Application of NiTi alloy coated with ZrO2 as a new fiber for solid-phase microextraction for determination of halophenols in water samples

A new fiber for solid-phase microextraction (SPME) employing a metallic support coated with an inorganic material is proposed. A nitinol alloy (NiTi) was used as the support material due to its super elasticity and shape memory properties. Zirconium oxide (ZrO2) was electrodeposited onto NiTi using chronoamperometry. The surface characteristics and morphology of the coated and uncoated support were evaluated through scanning electronic microscopy and dispersive energy microanalysis. This assembly was applied in the extraction of three halophenols from aqueous samples. A multivariate approach was used for optimization of the variables involved in the system. The Doehlert matrix was used for evaluation of the best derivatization conditions and a Box-Behnken design to obtain the best extraction conditions. In order to investigate the repeatability, one fiber was used for six extraction tests under similar conditions and the relative standard deviations (R.S.D.) were lower than 12.5%. Detection limits were lower than 0 30 ng mL(-1). Correlation coefficients were higher than 0.997. Extraction efficiency of the NiTi-ZrO2 fiber was similar to a PDMS 7 mu m commercial fiber, even though it had a lower coating thickness of 1.35 pm. Considering the amount extracted per unit volume, the NiTi-ZrO2 fiber had a better extraction profile when compared to commercial fibers. The new SPME fiber has a lifetime of over 500 extractions. Thus, it is a promising alternative for low-cost analysis, as the proposed fiber is robust, and easily and inexpensively prepared. (c) 2007 Elsevier B.V. All rights reserved.