Homocystine was for the first time, chemically linked to a highly cross-linked agarose support (Novarose) to be employed as a chelating adsorbent for preconcentration and AAS determination of nickel in table salt and baking soda. Nickel is quantitatively adsorbed on a small column packed with 0.25 ml of the adsorbent, in a pH range of 5.5–6.5 and simply eluted with 5 ml of a 1 mol l−1 hydrochloric acid solution.
A factorial design was used for optimization of the effects of five different variables on the recovery of nickel. The results indicated that the factors of flow rate and column length, and the interactions between pH and sample volume are significant.
In the optimized conditions, the column could tolerate salt concentrations up to 0.5 mol l−1 and sample volumes beyond 500 ml. Matrix ions of Mg2+ and Ca2+, with a concentration of 200 mg l−1, and potentially interfering ions of Cd2+, Cu2+, Zn2+ and Mn2+, with a concentration of 10 mg l−1, did not have significant effect on the analyte's signal. Preconcentration factors up to 100 and a detection limit of 0.49 μg l−1, corresponding to an enrichment volume of 500 ml, were obtained for the determination of the analyte by flame AAS. Application of the method to the determination of natural and spiked nickel in table salt and baking soda solutions resulted in quantitative recoveries. Direct ETAAS determination of nickel in the same samples was not possible because of a high background observed. 相似文献
There is an increasing need to address the potential risks arising from combined exposures to multiple residues from pesticides in the diet. Pesticide residue-related pollution is a problem that arises because of the increased use of pesticides in agriculture to meet the growing demands of food production. In this study, pesticide residue data were obtained based on an optimized extraction method. For this purpose, we established a method based on qu ick, e asy, ch eap, e ffective, r ugged, and s afe (QuEChERS) extraction for simultaneous determination of imidacloprid (IMI) and acetamiprid (ACT) in pistachio nuts. The parameters influencing the QuEChERS method were the sample-to-water ratio and adsorbent amounts. As a result, both were optimized to improve the recovery of the analytes as well as the clean-up efficiency of the pistachio matrix. Our results indicated that a freeze-out step and use of primary and secondary amines as an adsorbent led to much cleaner chromatograms with lower baseline drift, without using graphitized carbon black and C18-based adsorbent, which reduced both cost and time of analysis. Following extraction, the pesticide residues were separated and quantified by reverse-phase HPLC. For validation purposes, recovery studies were carried out using a concentration range from 20 to 2500 μg/L at nine levels. The suitable linearity, precision, and accuracy were obtained with HPLC–UV with recoveries of 70.37%–89.80% for IMI and 81.05%–113.57% for ACT, with relative standard deviations <12%. The validated method was successfully applied to the analysis of pistachio samples collected from a field trial to estimate maximum residue limits. There was no significant health risk for consumers via pistachio consumption. 相似文献
A four‐component reaction for the synthesis of 1,2‐dihydroisoquinoline derivatives is described. The Huisgen 1,4‐dipolar intermediate, which is produced from isoquinoline and an electron‐deficient acetylene compound 1 , reacts with H2O in the presence of diketene to produce 1,2‐dihydroisoquinoline derivatives 2 (Scheme 1). In addition, reaction of isoquinoline, dibenzoylacetylene (=1,4‐diphenylbut‐2‐yne‐1,4‐dione), and diketene in the presence of H2O leads to pyrroloisoquinoline derivative 7 . The structures of the compounds 2a – f and 7 were corroborated spectroscopically (IR, 1H‐ and 13C‐NMR, EI‐MS) and by elemental analyses. A plausible mechanism for the reaction is proposed (Schemes 2 and 3). 相似文献
An easy, efficient, and simple one-pot approach for the synthesis of 1,3-thiazolidine-2-thiones via multicomponent reaction is reported. The reaction of a primary amine with carbon disulfide in the presence of dibenzoylacetylene or bis(4-methyl-1-benzoyl)acetylene in a mixture of CH2Cl2 and H2O after 5 h, afforded the title compound as alkene diastereomers. 相似文献
A novel, convenient, and efficient approach to the synthesis of penta-substituted pyrroles has been reported based on the multicomponent reaction. Solvent-free condition for the formation of enaminones from primary amines and alkyl acetoacetates and it's reaction with fumaryl chloride lead to the formation of pyrroles that have halide, CH2CO2H, ester functional groups, and two alkyl substitutions. 相似文献
In this paper, a combined hollow fiber-based liquid three-phase microextraction and voltammetric method are applied for the first time as a highly selective and sensitive method of electrochemical analysis. Desipramine, used as a model compound was extracted from 8 mL aqueous solution (donor phase, 0.10 mol L−1 NaOH) through a thin phase of propyl benzoate inside the pores of a polypropylene hollow fiber and finally into a 10 μL acidic acceptor solution inside the hollow fiber. Three microelectrodes designed and constructed for the purposes of this study were placed into the two ends of the hollow fiber inside the acceptor solution, and voltammetric analysis was performed in-situ during the extraction. After 15 min, the final stable signal was used for analytical applications. Under the optimized conditions, an enrichment factor of 301 was achieved and the relative standard deviation (R.S.D.) of the method was 6.2% (n = 5). The calibration curve was obtained in the range of 5-5000 nmol L−1 with a reasonable linearity (R2 > 0.988) and the limit of detection (LOD) was found to be 0.8 nmol L−1. Finally, the applicability of the proposed method was evaluated by extraction and determination of desipramine in plasma and urine samples without any dilutions. 相似文献