The development of analytical strategies for the determinations of copper, lead and iron elements at trace levels by atomic absorption spectrophotometer

People live in a constant interaction with heavy metals due to their wide use in various branches of the industry. Although some metals have functional roles for vital metabolism, some have toxic effects on living organisms even at trace concentrations. Thus, determination of metals at low concentrations in different environmental and food samples is important for human health. Because of being fast and economical, Flame Atomic Absorption Spectrophotometry (FAAS) is the most commonly used method for metal determination even though its detection limits are higher than any other methods. One of the most common reasons for the high detection limits is the low nebulization efficiency. Apart from the structural deficiencies of the system, another reason of the detection limits to remain high is matrix effect. The effect of matrix on the analyte signal affects the accuracy and the sensitivity of the system. In this study, it was aimed to increase the analytical performance of the AAAS system in order to determine the copper (Cu), lead (Pb) and iron (Fe) elements in high accuracy and sensitivity. For this purpose, different preconcentration strategies and systems have been combined to achieve the highest efficiency. In this study; dispersive liquid liquid microextraction (DLLME) as a liquid phqs microextraction (LPME) method combined with slotted quartz tube (SQT) for Cu, stearic acid coated magnetic nanoparticle (SA-MNP) based solid phase microextraction (SPME) combined with SQT for Pb, and photochemical vapor generation (PVG) optimized for Fe were developed in order to determine these elements in FAAS system at trace levels. For the analytes, LPME-SQT-FAAS, SPME-MNP-SQT-FAAS and PVG-FAAS methods were developed, respectively for the determination of these elements at trace levels. In the determination of Cu by DLLME-SQT-FAAS method; the analyte was firstly seperated from the matrix by using preconcentration method, and then SQT was used to increase the atom-light interaction by ensuring that the atoms stay longer in the light path. In the study, the 2-[(E)-(Naphthalene-2-Ylimino)Methyl]Phenol ligand which was synthesized in our laboratory by the reaction of salicylaldehyde and 1-naphtylamine was used to form the coordinated copper complex before the extraction process. All parameters affecting complex formation, extraction and detection were optimized to increase the absorbance signal. Under the optimum conditions, an approximately 192 fold increase in sensitivity was recorded, corresponding to the 0.56 ng mL-1 as LOD value, comparing with the analytical performance values of the conventional FAAS system. The percent relative standard deviation (%RSD) of the lowest concentration was found to be 4.8%. Recovery studies have been carried out on samples of urine, lake water and mineral waters to test the accuracy and applicability of the developed method. As a result of the studies carried out at four different concentrations in the linear working range, recovery results between 82.2-106.3% were obtained. A matrix matching method using the developed analytical strategy was also applied and the recovery for the 175 ng mL-1 concentration was found to be 105.14%. In the determination of Pb by SPME-MNP-SQT-FAAS method; the preconcentration was carried out by SPME method using the modified surface area MNPs by coating with stearic acid. Then the extraction process was combined with SQT. Before extraction, magnetic nanoparticle (Fe3O4) was synthesized and coated with stearic acid (SA-Fe3O4). The extraction and instrumentation parameters wereoptimized to increase the sensitivity of the system. Calibration plots for each analytical systemwere established using optimum parameters. A sensitivity enhancement of about 31 times compared to the conventional AAAS method was observed with the LOD value of10.28 ng mL-1. The accuracy of the method was tested with recovery studies made with spiked two different concentrations of pepper and satisfactory results between 102.6-106.6% were obtained. In the determination of Fe, the volatile compound generation method allowed the matrix seperation and analyte to be delivered to the determinationzone without the necessity of nebulizer. In this part of the study, the method and instrument measurement parameters were examined one by one and optimum parameters of the method were determined. The detection limit for the study was recorded as 236.16 µg L-1 under the optimum conditions. It was observed that the system could be used as an alternative method for the determination of Fe.