Evaluation of the Electrostatic Contribution to the Retention of Modified Nucleosides and Nucleobases by Zwitterionic Hydrophilic Interaction Chromatography

Table 2

Contribution of electrostatic interactions to the ZIC-HILIC retention of the positively charged MNNs, at different salt concentrations ^(a).

Charged MNN	% of electrostatic interaction in retention
	Ammonium perchlorate
	0.25 mM	0.50 mM	1.00 mM	2.50 mM	(𝑘EI)0.25 mM
9mGua	25	21	17	6	0.45
1mGua	28	20	16	4	0.75
7mGua	52	46	39	23	1.66
	Potassium perchlorate
	0.25 mM	0.50 mM	1.00 mM	2.50 mM	(𝑘EI)0.25 mM
9mGua	26	24	20	6	0.54
1mGua	38	32	29	9	0.99
7mGua	49	44	38	16	1.85

(a) Isocratic elution: 80% ACN: 20% formic acid (2.6 mM, _wwpH = 3.1) with variable concentrations of ammonium or potassium perchlorate. Temperature: 20°C. Flow: 0.5 mL min⁻¹. Injection: 50 μL in ACN.