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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.
(i) LC/MS conditions
Column: C18 column9 (2.1mm i. d., 150 mm long, grain size 5μm)
Column temperature: 40℃
Mobile phase: 0.003% ammonia water - acetonitrile (58:42)10
Flow rate: 0.18 ml/min
Injection volume: 10μl
Ionization: Electro-spray ionization (ESI), negative mode
Fragmenter voltage: 90 V
Monitor ion: m/z = 227 (BPA) or 241 (BPA-16d)
(ii) GC/MS conditions
Column: Fused silica capillary column (0.25 mm i. d., 30 m long,
film thickness 0.25μm); 5% phenylmethylsilicone as the liquid
phase11
Column temperature: 70℃, 2 min -> 20℃/min -> 150℃ -> 10℃/min
-> 300℃/, 5 min
Injection port temperature: 250℃
Carrier gas: He, 1 ml/min
Injection method: Splitless, purging off, 1 min
Ion source temperature: 230℃
Ionization: Electron ionization, positive
Ionization voltage: 70 V
Monitor ion: m/z = 357, 372 (BPA) or 369 (13C-BPA)
[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 (in LC/MS) or 13C-BPA (in
GC/MS) to the analyte concentration.
(i) LC/MS
Prepare BPA solutions of 0.5-100 ng/ml containing 5 ng of
BPA-d16 as the isotope-labeled internal standard. Inject 10μl
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.
(ii) GC/MS
Place 10-200 mg BPA in test tubes. Add to each test tube 100 ng
13C-BPA (as the isotope-labeled internal standard), 200μl BSTFA
and acetone to a volume of 1 ml. Leave the solutions standing
overnight before analyzing with a GC/MS-SIM. Construct the
calibration curve based on the BPA/13C-BPA peak area ratios.
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