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A quantitative answer cannot exist in analysis without a qualitative component to give enough confidence that the result meets the analytical needs,especially for screening the non-targeted compounds in complex matrices.Quadrupole-time of flight mass spectrometry with ultra-high mass resolution and MS/MS capability plays a crucial role because the structural information including the accurate mass of both precursor and product ions can be provided.In this study,as shown in Figure 1,a full workflow of screening unknown compounds with diverse structures (such as toxic and illegal drugs,natural products,pharmaceutical impurities,etc.) in a series of real samples (including herbal medicines,food,biological matrices and pharmaceutical preparations) was exhibited based on the HPLC & CE-QTOF,involving database establishment based on accurate mass,data processing (Mass Feature Extract,MFE),database & library search and MS/MS confirmation.The key points and outstanding features by HPLC-QTOF technology for the unknown compound confirmation were discussed,with respect to the influence of HPLC conditions on QTOF detection,QTOF parameter optimization,sample preparation and MS/MS fragmentation mechanism.The quantitative analysis by LC-QTOF (with the 20 ppm EIC extracted window) was also investigated in bios-samples with regards to high-reliable confirmation and good sensitivity resulting from accurate mass and high-resolution.