Simultaneous Preconcentration of Fast Green FCF and Rhodamine B Using Deep Eutectic Solvent and Determination via High-Performance Thin Layer Chromatography

Table 2

Experimental conditions from central composite design analysis for the simultaneous preconcentration of fast green FCF and rhodamine B.

Run	pH	Volume of deep eutectic solvent (μL)	Concentration of salt (mol L^−1)	Stirrer time (min)
1	6.90	375	0.35	15
2	4.50	375	0.35	5
3	4.50	225	0.35	15
4	3.30	300	0.53	10
5	3.30	300	0.53	20
6	4.50	375	0.35	15
7	4.50	375	0.35	15
8	4.50	375	0.35	15
9	4.50	375	0.35	15
10	4.50	375	0.00	15
11	3.30	450	0.53	20
12	5.70	450	0.53	20
13	4.50	375	0.35	15
14	3.30	450	0.18	20
15	5.70	450	0.18	10
16	3.30	450	0.53	10
17	5.70	450	0.53	10
18	5.70	300	0.18	20
19	4.50	525	0.35	15
20	4.50	375	0.70	15
21	5.70	300	0.53	20
22	5.70	450	0.18	20
23	5.70	300	0.18	10
24	2.10	375	0.35	15
25	3.30	300	0.18	20
26	5.70	300	0.53	10
27	3.30	450	0.18	10
28	4.50	375	0.35	25
29	4.50	375	0.35	15
30	3.30	300	0.18	10