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Lecture 9 Volatiles. Determination Various GC techniques.

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Presentation on theme: "Lecture 9 Volatiles. Determination Various GC techniques."— Presentation transcript:

1 Lecture 9 Volatiles

2 Determination Various GC techniques

3 Partition Coefficients of some common solvents Water / air, 40º C Cyclohexane0.08 Hexane0.14 Xylene2.4 Toluene 2.8 Benzene2.9 Dichloromethane 5.6 Ethyl acetate62 Butanone140 Butanol650 2-Propanol830 Ethanol1360 Dioxane1620

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

5 An aliquot of blood (0.200 mL) in NaF + Na 2 C 2 O mL of 3 M NaCl with 1 mg/mL 1-propanol In 10 mL vial for Headspace Calibration: 0, 0.4, 0.8, 1.6, 3.2 mg/mL EtOH Blood alcohol

6 Peak-to-Peak Noise is around 0.1 Extraction from 40% K 2 CO ng/mL each Detection limit is at 1-2 ng/mL level In practice, carry over in column and glassware will limit the determination SP ºC 2 min 10ºC/min to 160ºC

7 Dannon Yogurt Grape Juice SP ºC 2 min 10ºC/min to 160ºC

8 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 2900 (15 acetone, 50 methanol) Orange Juice 600 Ethanol determination at ppmv level

9 EtOH + HONO → EtONO + HOH 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 An example of chemical use: Methyl nitrite ethyl nitrite Amyl nitrite Very volatile

10 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.

11 Butyl NitriteIsobutyl nitriteAmyl (Isoamyl Nitrite)Isoamyl Nitrite Formula CH 3 (CH 2 ) 2 CH 2 ONO (CH 3 ) 2 CHCH 2 ONO(CH 3 ) 2 CHCH 2 CH 2 ONO Molecular Weight Physical State Oily LiquidColourless LiquidTransparent Liquid Boiling Point (°C) Physical and Chemical Properties


13 isoflurane halothane enflurane methoxyflurane sevoflurane desflurane

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


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