Accurate determination of low levels of S in organic matrices by means of isotope dilution ICP-single quadrupole MS (e.g., for quantification of S components in reverse phase HPLC-ICP-MS experiments) is often not feasible. This work describes an accurate, sensitive and fast analytical method for the determination of S in organic matrices by means of a recently developed ‘triple quadrupole’ ICP-MS instrument, operated in MS/MS mode. The added value of the MS/MS approach for this application has been clearly visualised by varying the width of the bandpass of the first quadrupole analyzer from “fully open” (standard mode) down to single mass width (MS/MS mode). As a proof-of-concept, a biodiesel reference material has been analysed for its S content with the proposed method, using isotope dilution for calibration, and the results obtained were in excellent agreement with the certified value (within experimental uncertainty).