Hi All!

I'm analyzing lignin-derived phenols from mangrove sediment samples on Thermo Scientific Trace 1310 Gas Chromatograph interfaced to a Thermo Scientific TSQ8000 Triple Quadrupole Mass Spectrometer. My GC/MS condition is listed below.

Compared to the known values from laboratory standard, I found out that acidic lignin-derived phenols (syringic acid, vanillic acid, coumaric acid, and ferulic acid) and acetone syringone are underestimated. This problem only happened with these samples with long retention time (~23 to 31 min); nevertheless, I always yield accurate concentration of earlier compounds.

I've tried some basic maintenance like liner replacemnt and column trimming but they didn't help. Have you ever had this kind of problem before? Also, could you please guide me how to fix this issue?

Thank you so much!
Prakhin Assavapanuvat
Graduate student, UF

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Oven
Initial temperature 85.0 °C, hold for 1.00 min.
Ramp 4.0 °C/min until 216.0 °C, hold for 0.00 min.
Ramp 10.3 °C/min until 270.0 °C, hold for 6.00 min.

Front
Split mode
Carrier flow: He, constant, flow rate 1.000 mL/min, gas saver flow 20.0 mL/min, gas saver time 2.00 min
Inlet: temperature 260 °C, split flow 20.0 mL/min, split ratio 20.0
Septum purge: purge flow 5.0 mL/min

Back
Split mode
Carrier flow: He, constant, flow rate 1.000 mL/min gas saver flow 20.0 mL/min, gas saver time 2.00 min
Inlet: temperature 260 °C, split flow 10.0 mL/min, split ratio 10.0, splitless time 1.00 min
Surge: surge pressure 5.00 kPa, surge duration 0.00 min.
Septum purge: purge flow 10.0 mL/min

MS
MS transfer line temp: 280 °C
Ion source temp: 280 °C