Solid Phase Microextraction (SPME)

For the complete study of the NPnEO fate in the environment analytical methods for the isolation and separation of each oligomer should be established.

Chromatographic separations are the only way to quantify the levels of NPnEOs in the environmental samples. Normal-phase high-performance liquid chromatography (HPLC) can successfully separate the oligomers with large number of ethoxy units (n>3), while gas chromatography with mass spectrometric detector (GC/MS) is used for the determination of short ethoxy chain nonylphenol ethoxylates and carboxylated metabolites.

The problems faced by the analysts while trying to develop a method for the determination of NPnEOs are the lack of quantified standards and the sample pretreatment.

The solid-phase microextraction (SPME) is the alternative to the traditional methods of extraction. It is a fast, low-cost technique that requires not special laboratory equipment and organic solvents. A polymer or adsorbent-coated fused-silica fiber is exposed either directly to the sample (immersion SPME) or in the vapor phase (headspace SPME). The analytes are adsorbed to the fiber and when equilibrium is reached, the fiber is transferred to the GC injector or the SPME-HPLC interface for separation and quantitation (Pawliszyn, 1997). In case of polar analytes SPME can be combined with derivatization. Derivatization reaction may take place in the sample vial simultaneously with extraction (in-sample derivatization), in the GC injector port after the extraction, or on fiber prior to extraction.

The main objective of my work is to apply the SPME method in order to determine the nonylphenol ethoxylates and their metabolites in wastewater samples.

NONYLPHENOL ETHOXYLATES

Alkylphenol ethoxylates (APEOs) belong to the category of non-ionic surfactants and are

formatted during the reaction of an alkylphenol with ethylene oxide.

The major alkylphenols used for the production of APEOs are nonylphenol (NP) and octylphenol. Nonylphenol ethoxylates (NpnEOs) are widely used captivating approximately 80% of the surfactant world market while octylphenol ethoxylates take only 20%

Nonylphenol ethoxylates have been widely used in domestic detergents and cleaning industry. They are employed as well as emulsifiers, dispersants, antifoamers, dyeing assists, stabilizers, lubricants, spermicides and pesticide adjuvants. They occur in the aquatic environment through the effluents of the wastewater treatment plants.

During the wastewater treatment process, nonylphenol ethoxylates degrade and form more persistent and toxic metabolites that are detected mainly in the plant effluent. Biodegradation of NPnEO occurs with progressive shortening of the ethoxylate chain. The ethoxylates with 0,1 and 2 ethoxylate units (NP, NP1EO, NP2EO) are considered to be the metabolic products of NPnEO, together with carboxylated compounds (NP1EC, NP2EC)

Nonylphenol polyethoxylates are considered to be endocrine disrupting compounds. They are often detected in the final effluents of sewage treatment plants due to their persistence and absence of third-stage treatment. The effluent discharges pose a major environmental risk to the natural and human environment.