Cleanup Of Residues Research Articles

Simultaneous Reduction and Immobilization of Cr<sub>2</sub>O<sub>7</sub><sup>2-</sup> in Metakaolinite-Based Geopolymer Complexed Reductant

Reduction and immobilization of Cr (VI) as Cr2O72- is investigated by using metakaolinite-based geopolymer complexed reductant. Without reductants, the leached Cr concentration from metakaolinite-based geopolymer containing Cr (VI) is very high. Adding reductants as FeCl2·4H2O, FeSO4·7H2O, and Na2S·9H2O respectively during geopolymerization, the leached Cr concentration is below 5 mg L-1 with high Cr immobilization rate above 99 %. By comparison with the immobilization of Cr (III), the added reductants reduced Cr (VI) to Cr (III) which can be locked successfully in the amorphous structure of geopolymer. Meanwhile, Cr (VI) initial concentration is lower than 0.7 wt. % in metakaolinite-based geopolymer, the above reductants can all meet the requirements. While for Cr (VI) initial concentration larger than 0.7 wt. %, Na2S·9H2O is more appropriate. Such a simultaneous reduction and immoboilization process enables the feasibility of using metakaolinite-based geopolymer complexed reductant to implement a one-step procedure for chromite ore processing residue cleanup.

Development of immunoaffinity columns for pyraclostrobin extraction from fruit juices and analysis by liquid chromatography with UV detection

Pyraclostrobin belongs to a new generation of fungicides widely used to preserve high valuable crops. In the present study, three monoclonal antibodies with different affinities to this modern strobilurin have been evaluated for their usefulness in the production of immunoaffinity columns suitable for the solid-phase extraction, concentration, and clean-up of residues from food commodities. Different immunosorbents were produced and characterized in terms of antibody immobilization efficiency, immunosorbent binding capacity, optimum elution conditions, and reusability. Covalent coupling of the antibodies to Sepharose–CNBr gel took place with high yield (over 90%), whereas the immunosorbent efficacy to retain the analyte (from 28 to 68%) was shown to depend on the amount and type of antibody immobilized on the support. As a matter of fact, columns prepared with the monoclonal antibody PYs5#14 were able to selectively bound up to 53 μg of pyraclostrobin per gram of beads. Acetonitrile solutions were preferred over methanolic ones for analyte elution, and some immunosorbents could be reused at least 4–6 times provided that the amount of pyraclostrobin and the volume of sample did not overload the column. Effectiveness of the selected immunoaffinity column was evidenced by the development of an extraction procedure for pyraclostrobin residues from fruit juices and further determination by high-performance liquid chromatography with UV detection. A concentration factor of 50 times was achieved with the developed immunoaffinity column, which eventually resulted in a limit of quantification of 0.01 mg L −1. Finally, quantitative recoveries were obtained on apple juice and red grape must samples spiked with pyraclostrobin from 0.01 to 1 mg L −1.

One-step Cleanup of Chlorinated Insecticide Residues by Chromatography on Carbon-Celite Mixtures

Abstract one-step chromatographic cleanup technique for chlorinated insecticides has been developed in which carbon (Nuchar)-Celite mixtures are used. Insecticides are selectively eluted from the adsorbent with 20% (v/v) acetone in ethyl ether. Procedures are described for cleanup of residues in fat up to 0.8 g of fat and for cleanup of extracts of green leafy plant materials. Cleanup is satisfactory for paper chromatography. Aldrin, chlordane, DDD, DDE, DDT, dieldrin, endrin, heptachlor, heptachlor epoxide, Kelthane, lindane, Thiodan, and thiodandiol were recovered quantitatively or nearly so. Methoxychlor and toxaphene were partially recovered.