**4. Optimization of enrichment separation methods**

In the optimization of the methods used in the studies, to the recovery value of the elements to be determined parameters such as pH, amount of carrier element, amount of complexing agent or precipitating reagent, sample volume and effect of matrix components are examined.

#### **4.1 Effect of pH**

*Trace Metals in the Environment - New Approaches and Recent Advances*

**3.2 Synthesis of arylamido methyl methacrylate**

*Synthesis route of α-chloro-N-arylacetamide.*

spectroscopic techniques. FT-IR (cm<sup>−</sup><sup>1</sup>

**3.3 Synthesis of polymer resin**

path is given in **Figure 4**.

*Synthesis route of arylamido methyl methacrylate monomer.*

18.1 (CH3) [38, 39].

**Figure 2.**

Arylamido methyl methacrylate is synthesized as follows: 1.1 mol sodium methacrylate, 1 mol α-chloroacetamide, 0.1 mol NaI, and 0.1 mol TEBAC as catalyst are stirred in 100 mL acetonitrile at 80°C in a reflux condenser for 24 h in the presence of 100 ppm hydroquinone as the inhibitor. Then the solution is cooled to room temperature and neutralized with a 5% KOH solution. The organic layer is washed a few times with water, and the water layer is washed with diethyl ether several times. The diethyl ether layer and acetonitrile layer are aggregated and dried over anhydrous MgSO4 overnight. Diethyl ether and acetonitrile are evaporated. The organic layers are collected and the residue was distilled at 130°C at 5 mmHg to give a colorless liquid. (Yield: 80%). The synthesis reaction path is given in **Figure 3**.

H- and 13C-NMR

H-NMR (CDCl3,

): 3325 (NH); 3100–2800 (C─H); 1680

The structure of the monomer is confirmed by the FT-IR and 1

(>C═O); 1630 (CH2═C); 1580 (aromatic, C═C); 1230 (C─O─C). <sup>1</sup>

TMS): 9.1 (N-H); 8.0–6.7 (aromatics-H); 6.3–5.43 (CH2═C); 1.8 (CH3). 13C-NMR (CDCl3, TMS): 157.1–113.4 (aromatics-C); 134.4–124.2 (CH2═C); 168.1 (>C═O);

Arylamido methyl methacrylate-co-divinylbenzene polymer resin is prepared by copolymerizing of arylamido methyl methacrylate monomer (3.0 mmol) and divinylbenzene (3.0 mmol) as a crosslinker. The polymer resin is designed by the free radical solution polymerization technique in 1,4-dioxane and in a 50 mL sealed pyrex polymerization tube. The azobisisobutironitrile, AIBN is used at a 1:1 molar ratio as initiator. The reaction mixture is processed with nitrogen gas for 5 min in the polymerization tube and in an oil bath heated at 70 ± 1°C for 5 h. Later reaction, the formed polymer resin was kept at 25°C for cooling. The polymer resin was washed with ultra high pressure water, n-hexane and ultra high pressure water, respectively and then dried under vacuum at 40°C. The synthesis reaction

**72**

**Figure 3.**

The effect of pH on the precipitation of the studied trace elements such as Ni (II), Co (II), Cu (II), Mn (II), Cd (II), Zn (II), Pb (II) is investigated. The pH value plays an important role in the adsorption of sorbent-related ions and affects the state of sorption of heavy metals. Enrichment of metal ions pH effect is generally examined in the range of 1–8. Binding of analytes to the synthesized polymer resin in solid phase extraction (SPE) is known to be dependent on the pH of the samples solution. The pH value for quantitative SPE of the analytes is fixed by measurements of analytes in final solutions. All of the buffer solutions are prepared the pH 1–2 with 1 mol L<sup>−</sup><sup>1</sup> of KCl/HCl, pH 3–5 with 1 mol L<sup>−</sup><sup>1</sup> of CH3COONa/CH3COOH, pH 6–8 with 1 mol L<sup>−</sup><sup>1</sup> of CH3COONH4/CH3COOH.

#### **4.2 The effect of concentrations of eluents on the efficiency of analytes**

Elution of metals from the column is carried out using acids. The influences of various eluents on the recoveries of analytes are usually examined using 1, 2 and 3 M from each of HCl, HNO3 and H2SO4 and 10, 20, and 25 mL of these acid solutions.

#### **4.3 Effect of flow rates of solutions**

The contact time between the analytes and the complexing agent is the effect the recoveries of the analytes and the SPE time. This contact time is supplied to flow rate of the sample. The samples flow rates are usually examined in the range from 2 to 10 mL min<sup>−</sup><sup>1</sup> . The increase of sample flow rate, which reduces the interaction time between the analytes and the adsorbent. In order to achieve good precision,

a sample flow rate is generally chosen at 5 mL min<sup>−</sup><sup>1</sup> . The analytes desorption on the adsorbent also adhere to on the flow rate of the elution solutions.
