Synthesis and application of nitrogen-doped carbon dots as a matrix in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Abstract Nitrogen-doped carbon dots (N-CDs) were synthesized by microwave-assisted pyrolysis of citric acid and urea for use as an alternative matrix for the detection of small molecules using matrix-assisted laser desorption/ionization spectrometry (MALDI-MS). The synthesis of N-CDs is much simpler than that of other nitrogen-doped carbon matrices used in MALDI-MS, which has been a major limitation to its application. The synthesized N-CDs were characterized using various analytical methods. The high optical absorbance and good dispersibility of the obtained N-CDs showed them to be an ideal matrix for detecting analytes such as glucose, sucrose, amino acids, nilotinib, and polyethylene glycols. The application of N-CDs as a MALDI matrix improved the signal response of small molecules due to the specific aromatic structure and the doping of nitrogen atoms. The minimum detectable amounts using an N-CDs matrix in MALDI-MS were found to be in the range of 1 nmol–1 pmol, with a lower minimum detectable amount of arginine (1 pmol) than previously reported.