Improved extraction method for the determination of iron, copper, and nickel in new varieties of sunflower oil by atomic absorption spectroscopy

A simple and fast procedure is proposed for the extraction of iron (Fe), copper (Cu), and nickel (Ni) in 16 varieties of sunflower seed oil samples using an ultrasonic bath. The experimental parameters of the ultrasonic-assisted extraction (UAE) method were optimized to improve the sensitivity and detect the metals at trace levels in minimum time. Conventional wet acid digestion method was used for comparative purposes. The optimum recovery of all 3 metals was obtained by UAE for 7 min, while the separation of aqueous and organic phases after extraction using centrifugation (UAE-2) required 3 min, as compared to the conventional equilibration method (UAE-1) that required 90 min. The respective recoveries of Cu, Fe, and Ni obtained with UAE-2 were in the range of 95.8-97.5, 93.5-98.3, and 95.6-98.2%, respectively, for different varieties of sunflower oil samples. Accuracy was determined by the standard addition method. Under the optimum operating conditions, the limits of detection obtained from the standard addition curves were 21.7, 20.4, and 35.6 ng/mL for Fe, Cu, and Ni, respectively. The fact that all varieties of sunflower oil contain significant amounts of Fe, Cu, and Ni indicates the deterioration of sunflower oil quality immediately after extraction from seeds, which poses a threat to oil quality and human health.     

Temperature-induced dispersive solid-phase extraction as a new approach for preconcentration of Sudan dyes in water and food samples prior to the determination by high-performance liquid chromatography

This study introduced a new microextraction method named temperature-induced dispersive solid-phase extraction. The performance of the method was demonstrated with the determination of Sudan dyes in food and natural water samples. In this method, a low quantity of sorbent was added to the aqueous solution and the mixture was shaken manually for about one minute. Then, the solution was heated in an ultrasonic water bath, and the sorbent was dissolved. Subsequently, the solution was cooled down with ice water, and consequently, the solubility of the sorbent was reduced in the sample solution and became cloudy. The phase separation was accelerated by centrifugation. The upper liquid phase was picked up using a syringe, and the remainder was solved in methanol and introduced into the HPLC for analysis. Various parameters affecting the extraction yield were evaluated. Analytical parameters, including limits of detection (0.011–0.016 μg/L) and quantification (0.038–0.055 μg/L), relative standard deviations (2.3%–3.1%), and preconcentration factor (40) proved the high efficiency of the developed method for the analysis of Sudan dyes. The proposed method was used to measure Sudan dyes in water and food samples and showed good extraction recoveries (95.0%–103.5%).     

Binuclear cyclometalated organoplatinum complexes containing 1,1'-bis(diphenylphosphino)ferrocene as spacer ligand: kinetics and mechanism of MeI oxidative addition

The binuclear complex [Pt2Me2(ppy)2(mu-dppf)], 1, in which ppy = deprotonated 2-phenylpyridyl and dppf = 1,1'-bis(diphenylphosphino)ferrocene, was synthesized by the reaction of [PtMe(SMe2)(ppy)] with 0.5 equiv of dppf at room temperature. In this reaction when 1 equiv of dppf was used, the dppf chelating complex 2, [PtMe(dppf)(ppy-kappa1C)], was obtained. The reaction of Pt(II)-Pt(II) complex 1 with excess MeI gave the Pt(IV)-Pt(IV) complex [Pt2I2Me4(ppy)2(mu-dppf)], 3. When the reaction was performed with 1 equiv of MeI, a mixture containing unreacted complex 1, a mixed-valence Pt(II)-Pt(IV) complex [PtMe(ppy)(mu-dppf)PtIMe2(ppy)], 4, and complex 3 was obtained. In a comparative study, the reaction of [PtMe(SMe2)(ppy)] with 1 equiv of monodentate phosphine PPh3 gave [PtMe(ppy)(PPh3)], A. MeI was reacted with A to give the platinum(IV) complex [PtMe2I(ppy)(PPh3)], C. All the complexes were fully characterized using multinuclear (1H, 31P, 13C, and 195Pt) NMR spectroscopy, and complex 2 was further identified by single crystal X-ray structure determination. The reaction of binuclear Pt(II)-Pt(II) complex 1 with excess MeI was monitored by low temperature 31P NMR spectroscopy and further by 1H NMR spectroscopy, and the kinetics of the reaction was studied by UV-vis spectroscopy. On the basis of the data, a mechanism has been suggested for the reaction which overall involved stepwise oxidative addition of MeI to the two Pt(II) centers. In this suggested mechanism, the reaction proceeded through a number of Pt(II)-Pt(IV) and Pt(IV)-Pt(IV) intermediates. Although MeI in each step was trans oxidatively added to one of the Pt(II) centers, further trans to cis isomerizations of Me and I groups were also identified. A comparative kinetic study of the reaction of monomeric platinum(II) complex A with MeI was also performed. The rate of reaction of MeI with complex 1 was some 3.5 times faster than that with complex A, indicating that dppf in the complex 1, as compared with PPh 3 in the complex A, has significantly enhanced the electron richness of the platinum centers.     

Application of thiophene-2-carbaldehyde-modified mesoporous silica as a new sorbent for separation and preconcentration of palladium prior to inductively coupled plasma atomic emission spectrometric determination

A new and efficient method was described for an easy synthesis of functionalized mesoporous silica (MCM-41) using thiophene-2-carbaldehyde. This new chemically bonded analytical reagent was used as an effective sorbent for the solid phase extraction of palladium(II) ion from aqueous solutions. Conditions for effective adsorption of trace levels of palladium concentration were optimized with respect to different experimental parameters in batch process. Thiourea solution could efficiently elute adsorbed palladium(II) ion from the surface of the sorbent which then was determined by inductively coupled plasma atomic emission spectrometer (ICP-AES).Common coexisting ions did not interfere with the separation and determination. The preconcentration factor was 100 (1 ml elution volume) for a 100 ml sample volume. The limit of detection of the proposed method is 0.2 ng ml⁻¹. The maximum sorption capacity of sorbent under optimum conditions has been found to be 5 mg of palladium per gram of sorbent. The relative standard deviation under optimum conditions was 3.2% (n = 10). Accuracy and application of the method was estimated by using test samples of natural and synthetic water spiked with different amounts of palladium(II) ion.     

Part-per-trillion determination of chlorobenzenes in water using dispersive liquid-liquid microextraction combined gas chromatography-electron capture detection

In this study, a simple, rapid and efficient method, dispersive liquid-liquid microextraction (DLLME) combined gas chromatography-electron capture detection (GC-ECD), for the determination of chlorobenzenes (CBs) in water samples, has been described. This method involves the use of an appropriate mixture of extraction solvent (9.5 μl chlorobenzene) and disperser solvent (0.50 ml acetone) for the formation of cloudy solution in 5.00 ml aqueous sample containing analytes. After extraction, phase separation was performed by centrifugation and the enriched analytes in sedimented phase were determined by gas chromatography-electron capture detection (GC-ECD). Our simple conditions were conducted at room temperature with no stiring and no salt addition in order to minimize sample preparation steps. Parameters such as the kind and volume of extraction solvent, the kind and volume of disperser solvent, extraction time and salt effect, were studied and optimized. The method exhibited enrichment factors and recoveries ranging from 711 to 813 and 71.1 to 81.3%, respectively, within very short extraction time. The linearity of the method ranged from 0.05 to 100 μg l⁻¹ for dichlorobenzene isomers (DCB), 0.002-20 μg l⁻¹ for trichlorobenzene (TCB) and tetrachlorobenzene (TeCB) isomers and from 0.001 to 4 μg l⁻¹ for pentachlorobenzene (PeCB) and hexachlorobenzene (HCB). The limit of detection was in the low μg l⁻¹ level, ranging between 0.0005 and 0.05 μg l⁻¹. The relative standard deviations (R.S.D.s) for the concentration of DCB isomers, 5.00 μg l⁻¹, TCB and TeCB isomers, 0.500 μg l⁻¹, PeCB and HCB 0.100 μg l⁻¹ in water by using the internal standard were in the range of 0.52-2.8% (n = 5) and without the internal standard were in the range of 4.6-6.0% (n = 5). The relative recoveries of spiked CBs at different levels of chlorobenzene isomers in tap, well and river water samples were 109-121%, 105-113% and 87-120%, respectively. It is concluded that this method can be successfully applied for the determination of CBs in tap, river and well water samples.     

Stereospecific high-performance liquid chromatographic assay of acebutolol in human plasma and urine

A sensitive high-performance liquid chromatographic technique is described for the separation of R- and S-acebutolol in human plasma and urine. The procedure involves derivatization with the chiral reagent S-(+)-1-(1-naphthyl)ethyl isocyanate. The resulting diastereoisomers are quantified using normal-phase high-performance liquid chromatography with fluorescence detection (220/389 nm). Virtual baseline separation, free from interference, with achieved (resolution factor = 1.45). Excellent linearity (r greater than 0.998) was observed throughout the range 10-500 ng/l and 2-100 mg/l in plasma and urine, respectively. Inter-assay variability was less than 5% for each enantiomer at concentrations of 10 ng/ml. This method is applicable for the determination of the pharmacokinetics, in man, of acebutolol enantiomers in plasma and urine.     

硅胶键合N-丙基哌嗪n-丙酸钠作为可循环使用催化剂催化4H-吡喃衍生物合成(英文)

Silica‐bonded N‐propylpiperazine sodium n‐propionate(SBPPSP) was found to act as an efficient solid base for the preparation of a series of 4H‐benzo[b]pyran derivatives. SBPPSP was used as a recyclable heterogeneous solid base catalyst for the synthesis of 3,4‐dihydropyrano[c]chromenes, 2‐amino‐4H‐pyrans, 1,4‐dihydropyrano[2,3‐c]pyrazoles, and 2‐amino‐4H‐benzo[e]‐chromenes via the condensation reaction of dimedone, ethyl acetoacetate, 3‐methyl‐1‐phenyl‐1H‐pyrazol‐5(4H)‐ one, and α‐naphthol, respectively, with aromatic aldehydes and malononitrile in refluxing aqueous ethanol. The heterogeneous solid base showed similar efficiency when reused in consecutive reactions.     

Application of Polytyramine Nanoparticles to the Corrosion Protection of Copper

Electrochemical polymerization of tyramine was achieved on copper electrode surface from tyramine in 0.3 M oxalic acid (pH=1.2) solution by using cyclic voltammetry technique. The formation of polytyramine nanoparicles (PTN) were characterized by cyclic voltammetry (CV), fourier transform infrared‐attenuated total reflectance (FTIR‐ATR) spectroscopy and scanning electron microscopy (SEM). The corrosion behavior of PTN coated copper was investigated by means of the change of open circuit potential with exposure time (E_ocp t), electrochemical impedance spectroscopy (EIS) and anodic polarization curves in 3.5 % NaCl solutions at room temperature. The obtained results showed the shift of corrosion potential toward positive values for electropolymerized copper and a significant decrease in corrosion current and corrosion rate in comparison with bare copper, so that the PTNs coating could be used as an important protection against corrosion of copper.     

Determination of nickel using cold-induced aggregation microextraction based on ionic liquid followed by flame atomic absorption spectrometry

Cold-induced aggregation microextraction (CIAME) combined with flame atomic absorption spectrometry (FAAS) was applied to preconcentration and determination of nickel(II) ions in natural water samples. The proposed method used 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF ₆ ]) as the extraction solvent and 1-(2-thiazolylazo)-2-naphthol (TAN) as the complexing agent. The extraction solvent was dissolved in the sample solution at 45°C. After dissolving, the solution was cooled in the ice bath and a cloudy solution of IL fine droplets was formed due to the decrease of IL solubility. After centrifugation, the fine droplets of extractant phase were settled at the bottom of the conical-bottom centrifuge tube. Analysis was carried out by a FAAS. Several important parameters influencing the CIAME extraction efficiency such as pH, complexing agent concentration, extraction solvent volume, salt effect, solution temperature, extraction time, centrifugation time and heating time were investigated and optimized. Under the optimum conditions, the limit of detection (LOD) was 0.8 ng/mL, and the relative standard deviation (RSD) was 3.4% for 50 ng/mL of nickel. The performance of the method was evaluated for extraction and determination of nickel in tap, mineral and seawater samples, and satisfactory results were obtained.     

Determination of Toxic Elements in Muscle Tissues of Five Fish Species Using Ultrasound‐Assisted Pseudodigestion by Electrothermal Atomic Absorption Spectrophotometry: Optimization Study

A simple and rapid method is described for the determination of As, Cd, and Pb in muscle tissue of five freshwater fish species by ultrasound‐assisted pseudodigestion (USD). A Plackett‐Burman experimental design was used as a multivariate strategy for the evaluation of the effects of varying several variables at once. The variables such as sonication time (ST), sample mass of muscle tissues (SM), temperature of ultrasonic bath (T), nitric acid (A1), and mixture of acid and oxidant (A2) have been studied. From these studies, some variables showed significant effect on % recovery, and they were further optimized by a 2³+star central composite design, which involved 16 experiments. Optimum values of the variables were selected for the development of USD to determine the contents of As, Cd, and Pb in muscle tissue of five fish species, used as bioindicators for Lake Manchar (Sindh, Pakistan) to know whether consumption of these fishes threatens human health. The determination of three toxic elements under study was carried out by electrothermal atomic absorption spectrometry (ETAAS). The accuracy of the optimized procedure was evaluated by analysis of certified reference materials DORM‐2 (Dogfish Muscle Certified Reference Material for Trace Elements) and by comparison with conventional wet acid digestion methodology. No significant differences were observed for p=0.05 when comparing the values obtained by the proposed USD method and conventional digestion method (CDM) (paired t‐test). The average relative standard deviation of the USD method varied between 4.05%, 7.53%, and 4.55% for As, Cd, and Pb, respectively (n=10).