Nanocomposites of boronic acid-functionalized magnetic multi-walled carbon nanotubes with flexible branched polymers as a novel desorption/ionization matrix for the capture and direct detection of cis-diol-flavonoid compounds coupled with MALDI-TOF-MS

Novel boronic acid-functionalized magnetic multi-walled carbon nanotubes with flexible branched polymer (Fe 3 O 4 @MWCNTs@ε-PL@BA) nanocomposites were fabricated and applied as the desorption/ionization matrix for the MALDI-TOF-MS determination of low molecular weight flavonoids . The prepared nanocomposite was systematically characterized by various techniques. Compared to the traditional organic matrix, the proposed Fe 3 O 4 @MWCNTs@ε-PL@BA matrix has excellent ionization efficiency and low-background noise interference due to the MWCNTs unique electron-phonon interaction and the high introduction density of boronic acid functional groups. Good sensitivity and ultra-high salt tolerance of the Fe 3 O 4 @MWCNTs@ε-PL@BA-assisted MALDI-TOF-MS were permitted for the determination and quantification of flavonoids in actual samples. Noticeably, the limits of detection (LODs) for the target flavonoids were in the range 17–33 nM. The relative standard deviations (RSDs) of spot-to-spot and sample-to-sample (n = 10) were ≤ 9.8% and ≤ 10.1%, respectively. Furthermore, the wide linear ranges (0.1 – 500 µg/mL) and satisfactory calibration plot coefficients (R 2 > 0.99) of flavonoids were achieved by MALDI-TOF-MS with the Fe 3 O 4 @MWCNTs@ε-PL@BA matrix. Good recoveries (92–105.5%) were achieved for the target flavonoids in practical food samples. Hence, the prepared Fe 3 O 4 @MWCNTs@ε-PL@BA nanocomposites have applications in the selective and efficient capture of target flavonoids active biomolecules coupled with MALDI-TOF-MS determination in actual samples.