by
ant78se » Tue Feb 06, 2018 5:37 pm
GOM wrote:Out of interest, what exactly are your analytical conditions and which flavour essential oils are you checking?
The method is RTLocked to n-Pentadecane at 70.000 min,
Am I correct in assuming that pentadecane standard is eluting at 70 minutes?
If so, that seems to be rather late for this HP-5 phase.
Leffingwell have some useful purchasable databases for flavours and essential oils with retention indices that I have used successfully. (I have no affiliation to them)
http://www.leffingwell.com/baciseso.htm
Dear Ralph,
Thank you for the link!
The conditions are as following:
GC Agilent 7890A
Oven
Ramp ’C/min ’C Hold min
Initial 50 0.00
Ramp 1 2 280 0.00
Runtime 115 min
Inlet Split/Splitless
Temp 250 ’C
Mode Split
Carrier H2
Split Ratio 100:1
Injection volume: 0,2uL pure essential oil
Column HP- 5 part # 19091J-215
Mode Constant pressure
Pressure 38.1 kPa (adjusted to RTLock)
Outlet Pressure Ambient
Detector FID
Temp 300 ’C
Hydrogen 40 mL/min
Air 450 mL/min
Makeup Nitrogen 45 mL/min
The only difference is that Agilent use He as carrier gas so the pressure is tweaked a bit. I would personally start the method at 70'C because there are no constituents in essential oils eluting earlier, i would ramp 1'C/min to 100'C and then around 5'C/min to 280 then 10'C/min to 320'C.
I am checking around 60 different essential oils and a few are simple like for example Wintergreen has Methyl salicylate 99,5% and 6 other constituents in the remaning 0,5%. Then we have many more complex essential oils like Frankincense, Rose, Sandalwood, for example Spearmint (Mentha spicata oil) contains about 70 different natural constituents.
There are a lot of companies that are selling fake, old oxidized essential oils, other are adulterated crap. Aromatherapy is growing and people buy and use essential oils that are dangerous for their health every day but there are no autorities checking these companies. I know because i bought a bad essential oil a few years ago that turned my life up side - down. What i've learned from this is that are a lot of bandits everywhere selling everything to earn money without a conscience or a thought for another human being.
You might think now that essential oils are bad... well No, not all of them.
I'm setting this lab up myself, with my own money working for no profit, the only thing i want is to keep the customers safe because no one else seems to care (at least no one in EU).