Evaluation of Response Surface Methodology in Dispersive Liquid-Liquid Microextraction for Lead Determination Using Ionic Liquids

Behrooz Majidi,Farzaneh Shemirani,Rouhollah Khani

doi:10.4236/ajac.2011.28103

Abstract

This paper describes a dispersive liquid–liquid microextraction (DLLME) procedure using room temperature ionic liquids (RTILs) coupled with flame atomic absorption spectrometry detection with microsample intro-duction system capable of quantifying trace amounts of lead. In the proposed approach, ammonium pyr-rolidine dithiocarbamate (APDC) was used as a chelating agent and 1-hexyl-3-methylimmidazolium bis (trifluormethylsulfonyl)imid as an extraction solvent was dissolved in acetone as the disperser solvent. The binary solution was then rapidly injected by a syringe into the water sample containing Pb2+ complex. Some factors influencing the extraction efficiency of Pb2+ and its subsequent determination, including extraction and dispersive solvent type, pH of sample solution, concentration of the chelating agent and salt effect were inspected by a full factorial design to identify important parameters and their interactions. Next, a central composite design was applied to obtain the optimum points of the important parameters. Under the optimum conditions, the limit of detection (LOD) was 0.2 µg/L. The relative standard deviation (R.S.D) was 1.4% for 5 µg/L of Pb2+ (n = 7). The relative recovery of lead in seawater, blood, tomato and black tea samples was measured.

Highlights

Lead is a toxic element and can affect almost every organ or system in human body
The International Agency for Research on Cancer (IARC) has determined that inorganic lead is probably carcinogenic to human [1]
Lead is recognized worldwide as a poisonous metal. Due to these adverse effects, monitoring of lead in environmental, biological and food samples even at ultra trace level is very important. These analyses are difficult because such samples contain relatively low concentrations of lead, which fall below the detection limit of conventional analytical techniques, such as flame atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry

Summary

Introduction

The main target for lead toxicity is a nervous system. The quantification of lead in drinking water is very important considering the toxicity of this metal [3,4]. Lead is recognized worldwide as a poisonous metal Due to these adverse effects, monitoring of lead in environmental, biological and food samples even at ultra trace level is very important. These analyses are difficult because such samples contain relatively low concentrations of lead, which fall below the detection limit of conventional analytical techniques, such as flame atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry. Several preconcentration procedures to determine lead have been devised involving separation techniques, such as liquid-liquid extraction [5], coprecipitation [6], solid phase extraction [7], dispersive liquidliquid microextraction [8] and cloud point extraction [9]

Objectives

Results

Conclusion