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For standard and sample solutions:
-
Transfer 200 µl in a glass test tube.
Samples containing important amounts of fat like cake, chocolate should be defatted.
Therefore, take 4 cm 3 of the sample and IS solution and add 4 cm 3 hexane. Mix on
vortex during 10 minutes and centrifuge. Discard the upper layer with a Pasteur pipette.
Repeat the whole extraction procedure with the remaining layer and transfer 200 µl in a
test tube.
- Drying procedure 1 or 2:
- Procedure 1: place the test tube in the vacuum desiccator containing silicagel during at
least 4 hours.
- Procedure 2: add about 0,5 cm 3 dichloromethane, mix and dry under N 2 until constant
volume. Repeat the previous procedure until the sample is dry. To speed up the
procedure, warm-up at 30°C in an oil bath. Samples which easily foam e.g. dairy
products, should be dried by this procedure.
Derivatisation:
- Add 400 µl hydroxylamine-HCl solution, prepared by dissolving 0,67 g NH 2 OH.HCl in 25 cm 3
dry pyridine.
This solution can be stored in the refrigerator for 1 month.
- Mix 10 min. on vortex.
- Warm up and shake (± 200 RPM) in a heating block at 60 °C during 15 minutes, after 5 min.
shake a few seconds on vortex and continue heating.
- Centrifuge the tubes during 5 min. (± 2200 tr.) and dry under N 2 .
- Add 200 µl trimethylsylilimidazole (TMSI) and mix on vortex during 10 min.
- TMSI is stored in the refrigerator under N
2
.
- Add 1 cm 3 H 2 O bid. to neutralize the excess of TMSI, shake.
- Add 2 cm 3 isooctane and mix on vortex during 3 min, then centrifuge 5 min. (± 2200 RPM).
- 1 µl of the isooctane phase is injected.
FOS-01 w/SLV
FOR ERP USE ONLY
DO NOT DISTRIBUTE