Identification and quantification of immunoglobulin G (G1, G2, G3 and G4) in human blood plasma by high-resolution quadrupole-Orbitrap mass spectrometry

We described a method for quantification of IgG (IgG1, IgG2, IgG3 and IgG4) in a small amount of human blood plasma using high-resolution quadrupole-Orbitrap mass spectrometry (HR-Q-Orbitrap-MS). For screening surrogate peptides of targeted IgGs, samples were prepared by pellet digestion and identified by data-independent acquisition of Orbitrap MS. The quantification was performed by parallel reaction monitoring (PRM). The remarkable sensitivity and selectivity of PRM enable the detection of low abundance IgGs, or a little plasma. The assay linearity for external standard IgG proteins was obtained from 5 to 1000 mu g L-1 with a mean coefficient of determination (R-2) higher than 0.99. The inter-day (n = 6) and intra-day (n = 6) precisions obtained were from 3.6% to 11.5%. This report represents a comprehensive study so far of the use of Q-Orbitrap-MS for the identification and quantitation of IgGs in human blood plasma.