A Novel Glass Fiber Coated with Sol-Gel Poly-Diphenylsiloxane Sorbent for the On-Line Determination of Toxic Metals Using Flow Injection Column Preconcentration Platform Coupled with Flame Atomic Absorption Spectrometry

A novel simple and sensitive, time-based flow injection solid phase extraction system was developed for the automated determination of metals at low concentration. The potential of the proposed scheme, coupled with flame atomic absorption spectrometry (FAAS), was demonstrated for trace lead and chromium(VI) determination in environmental water samples. The method, which was based on a new sorptive extraction system, consisted of a microcolumn packed with glass fiber coated with sol-gel poly (diphenylsiloxane) (sol-gel PDPS), which is presented here for the first time. The analytical procedure involves the on-line chelate complex formation of target species with ammonium pyrrolidine dithiocarbamate (APDC), retention onto the hydrophobic sol-gel sorbent coated surface of glass fibers, and finally elution with methyl isobutyl ketone prior to atomization. All main chemical and hydrodynamic factors, which affect the complex formation, retention, and elution of the metal, were optimized thoroughly. Furthermore, the tolerance to potential interfering ions appearing in environmental samples was also explored. Enhancement factors of 215 and 70, detection limits (3 s) of 1.1 μg·L^-1 and 1.2 μg·L^-1, and relative standard deviations (RSD) of 3.0% (at 20.0 μg·L^-1) and 3.2% (at 20.0 μg·L^-1) were obtained for lead and chromium(VI), respec tively, for 120 s preconcentration time. The trueness of the developed method was estimated by analyzing certified reference materials and spiked environmental water samples.

Sorbents with non-covalently immobilized β-diketones for preconcentration of rare earth elements

A comparison of the efficiency of sorbents obtained by different methods of non-covalent immobilization of β-diketones on some low-polar matrices with respect to extraction of rare earth elements (REEs) was carried out. It was shown that sorbents containing reagent amounts of 1-8mmol/g can be obtained by sorption of reagents on low-polar matrices from aqueous and aqueous-organic solutions, and the value for the maximum capacity of the sorbent correlates with the specific surface of the matrix. Similar sorbents were also prepared by impregnating the matrix with reagent. It was found out that, under the chosen conditions, sorbents modified by extracting reagent from the aqueous solutions are more stable and extract lanthanum with higher distribution coefficients than those obtained by impregnation. We have found conditions for quantitative extraction of REEs from seawater in the proposed preconcentration systems (pH 4.0, minicolumn dimensions 2×10mm, v=4ml/min). It was shown that all REE may be quantitatively recovered in both ways: on modified sorbents and as complexes with reagents on unmodified matrices. We have proposed a sorbent for lanthanum preconcentration from large volumes of water samples (500ml). The sorbent is stable in dynamic conditions and is based on hyper cross-linked polystyrene modified with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (PMBP). Desorption could be carried out with 1-2M HNO₃. REEs were determined by ICP-MS, LODs achieved were in ng/l range.