Lignin Reductive Catalytic Fractionation (RCF) Monomers Analysis by Gas Chromatography Flame Ionization Detection (GC-FID)

This analysis uses 1,3,5-tri-tert-butylbenzene (TTB) as an internal standard. Prepare adequate volume to allow for addition of 1µL of TTB per 100 µL of sample or standard volume.

Create a 10,000 µg/mL internal standard working solution by weight of TTB using methanol as the diluent.

By weight, create individual 20,000 µg/mL stock solutions of all monomers (listed in Materials section) and use methanol as the diluent.

Combine the stock solutions to create a 1000 µg/mL mixed standard working solution in methanol.

For example, to prepare a 10 mL mixed standard working solution of woody RCF analytes (distinguished in Materials section), add 500 µL of each of the 20,000 µg/mL stock solutions (14 analytes) and add 3000 µL methanol.

Using the mixed standard working solution at 1000 µg/mL, create a calibration curve from 10 µg/mL to 1000 µg/mL with a minimum of five calibration points using methanol as the diluent.

Add 1 µL of 10,000 µg/mL TTB internal standard working solution per every 100 µL of calibration standard.

Example: 10 µL into 1000 µL or 5 µL into 500 µL

Oil Samples:

1. Weigh approximately 5-10 mg of oil into a GC vial and record weight.
2. Add a known volume of methanol to each vial containing sample (for example 1 mL).
3. Add 1 µL of 10,000 µg/mL TTB for every 100 µL of methanol added to the sample vial. Example: 10 µL into 1000 µL or 5 µL into 500 µL

Liquid Samples:

1. Aliquot a known volume of sample into a GC vial (for example 1 mL)
2. Add 1 µL of 10,000 µg/mL TTB for every 100 µL of methanol added to the sample vial. Example: 10 µL into 1000 µL or 5 µL into 500 µL

Analyze samples using an 8890 Agilent Gas Chromatograph (GC) or equivalent equipped with a flame ionization detector (FID) per the method parameters below:

Method Parameters

Split/Splitless Inlet Parameters:

Inlet Temperature: 280 °C

Injection Volume: 1 µL

Split Ratio: 2:1

Inlet Liner: split, single taper, glass wool, deactivated (see Materials)

Syringe: P/N 5181-8809

Wash Solvent: Methanol

Column:

HP5-MS (see Materials)

Carrier Gas: Helium

Flow Rate: 1 mL/min (constant flow)

Oven Parameters:

Maximum Oven Temperature: 280 °C

Detector Parameters:

Detector: FID

Detector Temperature: 300 °C

Air Flow: 400 mL/min

H2 Fuel Flow: 40 mL/min

Makeup Flow: 10 mL/min

Several strategies are utilized when performing this analysis to ensure instrument stability and reproducibility.

Calibration Curves

All compounds must have a correlation coefficient (r²) of 0.995 or greater using a linear calibration fit.

Calibration Verification Standards (CVS)

A calibration verification standard (CVS) is a standard from the calibration curve that is re-analyzed every 20 or fewer samples to ensure instrument drift remains within the determined acceptance criteria. Acceptable CVS recoveries for this analysis are within 15% of the expected amount. Acceptance criteria may differ between instruments and should be determined experimentally.