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. Author manuscript; available in PMC: 2014 May 23.
Published in final edited form as: Anal Chem. 2009 Jun 1;81(11):4210–4219. doi: 10.1021/ac802487q

Figure 2.

Figure 2

Improved sensitivity using metal free interface. (a)The total ion chromatogram reconstructed from the FTICR spectra acquired during the RPLC separation of 1 µg of β-casein with “reduced-metal” (top) and standard (bottom) interfaces. (b) FTICR spectra and neutral mass spectra (insets) of β-casein variant A2 with reduced-metal (top) and standard (bottom) interfaces. The injector (needle, loop and valve) and the stainless steel unions employed in the conventional RPLC system are capable of mimicking the Fe(III)-IMAC behavior and hence trap phosphorylated proteins/peptides. Stars in (a) indicate elution times of mass spectra in (b). Asterisks indicate noise peaks in (b).