Perfluorooctanoic Acid for Shotgun Proteomics
Figure 3
Total ion current chromatograms of the tryptic digest of OS membrane proteins.
(A) Residual PFOA in the tryptic digest of OS membrane proteins quantified by flow injection analysis. Different concentrations of the PFOA standard solution (50–350 pg) and samples in 1 µL of 0.1% formic acid and 50% acetonitrile were injected into a flowing carrier stream consisting of 0.1% formic acid and 50% acetonitrile at 40 µL/min that was directly connected to a mass spectrometer (QStar, Applied Biosystems, Foster City, CA) equipped with an electrospray ion source. The (M–H)− ion (m/z 413) of PFOA was monitored. An aliquot of the digest was analyzed by flow injection analysis after three cycles of evaporation in ethanol∶ethylacetate∶water∶TFA (0.33∶0.33∶0.33∶0.01, v/v/v/v) at 25°C in a speed-vac concentrator under low pressure of <10 mTorr (Sample 2). The remaining digest was subjected to another three cycles of evaporation in ethanol∶ethylacetate∶water∶TFA (0.33∶0.33∶0.33∶0.01, v/v/v/v) at 60°C in a speed-vac concentrator under atmospheric pressure of 760 Torr (Sample 1). (B) 1 µg of the digest from sample 2 analyzed by LC-MS/MS. (C) 1 µg of the digest from sample 1 analyzed by LC-MS/MS.