Urea
Reagents:
1. Trifluoroacetic anhydride (TFA Supelco 33165-U)
2. Methylene chloride (Dichloromethane, Fisher D151-4)
Procedure:
1. Add 200 ml of methylene
chloride and 50 ul of TFA to the urea sample.
2. Incubate at 70 degree centigrade C for 1 hour.
3. Dry sample under nitrogen
4. Add methylene chloride as solvent for GC/MS analysis.
GC/MS:
Instrument:
HP 5890 series II GC system is connected to the HP 5971A mass selective detector.
GC column: A 2m x 2mm-glass column was packed with
custom packing from Supelco. The specifications for the packing are ethylene glycol adipate (EGA) 0.65% on 80-100 mesh chromosorb
WAW.
Inlet Temperature: 200 degree centigrade.
Oven Temperature: 80 degree centigrade for 2 min, then 5 degree centigrade/min ramp
to 130 degree centigrade and hold for 1 min. Then 50 degree centigrade/min ramp to 200 degree centigrade and hold for 2
min. Retentiom time: 10.3 min.
Reference: Nissim,
Gas
Chromatographic-Mass of 15N Urea: Application to Human Metabolic
Studies. Clinica Chimica Acta. Vol. 109. pp295-304.