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[Calibration curve]
Prepare standard solutions containing 0.05, 0.1, 0.2, 0.5, 1 and
2 μg/ml of the standard material for each isoflavone. Inject 5
μl each of the solutions to the LC/MS. Obtain peak areas from
the SIM choromatograms, and construct the absolute calibration
curves.
[Preparation of sample solutions]
Add 15 ml of 80% methanol to 1 g feed and extract by
homogenization for 2 min. Centrifuge the extract at 3000 rpm and
separate the supernatant. Add purified water to 20 ml and
filtrate, as necessary, through a 0.45 μm Whatman syringe
filter.
[Detection and determination limits]
The detection limit is calculated from the peak height given by
the sample, quantity of the sample used, and the concentration
of the standard substance in the sample that would give a peak
height corresponding to S/N = 3.
[Note]
1 E.g. Agilent Technologies' Zonbax XDB.
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