Temperature response of a number of plastic dosimeters for radiation processing

Various plastic dosemeters are employed for dosimetry control of radiation processing within gamma and electron irradiation facilities.

The temperature response of a dosimeter is important when the dose to such a dosimeter is accumulated under varying irradiation temperatures. Such measurements would be significant for proper assessment of the dose for better process control, as well as, performance evaluation of dosimetry systems.

In this work we have developed a high current peltier junction temperature controller system for our Gammacell-220. This system has been designed to regulate the operating temperature of the irradiation chamber in the range of 0 to 80 C this system has been applied to measure the temperature response of the red perspex, a local clear PMMA, Gammex, Gammachrome, and Gafchromic dosimeters. The curves of relative performance or variation of the induced optical densities of the above dosemeters versus the irradiation temperature at fixed dose values are obtained.     

A New Kinetic‐Photometric Method for Determination of Carbimazole

A new kinetic photometric method for determination of carbimazole (CBZ) is described. The proposed method is simple, rapid, inexpensive and sensitive for the determination of CBZ in pure and tablet forms. This method is based on the inhibitory effect of carbimazole on the palladium(II)‐catalyzed reaction between neutral red (NR) and hypophosphite (HP) ions. The effect of various parameters such as dye, hypophosphite, and Pd(II) concentrations, pH, ionic strength, and temperature were optimized. The calibration graph was linear in the range 0.04–0.30 ppm (n = 9, r = 0.9972) and the detection limit was 0.02 ppm. The relative standard deviation of the developed method was 0.70% (n = 10). The proposed method was applied for the determination of carbimazole in pure and tablet forms.     

Electrochemical study of methylene blue incorporated into mordenite type zeolite and its application for amperometric determination of ascorbic acid in real samples

Methylene blue (MB) was incorporated into mordenite zeolite by ion exchange reaction in aqueous phase. The dye is strongly retained and not easily leached from the zeolite matrix. The solid was characterized by XRD prior to using it for the electrode preparation. This compound was incorporated into a carbon paste electrode for cyclic voltammetric and amperometric measurements. Methylene blue immobilized on the support underwent a quasi-reversible electrochemical redox reaction. In various electrolyte solutions and changing the pH between 2.0 and 7.0, the midpoint potential remained practically constant, i.e. 153.7±0.8 mV. This is not the usual behavior of MB, because in solution phase its midpoint potential changes considerably as the pH changes. The electrode made with this material was used for the mediated oxidation of ascorbic acid. The anodic peak current observed in cyclic voltammetry was linearly dependent on the ascorbic acid concentration. At a fixed potential under static conditions, the calibration plot was linear over the ascorbic acid concentration range 2.0×10⁻⁵ to 8.0×10⁻⁴ M. The detection limit of the method is 1.21×10⁻⁵ M, low enough for trace ascorbic acid determination in various real samples.     

Ultrasound assisted dispersive micro solid-phase extraction of four tyrosine kinase inhibitors from serum and cerebrospinal fluid by using magnetic nanoparticles coated with nickel-doped silica as an adsorbent

Nanoparticles (NPs) consisting of a magnetic Fe₃O₄ core and a nickel(II)-doped silica shell were prepared and are shown to be viable materials for selective magnetic extraction of trace quantities of the tyrosine kinase inhibitors (TKIs) imatinib, nilotinib, erlotinib and sunitinib. The NPs were characterized by scanning electron microscopy, transmission electron microscopy, DLS and XRD analysis, and the results revealed a uniform in size (with a typical diameter of 40 nm) and a core-shell structure. The magnetic nanoadsorbent displays good affinity of the TKIs, probably because of the affinity between the Ni(II) ions of the NPs with the nitrogen atoms in the TKIs. The magnetism of the NPs enables them to be quickly separated from serum and cerebrospinal fluid samples. Imidazole, with its higher affinity for Ni(II) than that of the TKIs, was used for desorption of the TKIs from the NPs prior to their quantification by HPLC with UV detection. The detection limits are as low as 200, 480, 130, and 250 ng·L￣¹ for imatinib, sunitinib, erlotinib, and nilotinib, respectively. The intra-day precisions (RSDs) were lower than 4.0 %. The method displays a wide linear range. It was applied to the determination of TKIs in (spiked) human serum and cerebrospinal fluid and gave recoveries in the range from 94.6 to 98.6 %.     

Innovative separation and preconcentration technique of coagulating homogenous dispersive micro solid phase extraction exploiting graphene oxide nanosheets

A uniquely novel, fast, and facile technique is introduced for the first time in which a scant amount of graphene oxide (GO), without modification, has been utilized in dispersive mode of solid phase extraction (SPE) for an efficient yet simple separation. The proposed method of coagulating homogenous dispersive micro solid phase extraction (CHD-µSPE) is based on coagulation of homogeneous GO solution with the aid of polyetheneimine (PEI). CHD-µSPE use full adsorption capacity of GO because in this method was used GO solution obtained from synthesis process without drying step and stacking nanosheets. In optimized condition, 30 µL GO solution (7 mg mL⁻¹), obtained in synthesis process, was injected into 1.5 mL the sample solution followed by immediate injection of 53 µL PEI solution (1 mg mL⁻¹). After inserting PEI, GO sheets aggregate and can be readily separated by centrifugation. PEI not only cause aggregation of GO, but also form three-dimensional network of GO with easy handling in following separation steps. Lead, cadmium, and chromium were selected as model analytes and the effecting parameters including the amount of GO, concentration of PEI, sample pH, extraction time, and type of desorption solvent were investigated and optimized. The results indicate that the proposed CHD-µSPE method can be successfully applied GO in dispersive mode of SPE without effecting on good capability adsorption of GO. The novel method was applied in determination of lead, cadmium, and chromium in water, human saliva, and urine samples by electrothermal atomic absorption spectrometry. The detection limits are as low as 0.035, 0.005, and 0.012 µg L⁻¹ for Pb, Cd, and Cr respectively. The intra-day precisions (RSDs) were lower than 3.8%. CHD-µSPE method showed a good linear ranges of 0.24–15.6, 0.015–0.95 and 0.039–2.33 µg L⁻¹ for Pb, Cd and Cr respectively. Method performance was investigated by determination of mentioned metal ions in river water, human urine and saliva sample with good recoveries in range of 94.2–103.0%. The accuracy of the method was underpinned by correct analysis of a standard reference material (SRM: 2668 level I, Urine).     

The mutual effect of metal sample and turboflame in LIBS signal enhancement

The main aim of the present study is to evaluate the mutual effect of copper sample and turboflame in laser induced breakdown spectroscopy (LIBS) signal enhancement. The use of copper sample leads to a signal enhancement in CN (B²Σ⁺–X²Σ⁺) 384.2–388.4 nm molecular transition, N_742nm, N_744nm, N_746nm (a triplet generated by the fine splitting of the 2s²2p²(³P)3s–2s²2p²(³P)3p transition) and H_{α, 656.3 nm} (as a flame inductor) atomic lines analysis. Additionally, increase in copper sample temperature with flame can enhance the Cu atomic line intensities (as copper sample inductors). Moreover, in this paper, the comparison between turboflame and alcohol flame on LIBS analysis was studied. LIBS signal intensity variation in a turboflame and turboflame coupled with copper sample at different laser pulse energies indicated that the low laser pulse energy could be compensated by using a copper sample that is coupled with turboflame and improved LIBS signal enhancement. For flames analysis, the use of metal sample in LIBS method is demonstrated to be costeffective, compact, and capable of signal enhancement.     

Electro-optical Kerr effect of azo-dye-doped liquid crystals using nulled intensity method

ABSTRACT

The electro-optical Kerr effect and pre-transition behavior have been investigated for different concentration of dimethyl-aminoazobenzene dye-doped nematic liquid crystal by using the nulled intensity method. Measurement results have showed that the molecular reorientation of liquid crystals induced by photoisomerization of azo dyes come about to increase an amount of Kerr constant at low percentages of dye concentration. Additionally, the results of pre-transition temperature which were obtained by extrapolating the invers Kerr constant as a function of temperature have been found to be in good agreement with predictions of the Landau-De Gennes model.     

Application of dispersive liquid–liquid microextraction followed by gas chromatography/mass spectrometry as effective tool for trace analysis of organochlorine pesticide residues in honey samples

A dispersive liquid–liquid microextraction (DLLME) method followed by gas chromatography/mass spectrometry (GC/MS) was applied for the trace determination of organochlorine pesticides in honey samples. The type and volume of organic extraction and disperser solvents, pH, effect of added salt content and centrifuging time and speed were optimized to find the appropriate extraction conditions. In DLLME, 30 µL of 1,2-dibromomethane (serving as extractant) and 1.5 mL of acetonitrile (serving as disperser) were applied. The limit of detection (3 s) and limit of quantification (10 s) for all the analytes of interest (organochlorine pesticides) varied from 0.004 to 0.07 and from 0.02 to 0.3 ng g^?1, respectively. The extraction recovery ranged from 91 to 100 %, and the enrichment factors ranged from 171 to 199. The relative standard deviation was <6 % for intraday (n = 6) and <8 % interday (n = 4) measurements. The proposed DLLME–GC/MS method was confirmed to be fast, simple to perform, friendly to environment and suitable for analysis of organochlorine pesticide residues at trace levels in honey samples.     

Preparation of polyphenylsulfone/graphene nanocomposite membrane for the pervaporation separation of cumene from water

Polyphenylsulfone (PPSU) was applied for the first time in the hydrophobic PV process. Nanocomposite membranes of PPSU/graphene (Gr) nanosheets were prepared and used to separate isopropyl benzene (cumene) from water via pervaporation (PV). Analysis of the mechanical properties of the membranes showed that the tensile strength and Young's modulus had an increasing trend with the incorporation of Gr into PPSU. The water contact angle of the membranes had a rising trend with the addition of Gr, confirming the improved hydrophobicity of membranes. In the PV experiments, the membrane containing 3.5 wt% Gr provided the highest separation factor, which was 4.5-fold as much as that of the neat PPSU membrane. Cumene separation from water by the PPSU/3.5 wt% Gr membrane was associated with the total flux of 132.73 gMH, the separation factor of 1566.36, and the PSI of 208,124.8 gMH.     

Viscosity of Ionic Liquids: Application of the Eyring’s Theory and a Committee Machine Intelligent System

Accurate determination of the physicochemical characteristics of ionic liquids (ILs), especially viscosity, at widespread operating conditions is of a vital role for various fields. In this study, the viscosity of pure ILs is modeled using three approaches: (I) a simple group contribution method based on temperature, pressure, boiling temperature, acentric factor, molecular weight, critical temperature, critical pressure, and critical volume; (II) a model based on thermodynamic properties, pressure, and temperature; and (III) a model based on chemical structure, pressure, and temperature. Furthermore, Eyring’s absolute rate theory is used to predict viscosity based on boiling temperature and temperature. To develop Model (I), a simple correlation was applied, while for Models (II) and (III), smart approaches such as multilayer perceptron networks optimized by a Levenberg–Marquardt algorithm (MLP-LMA) and Bayesian Regularization (MLP-BR), decision tree (DT), and least square support vector machine optimized by bat algorithm (BAT-LSSVM) were utilized to establish robust and accurate predictive paradigms. These approaches were implemented using a large database consisting of 2813 experimental viscosity points from 45 different ILs under an extensive range of pressure and temperature. Afterward, the four most accurate models were selected to construct a committee machine intelligent system (CMIS). Eyring’s theory’s results to predict the viscosity demonstrated that although the theory is not precise, its simplicity is still beneficial. The proposed CMIS model provides the most precise responses with an absolute average relative deviation (AARD) of less than 4% for predicting the viscosity of ILs based on Model (II) and (III). Lastly, the applicability domain of the CMIS model and the quality of experimental data were assessed through the Leverage statistical method. It is concluded that intelligent-based predictive models are powerful alternatives for time-consuming and expensive experimental processes of the ILs viscosity measurement.