In mass-spectrometry, simultaneous monitoring of several transitions enables increased assay specificity, but also can be used as a tool to improve the lower limit of quantification. In this report, we propose a new approach to low abundant analyte detection in complex samples. The method consists of collecting two and potentially more, different mass spectrometry transitions with further analysis of a product function. For example, C-peptide detection was evaluated with two transitions monitored (1007.7-147.2 and 1007.7-927.8). Further extension of the method is theoretically analyzed and its potential limitations are discussed.