**3.6. Lifetime of minicolumn**

The life of the sorbent was investigated by monitoring the analytical signal corresponding to solutions of Pb (100.0 mg L-1) or Cd (10.0 mg L-1) at the end of a work day and by counting the number of runs. It was observed that the packed minicolumn did not provide a significant change in the extraction, even when used 350 times.

Synthesis of a New Sorbent Based on Grafted PUF

**Amount of** 

**Cd (µg L-1) R (%)** 

for the Application in the Solid Phase Extraction of Cadmium and Lead 275

The transfer phase factor is defined as the ratio between the analyte mass in the original sample and that in the concentrate. Consumptive index (CI) quantifies the efficiency of an FI on-line column preconcentration system in terms of the sample volume consumed to achieve a defined EF. The term CI is defined as the sample volume (V), in mL, consumed to

The limits of quantification and detection of the method were also calculated. The detection limit was calculated using the following equation: 3sb/b, where sb is the standard deviation for eleven measurements of the blank, and b is the slope of the analytical curve for each

The accuracy of the proposed procedure was evaluated by determining the amounts of Cd and Pb in a certified reference material. The following material was analyzed: BCR-713, Wastewater (effluent) from the Institute for Reference Materials and Measurements (IRMM, Geel, Belgium). The results were 4.8 ± 0.5 µg L-1 for cadmium and 45 ± 4 µg L-1 for lead. According to the results, no significant difference was found between the results that were obtained and the certified values of the reference material (5.1 ± 0.6 µg L-1 and 47 ± 4 µg L-1

The preconcentration procedure was applied to determine the metal content in water samples. These real samples were collected at Jequié, Bahia, Brazil. Known concentrations of Cd and Pb were added to the samples to minimize the change in the matrix of the original sample. Recoveries of the spiked samples (2.0 and 30.0 g L-1 for cadmium and lead, respectively) were determined. The results shown in Table 3 demonstrate the applicability of the method. Recoveries (R) were calculated as follows: R (%) = {(Cm-Co)/m} x100, where Cm is the concentration of metal in a spiked sample, Co is the concentration of metal in a sample and m is the amount of metal spiked. The described procedure can be successfully applied to these matrices for the preconcentration and determination of cadmium and lead.

achieve a unit EF, expressed by the equation CI = V/EF (Fang et al., 1992).

metal. The limit of quantification was calculated as 10sb/b.

for cadmium and lead, respectively).

**Amostra** 

quantification, R: recovery.

characteristics.

**3.8. Application of the proposed procedure** 

**Amount of** 

**Cd (µg L-1) R (%)** 

**Added Found Added Found**

Tapwater Sample 1 0.0 < LOQ 93.5 0.0 < LOQ 95.7 2.0 1.87 ± 0.05 30.0 28.70 ± 0.98

Tapwater Sample 2 0.0 < LOQ 101.5 0.0 15.23 ± 0.98 96.8 2.0 2.03 ± 0.06 30.0 44.57 ± 2.59

The results obtained from this procedure are comparable to those of other preconcentration methods for Cd and Pb determination. Table 4 summarizes some of these methods and their

**Table 3.** Results for the determination of Cd and Pb using the proposed procedure. LOQ: limit of
