Determination of Fluoroquinolones in Pharmaceutical Formulations by Extractive Spectrophotometric Methods Using Ion-Pair Complex Formation with Bromothymol Blue

Table 1

The conditional stability constants (K_f) of the ion-pair complexes for FQs.

Sample	Vdrug (mL)	VBTB (mL)	A	n	n^⋀n		Kf	log Kf	Mean
Ofloxacin
1	0.25	2.25	0.202	0.1111	0.7834	0.3116	50204.7802	4.7007	6.08
2	0.5	2	0.272	0.2500	0.7071	0.1486	157048.9127	5.1960
3	0.75	1.75	0.336	0.4286	0.6955	0.0512	572507.7789	5.7578
4	1	1.5	0.419	0.6667	0.7631	0.0035	9562329.8320	6.9806
5	1.25	1.25	0.476	1.0000	1.0000	0.0000	_	_
6	1.5	1	0.432	1.5000	1.8371	0.0002	59414177.6247	7.7739
7	1.75	0.75	0.356	2.3333	7.2213	0.0026	1172246.1806	6.0690
Levofloxacin
1	0.25	2.25	0.137	0.1111	0.7834	0.5749	14789.8587	4.1700	6.04
2	0.5	2	0.313	0.2500	0.7071	0.1856	115961.3839	5.0643
3	0.75	1.75	0.432	0.4286	0.6955	0.0426	708574.1920	5.8504
4	1	1.5	0.559	0.6667	0.7631	0.0005	67745245.6475	7.8309
5	1.25	1.25	0.594	1.0000	1.0000	0.0000	_	_
6	1.5	1	0.53	1.5000	1.8371	0.0004	34165312.8945	7.5336
7	1.75	0.75	0.426	2.3333	7.2213	0.0042	682897.0665	5.8344
Ciprofloxacin
1	0.25	2.25	0.392	0.1111	0.7834	0.2112	83530.0520	4.9218	5.91
2	0.5	2	0.452	0.2500	0.7071	0.1265	178145.0100	5.2508
3	0.75	1.75	0.564	0.4286	0.6955	0.0345	828480.0305	5.9183
4	1	1.5	0.661	0.6667	0.7631	0.0036	8522213.4055	6.9306
5	1.25	1.25	0.752	1.0000	1.0000	0.0000	_	_
6	1.5	1	0.615	1.5000	1.8371	0.0026	4572267.1248	6.6601
7	1.75	0.75	0.538	2.3333	7.2213	0.0043	608798.6008	5.7845

—, not determined.