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. 2010 Dec 30;5(12):e15332. doi: 10.1371/journal.pone.0015332

Figure 3. Total ion current chromatograms of the tryptic digest of OS membrane proteins.

Figure 3

(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.