Sensitivity enhancement of flame atomic absorption spectrophotometer for various elements by developing analytical methods

Heavy metals are used in various branches of the industry due to their physical properties. Some metals are found in living metabolism and participate in important mechanisms, while others are toxic to living things even at low concentrations. Determination of heavy metals in water and soil samples at low concentrations is of great importance for human health. Because Flame Atomic Absorption Spectrophotometry (FAAS) is fast and economical, it is a commonly used method for metal detection. However, due to the low efficiency of the nebulizer used as the sampling system, the determination limits are higher than the other methods. In this study, it was aimed to increase the analytical performance of the FAAS system for the determination of zinc (Zn), manganese (Mn), cobalt (Co), nickel (Ni), lead (Pb) and cadmium (Cd) with high accuracy and sensitivity by developing new methods. For this purpose, studies have been carried out with SQT-FAAS, T-SQT-AT-FAAS, HG-AAS and PVG-AAS systems by using slotted quartz tube (SQT), atom trapping (AT), hydride generation (HG) and photochemical vapor generation (PVG) methods, respectively. The aim of the studies in SQT-FAAS system was to increase the atom-light interaction by prolonging the residence period of the analyte atoms on the light path through a slotted quartz tube positioned on the flame head for Zn, Mn, Co, Ni, Pb and Cd elements. Atom trapping studies for Pb and Cd elements were carried out in T-SQT-AT-FAAS system. Hydrogen gas has been sent to the system in order to increase the ambient temperature and create a reducing atmosphere to release the analyte atoms at the same time, as a new method in the literature. With the HG-AAS system, which was used for hydride-forming elements, analytes were converted to hydride compounds in a strong reducing environment. After the hydrides which are quite volatile were separated from the liquid matrix and rapidly transported to the atomizer, the matrix effect was eliminated and sharp signals were obtained. In this study, optimum working conditions and system analytical performance of the HG-AAS system for Cd and Pb elements were determined. The PVG-AAS system parameters have been optimized with the aim of increasing the sensitivity of the FAAS system and performing the determination at low limits without any matrix effects. This method is based on the formation of the volatile analyte derivatives by irradiating analyte solutions containing low molecular weight organic acids with the UV light. With this method, a unique PVG-AAS system has been developed and studies for Co, Ni, Cd elements have been carried out. Optimization studies in SQT-FAAS, T-SQT-AT-FAAS, HG-AAS and PVG-AAS systems for Zn, Mn, Co, Ni, Pb and Cd elements were carried out. The analytical performance of all systems under optimum conditions were evaluated. The limits of detection of each methods used for each element were compared. The accuracy of the systems was determined by analysis of certified reference materials. Water and soil samples were used to study the performance of the systems in light and heavy matrix real samples.