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Boardwalk :: Forum List Forum Category GC Troubleshooting
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 Dilution solvents / headspace analysis - 2005/11/28 18:12 I'm trying to determine the amount of phthalates in a varnish by GC. Since the varnish has a high viscosity I have to dilute it before manual injection. The phtalates I'm working with have very high boiling points (about 350ºC). What kind of solvent should I use to dilute the varnish? Is there any problem in repetibility when using volatile substances (like ketone, ethanol,..) as dilution solvents in cases like this?
What about headspace analysis? The varnish is also composed of some volatile substances. Wouldn't it be dangerous to heat the vials up to 350ºC?
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 Dilution solvents / headspace analysis - 2005/11/28 18:13 If you use Acetone or similar as the solvent, it is very easy to incorporate an internal standard, so quantitation is not a problem. For similar analyses we use diethyl phthalate as the internal standard because it is not often used in the materials we look at.
Headspace is NOT an option in my opinion but you seem to have fallen into the trap of believing that you need to heat samples to above their boiling point to carry out headspace analysis. This is not the case and can also be very dangerous. VOLATILITY is the property you should consider and NOT boiling point - the two are not necessarily linked.
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Boardwalk :: Forum List Forum Category GC Troubleshooting

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