A new pre-concentration procedure based on poly(styrene-co-maleamide and imide) copolymers modified with 2-hydrazinobenzothiazole prior to spectrophotometric monitoring of inorganic as (as As(III)) in edible vegetable oils.

This study describes the development of 2-hydrazinobenzothiazole modified-amide/imide co-polymers for the extraction/pre-concentration of trace As(III), from edible vegetable oils. Their characterization was realized by help of instrumental techniques. The method is based on pH-dependent complexation between As(III) and co-polymeric chelators in presence of 35-fold excess As(V), their selective extraction into the mixed micellar phase, and detected at pH 2.0 and 6.0 by UV-vis spectrophotometer. The variables affecting extraction efficiency were optimized. From pre-concentration of 20-mL sample, the good linear relationships were obtained in range of 1-40 and 3-75 µg/L with DLs of 0.32 and 1.00 µg/L. The accuracy was verified by analysis of a certified sample without and with spiking. The method was applied into the analysis of iAs levels of samples. The results show that the functional co-polymers are efficient chelators, and exhibit great potential for the selective extraction of As(III) from edible vegetable oils.

Application of a novel poly(SMAm)-Tris-Fe3O4 nanocomposite for selective extraction and enrichment of Cu(I) /Cu(II) from beer, soft drinks and wine samples, and speciation analysis by micro-volume UV-Vis spectrophotometry.

In this study, a novel functional nanocomposite was synthesized, characterized and selectively used in pH-controlled separation, pre-concentration and speciation analysis of Cu(I) and Cu(II) from sample matrices where extraction is assisted, facilitated and greatly enhanced by ultrasound energy. The hydrophilic composite material functionalized with tris(2-hydroxymethyl)aminomethane (Tris) and Fe3O4 NPs was characterized in detail by ATR-FT-IR, 1H NMR, XRD, EDX peaks and SEM images. After optimization of the main variables influencing extraction efficiency such as pH, volumes of buffer, modified copolymer in acetone, CTAB and Triton X-114 at fixed concentrations including sonication conditions, the Cu(I) and Cu(II) were monitored against a blank at 347 nm by micro-volume UV-vis spectrophotometer. A good linearity was obtained in the range of 2-140 and 5-150 µg L-1 for Cu(II) and Cu(I) with r2 ≥ 0.993. The limits of detection (LODs) of 0.66 and 1.60 µg L-1 for each analyte, were obtained from a pre-concentration of 70-fold. After validation, the method was applied to speciation of Cu(I), Cu(II), and total Cu in the pre-treated and diluted beverage samples before and after pre-oxidation of Cu(I) to Cu(II) due to be more sensitive of extraction process to Cu(II) at pH 6.0. The results were also compared with those obtained by FAAS analysis to ensure the reliability of the results. It was observed that there was a statistically good agreement between the results of both methods.

Use of 2-Hydrazinobenzothiazole-Modified Copolymer(s) as Potential Chelating Agent for Sensitive and Selective Determination of Low Levels of Mercury in Seafood by Ultrasound-Assisted Cloud-Point Extraction Combined with Spectrophotometry.

In this study, a new method was developed for the pre-concentration of trace mercury from seafood samples prior to analysis by spectrophotometry. The method is based on the complexation between 2-hydrazinobenzothiazole (2-HBT)-modified copolymer(s) and Hg(II) in the presence of an ionic surfactant, cetyltrimethylammonium bromide (CTAB), as sensitivity enhancer at pH 4.5 and the extraction of the complex into the surfactant-rich phase of polyethylene glycol tert-octylphenyl ether (Triton X-114) as the extractant. The variables affecting extraction efficiency were evaluated and optimized. Due to the observation that the modified copolymers are 2.5-fold more sensitive and selective to the Hg2+ ions than the CH3Hg+, the amounts of free Hg2+ and total Hg were determined at 325 nm by spectrophotometric detection of free Hg2+ and total Hg in the pre-treated and extracted fish samples using dilute acid mixture containing Triton X-114 and K2Cr2O7, before and after oxidation of CH3Hg+ to Hg2+ with mixture of KBr and KBrO3 in the acidic media. The amount of CH3Hg+ was calculated from the difference between total Hg and free Hg2+ amounts. The accuracy was tested by analysis of two certified samples. The results were statistically in good agreement with the certified values, and the precision was lower than 6.4%. The limits of detection were 1.40 (1.58) and 1.91 (2.11) µg L-1 for Hg2+ from the two calibration solutions spiked before the pre-treatment, respectively. It has been observed that there is no significant matrix effect by comparison of slopes of the calibration curves. The method was applied to seafood samples for speciation analysis of free Hg2+ and CH3Hg+. In terms of speciation, while total Hg is detected in the range of 12.6-143.8 µg kg-1, the distribution of mercury in seafood was in the range of 7.4-53.3 µg kg-1 for CH3Hg+ and in 8.3-90.5 µg kg-1 for free Hg2+.