For preparing the e-tag probes in situ during the synthesis of oligonucleotides, phosphoramidites or phosphates are provided, where the esters include alkyl groups, particularly of from 1 to 3 carbon atoms, and cyanoethyl groups, while for the phosphoramidite, dialkylamino, where the alkyl groups are of from 1-4 carbon atoms, while the other group would be a protected hydroxy, where the protecting