Fluorescence tagging of glycans and other biomolecules through reductive amination for enhanced ms signals

A method for conjugating a biomolecule containing at least one ketone group or aldehyde group, the method comprising:

• reacting the biomolecule with a compound of Formula XB:
• or a salt or solvate thereof, wherein:
• R1 is selected from the group consisting of hydrogen, halogen, C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, C1-C6 alkanoyl, C1-C6 haloalkyl, C1-C6 haloalkenyl, C1-C6 haloalkynyl, C1-C6 cycloalkyl, C1-C6 acyloxy, hydroxy, amino, C1-C6 alkylamino, amido, nitro, C1-C6 alkylthio, C1-C6 alkylsulfinyl, C1-C6 alkylsulfonyl, sulfonate, sulfonic acid, —N3, —SH, —SCH3, —C(O)CH3, —CO2CH3 and —CO2H;
• R3b is
• and
• z=1−12;
• wherein reacting the biomolecule with the compound of Formula XB is done under conditions that facilitate reductive amination in the presence of a reducing agent, thereby forming a conjugate.