Hi, I'm experiencing problem with recovery of formaldehyde at LOQ level. I have derivatized the formaldehyde with 1% p-toluenesulfonic acid in Ethanol. I'm using HS-GC-FID (Model # 8890) and getting inconsistent areas. I'm using DB-1 column, the vial equilibration time is 10 min and HS oven temp is 100 c. Is it possible that derivatization is not getting completed in 10 min? Any help/ advice will be appreciated. TIA.