Application of nanoring amino-functionalized magnetic polymer dispersive micro-solid-phase extraction and ultra fast liquid chromatography–tandem mass spectrometry in dicyandiamide residue analysis of powdered milk

In this study, a rapid and accurate ultra-fast liquid chromatography–tandem quadrupole mass spectrometry (UFLC–MS/MS) method combined with dispersive micro-solid-phase extraction (d-µ-SPE) using a core–shell nanoring amino-functionalized magnetic polymer (CS-NR-MP) was established and validated to determine trace dicyandiamide (DCD) in powdered milk. The developed d-µ-SPE cleanup procedure can dramatically reduce the matrix in samples, and lead to a significant reduction in absolute matrix effects. Chromatographic separation was performed on an Acquity UPLC BEH Amide column by using water–acetonitrile (9:91, v/v) as the mobile phase within 2 min. DCD was quantitatively analyzed by using DCD-15N213C2 as an internal standard. The results showed that the recoveries were between 99.8 and 105.6% with RSDs in the range of 0.5–4.9%. The target compound had good linearity in the range of 0.1–20.0 µg L−1 with a correlation coefficient (r) of 0.9996. The limit of quantification (LOQ) was 0.06 µg kg−1. This method can be used for the rapid and sensitive determination of ultratrace DCD residue in powdered milk samples.