INTRODUCTION

Codeine is one of the main alkaloids in poppy seed having pharmacological and toxicological activity (Fig. 1). As a drug, codeine is widely used as a good analgesic and cough suppressant agent [1,2]. It is a derivative of morphine, one of the best known drug abuses. Excessive or habitual use of these drugs causes toxic symptoms. Additionally, it has been reported that addiction to poppy drug abuse leads to a lot of sever social problems [3]. Thus, the rapid separation and determination of small level of codeine in biological fluid is of vital interest in clinical toxicology, control of drug abuse and forensic cases.

A wide rang of analytical methods have been reported for the determination of codeine such as gas chromatography [4,5], high performance liquid chromatography [6,7] and ion selective electrode [8]. Sample preparation techniques prior to instrumental analysis were based on liquid-liquid extraction (LLE) [9] and solid phase extraction (SPE) [10-13]. Unfortunately, these methods require a large sample volume and are time consuming. In particular, the traditional liquidliquid extraction method used large amounts of hazardous, volatile organic solvents. So, in recent years, the green liquidliquid extraction and cloud point extraction (CPE) have been employed in analytical chemistry. The use of preconcentration step based on phase separation by cloud point technique offers a convenient alternative to more conventional extraction system. Compared with the traditional organic liquid-liquid extraction, cloud point extraction requires a very small amount of relatively nonflammable and nonvolatile surfactants that are friendly to the environment. The first applications of phase separation based on cloud point phenomenon refer to the extraction of metal ions forming complexes sparingly soluble in water. Another application focuses on the isolation and purification of species of biological interest, mainly proteins [14]. This methodology was used first by Bordier [15] for the separation of hydrophilic proteins in biological membranes, using solution of Triton X-114 as an extractant [16,17]. Furthermore, this surfactant has been used for the preconcentration of vitamins A and E without their decomposition. The efficiency extraction with Genapol X-080 for vitamins A and E in blood and serum samples has been shown to be comparable to that obtained using an official method, which validates this method for quantification of the said vitamins in blood samples [18]. Furthermore, surfactant aggregates have been widely used as drug delivery vehicles [19,20] because they have low viscosity, small aggregate size, simple preparation and long shelf-life. In fact, micellar solubilization is one of the most important properties of surfactant solution, widely used in pharmaceutical, food, detergency and cosmetic industries, enhanced oil recovery and so forth [21].