Soylak et al.: Journal of aoaC InternatIonal Vol. 95, no. 6, 2012 1797 Received September 22, 2010. Accepted by AK January 24, 2011. 1 Visiting professor at King Saud University, Riyadh, Saudi Arabia. 2 Corresponding author’s e-mail: m_ghaedi@mail.yu.ac.ir DOI: 10.5740/jaoacint.10-370 RESIDUES AND TRACE ELEMENTS A cloud point extraction procedure for the preconcentration of Pb 2+ in various samples following complexation with 2,2′-(1E,1′E)-1,1′-(2,2′- azanediylbis(ethane-2,1-diyl)bis(azan-1-yl-1-ylidene)) bis(ethan-1-yl-1-ylidene)diphenol in Triton X-114 after centrifugation is reported. A 0.5 mL portion of methanol acidified with 1.0 M HNO 3 was added to the surfactant-rich phase prior to analysis by flame atomic absorption spectrometry. The influence of analytical parameters—including pH, concentrations of ligand, Triton X-114, and HNO 3 , bath temperature, heating time, and centrifugation rate and time—were optimized, and the effect of the matrix ions on the recovery of Pb 2+ was investigated. An LOD of 1.9 ng/mL along with a preconcentration factor of 50 with RSD of 1.0% for Pb 2+ were achieved. The proposed procedure was applied to the analysis of various real samples. T he extensive use of lead (Pb) in industry has led to serious hazards for human health because of its presence in natural water, potable water, soil, and air (1–3); therefore, its determination is very important. The need for highly reliable methods and techniques for the determination of trace heavy metals has been recognized. For that purpose, it is necessary to utilize either a very sensitive instrumental technique or enrichment/separation methods for the quantification of low concentrations of metals. Several analytical techniques, such as inductively coupled plasma (ICP)-atomic emission spectrometry and ICP/MS, are available for the determination of trace amounts of lead with sufficient recovery for most of applications, but the required instruments are expensive, day-to-day maintenance cost is high, and various types of inherent interferences appear to be very common with these techniques. Despite the selectivity and recovery of analytical techniques such as flame atomic absorption spectrometry (FAAS), there is a crucial need for the separation and preconcentration of trace amounts of metal ions from the matrix prior to their determination, due to the low concentrations of these elements in environmental samples (3– 13). The development of chemical and physicochemical methods for trace analysis is mainly in search of suitable techniques with special emphasis on the simplicity and precision of the method, low LOD, and elimination of matrix effects even in samples with complex composition (14–22). Micelles and other organized amphiphilic assemblies are increasingly utilized in analytical chemistry, especially in separation and preconcentration procedures. Their unique microheterogeneous structures capable of selective interaction with different solute molecules can strongly modify solubility, chemical equilibrium, kinetics, and spectroscopic properties of analytes and reagents (22–25). Hydrophobic species (hydrophobic organic compounds or metal ions after reaction with a suitable hydrophobic ligand) present in samples are able to interact with the micelles, thus being concentrated in the small volume of the surfactant-rich phase. The small volume of the surfactant-rich phase obtained with this methodology permits the design of extraction schemes that are simple, cheap, highly efficient, fast, and of lower toxicity than techniques that use organic solvents. Triton X-114 was chosen as the nonionic surfactant because of its low cloud-point temperature and high density of the surfactant-rich phase as well as its low cost, commercial availability, and low toxicity. A literature survey did not show any application of 2,2′-(1E,1′E)- 1,1′-(2,2′-azanediylbis(ethane-2,1-diyl)bis(azan-1-yl-1-ylidene)) bis(ethan-1-yl-1-ylidene)diphenol (AEDBABEYD) as a complexing agent for metal ions in cloud point extraction (CPE). This paper reports the simultaneous preconcentration of Pb 2+ after the formation of a complex with AEDBABEYD and later determination by FAAS using Triton X-114 as a surfactant. The proposed method was applied to the determination of metal ions in some real samples with complicated matrixes. Experimental Instrumentation A PerkinElmer (Waltham, MA) 3110 atomic absorption spectrometer with a lead hollow-cathode lamp was used for absorbance measurements at 283.3 nm. All measurements were carried out without background correction. The instrumental parameters were adjusted according to the manufacturer’s recommendations. An ALC PK 120 centrifuge (Buckinghamshire, UK) was used to accelerate the phase separation process. A Sartorious PT-10 pH meter (Goettingen, Cloud Point Extraction and Flame Atomic Absorption Spectrometry Determination of Lead (II) in Environmental and Food Samples Mustafa soylak 1 and Erkan yilMaz University of Erciyes, Chemistry Department, 38039 Kayseri, Turkey MEhrorang ghaEdi 2 and Mortaza MontazErozohori Yasouj University, Chemistry Department, Yasouj, Iran 75914-353 Marjan shEibani Islamic Azad University, Chemistry Department, Omidiyeh Branch, Omidiyeh, Iran Downloaded from https://academic.oup.com/jaoac/article/95/6/1797/5655325 by guest on 13 December 2023