**2.1. Apparatus**

A Perkin Elmer (Norwalk, CT, USA) model AAnalyst 200 atomic absorption spectrometer equipped with a deuterium lamp for background correction was used for absorbance measurements. The wavelength value for the hollow cathode lamp for cadmium and lead was 228.8 nm and 283.3 nm, respectively. The flow rate of acetylene and air in the burner were 2.5 and 10.0 L min-1, respectively. The nebulizer flow rate was 8.0 mL min-1.

A Digimed (model DM 20, São Paulo, Brazil) pH meter was used to measure the pH of metal solutions. The preconcentration procedure was performed on a simple on-line system involving two steps: preconcentration and elution. The system consists of a Milan model 204 (Colombo, Brazil) four-channel peristaltic pump operated with silicone tubes and a six-port Rheodyne valve model 5041 (Cotati, USA). Teflon tubes were used in the construction of the system. Polyvinyl chloride (PVC) was used in the construction of the minicolumn (3.50 cm in length and an internal diameter of 4.0 mm). The minicolumn was filled with 400 mg of the synthesized sorbent.

The infrared spectrum was obtained using KBr pellets at 1.0% (w/w) in a Perkin Elmer Spectrum One FTIR spectrometer. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) curves were obtained in a Shimadzu TGA-50H apparatus in an aluminum cell under air or N2 (50 mL min-1) and scanned between the temperature values of 0.0 to 800.0 °C at a heating rate of 20 °C min-1.

#### **2.2. Reagents**

266 Polyurethane

Nile blue A

Methylene Blue

Methylene blue

Brilliant green

Methylene blue

spectrophotometry.

**2. Experimental** 

the synthesized sorbent.

values of 0.0 to 800.0 °C at a heating rate of 20 °C min-1.

**2.1. Apparatus** 

**Reagent Analyte** 

Zn(II)

Hg(II)

**Limit of detection (µg L-1)** 

Cd(II) <5,0 40

Ag(I) <5,0 40

Penicillin G 12 14

Ampicillin 19 11

Rosaniline Cd(II) ----- 100 Wastewater (Moawed, 2004) Hg(II)

Rhodamine B U(VI) ----- ----- Wastewater (M.F. El-Shahat et al., 2007)

**Table 1.** Procedures involving grafted PUF applied in the preconcentration of chemical species by

A Perkin Elmer (Norwalk, CT, USA) model AAnalyst 200 atomic absorption spectrometer equipped with a deuterium lamp for background correction was used for absorbance measurements. The wavelength value for the hollow cathode lamp for cadmium and lead was 228.8 nm and 283.3 nm, respectively. The flow rate of acetylene and air in the burner

A Digimed (model DM 20, São Paulo, Brazil) pH meter was used to measure the pH of metal solutions. The preconcentration procedure was performed on a simple on-line system involving two steps: preconcentration and elution. The system consists of a Milan model 204 (Colombo, Brazil) four-channel peristaltic pump operated with silicone tubes and a six-port Rheodyne valve model 5041 (Cotati, USA). Teflon tubes were used in the construction of the system. Polyvinyl chloride (PVC) was used in the construction of the minicolumn (3.50 cm in length and an internal diameter of 4.0 mm). The minicolumn was filled with 400 mg of

The infrared spectrum was obtained using KBr pellets at 1.0% (w/w) in a Perkin Elmer Spectrum One FTIR spectrometer. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) curves were obtained in a Shimadzu TGA-50H apparatus in an aluminum cell under air or N2 (50 mL min-1) and scanned between the temperature

were 2.5 and 10.0 L min-1, respectively. The nebulizer flow rate was 8.0 mL min-1.

**Enrichment**

**factor Sample Ref** 

Cd(II) ----- ----- Wastewater (M.F. El-Shahat et al., 2003)

Hg(II) <5,0 40 Wastewater (Moawed et al., 2003)

Amoxicillin 15 16 Antibiotics (M.F. El-Shahat et al., 2010)

Ultrapure water from an Elga Purelab Classic was used to prepare all solutions. Working solutions of cadmium and lead at the µg L-1 level were prepared daily by diluting a 1000 µg mL-1 solution of each element (Merck). Hydrochloric acid solutions were prepared by direct dilution of the concentrated solution (Merck) with ultrapure water. Acetate buffer solutions (pH 4.0-6.0), borate (pH 7.0-8.5) and ammonia (pH 9.0-9.5) were used to adjust the pH. The reagents 2,4- toluene diisocyanate (Aldrich), tin(II) 2-ethylhexanoate (Aldrich), dimethylamino-1-propanol (Aldrich), polyethylene glycol (Aldrich) and silicone oil AP 100 (Aldrich) were used in the synthesis of the sorbent.

#### **2.3. Synthesis of the reagent Me-BTAP**

The synthesis of the reagent 2-[2´-(6-methyl-benzothiazolylazo)]-4-aminophenol (Me-BTAP) was performed as described previously (Lemos et al., 2006a). The production of the reagent has been completed in two steps: diazotization of 6-methyl-2-aminobenzothiazole followed by the coupling of the diazotized product with 4-aminophenol. The diazotization reaction was performed by dissolving 6-methyl-2-aminobenzothiazole (3.0 g) in 50 mL of a 6.0 M hydrochloric acid solution. Then, a solution of 2.0 g of sodium nitrite in 20 mL of water at 0- 5 C was added dropwise, and the mixture was stirred at a constant temperature of 0–5 C for 1 h. The diazotate mixture was added dropwise to a solution of 3.0 g of 4-aminophenol in 20 mL of an 1.0 M sodium carbonate solution at 0–5 C under vigorous stirring. The system was allowed to stand overnight in a refrigerator at 0–5 C. The resulting dark-green precipitate was filtered and purified by recrystallization in ethanol. The proposed structure of Me-BTAP is shown in Figure 1.

**Figure 1.** Proposed structure of Me-BTAP.

#### **2.4. Synthesis of the sorbent**

Preparation of the grafted sorbent was performed according to the following procedure (El-Shahat et al., 2003; Moawed, 2004): 20.00 g of polyethylene glycol and 0.04 g of dimethylamino-1-propanol were added to 1.0 g of distilled water under vigorous stirring. Next, silicone oil (0.05 g) and tin(II) 2-ethylhexanoate (0.04 g) were added to the mixture. The system was shaken to obtain a homogeneous mixture. The reagent Me-BTAP (0.02 g) was then added, and the mixture was stirred for ten minutes. Afterward, approximately 13.0 g of toluene diisocyanate was added gradually. The resulting polymer was cut into small pieces and washed with 1.0 M HCl, ethanol and water. After washing, the polymer was dried at room temperature.

#### **2.5. Procedure for preconcentration**

Solutions containing Cd and Pb were adjusted to pH 7.5 with borate buffer. These solutions were passed through the sorbent minicolumn that contained the PUF-Me-BTAP. At this stage, the elements are sorbed onto the solid phase. After preconcentration (120 s), the position of the six-port valve was changed, and an eluent flow was passed through the minicolumn. The eluent transported Cd (II) or Pb (II) to the nebulizer of the flame atomic absorption spectrometer. The analytical signal was then measured as the peak height (absorbance).

Synthesis of a New Sorbent Based on Grafted PUF

for the Application in the Solid Phase Extraction of Cadmium and Lead 269

The graphs of TGA for Me-PUF BTAP in N2 (Figure 3) and O2 (Figure 4) show that there are no significant differences related to the atmosphere used during the degradation process for

**Figure 3.** Thermogravimetric curve of the material PUF-Me BTAP under an N2 environment.

0 100 200 300 400 500 600 700 800 900

C)

Temperature (<sup>o</sup>

**Figure 4.** Thermogravimetric curve of the material PUF-Me BTAP under an O2 environment.

0 200 400 600 800

C)

Temperature (<sup>o</sup>

the amount of steps, temperature ranges and loss of mass.

0

0

20

40

60

Mass (%)

80

100

20

40

Mass (%)

60

80

100
