Dispersive solid phase micro-extraction of dopamine from human serum using a nano-structured Ni-Al layered double hydroxide, and its direct determination by spectrofluorometry

We report on a simple method for dispersive solid-phase micro-extraction of dopamine (DA) from human serum. It is based on a layered double hydroxide (LDH) of nickel-aluminum, which acts as the extractant. DA is extracted at pH 8 using the LDH sol solution as a dispersed solid-phase extractor. The extracted DA is quantified by spectrofluorometry at 285?nm excitation and 315?nm emission wavelengths. A comparison of the fluorescence of DA in bulk solution and that of DA intercalated in the LDH revealed a nearly 5-fold improvement in intensity. Factors such as pH, concentration of LDH in the sol solution, and temperature were optimized. Under these conditions, the limit of detection is 0.015?μg?L^?1. The inter- and intra-day relative standard deviations for six replicate determinations of 1?μg?L^?1 DA were 1.7 and 1.1?%, respectively. The method was successfully applied to the determination of DA in human serum samples.

Using multi-criteria decision-making methods to select the best location for the construction of a biomass power plant in Iran

Journal of Thermal Analysis and Calorimetry - Biomass is one of the most convenient types of renewable energy resources around the world. Densely populated areas all over the globe produce a vast...     

Modeling and optimization of energy systems

Journal of Thermal Analysis and Calorimetry -     

A review on the properties,preparation, models and stability of hybrid nanofluids to optimize energy consumption

Journal of Thermal Analysis and Calorimetry - These days, the importance of energy consumption has led scientists to optimize thermal devices. One of the solutions proposed for this purpose is...     

Heat transfer and fluid flow of pseudo-plastic nanofluid over a moving permeable plate with viscous dissipation and heat absorption/generation

Journal of Thermal Analysis and Calorimetry - The purpose of the present study is investigating the heat transfer of non-Newtonian pseudo-plastic nanofluid flow on a moving permeable flat plate...     

Fuzzy goal programming for multiobjective transportation problems

Several fuzzy approaches can be considered for solving multiobjective transportation problem. This paper presents a fuzzy goal programming approach to determine an optimal compromise solution for the multiobjective transportation problem. We assume that each objective function has a fuzzy goal. Also we assign a special type of nonlinear (hyperbolic) membership function to each objective function to describe each fuzzy goal. The approach focuses on minimizing the negative deviation variables from 1 to obtain a compromise solution of the multiobjective transportation problem. We show that the proposed method and the fuzzy programming method are equivalent. In addition, the proposed approach can be applied to solve other multiobjective mathematical programming problems. A numerical example is given to illustrate the efficiency of the proposed approach.     

Photocatalytic oxidation of primary and secondary benzylic alcohols to carbonyl compounds catalyzed by H3PW12O40/SiO2 under an O2 atmosphere

An efficient, selective and green procedure for the photocatalytic oxidation of primary and secondary benzylic alcohols to the corresponding aldehydes and ketones has been achieved using silica-encapsulated H₃PW₁₂O₄₀ as a recyclable heterogeneous photocatalyst in acetonitrile under oxygen gas as the sole reoxidant of the catalyst.     

A promising electrochemical sensing platform based on copper nanoparticles-decorated polymer in carbon nanotube electrode for monitoring methimazole

In this paper, a novel and convenient electrochemical sensor for detection of methimazole (MMI) by differential pulse voltammetry is presented. This sensor was fabricated by dripping well-dispersed MWCNTs onto glassy carbon electrode (GCE) surface, and then poly-l-Arg (P-L-Arg) film was deposited on the electrode. Finally, Cu nanoparticles (CuNPs) were electrochemically deposited on the resulting film by using cyclic voltammetry to prepare CuNPs-P-L-Arg/MWCNTs/GCE. The surface morphology of the electrodes has been studied by scanning electron microscopy. Studies reveal that the irreversible oxidation of MMI was highly facile on CuNPs-P-L-Arg/MWCNTs/GCE. The dynamic detection range of this sensor to MMI was 5.2–50 µM, with the detection limit of 2 µM. A new voltammetric method for determination of MMI was erected and shows good sensitivity and selectivity, very easy surface update and good stability. The analytical application of the modified electrode is demonstrated by determining MMI in biological fluids (serum).     

Comparison of GC and HPLC Methods for Quantitative Analysis of Tinuvin 622 After Saponification in Polyethylene

This study describes the sample preparation and two chromatographic techniques for determination of Tinuvin 622 in polyethylene. The first part of the two methods consisting of dissolving the polyethylene in boiling xylene is followed by addition of a methanolic solution of potassium hydroxide. The polymeric light stabilizer, Tinuvin 622, is thereby saponified to 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (diol). Addition of the methanolic solution of the saponification reagent simultaneously precipitates the polyethylene matrix. Then the diol is quantified using either gas chromatography (GC) or high performance liquid chromatography (HPLC). For GC, a Macherey Nagel Optima-17 capillary column (30m×0.25mm ID, film thickness 0.25µm) is used. Nitrogen is used as carrier gas and make-up gas. The detection system is a flame ionization detector. For HPLC, an octadecyl silane (ODS) column (30cm×4mm, particle size 5µm) and a mobile phase methanol: water mixture (3:97, v/v) are used. Detection of analyte is carried out at 215nm. Both methods can be used to determine Tinuvin 622 in polyethylene in the concentration range of 0.02–1%, which represents the usual application concentration.