No abstract

No abstract

The reaction pathways of acid rain formation from reaction of sulfur dioxide vapor and water vapor on the singlet potential energy surface have been investigated theoretically. The calculated results show that the reactants are initially associated with the adduct SO 2 -H 2 O through a barrier less process. Subsequently, via a variety of transformations of isomer SO 2 -H 2 O, three kinds of products H 2 SO 3 , SO 3 ? H 2 , and H 2 O 2 ? 3 SO are obtained. The cleavage and formation of the chemical bonds in the reaction pathways have been discussed using the structural parameters. Also, by means of the transition states and their connected intermediates or products at the CCSD(T)//B3LYP level, mechanism of H 2 O ? SO 2 reaction on the singlet potential energy surface are plotted. The calculation results show that the most suitable reaction pathways are the formation of H 2 SO 3 . Finally, the rate constants have been calculated only for these suitable pathways by the RRKM and TST theories at temperature range of 250-2500 K.

A sensitive and fast micro-solid-phase extraction (μ-SPE) coupled with dispersive liquid-liquid micro-extraction (DLLME) was reported before micelle enhanced spectrofluorimetric detection for determination of ciprofloxacin antibiotic in human plasma samples. The DLLME was performed using methanol as disperser and 1-octanol as extracting solvent. Oleic acid-modified Fe 3 O 4 nanoparticles (as hydrophobic adsorbents) were applied in μ-SPE step to extract the analyte from DLLME procedure. The method uses the advantageous of high surface area and strong superparamagnetism of these nanoparticles to many avoid labourhood column/cartridge-passing processes of traditional SPE. The major parameters affecting signal enhancement and analyte recovery were evaluated and optimised. Under the optimal conditions, the calibration curve (with calibration equation of I f = 2.5826 C + 10.273) was linear in the range 0.5-600 μg L −1 (R 2 = 0.997) with low limit of detection of 0.21 µg L −1 and limit of quantification of 0.63 µg L −1. The intra-day and inter-day precisions (as relative standard deviation) were in the range of 1.01-1.67% and high recoveries in the range of 93.5-102.4% were obtained. The results demonstrated that the proposed method is easy, low cost, and accurate. In addition, it confirms that choosing extraction solvent was not restricted to the high-density solvents which can extent the versatility of DLLME.

No abstract