Chiral discrimination of drugs by DNA tetranucleotides under electrospray ionisation conditions.

The DNA tetranucleotides, extended versions of GCA at the 3'-end or 5'-end, were used as chiral selectors for the chiral discrimination of atenolol, DOPA, tamsulosin, valacyclovir and zolmitriptan. Chiral discrimination was achieved by investigating the collision-induced dissociation spectra of the [X+Y-2H](2-) ion generated by electrospraying a solution mixture of tetranucleotide (X) and R- or S-analyte drug (Y). The relative abundances of the precursor ion and the product ion, resulting from the loss of drug, were considered for measuring the degree of chiral discrimination. Among all the tetranucleotides studied, AGCA showed the highest chiral discrimination. The present study emphasised the position of an adenine base in the tetranucleotide in chiral discrimination. The suitability of the method for the measurement of optical purity was also demonstrated in the case of zolmitriptan.