Determination of Low Levels of Lead in Beer Using Solid-Phase Extraction and Detection by Flame Atomic Absorption Spectrometry

Table 2

Values used for the construction of the response surface using central composite design.

Eluent concentration (mol L^−1)	Adsorbent mass (mg)	Eluent flow rate (mL min^−1)	pH
1.50	60	0.7	7
1.50	60	0.7	9
1.50	60	1.3	7
1.50	60	1.3	9
1.50	100	0.7	7
1.50	100	0.7	9
1.50	100	1.3	7
1.50	100	1.3	9
2.50	60	0.7	7
2.50	60	0.7	9
2.50	60	1.3	7
2.50	60	1.3	9
2.50	100	0.7	7
2.50	100	0.7	9
2.50	100	1.3	7
2.50	100	1.3	9
1.00	80	1.0	8
3.00	80	1.0	8
2.00	40	1.0	8
2.00	120	1.0	8
2.00	80	0.4	8
2.00	80	1.6	8
2.00	80	1.0	6
2.00	80	1.0	10
2.00	80	1.0	8
2.00	80	1.0	8
2.00	80	1.0	8
2.00	80	1.0	8
2.00	80	1.0	8