Lecture 9 Volatiles Determination Various GC techniques Partition

Lecture 9 Volatiles

Determination Various GC techniques

Partition Coefficients of some common solvents Water / air, 40º C Cyclohexane Hexane Xylene Toluene Benzene Dichloromethane Ethyl acetate Butanone Butanol 2 -Propanol Ethanol Dioxane 0. 08 0. 14 2. 8 2. 9 5. 6 62 140 650 830 1360 1620

GC/FID In 1 min, the concentration in a headspace drop (red) is close to that in a source aqueous solution (blue)

Blood alcohol An aliquot of blood (0. 200 m. L) in Na. F + Na 2 C 2 O 4 + 2. 00 m. L of 3 M Na. Cl with 1 mg/m. L 1 -propanol In 10 m. L vial for Headspace Calibration: 0, 0. 4, 0. 8 , 1. 6, 3. 2 mg/m. L Et. OH

Extraction from 40% K 2 CO 160 ng/m. L each Detection limit is at 1 -2 ng/m. L level In practice, carry over in column and glassware will limit the determination SP-1500 100ºC 2 min 10ºC/min to 160ºC Peak-to-Peak Noise is around 0. 1

Dannon Yogurt SP-1500 100ºC 2 min 10ºC/min to 160ºC Grape Juice

Ethanol determination at ppmv level Some results (in ppmv): Light sour cream 47(2) (Standard addition 48(3)) Dannon Yogurt 195(5) (Standard addition 198(8)) Kefir 12(3) Buttermilk 16(3) Some Yogurt samples up to 600 Grape Juice Orange Juice 2900 (15 acetone, 50 methanol) 600

Very volatile Et. OH + HONO → Et. ONO + HOH ethyl nitrite An example of chemical use: C 6 H 5 NHOH + C 4 H 9 ONO + NH 3 → NH 4[C 6 H 5 N(O)NO] + C 4 H 9 OH Amyl nitrite Methyl nitrite

Poppers Effects are instantaneous and brief, but intense. These effects are caused by a sudden surge of blood to the heart and brain; Light-headedness, giddiness, heat flush or heightened sensual awareness may also result. This is known as a 'head rush'; Some users may also experience the impression of time slowing down; The effects fade two to five minutes after use; Users are often left with a headache.

Physical and Chemical Properties Butyl Nitrite Isobutyl nitrite Amyl (Isoamyl Nitrite) Formula CH 3(CH 2)2 CH 2 ONO (CH 3)2 CHCH 2 ONO Molecular Weight 103. 12 117. 15 Physical State Oily Liquid Colourless Liquid Transparent Liquid 67 97 -99 Boiling Point 78. 2 (°C)

isoflurane desflurane enflurane halothane methoxyflurane sevoflurane

Semivolatiles: Headspace with various trap techniques Cooled trap and GC inlet