Use of Functionalized Resin for Matrix Separation and Trace Elements Determination in Petroleum Produced Formation Water by Inductively Coupled Plasma Mass Spectrometry

Table 2

Doehlert experimental design for solid-phase extraction optimization.

Experiment number	Sample pH	Sample flow rate (mL min^−1)	Buffer concentration (mol L^−1)	Recoveries (%)					OR
				Cu	Ni	Pb	Cd	Co
1	7.0	7.2	0.0300	77.13	83.53	76.60	74.16	76.00	3.89
2	6.0	6.0	0.0200	73.64	83.70	81.95	80.27	82.34	4.04
3	6.0	6.0	0.0400	77.06	85.66	83.57	84.62	84.04	4.17
4	8.0	6.0	0.0200	82.22	91.45	94.58	96.56	84.96	4.52
5	8.0	6.0	0.0400	84.75	92.32	95.61	97.40	85.90	4.58
6	5.0	4.8	0.0300	98.04	82.70	54.75	19.76	84.78	3.42
7.1	7.0	4.8	0.0300	84.73	93.00	90.97	89.89	88.67	4.50
7.2	7.0	4.8	0.0300	86.55	94.45	89.02	88.05	86.39	4.47
7.3	7.0	4.8	0.0300	89.42	94.11	88.28	90.52	94.30	4.59
8	9.0	4.8	0.0300	72.56	104.97	99.10	100.42	95.48	4.74
9	6.0	3.6	0.0200	93.95	90.96	93.70	95.725	82.78	4.60
10	6.0	3.6	0.0400	94.19	91.84	94.68	97.42	89.12	4.70
11	8.0	3.6	0.0200	92.83	99.62	95.20	97.59	94.94	4.83
12	8.0	3.6	0.0400	96.49	102.78	98.02	100.03	96.15	4.96
13	7.0	2.4	0.0300	91.53	101.05	90.89	94.36	94.24	4.74

OR, overall response.