A Liquid Membrane-Based Green Method for the Separation and Determination of Lead in Saline Waters

ABSTRACT

In this work, the authors proposed a new liquid membrane-based method for the determination of lead in saline waters. In this case, the new method is based on lead quantification by inductively coupled plasma-mass spectrometry (ICP-MS) after a preconcentration step by means of a bulk liquid membrane (BLM) system. With no sample manipulation, the system transports and preconcentrates the analyte ions in the sample into the acidic receiving solution, by means of an organic membrane containing di-(2-ethylhexyl)-phosphoric acid (DEHPA) acting as a chemical carrier. The chemical variables controlling Pb²⁺ permeation through the membrane were studied by use of a modified simplex approach. The most appropriate preconcentration rates were found at sample pH 4.7, maintained with a 0.08-M acetate buffer solution, a 0.07-M DEHPA concentration, and a 0.23-M HNO₃ receiving solution. Under these conditions, an extraction yield of 93.8 ± 0.1% and a preconcentration factor of 4.2 were obtained, thus allowing lead selective separation and accurate determination in real samples at environmental concentration levels. The system was tested with several real samples from the Gulf of Cádiz containing lead at the low ppb levels.

KEYWORDS:

• green analytical chemistry
• heavy metals
• lead
• liquid membrane
• saline water
• seawater

ACKNOWLEDGMENTS

This work was supported by the Spanish Ministerio de Educación y Ciencia (CTM2007-64678/TECNO). The authors acknowledge the collaboration of the Servicio Central de Ciencia y Tecnología (División de Espectroscopía) of the University of Cádiz. M. Benomar acknowledges Agencia Española de Cooperación Internacional for the financial support of his grant.

Notes

^a P = permeability coefficient.

^b I = initial; R = reflection; E = expansion; C⁻ = negative contraction.

^c Experimental F-value (Critical F-value = 2.06).^{[ 18 ]}

^a critical t-value (3,0.05) = 3.18.