Fig. 3

a Scheme of the parallel hybrid RP-μHPLC-ICP-QQQ with on-line ³⁴S isotope dilution and LC-ESI-QToF analyses for the absolute quantitative analysis of the major toxins identified by mass profiling in the venom of the Mozambique spitting cobra, Naja mossambica [48]. b Overlay of ESI-QToF protein (blue trace, left y-axis) and ICP-QQQ ³²S (red trace, right y-axis) chromatograms allowed peak correlation of ICP-QQQ and ESI-QToF spectra. The resolution (50000) and mass accuracy (0.2 ppm) of the ESI-QToF instrument employed allowed accurate protein identification by mass profiling, and the observed excellent peak patterns matching enabled correlating molecular peak identity and elemental S quantitation. Relation of the integrated mass flow peak areas results in sulfur quantification using the equation displayed in (c) panel. C_S, sulfur concentration in the sample; C_Sp, sulfur concentration in the ³⁴S spike; W_S and W_Sp, weighted mass of sample and spike, respectively; Aw_S, sulfur atomic weight in the sample; Aw_Sp, sulfur atomic weight in the spike; A^a _Sp, ³⁴S abundance in the spike; A^b _S, ³²S abundance in the sample, R_M, the ³²S/³⁴S ratio in the mixture; R_Sp, the ³²S/³⁴S ratio in the spike; and R_S, the ³²S/³⁴S ratio in the sample