Isocratic Resolution of Fluoroquinolone-Based Antibiotics on the Phenylethyl-Bonded Phase under Nonaqueous Elution: A Consideration of the Separation Mechanism

Table 2

Chromatographic data for 9 quinolone-based antibiotics and their precursors under basic nonaqueous elution on the phenylethyl-bonded stationary phase.

	NA (6)	CIN (8)	ENR (3)	DIFL (10)	PEFL (4)	OFL (1)	LOM (9)	CIP (2)	PA (5)
Structure
490/10/1/0.5					;
490/10/1/1					;
490/10/1/1.5			;		;
490/10/1/2			;		;
490/10/1/4			;		;

quinolone-based compounds are listed, from left to right, in the same order as that eluted with 490/10/1/2 mobile phase on the phenylethyl-bonded stationary phase shown in Figure 1. NA, CIN, ENR, DIFL, PEFL, OFL, LOM, CIP, and PA are abbreviations for nalidixic acid, cinoxacin, enrofloxacin, difloxacin, pefloxacin, ofloxacin, lomefloxacin, ciprofloxacin, and pipemidic acid, respectively. capacity and selectivity factors are calculated according to the equations and . The value of the column is 2.96 minutes. means no separation. elution order is reversed, as compared to that with 490/10/1/2 mobile phase described above. An optically active carbon is associated with an asterisk for distinction.