All LC and MS conditions were as previously described [22 (link)]. Briefly, the concentration and purity of unlabeled analytes, which were prepared new before each extraction, were determined using a Shimadzu HPLC/DAD system (Shimadzu, Kyoto, Japan) equipped with a reversed phase column (C18 EC, 250 × 3 mm, 5 µm, 100 Å, precolumn: C18, 8 × 3 mm, Machery-Nagel, Düren, Germany). The mobile phases for gradient solution were (A) 0.1% acetic acid and (B) methanol.
LC-MS/MS measurements of samples were performed on a Shimadzu Nexera X2 UHPLC system (Shimadzu, Kyoto, Japan) equipped with a Raptor ARC-18 column (2.7 µm, 100 × 2.1 mm, precolumn: 2.7 µm, 5 × 2.1 mm, Restek, Bad Homburg, Germany). The mobile phases for the binary gradient consisted of (A) 0.1% formic acid and (B) acetonitrile with 0.1% formic acid at a flow rate of 0.4 mL/min.
The LC was interfaced with a triple quadrupole ion trap mass spectrometer (LCMS-8050, Shimadzu, Kyoto, Japan). Samples were measured in the ESI positive mode as previously described [22 (link)].
LC-MS/MS measurements of samples were performed on a Shimadzu Nexera X2 UHPLC system (Shimadzu, Kyoto, Japan) equipped with a Raptor ARC-18 column (2.7 µm, 100 × 2.1 mm, precolumn: 2.7 µm, 5 × 2.1 mm, Restek, Bad Homburg, Germany). The mobile phases for the binary gradient consisted of (A) 0.1% formic acid and (B) acetonitrile with 0.1% formic acid at a flow rate of 0.4 mL/min.
The LC was interfaced with a triple quadrupole ion trap mass spectrometer (LCMS-8050, Shimadzu, Kyoto, Japan). Samples were measured in the ESI positive mode as previously described [22 (link)].
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