GC-C and GC-Pyrolysis IRMS Short Course: Putting the Gas In Gas Chromatography Paul Eby

GC-C and GC-Pyrolysis IRMS Short Course: Putting the Gas In Gas Chromatography Part 1: Standards Part 2: GC Set Up Part 3: Combustion & Pyrolysis

Part 1: Standards

- Thermo Fisher product literature Thermo GC IsoLink - Thermo Fisher product literature Potential Sources of Error: Sample handling - Injection - Interferences Column effects - Reactors - Poor separation Leaks - Open split - Integration

How to Introduce a Standard A separate run of the same compound Spike all samples with a reference material that does not interfere AVOID USING A REFERENCE GAS PULSE AS YOUR STANDARD!!!!!!!

Identical Treatment The reference and sample should be measured in the same way The reference and sample should be the same compound (or class of compound) 3) The reference and sample should be as similar in composition and concentration as possible

GSQ PLOT column 60m, 0.32mm ID, 30C

dD on CH4 and H2 60m GSQ PLOT column

Where Do You Find Reference Materials? NIST / IAEA Commercial Products Make it yourself Beg/borrow/steal

A New Natural Gas Standard? Something to replace SRM8559, 8560, 8561 An effort is underway, headed by Dr. Ellis at USGS Probably won’t be ready until 2015

Commercial Products Oztech – Chuck Douthitt - Lecture bottles of pure Hydrogen, Carbon Dioxide and Nitrogen - Isogeochem Wiki CO2 (d13CPBD, d18OPDB) (-3.6, -16), (-10.5, -10), (-40.7, -30), (-44.5, -31), (-47.6, -37) H2 (dDSMOW) (+100), (0), (-60), (-120), (-160), (-225), (-400), (-800) N2 (d15NAIR) (0)

Commercial Products 2) Isometric Instruments – Michael Whiticar - Lecture bottles of Methane mixtures in air - Isogeochem Wiki - 250, 2500, and 25000 ppm - d13C of -66.5, -54.5, -38.3, and -23.9 ‰ - dD in progress

Commercial Products 3) Indiana University – Arndt Schimmelmann Isogeochem wiki Pure compounds and mixtures dD, d13C, d15N, and d18O GC and EA - n-Alkanes (C1 to C50) Fatty acid esters Aromatics Nitrogen containing organics

Make It Yourself Find a way to compare your material to one of these:

Make It Yourself Dual Inlet / Off-line Methods Pure CO2 vs Pure CO2 (SRM 8562, 8563, 8564) Problem with CO2 tanks containing liquid Pure Hydrocarbons vs Pure CO2 Hydrogen?

Make It Yourself 2) Elemental Analyzer Methods Plenty of EA standards available from NIST/IAEA for 13C

Make It Yourself 2) Elemental Analyzer Methods Even liquids and gases!!!!! Oztech standards

Make It Yourself 2) Elemental Analyzer Methods How about Hydrogen?

Make It Yourself 2) Elemental Analyzer Methods How about Hydrogen? HDevice: - SMOW, GISP, SLAP - Oztech H2 standards - Methane, ethane, propane, butane - Liquid hydrocarbons? - Check the temperature!

Make It Yourself 2) Elemental Analyzer Methods How about Hydrogen? TC/EA: - SMOW, GISP, SLAP - Oztech H2 standards - Methane, ethane, propane, butane - Liquid hydrocarbons? - Solids autosampler

Make It Yourself 2) Elemental Analyzer Methods How about Hydrogen? Other Instruments: - Elementar Vario PYRO Cube - Thermo FLASH HT

Beg/Borrow/Steal…. How much trust do you give these standards? How were they created? Are they traceable to NIST/IAEA standards?

How Many Standards Do You Need? One is okay, two is good, three is better Range should bracket that of your samples A single standard is better than two close together

How Many Standards Do You Need?

How Many Standards Do You Need?

How Many Standards Do You Need?

How Many Standards Do You Need?

How Many Standards Do You Need?

How Many Standards Do You Need? Mixture Available from Indiana University compound dD d13C C-16 -9.1 ‰ -26.15 ‰ C-17 -117.9 ‰ -31.88 ‰ C-25 -254.1 ‰ -28.48 ‰ C-29 -179.3 ‰ -31.08 ‰

How do you inject samples? Part 2: GC Set Up How do you inject samples? Gases Liquids 6-Port Valve Split/Splitless Injector

Points to Remember: - Septum damage - Different types of liners - Cleaning the liner - Capillary insertion - Ferrule can leak - Temperature

6 Port Valve for Injection of Gas Produced by Valco Rheodyne? Exchangeable sample loops 5 uL to 1 mL 2 positions: load and inject 1/8” vs 1/16” ports Rotor replacement

6 Port Valve for Injection of Gas column He sample waste Max loop size: 1.0mL  20ppm CH4 Max loop size without focusing: 100uL  200ppm Min loop size: 5uL  5% CH4

Internal Volume Valve for Injection of Gas column He sample waste Sample volume is the path etched on the rotor 0.06 uL to 2 uL  100% CH4 (0.5uL)

Regulating Column Flow sample column waste He Electronic Flow Controller? Mechanical Pressure Regulator? Mechanical Flow Controller?

Electronic Flow Controller Most new GC’s have them Great for split/splitless injectors Difficult for 6-port valves Be mindful of the two types: Mass flow controller Electronic pressure controller (calculates flow)

Mechanical Pressure Regulator Common on older GC’s Set the head pressure on the column Flow varies depending on the column temp Operates by adjusting the tension on a diaphragm

Mechanical Flow Controller Common on older GC’s Maintain a constant flow Vary the head pressure as column temp changes Needle valve Combo Valve from Valco

Mechanical Flow Controller sample column waste He Pressure gauge shows column head pressure Rises as you go through Temp ramp (constant flow) Pressure drops to zero for a leak Pressure increases to inlet pressure for a plug

Handling Gas Samples Canisters or bombs Teflon baggies Wheaton bottles

Gas Tight Syringe

Chromatographic Issues Baseline Separation

Chromatographic Issues Baseline Separation Separation is generally worse than normal GC-MS Broadening in the source

Chromatographic Issues When is it a Good Peak? Separate runs of pure compounds Sensitivity analysis of integration

Chromatographic Issues When is it a Good Peak? 45/44 is NOT homogenous through the peak Tails are important for the integration

Chromatographic Issues Air Peak Integrates at +500 permil Why does air show up on 44/45/46?

Chromatographic Issues Air Peak

Chromatographic Issues Air Peak

Chromatographic Issues Air Peak Masses 48, 49, 50

Part 3: Combustion and Pyrolysis Converting your peaks to H2 and CO2

Combustion A good resource: Performance and Optimization of a Combustion Interface for Isotope Ratio Monitoring Gas Chromatography/Mass Spectrometry Dawn A. Merritt, Katherine H. Freeman, Margaret P. Ricci, Stephen A. Studley, J. M. Hayes Anal. Chem., 1995, 67(14), pp 2461–2473

Combustion Ceramic Tube 0.5 mm ID Alumina (inert, gas impermeable) Metal wires - 0.1mm diameter - Copper or nickel - Platinum 3) Oxygen

Combustion Input capillary should be inserted 1cm Capillary Tubing from GC ZV Fitting ZV Fitting Alumina Tube Wire Input capillary should be inserted 1cm Wires need to be centered in the hot zone Approx 15cm in a 30cm tube

What Metal? Copper/Platinum Trouble with methane - 3 Cu and 1 Pt wire Nickel/Platinum - 3 Ni and 1 Pt wire - 1050°C 3) Copper/Nickel/Platinum - 950°C Trouble with methane Holds on to oxygen longer Longer life Higher Temperature Hybrid

Thermo Oxidation Reactor

Oxidation Periodic Reoxidation Can run out of O2 - 100% O2 - Backflush 2) Oxygen Bleed - Trickle in 1% O2 in He - Always On Can run out of O2 Can’t use for a while Constantly regenerating Never run out Difficult to balance

Pyrolysis: Shouldn’t this be easy? Just an empty ceramic tube Conditioning required 1450°C

Pyrolysis: Shouldn’t this be easy? Conditioning is necessary to deactivate the interior surface Large quantity of a hydrocarbon will deposit carbon If you do too much you can block the tube:

Pyrolysis: Shouldn’t this be easy? If you don’t do enough: Alumina is actually a poor choice of materials Water of combustion

Pyrolysis: Water Trouble No Nafion trap required Water contamination injected with the sample: