Thesis (M.Sc.)--Chulalongkorn University, 2015

Lead (II) and cadmium (II) were determined by a flow-based analysis with spectrophotometric detection. Quercetin (Querc) and cetyltrimethylammonium bromide (CTAB) were used as a complexing agent and a surfactant, respectively. The absorbance of the yellow-colored complexes (Pb-Querc and Cd-Querc) were measured in Tris(hydroxymethyl)aminomethane buffer (pH 8.9) within the wavelength of 420-470 nm. The optimal condition was obtained by using 800 mgL-1 quercetin reagent (20 µL) in solution with 3.0 mmol L-1 CTAB (150 µL). The sample solutions were determined by a sequential injection spectrophotometer using deionized water as a carrier. The linear relationship between absorbance and concentration of metals were obtained over the concentration range from 20-100 µg L-1 for both Cd (II) and Pb (II). The limit of detection (LOD) of Cd (II) was 2 µg L-1 and the limit of quantification (LOQ) was 8 µg L-1. The limit of detection (LOD) of Pb (II) was 2 µg L-1 and the limit of quantification (LOQ) was 7 µg L-1. The relative standard deviations were 3.6% (n=7) and 3.4% (n=7) for 20 µg L-1 Cd (II) and Pb (II), respectively. The optimal condition was applied with the developed device for the determination of Cd (II) and Pb (II) in water. The alternative light source, LED (light-emitting diode), was also used for a miniaturization purpose.