try to use the same phase and phase ratio to get similar elution order.

Smaller bore columns have lower capacity. You may have overloading on high level calibration standards, or samples

You may need to use pulsed injection to load sample into small bore columns when using a low flow rate.

The flow range for your H2 setup is limited on the low side by the flow to get 35 cm/sec and on the high side by the vacuum pump capacity


21

Using the Agilent Flow Calculator: Set Linear Velocity to 35 for H2 Carrier

Inlet pressure is too low Set inlet pressure to 5 psig

If Inlet Pressure Too Low, Raise Flow


22

Using the Agilent Method Translator: 30m x 0.25 mm id x 0.25 um Checkout Column with Perf Turbo

Meets flow requirements for pump and column efficiency with 2x speed gain


23

Using the Agilent Method Translator: With Perf Turbo and Std Turbo

For 20m x 0.18 mm id x 0.18 um Column:− Meets flow

requirements for standard turbo pump.

− Flow here is chosen to give a 2.5 x speed gain.


24

Initial Startup with Hydrogen


25

Initial Problems with Switching GC/MS Methods to from He to H2 Carrier Gas

High background that looks like hydrocarbons

Reduced signal to noise (worse MDL)

Significant tailing for many compounds


26

Switch to H2 1st Problem: High Background

You will see this throughout work with H2. • It will get much smaller with time and

use.

• It used to takes days or weeks for background to fall to acceptable levels.

Agilent developed a new conditioning protocol to clean-up the background much faster.(see later slide)


27

GC/MS Toxicology Analyzer Checkout Sample

2 4 6 8 10 12 14 16 18

1 Amphetamine2 Phentermine3 Methamphetamine4 Nicotine5 Methylenedioxyamphetamine(MDA)6 Methylenedioxymethamphetamine(MDMA)7 Methylenedioxyethylamphetamine8 Meperidine9 Phencyclidine10 Methadone11 Cocaine12 SKF-525a (RTL Compound)13 Oxazepam14

Tetrahydrocannabinol

15

Codeine

18

Lorazepam16 Diazepam17 Hydrocodone

19 Oxycodone20 Temazepam

22 Diacetylmorphine23 Nitrazepam24 Clonazepam25 Alprazolam26 Verapamil27 Strychnine28 Trazodone

21 Flunitrazepam

1

2 3

4

5

6

7

8

9

1011

12

14

15

17

18

19

21

13

16

20

22

23 24

2526 27

28

5 ng/uL each compound


28

Switch to H2 2nd Problem – Peak Tailing

2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.000

200000

400000

600000

800000

1000000

12000001400000

1600000

1800000

2000000

Time-->

Abundance

Hydrogen

4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.000200000400000600000800000

10000001200000140000016000001800000200000022000002400000260000028000003000000

Time-->

Abundance

Helium

Immediately after conversion to H2, peak shapes on TIC are poor and tailing badly.

20m x 0.18mm id x 0.18 um DB-5MSUI


29

Switch to H2 3rd Problem: Spectrum Changes over Peak Profile

7.20 7.40 7.60 7.80 8.00 8.20 8.40 8.60 8.80 9.00

40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 3400

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

m/z-->

Abundance

Average of 8.018 to 8.036 min.: ToxCKO_H2_4.D\data.ms82182

42

105

5568

303198122 167152 272135 215 244230 259 341288 327

40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 3400

2000

4000

6000

8000

10000

12000

14000

m/z-->

Abundance

Average of 8.048 to 8.085 min.: ToxCKO_H2_4.D\data.ms91

78

4164

115 167128141 207191 221154 281242 300265 341327314

Tail SpectrumPeak Spectrum

Cocaine

Cocaine Not Cocaine

There is More Happening Here than Simple Peak Tailing


30

Main Ions of Cocaine Do Not Tail. Tail Made Up of Other Ions

Tail is not cocaine ionsCocaine

Tail is different than peak. May be formed from catalytically shredded main component. This problem is reduced with time


31

H2 ConversionConsiderations for Success


32

Agilent’s Recipe for H2 Success: Minimizing the Time for Chromatography and Background to Stabilize1. Have a good source of clean hydrogen like a >99.9999% purity hydrogen

generator. 2. Keep H2 flow limited to value suitable for your pumping system3. Use optional Hydrogen draw out lens 4. After setup, purging and pump down:

– Set the source to max temp for your source (check to see what yours is)– Reduce the EMV to 800V– Leave the FILAMENT ON overnight. This cleans up background rapidly.

5. Peak shape will be much better and background will be much lower in the morning.

6. Lower the source temp to method value, retune, and run some samples7. It is a good idea to have an extra set of filaments on hand in case one

burns out. This hasn’t been a problem, but a good idea.


33

Agilent’s Recipe for H2: Success

2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.00

200000400000600000800000

100000012000001400000160000018000002000000220000024000002600000

Time-->

Abundance

• Peak Shape Much Better • Background is Lower• Better Signal-to-Noise


34

Agilent Toxicology Analyzer

Features: • Configured, tuned and tested for the application • Retention time locked (RTL) with DRS database• Constant flow to MS• Backflush to reduce cycle time and remove matrix artifact

Challenge: • Convert from He to H2 carrier without altering performance

criteria


35

He Constant Flow Toxicology Analyzer

7890A GC

LiquidInjector

Column

AUX EPC

15 m X 0.25 mm id X 0.25 um DB-5MSUI

5975CMSD

S/S Inlet

~12psi

Vent

1m x 0.15 mm id1.7 mL/min

PUU

Parameters:• Constant Flow to MS• RTL DRS Method


36

H2 Constant Flow Toxicology Analyzer

7890A GC

LiquidInjector

Column

AUX EPC

15 m X 0.25 mm id X 0.25 um DB-5MSUI

5975CMSD

S/S Inlet

~8psi

Vent

0.81m x 0.12 mm id1.7 mL/min

PUU

Parameters: Constant Flow to MS RTL DRS Method

No Change in Performance


37

Converting Toxicology Analyzer from He to H2

3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.000

200000

400000

600000

800000

1000000

1200000

Time-->

Abundance

3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.000

200000

400000

600000

800000

1000000

1200000

Time-->

Abundance

Hydrogen

Helium

Toxicology Check Out Mix


38

Switching GC/MS Methods to from He to H2 Carrier Gas

Reduced high background that looks like hydrocarbons

Improved signal-to-noise relative to pre-conditioned state

Reduced tailing for many compounds


39

Performance Expectations


40

Performance Expectations

Signal-to-noise ratio is often worse by about 2-5 x. This obviously varies from compound to compound

While most spectra remain same, there are always exceptions. Users should check the reference spectra for important targets to make sure they have not changed

Same comment for target/qualifier ratios

Some compounds may disappear at low levels. Examples include: some nitrogen and oxygen containing compounds (alcohols, aldehydes, ketones) like those found in flavor samples


41

Library Match Factors – Helium and Hydrogen Carrier Gas Comparison

In general, these 20 spectra in hydrogen carrier show lower match factors than in helium carrier gas. They can still be properly identified in library search.

Helium Hydrogen Helium HydrogenDichlorvos 924 867 929 904Mevinphos 925 852 973 967Ethalfluralin 927 897 927 897Trifluralin 897 856 897 857Atrazine 914 901 915 908BHC‐gamma (Lindane, gamma HCH) 925 858 931 878Chlorpyrifos‐methyl 922 897 926 908Heptachlor 926 851 929 856Malathion 916 836 953 846Chlorpyrifos 901 890 902 892DDE, p,p'‐ 934 903 946 940Dieldrin 926 903 927 903Hexazinone 901 832 906 912Propargite 851 821 857 829Leptophos 884 847 884 847Mirex 903 881 914 934Fenarimol 905 872 908 877Coumaphos 864 804 870 813Etofenprox (Ethofenprox) 906 842 916 843

NIST (Forward) NIST (Reverse)


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Lindane

5x10

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

+EI Scan (8.148 min) 20mix_RTL_2.D

180.8

108.8 218.8

146.884.951.0

95.960.9 253.7289.7

5x10

00.10.20.30.40.50.60.70.80.9

11.11.21.31.4

+EI Scan (8.152 min) RTlock_1.D

78.0

180.8

110.9

218.8

146.9

95.961.0253.7

Counts vs. Mass-to-Charge (m/z)40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540

NIST Forward Match = 925

Helium Carrier Gas

Hydrogen Carrier Gas

Observations• Ion ratios changed• Extra peaks in H2



43

Heptachlor

5x10

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

+EI Scan (9.335 min) 20mix_RTL_2.D

99.9

271.6

236.765.0134.8

159.8 336.6193.7114.984.9 300.6216.751.0 371.8

5x10

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

+EI Scan (9.332 min) RTlock_1.D

66.0

99.9

271.7236.7

159.8 195.8134.984.9 336.7218.8

Counts vs. Mass-to-Charge (m/z)40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540

Helium Carrier Gas

Hydrogen Carrier Gas



Observations• Ion ratios changed


44

Other Considerations:H2 is not an inert gas, and therefore inertness problems will still exist or be worse.

Use the lowest inlet temp that works (to reduce reactions with H2)Use pulsed injection, especially with small bore columnsConsider using an MMI in cold splitless mode for fragile compoundsUsing a deactivated S/SL weldments might help (but don’t ever scrub it) Avoid using methylene chloride as a solvent (especially wet).

– At higher inlet temps (like >280C), HCl is formed and causes problems. – If must be used, use lowest inlet temp and maybe a deactivated S/SL

weldment, or Multimode inletAvoid carbon disulfide as a solventUse liners with a taper at bottom to minimize sample contact with gold seal

– Use Agilent Ultra Inert Liners.


45

Hydrogen Carrier Summary

1. Get a GOOD hydrogen generator and plumb it properly

2. Pick a column that meets the flow needs of method andMSD pump

3. Do magnet update (if necessary) and install Hydrogen draw out lens

4. After purging and pump down, set source to max temp and EM to 800V. Leave filaments on all night.

5. Reset source temp, retune, and run samples. Run practice samples for a few days to make sure system has stabilized

6. Source cleaning will be needed much less frequently


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For additional information please visit:

http://www.agilent.com/chem/heliumupdate

Thank You for Your Attention


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