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[Apparatus and conditions]
Use a high performance liquid chromatograph/mass spectrometer
(LC/MS) and a gas chromatograph/mass spectrometer (GC/MS).
Typical conditions are described below.
Column: C18 column6
(2.1mm i. d., 150 mm long, grain size 5 μm)
Column temperature: 40℃
Mobile phase: 0.003% ammonia water - acetonitrile (58:42)7
Flow rate: 0.18 ml/min
Injection volume: 10 μl
Ionization: Electro-spray ionization (ESI), negative mode
Fragmenter voltage: 90 V
Monitor ion: m/z = 227 (BPA) or 241 (BPA-16d)
[Calibration curve]
Prepare the calibration curves for quantitative analysis using
internal standards as described below. The curve converts the
peak area ratio for BPA and BPA-d16 to the analyte
concentration.
Prepare BPA solutions of 0.5-100 ng/ml containing 10 ng of
BPA-d16 as the isotope-labeled internal standard. Inject 10 μl
of this solution into the LC/MS. Obtain selected ion monitoring
(SIM) chromatograms for the monitor ions (m/z = 227 and 241) and
determine the peak areas. Construct the calibration curve by
plotting the BPA/BPA-d16 peak ratio vs. BPA concentration.
[Preparation of sample solutions]
Add 10 ng BPA-d16 as the internal standard to 1 g feed. Extract
BPA by homogenizing in 25 ml acetonitrile. Centrifuge the
extract for 5 min at 3000 rpm, separate the supernatant and
evaporate to dryness under reduced pressure. Dissolve the
residue in 5 ml acetone, and charge the alumina-A cartridge3, 8
with the solution. After washing the cartridge with 5 ml
acetone, elute BPA with 5 ml water. Charge the polymer
gel-filled cartridge4 with the eluent, wash with 3 ml water and
3 ml 20% methanol, and leach BPA with 3 ml methanol. Evaporate
the eluent to dryness under reduced pressure. Dissolve the
residue in 1 ml 40% methanol to obtain the sample solution.
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