Highly sensitive strategy for identification of trace chemicals in complex matrix: Application to analysis of monacolin analogues in monascus-fermented rice product.

Trace analysis of chemical analogues was always a hot topic and attracted the researchers' attentions. In this study, a database/multi-step filtering strategy was developed by using HPLC-Chip-MS system for comprehensive characterization of monacolin analogues in monascus-fermented rice product (MFRP). This strategy mainly included three steps, including chemical profile of MFRP by HPLC-Chip-MS, establishment of monacolin analogue database, multi-step filtering of monacolins based on modified mass defect filtering. All target compounds showed the symmetrical peak shapes and high MS response by using nanoflow HPLC-Chip-MS. According to the previous literature and experimental MS data, a database including 720 monacolin analogues was established. The original 522 ions in MFRP were automatically extracted by molecular feature extraction function. And then, through rectangular mass defect filtering and analogues distribution area filtering, 298 ions were further excluded. Finally, a total of 84 monacolins including 16 new compounds were unambiguously identified or tentatively characterized based on MS/MS information. In comparison with conventional mass defect filtering method, the proposed method was accurately able to exclude false positive results. The 438 false positive results were excluded in our study, while only 250 ones would be filtered out by using conventional method. This study provided a sensitive and powerful method for rapidly characterization of trace chemicals in complex matrix.